This research examines the role of actin cytoskeleton filaments in chondroinduction by cyclic hydrostatic pressurization. A chondroinductive hydrostatic pressurization system was developed and characterized. A pressure of 5 MPa at 1 Hz frequency, applied for 7200 cycles (4 hours intermittent) per day, induced chondrogenic differentiation in C3H10T1/2 cells while 1800 cycles (1 hour intermittent) did not induce chondrogenesis. Quantitative analysis of chondrogenesis was determined as sulfated glycosaminoglycan synthesis and rate of collagen synthesis while qualitative analysis was obtained as Alcian Blue staining and collagen type II immunostaining. Actin disruption using 2 uM Cytochalasin D inhibited the enhanced sGAG synthesis in the chondroinductive hydrostatic pressurization environment and significantly inhibited rate of collagen synthesis to the mean level lower than that of the non-pressurized group. These results suggest an involvement of actin cytoskeleton filaments in mechanotransduction of cyclic hydrostatic pressure.

No description available.

Osteoarthritis (OA) ist eine degenerative Erkrankung des hyalinen Knorpels. Knorpel ist ein avaskuläres Gewebe. Wenn dieser beschädigt wird, ist es schwierig, ihn zu reparieren. Der Gelenkknorpel ist verantwortlich für die glatte, reibungs- und schmerzlose Bewegung des Kniegelenks. Schwere Verluste oder die komplette Zerstörung des Gelenkknorpels führen zu hoher Reibung und Schmerzen bei der Bewegung des Kniegelenks, wie es oft in den späten Stadien der OA der Fall ist. Der komplette Gelenkersatz bleibt die ultimative Lösung. Jedoch gibt es viele andere Möglichkeitenden Knorpel über die Implantation von Stammzellen zu reparieren oder zu regenerieren, jedoch oft mit schwerwiegenden Folgen. Die Transplantation embryonaler Stammzellen kann beispielsweise zu Teratombildung führen. Die Nutzung von induzierten pluripotenten Stammzellen ermöglicht die Virusintegration in das Genom. Alternativ entstand das Konzept der Vorläufer- oder Reparaturzellen in situ. Beispielsweise fand man in späten Stadien der Osteoarthritis im menschlichen Knorpel chondrogene Vorläuferzellen mit migratorischen Fähigkeiten (CPCs). Bei Knorpelregeneration mit diesen Zellen sind bisher keine Risokofaktoren bekannt. Sie haben eine enorme Fähigkeit für die Knorpelreparatur ohne das schwerwiegende Risikofaktoren bisher bekannt waren. Allerdings bestehen noch Fragen zum Beispiel wie man CPCs in situ induziert, um das Gewebe auf physiologische Weise zu reparieren. Zweitens haben CPCs eine begrenzte Lebensdauer, zumindest in vitro. Darüber hinaus gibt es keine verfügbare optimierte Methode, um eine vollständige chondrogene Differenzierung von Stammzellen zu erreichen. Vor kurzem wurden primäre Zilien gefunden, die hilfreich für die Stammzelldifferenzierung sein könnten. Diese Zilien arbeiten als Dual-Sensor für mechanochemische Signale. Dieser Sensor wurde auch auf CPCs gefunden, bei Chondrozyten gewonnen aus Kiefergelenken (TMJ) von Discoidin-Domänen- Rezeptor-1- Knockout- Mäusen (DDR- 1 KO). OA ist nicht nur auf die großen Gelenke beschränkt, sondern wirkt sich auch auf die kleinen Gelenke wie das Kiefergelenk aus. Es ist gut bekannt, dass Chondrozyten im Gelenkknorpel keinen direkten Zell-zu-Zell-Kontakt besitzen vielmehr beruht die Kommunikation auf Zell-Matrix - Wechselwirkungen über Zellrezeptoren z.B Integrine oder DDRs. DDR -1- KO-Mäuse zeigen typische Symptome der Arthrose des Kiefergelenkknorpels. Die aus dem Kiefergelenknorpel der DDR - 1 KO Mäuse abgeleiteten Chondrozyten behielten ihre Arthroseeigenschaften. Einerseits wiesen sie eine hohe Expression von runx2 und Kollagen Typ I als typische osteogene Signaturen auf sowie andererseits eine geringe Expression von sox9, Kollagen Typ II und Aggrecan, welche relevant für die chondrogene Differenzierung sind. Die osteoarthritischen Charakteristika könnten zu einem normalen Chondrozyten- Typ umgekehrt werden über den Knockdown von runx2 oder der Exposition dieser Zellen in einer dreidimensionalen Umgebung und in Gegenwart von extrazellulärer Matrix (ECM) -Komponenten wie Laminin und Nidogen. Die Umkehr in Richtung des chondrogenen Phänotyps ist auch für die Pathogenese der Meniskusdegeneration von großer Bedeutung. Der Meniskus ist in den meisten Fällen der Ausgangspunkt für die Entwicklung von OA des Kniegelenks. Der Meniskus ist ein Bindegewebsknorpel, der als Stoßdämpfer wirkt. Hierbei verschlimmert eine Menikusschädigung die OA Pathogenese durch verstärkten Knorpelabbau. Der innere Teil des Meniskus ist avaskulärer Natur und hat eine sehr begrenzte Eigenreparaturfähigkeit. Es gibt jedoch andere Möglichkeiten, wie die teilweise Entfernung des Meniskus, die zu einer kurzfristigen Entlastung führt. Dies verhindert jedoch nicht die langfristigen Folgen, die letztlich zur Entwicklung von OA führen. Der innere Teil des menschlichen Meniskus birgt einzigartige Vorläuferzellen (MPC) und kann zur Meniskus-Regeneration über den TGFß -Signalweg aktiviert werden. Darüber hinaus wurden Maus-Meniskus-Progenitorzellen (MMPCs) in gesundem Meniskusgewebe untersucht. Diese Zellen wurden mittels immunohistochemischen Techniken ex vivo charakterisiert und behielten ihre Stammzelleigenschaften auch in vitro. Mit der Anwendung verschiedener Stammzellen zur Therapie der Knorpelregeneration sind viele kritische Konsequenzen assoziiert. Im Fokus standen deshalb gewebespezifische Zellen auch in situ Vorläuferzellen genannt, die bereits in erkranktem Knorpel vorhanden sind. Diese Zellen können sich in chondrogener Richtung entwickeln. Hierfür benötigen sie möglicherweise nur geringe Manipulationen, um daraufhin hyalinen Knorpel zu produzieren.

Growth plate injuries account for 15-30% of long bone fractures in children. About 10% of these result in significant growth disturbances due to formation of a boney bar. If not treated correctly, this can lead to life-lasting consequences of limb length inequalities and angular deformities. Current treatments for growth plate injuries include removal of boney bar and insertion of fat, silicone, bone cement, etc.. This treatment y is inadequate, leaving almost half of these patients with continued deformities. This dissertation reports characterization of a DNA–containing porous poly(lactic-co-glycolic acid) (PLGA) scaffold system, chondrogenesis using insulin-like growth factor I (IGF-I) plasmid-releasing scaffolds in vitro, and in vivo testing of IGF-I plasmid-releasing scaffolds to regenerate growth plate . Controlled release of naked and DNA complexed with polyethylenimine (PEI) was achieved from porous PLGA scaffolds. PEI affected release of complexes from PLGA scaffolds, as PEI:DNA complexes were released at a lower rate compared to naked DNA encapsulated in low molecular weight (LMW) and high molecular weight PLGA scaffolds, as well as hydrophilic and hydrophobic PLGA scaffolds. Hydrophilicity and molecular weight of PLGA affected the release profiles of both naked DNA and PEI:DNA complexes from the scaffolds, as evidenced by later peak DNA and PEI:DNA release with increasing hydrophilicity and molecular weight. LMW hydrophilic PLGA scaffolds supported growth and chondrogenic differentiation of mesenchymal multipotent D1 cells, chondrocytes, and bone marrow cells (BMCs) in vitro. Culturing BMCs on IGF-I plasmid-encapsulated scaffolds resulted in elevated expression of IGF-I compared to blank scaffolds. Removal of boney bar and implantation of IGF-I plasmid-releasing LMW PLGA scaffolds in a rabbit model of growth plate injury resulted in some improvement of leg angular deformity compared to no scaffold implantation. Histological analysis of the newly developed cartilage showed growth plate-like columnar arrangement of chondrocytes in a defect that received IGF-I plasmid encapsulated scaffold, although the level of organization of newly formed cartilage was inferior to that of native growth plate. This appears to be the first report of the regeneration of growth plate-like structure without the use of stem cells in an animal model of physeal injury.

Orientador: Elenice Deffune / Banca: Sérgio Luis Felisbino / Banca: João Tadeu Ribeiro Paes / Resumo: Levando-se em consideração avanços tecnológicos na área médica e o impacto dos programas de saúde que determinaram curvas de longevidade cada vez maiores e taxas de natalidade cada vez menores, o novo desafio do gestor público são as conseqüências: o envelhecimento e a vida como uma "doença crônica". Entre os principais desafios está a abordagem das doenças crônico-degenerativas que determinam o aumento de lesões cartilaginosas articulares. A débil capacidade de regeneração e as limitações das alternativas de tratamento fazem as técnicas derivadas da biotecnologia, como o transplante autólogo de condrócitos (TAC) e o uso de células-tronco, o foco das investigações. O TAC requer coleta de material cartilaginoso de área sadia, podendo causar nova lesão; no entanto, pode-se evitar este perigo com o uso de células-tronco. As células-tronco mesenquimais, adultas, podem se diferenciar em condrócitos mediante o uso de meio de cultura específico em consonância a um arcabouço 3D, mas muitos problemas como evitar a calcificação e estimular a condrogênese em meio favorável constituem o desafio para os pesquisadores na atualidade. 1) produzir anticorpo monoclonal específico a CTMs de coelho para monitorá-las, 2) determinar o volume ideal de coleta de medula óssea para microencapsulação e condrogênese, 3) realizar a microencapsulação das CTMs em novos arcabouços: BIOGEL3D e BACTCELL3D, comparando seu desempenho com o modelo clássico em alginato. Foram utilizados 25 coelhos Nova Zelândia sendo divididos em diferentes grupos em função do volume de MO coletado: G1 = 6mL, G2 = 9mL, G3 = 12mL, G4 = 15mL e G5 = volume ideal de coleta determinado pelos indicadores dos outros grupos. O material coletado foi diluído 1:2 em RPMI 1640 com 3.000U de heparina sódica. Após a contagem celular, as amostras foram submetidas a separação em gradiente... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Technological advances in the medical area combined with the impact of health programs that enhance longevity, together with lower natality rates created new challenges to the public manager such as aging and life as a "chronic disease". Among the major problems are the chronic degenerative diseases that increase articular lesions. The limited regeneration capabilities and the limitations of actual treatment alternatives made biotechnology derived techniques the focus of investigations. The autologous chondrocyte transplantation (ACT) requires a small biopsy of health cartilage, which can lead to a new lesion. However, the use of stem cells can avoid this possibility. Mesenchymal stem cells (MSCs) can differentiate into chondrocytes by using a specific culture medium together with a 3D scaffold, but some questions such as the risks of calcification remain as key factors to researchers. 1) to produce a monoclonal antibody that recognizes MSCs in order to characterize them, 2) to determine the optimal bone marrow collection volume for cell microencapsulation and chondrogenesis and 3) to microencapsulate MSCs in two novel scaffolds: BIOGEL3D and BACTCELL3D, comparing them with sodium alginate. 25 New Zealand rabbits were divided into 5 groups related to bone marrow collection volume: G1 = 6mL, G2 = 9mL, G3 = 12mL, G4 = 15mL and G5 = optimal volume determined by the study. The collected material was diluted in RPMI1640 medium 1:2, with 3000U sodium heparin. After cell count and viability assessment the samples were submitted to density gradient centrifugation in order to isolate the lymphomononuclear (LMN) fraction. These cells were seeded to obtain and expand the MSCs in DMEM Knockout® (InvitrogenTM) supplemented with antibiotic/antimycotic, Lglutamine, essential aminoacids, non essential aminoacids and fetal bovine serum (all from InvitrogenTM). The cells were cultivated in 5% CO2 ...(Complete abstract click electronic access below) / Mestre

Humans and mice lack the broad regenerative capacity of Urodele amphibians, capable only of partial regeneration of the terminal phalanx (P3), i.e., amputation mid-way through P3 results in essentially complete regeneration of the digit tip mediated via blastema formation and subsequent direct bone formation, culminating in distal bone growth, patterning, and function. Conversely, amputation injuries occurring proximal to the mid-point of P3 result in scar formation. Here, in part, we studied the endochondral bone healing response following amputation of the middle phalanx (P2). We showed the endochondral ossification healing response post amputation of P2 is analogous to the fracture healing response of P2 and other long bones of the body, ultimately proving useful in yielding insight into effectively inducing regeneration of the amputated digit. We showed the periosteal-derived chondrocytes of P2 play an integral role in the bone healing process in that they provide a template for subsequent bone formation following amputation injury. We also showed the periosteal-derived cells can be targeted through the temporal application of BMP2 to accumulate and proliferate at the distal digit tip and thus induce regeneration of the amputated bone. Our studies indicated that P2 amputation injuries of various time points, i.e. previously healed injuries, can be induced to regenerate via re-wounding of the periosteal tissue and subsequent BMP2 application, and thus is immeasurably promising from a translational therapeutic perspective. Lastly, we studied the fracture healing response in conjunction with the intramembranous regeneration response of P3. Following fracture of the digit, we showed the relative lack of periosteal callus formation, the lack of periosteal chondrogenesis, and a novel endosteal/marrow chondrogenic response. Unlike P2, the periosteal tissue of the fractured P3 bone does not respond to BMP2-treatment via endochondral bone growth, instead the bone heals via intramembranous ossification, possibly via intrinsic differentiation limitations and extrinsic factors. Notably, we showed that in the absence of the periosteal tissue of the amputated P3 bone, the regeneration response was greatly attenuated. Taken together, our work blending regeneration and fracture repair may prove useful in enhancing regeneration studies with methods and ideas not previously considered. / acase@tulane.edu

Tissue engineering applies principles of biology and engineering to the development of functional substitutes for damaged or lost tissues. Tools for the neo-generation of tissue in tissue engineering research include cells, biomaterials and soluble factors. One main obstacle in tissue engineering is the limited availability of autologous tissue specific progenitor cells. This has led to interest into using autologous cells with stem cell plasticity. Bone marrow derived stem cells were the first adult stem cells shown to have multilineage potential. Since, several reports have been published indicating that cells from other tissues; fat, muscle, connective tissue e.g., possess potential to differentiate into lineages distinct from their tissue of origin. The optimal cell type for use in tissue engineering applications should be easy to obtain, cultivate and store. The human dermal fibroblast is an easily accessible cell source, which after routine cell expansion gives a substantial cell yield from a small skin biopsy. Hence, the dermal fibroblast could be a suitable cell source for tissue engineering applications.The main aim of this thesis was to investigate the differentiation capacity of human dermal fibroblasts, and their possible applications in bone and cartilage tissue engineering applications. Human dermal fibroblasts were shown to differentiate towards adipogenic, chondrogenic, and osteogenic phenotypes upon subjection to specific induction media. Differentiation was seen both in unrefined primary cultures and in clonal populations (paper I). Fibroblasts could be used to create three-dimensional cartilage- and bone like tissue when grown in vitro on gelatin microcarriers in combination with platelet rich plasma (paper II). 4 weeks after in vivo implantation of osteogenic induced fibroblasts into a fracture model in athymic rats, dense cell clusters and viable human cells were found in the gaps, but no visible healing of defects as determined by CT-scanning (paper III). After the induction towards adipogenic, chondrogenic, endotheliogenic and osteogenic lineages, gene expression analysis by microarray and quantitative real-time-PCR found several master regulatory genes important for lineage commitment, as well as phenotypically relevant genes regulated as compared to reference cultures (paper IV). In conclusion, results obtained in this thesis suggest an inherent ability for controllable phenotype alteration of human dermal fibroblasts in vitro. We conclude that dermal fibroblasts could be induced towards adipogenic, chondrogenic, endotheliogenic or osteogenic novel phenotypes which suggest a genetic readiness of differentiated fibroblasts for lineage-specific biological functionality, indicating that human dermal fibroblasts might be a suitable cell source in tissue engineering applications.

Estrogen-receptor-related receptor gamma, ERRγ, is highly expressed in cartilage and upregulates the chondrogenic transcription factor, Sox9, in a chondrocytic cell line. To assess the effect of increasing ERRγ activity on cartilage in vivo, we generated transgenic animals driving ERRγ expression with a chondrocyte-specific promoter. I verified that one transgenic line exhibited 26% increased ERRγ protein at E14.5. No major morphological defects were seen at this stage, but I observed significant reduction in the size of the appendicular skeleton in P7 mice, such that all elements of the appendicular skeleton were significantly reduced by 4 – 10%. I continued the phenotype analysis at the histological level and found that the P7 animals displayed significantly reduced growth plate height, caused by deficiencies in the size of the proliferative and hypertrophic zones of the growth plate. This suggests a previously unknown role for ERRγ in regulating endochondral ossification in growth plate chondrocytes.

Estrogen-receptor-related receptor gamma, ERRγ, is highly expressed in cartilage and upregulates the chondrogenic transcription factor, Sox9, in a chondrocytic cell line. To assess the effect of increasing ERRγ activity on cartilage in vivo, we generated transgenic animals driving ERRγ expression with a chondrocyte-specific promoter. I verified that one transgenic line exhibited 26% increased ERRγ protein at E14.5. No major morphological defects were seen at this stage, but I observed significant reduction in the size of the appendicular skeleton in P7 mice, such that all elements of the appendicular skeleton were significantly reduced by 4 – 10%. I continued the phenotype analysis at the histological level and found that the P7 animals displayed significantly reduced growth plate height, caused by deficiencies in the size of the proliferative and hypertrophic zones of the growth plate. This suggests a previously unknown role for ERRγ in regulating endochondral ossification in growth plate chondrocytes.

<p>Articular cartilage is the thin, load-bearing connective tissue that lines the ends of long bones in diarthroidal joints, providing predominantly a mechanical function. Because cartilage is avascular and aneural, it has little capacity for self-repair if damaged. One repair strategy is through a functional tissue engineering approach using adipose-derived stem cells (ASCs). ASCs are an abundant progenitor cell source easily obtained through a minimally invasive liposuction procedure. When appropriately stimulated, ASCs have demonstrated significant potential for chondrogenic differentiation. Though studies have demonstrated the ability of ASCs to synthesize cartilage-specific macromolecules, a more thorough understanding of factors that modulate ASC chondrogenesis is required. Accordingly, the central aim of this dissertation was to study the chondrogenic response of ASCs to biochemical, biomechanical, and biomaterial factors.</p><p>We hypothesized that factors, other than TGF-beta and dexamethasone, would improve ASC chondrogenesis. BMP-6 emerged as a potent regulator of ASC chondrogenesis, particularly in early culture, as noted by significant upregulation of cartilage-specific extracellular matrix (ECM) genes and downregulation of cartilage hypertrophy markers.</p><p>Hypothesizing that biomechanical factors would accelerate the formation of cartilage-specific macromolecules, we designed and manufactured an instrument to apply dynamic deformational loading to ASC seeded constructs. Dynamic loading significantly inhibited ASC metabolism and downregulated cartilage-specific ECM genes. However, 21 days of dynamic loading induced the production of type II collagen, a principal component of articular cartilage.</p><p>We hypothesized that a biomaterial derived from cartilage would serve as a bioactive scaffold and induce chondrogenic differentiation. The novel, ECM-derived scaffold promoted the most robust differentiation of ASCs relative to both biochemical and biomechanical factors, particularly noted by a type II collagen-rich matrix after 28 days of culture. After 42 days of culture, biphasic mechanical testing revealed an aggregate modulus of 150 kPa, approaching that of native cartilage. These data suggest that the ECM-derived scaffold may retain important signaling molecules to drive differentiation or that ASC differentiation is dependent on proper cell anchorage.</p><p>In summary, we have shown that biochemical, biomechanical, and biomaterial factors have strong influences on the chondrogenic potential of ASCs. Optimization of these factors will ultimately be required to successfully engineer a functional tissue.</p> / Dissertation