Les études cliniques et in vitro suggèrent que la sclérose de l’os sous-chondral due aux ostéoblastes (Ob) anormaux est impliquée dans la progression de l’ostéoarthrose (OA). Les Ob OA humains isolés à partir d’os sous-chondral sclérosé montrent un phénotype altéré, un niveau réduit de signalisation Wnt/β-caténine canonique et une minéralisation in vitro réduite. Il existe également deux voies non-canoniques, Wnt/PKC et Wnt/PCP qui ont étés décrites dans la littérature. Cependant, il n’existe aucune étude qui traite de ces deux voies dans les Ob OA. Ces voies sont activées après qu’un ligand Wnt non-canonique tel que Wnt-5a se lie à un récepteur Wnt couplé à des corécepteurs de la voie non-canonique. Ceci enclenche, respectivement pour la voie Wnt/PKC-Ca2+ et Wnt/PCP, la phosphorylation de PKC (p-PKC) et la phosphorylation de JNK (p-JNK) et agit sur les cibles en aval. Nous avons voulu déterminer s’il était possible de constater des altérations dans les voies Wnt non-canoniques dans les Ob OA. Nous avons préparé des cultures primaires d’ostéoblastes sous-chondral humains à partir de plateaux tibiaux de patients OA subissant une arthroplastie totale du genou, ainsi qu’à partir de plateaux tibiaux recueillis à l’autopsie de patients « normaux ». L’expression des gènes impliqués dans les voies Wnt/PKC et Wnt/PCP a été évaluée par RT-qPCR et la production par Western Blot des protéines, ainsi que celle de p-PKC et p-JNK et que l’activité des facteurs NFAT et AP-1 utilisés par ces deux voies. L’activité phosphatase alcaline (ALPase) et la quantité d’ostéocalcine (OC) ont étés évaluées respectivement à l’aide d’hydrolyse de substrat et d’ELISA. Le niveau de minéralisation a été évalué par la coloration au rouge Alizarine. Nos résultats montrent que l’expression et la production de Wnt-5a étaient augmentées dans les Ob OA comparées aux Ob N et LGR5 était significativement plus élevée. De plus, l’expression de LGR5 est directement régulée via la stimulation ou la diminution de Wnt-5a, à la fois au niveau de l’ARNm et des protéines. Par ailleurs, Wnt-5a a stimulé la phosphorylation de JNK et de PKC ainsi que l’activité NFAT et AP-1. Les niveaux de minéralisation ainsi que d’activité ALPase et de sécrétion d’OC ont aussi été affectés par les changements du niveau de Wnt-5a. Ces résultats suggèrent que Wnt-5a, qui est augmentée dans les OA Ob, peut stimuler les voies Wnt non-canoniques et affecter le phénotype et la minéralisation des OA Ob humains. / Clinical and in vitro studies suggest that subchondral bone sclerosis due to abnormal osteoblasts (Ob) is involved in the progression and/or onset of osteoarthritis (OA). Human Ob isolated from sclerotic subchondral OA bone tissue show an altered phenotype, a decreased canonical Wnt/ß-catenin signaling pathway (cWnt), and a reduced mineralization in vitro. Besides the cWnt pathway, at least two non-canonical signaling pathways, the Wnt/PKC and Wnt/PCP pathway have been described. These pathways are activated when a non-canonical Wnt ligand like Wnt-5a binds to a Wnt receptor coupled with non-canonical co-receptors. This activates, respectively for Wnt/PKC-Ca2+ and Wnt/PCP, the phosphorylation of PKC (pPKC) and the phosphorylation of JNK (pJNK) and their effect on downstream targets. However, there are no reports of either pathway in OA Ob. Here, we studied if alterations of the non-canonical pathways could be observed in OA Ob. We prepared primary human subchondral Ob using the tibial plateaus of OA patients undergoing total knee arthroplasty, or from tibial plateaus of normal individuals at autopsy. The expression of genes involved in Wnt/PKC and Wnt/PCP was evaluated by RT-qPCR and their protein production by Western blot analysis, in addition to p-PKC and p-PCP and NFAT and AP-1 activity with luciferase. Alkaline phosphatase activity and osteocalcin levels were evaluated respectively by substrate hydrolysis and ELISA respectively, and mineralization levels were evaluated with Alizarin red staining. OA Ob showed an increased alkaline phosphatase activity and osteocalcin release. The expression of Wnt5a was increased in OA Ob compared to normal. The expression of LGR5 was significantly increased in these cells. Moreover, the expression and production of LGR5 is directly modulated via the stimulation or inhibition of Wnt5a. However, Wnt5a did not stimulate the expression of LGR4. Wnt5a increased the phosphorylation of PKC and JNK as well as NFAT and AP-1 activity. Mineralization levels as well as alkaline phosphatase activity and osteocalcin secretion levels were also linked with changes in Wnt-5a levels. These data indicate that Wnt5a, which is increased in OA Ob, can directly stimulate the Wnt/PKC and Wnt/PCP pathways and this can affect the phenotype and mineralization observed in human OA Ob.

La régénération osseuse est un processus impliquant de nombreux types cellulaires comme les ostéoblastes, les chondrocytes ou les cellules stromales mésenchymateuses (CSM). Les CSM possèdent des capacités de différenciation suggérant leur implication dans ce processus de réparation. La régénération osseuse est le fruit de la coordination complexe de l'activité de nombreux facteurs de croissance. Parmi eux, l'« Heparin affin regulatory peptide » (HARP) est fortement exprimé dans le callus durant la régénération mais son rôle n'est pas clairement établi. Le but de ce travail de thèse a été (1) d'évaluer les effets de HARP sur les propriétés de migration, de prolifération et de différenciation des CSM in vitro ; (2) évaluer la capacité de HARP à induire une formation osseuse ou une régénération osseuse in vivo.Nos résultats démontrent que HARP est chémoattractant pour les CSM et potentialise leur prolifération. De plus, nous montrons pour la première fois que le traitement de CSM par HARP durant leur chondroinduction conduit à une différenciation chondrocytaire de type hypertrophique. Ce type cellulaire est primordial dans les derniers stades de la formation osseuse endochondrale qui se met en place durant la croissance osseuse, mais également durant la réparation. L'implantation de biomatériaux associés à HARP dans un défaut osseux de condyle fémoral a conduit à la formation de cartilage et d'os dans l'implant, reproduisant le mécanisme physiologique de formation osseuse endochondrale. Le biomatériau seul n'a été envahi que par du tissu fibreux.Durant les processus de réparation tissulaire, les glycosaminoglycannes (GAG), des chaînes polysaccharidiques sulfatées, composants majeurs de la matrice extracellulaire, participent à la modulation des effets des facteurs de croissance durant la réparation. Récemment, des mimétiques structuraux et fonctionnels des GAG ont été développés. Durant ma thèse, j'ai été associé au travail d'un doctorant de l'équipe de P.Albanese, qui a montré que des mimétiques de GAG induisent une différenciation ostéoblastique des CSM en l'absence de traitement ostéoinducteur. L'implantation sous-cutanée de biomatériaux covalemment associés aux mimétiques ont également été menées, et ont permis d'observer des potentialisations des processus de vascularisation de l'implant et de l'activité ostéoclastique. Ces resultats ont permis de valider l'interêt des GAG mimétiques dans le cadre des thérapies de régénération osseuse.Cette étude démontre pour la première fois les effets chondroinducteurs directs de HARP sur la production de molécules de la matrice cartilagineuse par les CSM in vitro, mais également sur la synthèse de tissu cartilagineux in vivo. Les effets de HARP observés sur la régénération osseuse confirment qu'il pourrait être un bon candidat en chirurgie orthopédique en permettant une régénération de type endochondrale typique de la réparation physiologique. De plus les nouvelles stratégies developpées dans le laboratoire sur la fonctionnalisation covalente de biomateriaux par des GAG mimétiques, meriteraient d'etre testées en association avec HARP, afin d'augmenter sa demi-vie et de controler son relarguage et ses activités biologiques in vivo. / Bone regeneration is a complicated process which involved many cellular types such as osteoblasts, chondrocytes and mesenchymal stromal cells (MSC). MSC can differentiate toward chondrocytes and osteoblasts, suggesting their implication in bone regeneration processes. Bone reparation involved a complex coordination of growth factors. Among them, heparin affin regulatory peptide (HARP) is found in callus during regeneration. However, its role is poorly understood. The aim of this thesis was (1) to evaluate HARP effects on proliferation, migration and differentiation of MSC in vitro, (2) to evaluate HARP ability to promote bone regeneration or bone formation.Our results demonstrate that HARP has chemoattractive and proliferative properties on human MSC. Moreover, we show for the first time that HARP commits human MSC toward hypertrophy during chondrogenesis. This is of great interest since hypertrophic chondrocytes are of primary importance in the late stage of endochondral bone formation. We further tested the association of HARP to scaffolds in a model of bone regeneration in femoral defect in rat. HARP associated scaffolds showed an invasion of cartilage and bony tissues, mimicking endochondral bone formation, whereas scaffold alone was just filled with fibrous tissue.During regenerative processes glycosaminoglycans, polysaccharides sulfated chains, are known as major components of the extracellular matrix and modulate the effects of growth factors during regenerative processes. Recently, structurally and functionally mimetics of GAG had been developed. During my PhD thesis, I was associated to the work of a doctoral student of P. Albanese who showed that GAG mimetics induce osteoblastic differentiation of MSC without any other osteoinductive treatment. The ectopic implantation of mimetic associated scaffolds didn't show effects on osteoformation but induced an enhancement of vascularization and of osteoclastic activity, both related to tissue remodeling. These results validate that GAG mimetics are of great interest in bone regenerative field.This study demonstrates for the first time the chondroinductive potential of HARP through its ability to induce cartilage specific matrix production by MSC in vitro but also by inducing cartilage tissue synthesis in vivo. The effects of HARP observed on bone regeneration, by inducing an endochondral bone formation similar to that observed in normal bone regeneration, confirm that HARP could be a good candidate in orthopedic surgery. Moreover, scaffold covalently linked with GAG mimetics should be tested in association with HARP. This strategy could increase the half life, control the release and potentiate HARP properties in vivo.

Apesar do grande potencial de regeneração do tecido ósseo, em algumas situações a extensão da lesão impede que o tecido se repare completamente. Como uma alternativa em relação aos tratamentos convencionais, a terapia celular tem sido considerada como promissora para o reparo de defeitos ósseos. No entanto, poucos estudos investigaram a terapia celular utilizando osteoblastos, portanto, avaliamos o efeito da injeção direta de osteoblastos na regeneração do tecido ósseo. Como os osteoblastos têm origens embrionárias diferentes, foi comparado in vitro o potencial osteogênico de osteoblastos derivados da crista neural, do mesoderma e de ambas as origens embrionárias. Considerando a necessidade de grande número de células para a terapia, foi comparado o efeito de uma subcultura, como meio de aumentar a quantidade de células, no potencial osteogênico dos osteoblastos. Para avaliação da regeneração dos defeitos, osteoblastos foram injetados diretamente nesses defeitos. Osteoblastos foram obtidos da calvária de ratos recém-nascidos (Wistar), sendo que os derivados da crista neural foram isolados dos ossos frontais (OB-CN); os do mesoderma isolados dos ossos parietais (OB-MS); e de ambas as origens embrionárias isolados de toda a calvária (OB-Cal). O efeito da subcultura no potencial osteogênico foi avaliado em OB-Cal ou na primeira passagem dessa cultura (OB-Cal P1). Após até 14 dias em cultura, foram avaliadas a proliferação celular, atividade de fosfatase alcalina (ALP), formação de matriz extracelular mineralizada e a expressão dos genes marcadores osteoblásticos: fator de transcrição runt-related 2 (RUNX2), ALP, osteocalcina (OC) e sialoproteína óssea (BSP). Para avaliar a regeneração do tecido ósseo, foram criados defeitos de 5 mm de diâmetro na calvária de ratos Wistar, que após 2 semanas foram tratados com 5 x 106 osteoblastos derivados de OB-Cal P1, por meio de injeção local. Ao final de 4 semanas, a formação óssea foi avaliada por microtomografia computadorizada e análise histológica. Os dados foram comparados por ANOVA, seguido do teste de Student-Newman-Keuls, ou teste t, quando apropriado, considerando o nível de significância de 5%. A comparação do potencial osteogênico em relação à origem embrionária mostrou que, os OB-MS apresentaram maior proliferação mas não houve diferença entre as culturas no evento final da diferenciação osteoblástica, que é a formação de matriz mineralizada. No entanto, como as culturas de OB-Cal apresentaram maior expressão gênica de marcadores iniciais, intermediários e finais dessa diferenciação; e considerando que, essas culturas são aquelas nas quais é possível obter o maior número de células, optamos por utilizar essas culturas na avaliação da formação óssea induzida pela terapia celular. Além disso, os resultados mostraram que os OB-Cal P1 tem seu potencial osteogênico reduzido, mas considerando que a subcultura permite a obtenção de maior número de células, são uma boa escolha para a terapia celular. Tanto que, ao avaliar in vivo a capacidade regenerativa das OBCal P1 no reparo dos defeitos ósseos, as análises microtomográficas e histológicas mostraram que que a terapia celular com injeção local de osteoblastos obtidos de fragmentos ósseos da calvária constitui uma estratégia adequada para estimular o reparo ósseo / Despite of the great potential of regeneration of the bone tissue, in some situations the extension of the lesion prevents the tissue from repairing completely. As an alternative to conventional treatments, cell therapy has been considered a promising strategy for the repair of bone defects. However, few studies investigated cell therapy using osteoblasts, therefore, we evaluated the effect of direct injection of osteoblasts on the regeneration of bone tissue. Since osteoblasts have different embryonic origins, the osteogenic potential of osteoblasts derived from neural crest, mesoderm and both embryonic origins was compared in vitro. Considering the need for a large number of cells for the therapy, the effect of a subculture, a common way to increase the amount of cells, on the osteogenic potential was also compared. Then, osteoblasts were injected directly into bone defects to evaluate the regeneration of bone tissue. Osteoblasts were obtained from the calvaria of newborn rats (Wistar), the neural crest derivatives were isolated from the frontal bones (OB-CN); those of the mesoderm isolated from the parietal bones (OB-MS); and from both embryonic origins isolated from the entire calvaria (OB-Cal). The effect of the subculture on the osteogenic potential was evaluated in OB-Cal and in its firstpassage (OB-Cal P1). After up to 14 days, all cultures were assayed for cell proliferation, alkaline phosphatase activity (ALP), mineralized extracellular matrix formation and the expression of the osteoblastic marker genes: runtrelated transcription factor 2 (RUNX2), ALP, osteocalcin (OC) and bone sialoprotein (BSP). To evaluate the effect of cell injection on bone regeneration, defects of 5 mm diameter were created in the calvaria of Wistar rats, that after 2 weeks were injected with 5 x 106 OB-Cal P1-derived osteoblasts. Vehicle injections were used as control. At the end of 4 weeks, the bone formation was evaluated by computerized microtomography and histological analysis. Data were compared by ANOVA, followed by the Student-Newman-Keuls test, or ttest, when appropriate, and the level of significance was set at 5%. The comparison of the osteogenic potential related to the embryonic origin showed that the OB-MS presented a greater proliferation but there was no difference between the cultures in the final event of the osteoblastic differentiation, that is the formation of mineralized matrix. However, as OB-Cal cultures showed greater gene expression of initial, intermediate and final markers of this differentiation; and considering that these cultures are those in which it is possible to obtain the largest number of cells, we selected these cultures for evaluating the bone formation induced by the cell therapy. In addition, the results showed that OB-Cal P1 still holds its osteogenic potential and despite being lower than that of OB-Cal as the subculture allows obtaining more cells, it has been considered as a good choice for cell therapy. In agreement with this, OB-Cal P1-derived osteoblasts injected into the bone defects were capable of inducing more bone formation than control, as revealed by microtomographic and histological analyzes. Therefore, it supports the idea that cell therapy with local injection of osteoblasts obtained from calvarial bone fragments is an adequate strategy to stimulate bone formation

Considerando-se que o tabagismo afeta a maioria dos sistemas do corpo humano, que os estudos concentram-se mais sobre os efeitos deletérios do tabaco em doenças cujos órgãos vitais são afetados e que seu impacto na formação e na consolidação óssea ainda não está estabelecido, a proposta neste estudo foi avaliar os efeitos da exposição à fumaça de cigarro no mecanismo de consolidação e remodelamento da matriz óssea e relacioná-los ao processo inflamatório desencadeado por fratura em modelo desenvolvido em camundongos. Para isso, camundongos C57BL6 machos foram distribuídos em quatro grupos: C (n=29) expostos ao ar ambiente; F (n=23) expostos ao ar ambiente e submetidos à osteotomia da tíbia direita; CS (n=29) expostos à fumaça de cigarro; FCS (n=23) expostos à fumaça de cigarro e submetidos à osteotomia da tíbia direita. Nossos dados indicaram diminuição do volume trabecular, da mineralização, MS/BS% (p < 0,05), e da formação óssea, MAR (p=0,0004), bem como aumento de osteoclastos, Oc.S/BS% (p=0,0361), e de reabsorção óssea, ES/BS% (p=0,0114), no grupo CS, quando comparado ao grupo C. Identificamos uma elevação significativa de IL-6 nos grupos CS e FCS (p < 0,001) na comparação com os grupos C e F (p < 0,05). Observamos diminuição de VEGF nos grupos CS e FCS, quando comparados com os grupos C e F (p=0,01). O índice de IGF demonstrou-se diminuído nos grupos CS e FCS, quando comparados com os grupos C e S (p < 0,05). A matriz fibrilar apresentou um intenso remodelamento, caracterizado pelo aumento da expressão de Colágeno V na avaliação por imuno-histoquímica nos grupos CS, F e FCS, comparados com C (p < 0,05), e da expressão dos genes COL5A1 (p < 0,0001) e COL5A2 nos grupos F e FCS (p < 0,0001). Identificamos também diminuição significativa de Colágeno I nos grupos CS, F e FCS, comparados com C (p < 0,001), e da expressão dos genes COL1A1 no grupo CS (p=0,008) e COL1A2 nos grupos CS, F e FCS (p=0,005). Nosso estudo mostra que a exposição à fumaça de cigarro altera a composição das fibras de colágeno pertencentes à matriz fibrilar óssea, retarda a mineralização e modifica a interação entre os diferentes tipos de colágeno, importantes no desempenho funcional do osso / Introduction: The impact of cigarette smoke on bone metabolism is not yet fully understood. This study aimed to verify the effects of cigarette smoke exposure in bone healing in an experimental tibial fracture model, evaluating the mineralization process, bone cellular differentiation/function and collagen types deposition. Materials and Methods: C57BL/6 male mice were assigned into four groups: C(n=29): exposure to room air; F(n=23): exposure to room air and right tibia osteotomy; CS(n=29): exposure to cigarette smoke; FCS(n=23): exposure to cigarette smoke and right tibia osteotomy. Results: Histomorphometry of Bone Mineral Matrix revealed that cigarette smoke exposure significantly reduced thickness of bone trabeculae, associated with a decrease in mineralizing surface and in rate of mineral apposition, which was reflected in lower bone formation rate and consequently in a longer time for mineralization. Both resorption surface and osteoclastic surface were higher in the CS group, evidencing the increase of the resorptive action of cigarette smoke. Histomorphometry of Bone Fibrillar Matrix: Type I collagen demonstrated a decrease in CS and FCS compared to C (p < 0.01); Type V collagen demonstrated an increase in CS, FC and FSC compared to C (p < 0.0001). The cytokines expression evaluation demonstrated that only CS exposure has already induced a VEGF and IGF decrease with a concomitant increase in IL-6 and these changes were intensified under fracture conditions. COL1A1 gene expression was reduced in the CS and FCS groups, similar result was observed in COL1A2 evaluation. COL5A1 gene expression, showed an increase in CS and Fracture groups while the COL5A2 gene expression increase was detected only in Fracture groups. Conclusion: Cigarette smoke exposure alters bone matrix composition and worsens bone mineralization, leading to bone fragility by increasing collagen V synthesis and deposition and impairing collagen I fibril forming and assembling

A crescente demanda clínica para regeneração óssea tem dirigido esforços significativos para o desenvolvimento de novos biomateriais, incluindo aqueles aplicados em terapias baseadas em engenharia de tecidos. Neste contexto, os biovidros são considerados uma boa alternativa mas as suas propriedades mecânicas têm limitado a sua aplicação. Para melhorar tais propriedades sem afetar a biocompatibilidade, um novo material vitrocerâmico bioativo do sistema P2O5-Na2O-CaO-SiO2, chamado Biosilicato® com duas fases cristalinas (BioS-2P) foi desenvolvido. No entanto, os efeitos da adição das fases cristalinas sobre o comportamento biológico do BioS-2P ainda não foram estudados. Assim, os objetivos deste estudo foram investigar a capacidade do BioS-2P em induzir, in vitro, a diferenciação osteoblástica de células-tronco mesenquimais (CTMs); a capacidade do BioS-2P em aumentar, in vitro, a atividade dos osteoblastos em fase inicial de diferenciação (OBs) e osteoblastos da linhagem UMR-106 (UMRs); e a capacidade do BioS-2P em conduzir e induzir a neoformação óssea, in vivo, associado ou não a células. Células derivadas da medula óssea obtidas de fêmures de ratos foram cultivadas em meio de crescimento para obtenção de CTMs ou em meio osteogênico para obtenção de OBs. Essas células e UMRs foram cultivadas sobre discos de BioS-2P, Bioglass® 45S5 (45S5) e plástico de cultura (Controle) e utilizadas nas avaliações in vitro. Para as avaliações in vivo, defeitos de 5 mm criados em calotas de ratos foram implantados somente com arcabouços de BioS-2P ou com arcabouços de BioS-2P associados às CTMs ou aos OBs. Os dados foram comparados por teste não paramétrico de Kruskal-Wallis seguido pelo teste de Student Newman-Keuls, e o nível de significância adotado foi de 5%. As CTMs foram caracterizadas por apresentarem alta porcentagem de células expressando os marcadores de superfície CD29 e CD90 e baixa porcentagem expressando CD31, CD34, CD45 e CD106. A diferenciação osteoblástica das CTMs foi confirmada pela expressão dos genes marcadores da diferenciação osteoblástica fosfatase alcalina (ALP), runt-related transcriptor factor-2 (RUNX2), sialoproteína óssea (BSP) e osteocalcina (OC). CTMs cultivadas sobre discos de BioS-2P em meio não-osteogênico apresentaram diminuição da proliferação e aumento da atividade de ALP e da expressão dos genes marcadores da diferenciação osteoblástica ALP, RUNX2, osterix (OSX), proteína óssea morfogenética-4 (BMP-4), osteopontina (OPN) e OC, comprovando seu potencial osteoindutor similar ao 45S5. O BioS-2P foi capaz de aumentar a atividade de OBs e UMRs de maneira similar àqueles cultivados sobre o 45S5. OBs apresentaram diminuição na proliferação e aumento da atividade da ALP e da expressão dos genes marcadores da diferenciação osteoblástica RUNX2, OSX, BMP-4, OPN e OC. A análise em larga escala da expressão de mais de 23.000 genes mostrou que o BioS-2P induziu a sobre-expressão de genes envolvidos no aumento da atividade osteoblástica e a repressão de genes envolvidos na diminuição dessa atividade, em comparação com o Controle. Ao menos em parte, esse aumento da atividade osteoblástica foi atribuído à modulação das vias de sinalização proteíno-quinases ativadas por mitógenos (MAPK) e Wnt Canônica, e à modulação da expressão de microRNAs. UMRs crescidos sobre o BioS-2P corroboraram esses achados, pela capacidade em formar matriz mineralizada e por apresentarem aumento na expressão das proteínas ALP, RUNX2, dentin matrix protein-1 (DMP-1) e OPN. Arcabouços de BioS-2P (5 mm de diâmetro e 2 mm de altura com porosidade de 76 ± 5% e com tamanhos de poros variando entre 100 e 800 &micro;m) implantados em defeitos na calota de ratos estimularam a formação de tecido ósseo, que ocorreu tanto na periferia como no interior dos defeitos e em íntimo contato com o material. A morfometria por microtomografia computadorizada não evidenciou qualquer diferença entre os parâmetros volume ósseo, volume ósseo/volume total, superfície óssea, superfície/volume ósseo, número de trabéculas, separação trabecular e espessura trabecular, avaliados na 4a, 8a e 12a semanas de implantação. As CTMs e os OBs foram carreados para os arcabouços de BioS- 2P (com eficiência de 90% e 81%, respectivamente) e essas células permaneceram nos defeitos por 14 dias. A combinação de arcabouços de BioS-2P com CTMs ou OBs, implantados por 8 semanas, resultou no mesmo padrão de formação óssea daquele observado para o arcabouço sem células. No entanto, essa combinação não resultou em aumento na quantidade de osso formado. Os resultados evidenciaram a capacidade do BioS-2P em induzir a diferenciação osteoblástica de CTMs e estimular a atividade osteoblástica de OBs, o que resultaria na neoformação óssea observada in vivo. No entanto, a combinação de BioS-2P com CTMs e OBs não foi capaz de aumentar a formação óssea e induzir o reparo dos defeitos ósseos. / The increasing clinical demand for bone regeneration has driven significant efforts to develop new biomaterials including those for tissue engineeringbased therapies. In this context, bioglasses emerges as a good alternative, but their use has been limited mainly due their poor mechanical properties. To improve these mechanical properties without affecting biocompatibility, a novel bioactive glass-ceramic of the P2O5-Na2O-CaO-SiO2 system, named Biosilicate® with two cristallyne phases (BioS-2P) was developed. However, the effects of these two phases on BioS- 2P biological behavior have not yet been evaluated. Thus, the aims of this study were to investigate the BioS-2P capability of inducing in vitro mesenquimal stem cell differentiation (MSC) towards osteoblasts; the BioS-2P capability to increase in vitro activity of osteoblasts derived from rat bone marrow at early stages of differentiation (OBs) and osteoblasts from rat cell line UMR- 106 (UMRs); and the BioS-2P capability to drive and induce bone formation in vivo, associated or not with cells. Bone marrow cells harvested from rat femurs were cultured either in growth media to obtain MSCs or in osteogenic media to obtain OBs. MSCs, OBs and UMRs were cultured on discs of BioS-2P, Bioglass® 45S5 (45S5) and tissue culture polystyrene (Control). For in vivo evaluations, 5-mm rat calvarial surgical defects were filled with BioS-2P with or without MSCs or OBs. Data were compared by non-parametric Kruskal-Wallis test followed by Student Newman- Keuls test and the significance level was set at 5%. MSCs were characterized by presenting high percentage of CD29 and CD90 surface markers and low percentage of CD31, CD34, CD45 and CD106 surface markers. Osteoblastic differentiation of MSCs was detected by gene expression of bone markers alkaline phosphatase (ALP), runt-related transcritption factor 2 (RUNX2), bone sialoprotein (BSP) and osteocalcin (OC). MSCs cultured on Bios-2P discs under non-osteogenic conditions exhibited a decrease on cell proliferation and an increase on ALP activity and gene expression of bone markers ALP, RUNX2, osterix (OSX), bone morphogenetic protein-4 (BMP-4), osteopontin (OPN) and OC, confirming its osteoinductive potential similar to 45S5. Also, BioS-2P increased the OBs and UMRs activity, similar to 45S5. OBs cultured on Bios-2P discs presented a decrease in cell proliferation and an increase on ALP activity and gene expression of bone markers RUNX2, OSX, BMP-4, OPN and OC. The large-scale analysis of over 23,000 genes showed that the BioS-2P induced overexpression of genes positively related to osteoblastic activity and repression of genes negatively related with its activity, compared with control. At least in part, the increase on OBs activity was associated to the modulation of two main signaling pathways, the mitogen activated protein kinases (MAPK) and the Canonical Wnt, and the modulation of microRNAs expression. These findings were corroborated by UMRs grown on BioS-2P, which produced mineralized matrix and exhibited increased expression of the ALP, RUNX2, dentin matrix protein-1 (DMP-1) and OPN proteins, than on control. BioS-2P scaffolds (5 mm diameter and 2 mm heigh, presenting 76 ± 5% of total porosity, with poros size ranging from 100 to 800 &micro;m) implanted in calvarial defects promoted new bone formation in close contatc to BioS-2P, both on periphery and in the center of the defect. The computed microtomography morphometry showed no difference between the evaluated parameters bone volume, bone volume / total volume, bone surface, surface / bone volume, number of trabeculae, trabecular separation and trabecular thickness, measured at 4, 8 and 12 weeks. MSCs and OBs were seeded into the scaffold (with efficiency of incorporation 90% e 81%, respectively) and they remained on the defects for 14 days. After 8 weeks, the same pattern of bone formation was observed, however, the combination of BioS-2P with cells did not increase the amount of new bone. The results showed the BioS-2P ability to induce osteoblastic differentiation of MSCs and to stimulate osteoblastic activity, resulting in new bone formation in vivo. However, the combination of BioS-2P with MSCs and OBs was not able to increase bone formation and induce the repair of bone defects.

Células-tronco mesenquimais derivadas de medula óssea (CTMs-MO) e de tecido adiposo (CTMs-TA) são uma ferramenta atrativa para a reparação do tecido ósseo baseada na terapia celular. No presente estudo, foi investigado o potencial osteogênico e adipogênico de CTMs-MO e CTMs-TA, assim como o efeito da intercomunicação entre osteoblastos e adipócitos na expressão do fenótipo celular. CTMs-MO e CTMs-TA de ratos foram cultivadas em meios de crescimento, osteogênico e adipogênico para avaliar a diferenciação osteoblástica e adipocítica. Adicionalmente, osteoblastos e adipócitos foram cocultivados de forma indireta para investigar o efeito dos adipócitos sobre os osteoblastos e vice versa. CTMs-MO e CTMs-TA apresentaram potencial tanto osteogênico quanto adipogênico em condições não indutoras de diferenciação. No entanto, quando expostas ao meio osteogênico, as CTMs-MO exibiram maior expressão gênica de RUNX2, fosfatase alcalina e osteocalcina, expressão proteíca de RUNX2 e maior formação de matriz extracelular mineralizada comparadas às CTMs-TA. Por outro lado, em condições adipogênicas, as CTMs-TA apresentaram maior expressão gênica de PPAR&gamma;, proteína adipocítica 2 e resistina, expressão proteíca de PPAR&gamma; e maior formação de acúmulo lipídico comparadas às CTMs-MO. A presença de adipócitos em coculturas indiretas inibiu a expressão do fenótipo osteoblástico, enquanto os osteoblastos não apresentaram um efeito marcante sobre a expressão do fenótipo adipocítico. Em conclusão, o presente estudo mostrou que as CTMs-MO são mais osteogênicas enquanto as CTMs-TA são mais adipogênicas. Adicionalmente, foi observado que a intercomunicação entre osteoblastos e adipócitos pode afetar negativamente o reparo ósseo. Assim, postulamos que o maior potencial osteogênico das CTMs-MO as tornam a escolha mais adequada para a indução do reparo ósseo baseado na terapia celular. / Mesenchymal stem cells from bone marrow (BM-MSCs) and adipose tissue (AT-MSCs) are attractive tools for cell-based therapies to repair bone tissue. In the present study, we investigated the osteogenic and adipogenic potential of BM-MSCs and AT-MSCs as well as the effect of crosstalk between osteoblasts and adipocytes on cell phenotype expression. Rat BM-MSCs and AT-MSCs were cultured either in growth, osteogenic or adipogenic medium to evaluate osteoblast and adipocyte differentiation. Also, osteoblasts and adipocytes were indirectly cocultured to investigate the effect of adipocytes on osteoblast differentiation and vice versa. BM-MSCs and AT-MSCs exhibit osteogenic and adipogenic potential under non-differentiation-inducing conditions. However, when exposed to osteogenic medium, BM-MSCs exhibited higher gene expression of RUNX2, alkaline phosphatase and osteocalcin, RUNX2 protein expression and more extracellular matrix mineralization compared with AT-MSCs. Conversely, under adipogenic conditions, AT-MSCs displayed higher gene expression of PPAR&gamma;, fatty acid binding protein 4 and resistin, PPAR&gamma; protein expression and more lipid accumulation compared with BM-MSCs. The presence of adipocytes as indirect coculture repressed the expression of osteoblast phenotype while osteoblasts did not exert remarkable effect on adipocyte phenotype expression. In conclusion, the present study showed that BM-MSCs are more osteogenic while AT-MSCs are more adipogenic. Also, we observed that the crosstalk between osteoblasts and adipocytes may negatively impact bone repair. Thus, we postulate that the higher osteogenic potential of BM-MSCs makes them the first choice for inducing bone repair in cell-based therapies.

La Cathepsine K est parmi la plus efficace des collagénases de mammifère pour cliver la triple hélice de collagène de type-1. Nous avons développé une série d'azanitriles, (CKI-8 and CKI-13) inhibiteurs de cathepsine K. CKI-8 (un isomère de CKI-13) et CKI-13 ne sont pas toxiques sur les osteoblastes Saos-2 et les cellules RAW 264.7 jusqu' à une concentration de 1000 nM, tandis qu'ils ne le sont pas jusqu'à une concentration de 100 nM sur les osteoclastes. CKI-8 n'affecte pas l'activité de la phosphatase alkaline ainsi que la minéralisation induite par les Saos-2 et par les osteoblastes primaires. CKI-13 diminue de 35 % la minéralisation induite par les Saos-2 tandis qu'il n'affecte pas la minéralisation induite par les osteoblastes primaires. L'addition de CKI-13 diminue l'activité de la phosphatase alkaline d'environ 20% (Saos-2) et de 40 % (osteoblastes primaires). La résorption osseuse sur des tranches d'os d'origine bovine est diminuée avec 10 nM de CKI-13, 100 nM de CKI- 8 et 100 nM d'inhibiteur commercial E64. CKI-8 et CKI-13 diminuent la mobilité des osteoclastes. Nous avons développé un dosage d'hydrolyse de PPi par la phosphatase alkaline au moyen de l'IR, ayant l'avantage de fonctionner sur des vésicules matricielles et des cellules avec des substrats naturels à un pH physiologique. La bande de PPi localisée à 1107 cm-1 (∑= 2158 ± 211 M-1.cm-1) et celles de Pi localisées à 1076 cm-1 (∑= 1346 ± 116 M-1.cm- 1) et à 991 cm-1 (∑= 493 ± 49 M-1.cm-1) ont servis à mesurer les concentrations du substrat et du produit / Cathepsin K is among the most potent mammalian collagenase, capable of cleaving the triple helix in type-I collagen. We developed a series of azanitriles (CKI-8 and CKI-13) which are inhibitors of cathepsin K. CKI-8 (an isomer of CKI-13) and CKI-13 did not induce significant toxicity on osteoblasts Saos-2 and RAW 264.7 cells up to 1000 nM, while they were not toxic on mature osteoclasts up to 100 nM. Commercial E64 inhibitor was not toxic in primary osteoclast cells up to 1000 nM. CKI-8 did not affect alkaline phosphatase activity as well the mineralization induced by Saos-2 cells and by primary osteoblasts. CKI-13 decreased by 35% the mineralization induced by Saos-2 cells while it did not on mineralization induced by primary osteoblasts. Addition of CKI-13 decreased alkaline phosphatase activity by around 20% (Saos-2 cells) and 45% (primary osteoblasts). Bone resorption on bovine slices decreased significantly with 10 nM of CKI-13, with 100 nM of CKI-8 and commercial inhibitor E64. Our findings indicated that CKI-8 and CKI-13 inhibited bone resorption and affected the mobility of osteoclast. To monitor directly the PPi hydrolytic activity by alkaline phosphatase, we developed an infrared (IR) assay taking the advantage to use natural substrate under physiological pH in matrix vesicles and in living cells. PPi band located at 1107 cm-1 (∑= 2158 ± 211 M-1.cm-1) and Pi bands located at 1076 cm-1 (∑= 1346 ± 116 M-1.cm-1) and at 991 cm-1 (∑= 493 ± 49 M-1.cm-1) served to measure the substrate and the product concentrations

[Truncated abstract] Intracellular communication between osteoclasts and osteoblasts is imperative to maintain bone integrity. A myriad of molecules are responsible for regulating osteoblast and osteoclast activity. In particular, it is well documented that osteoblast-derived factors are crucial in directly controlling osteoclast formation and function. Since bone formation is coupled to bone resorption, it would be expected that osteoclasts also have some role in regulating the growth and function of osteoblast cells. However, despite extensive research upon osteoclast and osteoblast biology, the mechanisms by which osteoclasts regulate osteoblast growth and function is not well understood. In an attempt to further elucidate the mechanisms by which osteoclasts and osteoblasts communicate, the technique of subtractive hybridisation was used to identify a novel osteoclastderived factor identical to that of mouse Seminal Vesicle Secretion VII (SVS VII). Previous characterisation of the gene in bone demonstrated that SVS VII was abundantly and specifically expressed by mature osteoclasts (Phan, 2004). Additional research hinted that SVS VII acted as a novel osteoclast-derived factor, that by paracrine mechanisms, targeted osteoblast function (Phan, 2004). However, it remained open as to whether the SVS VII molecule did uniquely target the osteoblast, and whether this interaction influenced bone formation in vivo. Therefore, this thesis endeavoured to functionally characterise the role of the SVS VII molecule in the bone environment. ... Further work is needed to identigy a clear consensus binding sequence, to determine the specificity of the interaction between SVS VII protein and each phage clone, and to isolate a specific binding partner for SVS VII. In conclusion, the studies of this thesis sought to characterise the significance of SVS VII expression by mature osteoclasts, relative to its effects on osteoblast behaviour, but failed to conclusively determine a role for SVS VII in bone. Given that the effects of SVS VII on in vitro osteoblast activity and function are minimal, it is doubtful that SVS VII primarily acts as a paracrine factor integral to osteoblast function. Therefore, these findings conflict with those presented previously (Phan, 2004). However, it was demonstrated that SVS VII treatment was associated with in vivo effect on the skeleton, suggesting that SVS VII may target other elements of the bone microenvironment. Via mechanisms not yet understood, which possibly involves additional factors of the bone 11 extracellular matrix, SVS VII may target a subset of osteoprogenitor cells within the bone environment and act to regulate their proliferation. Therefore, SVS VII may enhance osteogenic precursor cell number at sites of bone formation which would increase the pool of cells that can differentiate down the osteoblast linage and contribute to bone formation. In this regard, SVS VII might function in a manner homologous to the Ly-6 molecule Sca-1 and act as an important factor that maintains a balance between the bone formation and resorption process. Clearly, more work focusing on alternative facets of bone biology is needed to identify whether there is a significant role for SVS VII in skeletal tissue.

<p>This thesis describes a method of growing a highly adherent nano-porous alumina coating on titanium implant materials, a design which might be useful in hard tissue replacement. Alumina layers were formed by anodisation of aluminium, which had been deposited on titanium and titanium alloys by electron beam evaporation. Mechanical testing showed the coatings’ shear and tensile strength to be ~20MPa and ~10MPa respectively. </p><p>Human osteoblasts were cultured on purchased membranes, produced in the same way with similar characteristics as the coating mentioned above. Cell viability, proliferation and phenotype were assessed by measuring redox reactions, DNA, tritiated thymidine incorporation and alkaline phosphatase production. Results showed normal osteoblastic growth patterns with increasing cell numbers the first two weeks after which cell growth decreased and alkaline phosphatase production increased, indicating that osteoblastic phenotype was retained on the alumina. Flattened cell morphology with filipodia attached to the pores of the material was seen. </p><p>Implants frequently trigger inflammatory responses due to accumulation and activation of cells such as polymorphonuclear granulocytes (PMN), also called neutrophils. Activation and morphology of human PMN in response to nano-porous alumina with two pore sizes (20 and 200 nm) was investigated by luminol-amplified chemiluminescence, granule enzyme deposition measurement, optical and scanning electron microscopy. Activation was observed on both membrane types, however less pronounced on the 200 nm alumina. For both membranes a decrease in activation was seen after coating with fibrinogen, collagen I and serum (more pronounced for the two latter). On fibrinogen-coated alumina many flattened cells were observed, indicating frustrated phagocytosis. Finally when culturing osteoblasts on non-coated and collagen-coated membranes (after exposure to PMN) many more cells had established on the protein-coated surface after 24 h. </p><p>The overall results indicate that it might be possible to produce a novel bone implant coating by anodisation of aluminium deposited on titanium and that this material will support osteoblast adhesion and proliferation. Furthermore neutrophil activation can be suppressed when coating the alumina with collagen I, which is beneficial considering the fact that this protein also is essential for bone formation.</p>

This thesis describes a method of growing a highly adherent nano-porous alumina coating on titanium implant materials, a design which might be useful in hard tissue replacement. Alumina layers were formed by anodisation of aluminium, which had been deposited on titanium and titanium alloys by electron beam evaporation. Mechanical testing showed the coatings’ shear and tensile strength to be ~20MPa and ~10MPa respectively. Human osteoblasts were cultured on purchased membranes, produced in the same way with similar characteristics as the coating mentioned above. Cell viability, proliferation and phenotype were assessed by measuring redox reactions, DNA, tritiated thymidine incorporation and alkaline phosphatase production. Results showed normal osteoblastic growth patterns with increasing cell numbers the first two weeks after which cell growth decreased and alkaline phosphatase production increased, indicating that osteoblastic phenotype was retained on the alumina. Flattened cell morphology with filipodia attached to the pores of the material was seen. Implants frequently trigger inflammatory responses due to accumulation and activation of cells such as polymorphonuclear granulocytes (PMN), also called neutrophils. Activation and morphology of human PMN in response to nano-porous alumina with two pore sizes (20 and 200 nm) was investigated by luminol-amplified chemiluminescence, granule enzyme deposition measurement, optical and scanning electron microscopy. Activation was observed on both membrane types, however less pronounced on the 200 nm alumina. For both membranes a decrease in activation was seen after coating with fibrinogen, collagen I and serum (more pronounced for the two latter). On fibrinogen-coated alumina many flattened cells were observed, indicating frustrated phagocytosis. Finally when culturing osteoblasts on non-coated and collagen-coated membranes (after exposure to PMN) many more cells had established on the protein-coated surface after 24 h. The overall results indicate that it might be possible to produce a novel bone implant coating by anodisation of aluminium deposited on titanium and that this material will support osteoblast adhesion and proliferation. Furthermore neutrophil activation can be suppressed when coating the alumina with collagen I, which is beneficial considering the fact that this protein also is essential for bone formation.