Made available in DSpace on 2014-06-11T19:35:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-10-08Bitstream added on 2014-06-13T19:45:08Z : No. of bitstreams: 1 limaneto_jf_dr_botfmvz.pdf: 5509939 bytes, checksum: 6d585da226479576f95a5b051bde27a2 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A célula-tronco (CT) é definida como uma célula com capacidade de gerar diferentes tipos celulares e reconstituir diversos tecidos. Além disso, a CT apresenta propriedades de auto-renovação, gerando cópias idênticas a si mesma. De acordo com sua origem, as células-tronco podem ser chamadas de adultas e embrionárias. As células-tronco adultas (CTA) mais utilizadas nas clínicas de terapia celular são as células-tronco hematopoiéticas e as células tronco mesenquimais, encontradas principalmente na medula óssea, tecido adiposo e no sangue do cordão umbilical. As células-tronco embrionárias (CTE) são derivadas da massa celular interna de embriões no estágio de blastocisto. Desta maneira este trabalho teve como objetivo desenvolver uma metodologia adequada para o isolamento, cultivo e caracterização de células tronco embrionárias e mesenquimais de eqüinos, além de verificar a capacidade que as células possuem em se diferenciar in vitro em outros tipos célulares. Foi coletado sangue da medula óssea de eqüinos entre 8 e 15 anos de idade. As células tronco mesenquimais foram isoladas após a primeira e segunda passagem. As células foram caracterizadas com marcadores de superfície CD34 (mononucleares) e CD44 (mesenquimais). Após isolamento e caracterização, as células tronco mesenquimais foram diferenciadas para as linhagens osteogênica, adipogênica, condrogênica e neurogênica. A confirmação da diferenciação das células tronco foi realizada por marcadores teciduais específicos. Estas células também, foram capazes de expressarem marcadores neurais. Para o isolamento das células tronco embrionária eqüina, embriões com oito a nove dias foram coletado e a massa celular interna (MCI) isolada mecanicamente. Após o isolamento, a MCI foi transferida para a placa de cultivo previamente preparada com monocamada de fibroblastos para o desenvolvimento... / The stem cell (SC) is defined as cells with the capacity of generate different cellular types and rebuild various tissues. Moreover, the SC has a selfregenerate ability, generating identical copies of itself. According to its origins, the SC can be named as “adult” or “embryonic”. The adult stem cell (ASC) more often used in clinical trials and cellular therapy, are the hematopoietic stem cells and the mesenchymal stem cells, isolated mainly from the marrow bone, adipose tissue and umbilical cord blood. The embryonic stem cells (ESC) are obtained from the inner cell mass of embryos at the blastocyst stage. In this way the present study had as objective to develop an adequate methodology of isolation, culture and characterization of embryonic and mesechymal stem cells from horses, verifying the capacity of those cells to differentiate in vitro into different cells types. Bone marrow blood was collected from horses, aging from 8 to 15 years and filtered with a donation blood kit filter, to avoid clots. The mesenchymal stem cells were isolated after the first and the second passage. The SC were characterized using surface markers CD34 (monuclear) and CD44 (mesenchymal). After the isolation and characterization, the mesenchymal stem cells were differenced into osteogenic, adipogenic, condrogenic and neurogenic lineage. The cells differentiations were confirmed using specific tissue markers. To isolate the embryonic stem cells equine embryos with 8 to 9 days were used. The inner cell mass (ICM) were extract mechanically and transferred to a culture dish previously prepared with fibroblasts monolayer to colony formation and development. The colonies were characterized with pluripotency markers and then submitted to a differentiation process into neurogenic lineage, confirmed by specific neural tissue markers

Made available in DSpace on 2015-09-17T15:24:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2014-12-17. Added 1 bitstream(s) on 2015-09-17T15:47:10Z : No. of bitstreams: 1 000844099.pdf: 1423355 bytes, checksum: 8649e82cdb205c9cea62cc32e42d5564 (MD5) / Os processos de reparo da polpa dentária frente a procedimentos conservadores passam, em geral, pelo confronto entre possíveis microrganismos presentes na área da exposição e as células responsáveis pela diferenciação e produção de tecido mineralizado. Entretanto, a literatura ainda necessita de informações sobre o efeito direto de produtos bacterianos sobre este processo. O objetivo deste estudo foi avaliar os efeitos do lipopolissacarídeo (LPS) bacteriano (E. coli) sobre células progenitoras da polpa dental, utilizando-se condições basais e com mineralização préinduzida por meio osteogênico. Para isso, células progenitoras caracterizadas foram submetidas a diferentes concentrações de LPS bacteriano (com ou sem indutor da mineralização [lM]), para observação da atividade de fosfatase alcalina (ALP). A concentração mínima de 200 ng/ml, para se verificar alteração de atividade enzimática de ALP, foi usada para se observar os efeitos funcionais de mineralização (pelo alizarin vermelho - ARS), expressão das citocinas IL-1β e TNF-α, além da expressão dos genes DSPP e DMP-1. Os dados quantitativos foram analisados por ANOVA e teste de Tukey. As células em meio osteogênico com as diferentes concentrações de LPS apresentaram baixa atividade da ALP no curto prazo, comparadas às tratadas com meio α-MEM. Estas apresentaram alta atividade, comparadas ao controle. 200 ng/ml do LPS afetaram o processo de mineralização ao longo do tempo, reduzindo a ação de mineralização dos grupos que o associaram ao indutor de mineralização. Houve expressão de IL-1β e TNF-α para todos os grupos em todos os tempos, além disso, para a IL-1β, o grupo que associou os 200ng/ml de LPS com o meio indutor após 7 dias apresentou maior expressão. Houve expressão do gene DMP-1 e não expressão de DSPP e ocorreu uma maior expressão gênica nos grupos tratados com meio indutor da mineralização no gene DMP-1 . Esses achados / Dental pulp repair processes due to conservative procedures are, in general, affected by the conflicts between possible microorganisms at the area of exposure and cells responsible for differentiation and production of mineralized tissue. However, the literature still lacks information on how bacterial products affect these processes directly. The purpose of this study was to evaluate the bacterial lipopolysaccharide (E. coli LPS) effects on dental pulp progenitor cells, regarding the expression of differentiation genes and function of mineralization, using basal conditions and pre-induced mineralization by osteogenic media. Characterized progenitor cells was initially submitted to different LPS concentrations (with or without osteogenic medium [lM]), to observe alkaline phosphatase activity (ALP). The minimal concentration (200 ng/ml) to observe phosphatase enzymatic activity was used to assess the functional mineralization effects (by alizarin red staining - ARS), cytokine production (IL-1β e TNF-α), besides the gene expression for odontoblast differentiation markers (DSPP and DMP-1). Quantitative data will be statistically analyzed by ANOVA and Tukey's test. Cells in osteogenic medium with different concentrations of LPS showed low ALP activity shortterm compared to those treated with α-MEM. These showed high activity, compared to control. 200 ng/ml of LPS did affect the mineralization process over time, reducing the action of mineralization of the groups that have associated LPS with the IM. There was expression of IL-1β and TNF-α for all groups at all times, additionally, IL-1β for the group that has associated 200 ng/ml of LPS with osteogenic media after 7 days showed higher expression. There was expression of DMP-1 and DSPP genes and the expression in groups treated with IM was greater in DMP-1. These findings suggest that the inflammatory potential of LPS on the pulp progenitor cells contribute to an early mineralization ...

Master of Science / Department of Plant Pathology / William Bockus / Robert Bowden / Stem rust, caused by the fungus Puccinia graminis f. sp. tritici, has historically been one of the most important diseases of wheat. Although losses have been much reduced in the last fifty years, new highly virulent races of the pathogen have recently emerged in East Africa. These new races are virulent on nearly all of the currently deployed resistance genes and therefore pose a serious threat to global wheat production. The spring wheat variety ‘Kingbird’ is thought to contain multiple quantitative trait loci (QTLs) that provide durable, adult-plant resistance against wheat stem rust. Stem rust-susceptible Kansas winter wheat line ‘KS05HW14’ was backcrossed to Kingbird and 379 recombinant lines were advanced to BC₁F₅ and then increased for testing. The lines were screened for stem rust resistance in the greenhouse and field in Kansas and in the field in Kenya over multiple years. We identified 16,237 single nucleotide polymorphisms (SNPs) with the Wheat 90K iSelect SNP Chip assay. After filtering for marker quality, linkage maps were constructed for each wheat chromosome. Composite interval mapping and multiple-QTL mapping identified seven QTLs on chromosome arms 2BL, 2DS, 3BS, 3BSc, 5DL, 7BL, and 7DS. Six QTLs were inherited from Kingbird and one QTL on 7BL was inherited from KS05HW14. The location of the QTL on 2BL is approximately at locus Sr9, 3BS is at Sr2, 3BSc is at Sr12, and 7DS is at Lr34/Yr18/Sr57. Although no QTL was found on 1BL, the presence of resistance gene Lr46/Yr29/Sr58 on 1BL in both parents was indicated by the gene-specific marker csLV46. QTLs on 2DS and 5DL may be related to photoperiod or vernalization genes. Pairwise interactions were only observed with race QFCSC, most notably occurring with QTLs 2BL and 3BSc. These results confirm that there are multiple QTLs present in Kingbird. Ultimately, the identification of the QTLs that make Kingbird resistant will aid in the understanding of durable, non-race-specific resistance to stem rust of wheat.

Orientador: Bruno Das Neves Cavalcanti / Banca: Cláudio Antonio Talge Carvalho / Banca: Aletéia Massula de Melo Fernandes / Resumo: Os processos de reparo da polpa dentária frente a procedimentos conservadores passam, em geral, pelo confronto entre possíveis microrganismos presentes na área da exposição e as células responsáveis pela diferenciação e produção de tecido mineralizado. Entretanto, a literatura ainda necessita de informações sobre o efeito direto de produtos bacterianos sobre este processo. O objetivo deste estudo foi avaliar os efeitos do lipopolissacarídeo (LPS) bacteriano (E. coli) sobre células progenitoras da polpa dental, utilizando-se condições basais e com mineralização préinduzida por meio osteogênico. Para isso, células progenitoras caracterizadas foram submetidas a diferentes concentrações de LPS bacteriano (com ou sem indutor da mineralização [lM]), para observação da atividade de fosfatase alcalina (ALP). A concentração mínima de 200 ng/ml, para se verificar alteração de atividade enzimática de ALP, foi usada para se observar os efeitos funcionais de mineralização (pelo alizarin vermelho - ARS), expressão das citocinas IL-1β e TNF-α, além da expressão dos genes DSPP e DMP-1. Os dados quantitativos foram analisados por ANOVA e teste de Tukey. As células em meio osteogênico com as diferentes concentrações de LPS apresentaram baixa atividade da ALP no curto prazo, comparadas às tratadas com meio α-MEM. Estas apresentaram alta atividade, comparadas ao controle. 200 ng/ml do LPS afetaram o processo de mineralização ao longo do tempo, reduzindo a ação de mineralização dos grupos que o associaram ao indutor de mineralização. Houve expressão de IL-1β e TNF-α para todos os grupos em todos os tempos, além disso, para a IL-1β, o grupo que associou os 200ng/ml de LPS com o meio indutor após 7 dias apresentou maior expressão. Houve expressão do gene DMP-1 e não expressão de DSPP e ocorreu uma maior expressão gênica nos grupos tratados com meio indutor da mineralização no gene DMP-1 . Esses achados / Abstract: Dental pulp repair processes due to conservative procedures are, in general, affected by the conflicts between possible microorganisms at the area of exposure and cells responsible for differentiation and production of mineralized tissue. However, the literature still lacks information on how bacterial products affect these processes directly. The purpose of this study was to evaluate the bacterial lipopolysaccharide (E. coli LPS) effects on dental pulp progenitor cells, regarding the expression of differentiation genes and function of mineralization, using basal conditions and pre-induced mineralization by osteogenic media. Characterized progenitor cells was initially submitted to different LPS concentrations (with or without osteogenic medium [lM]), to observe alkaline phosphatase activity (ALP). The minimal concentration (200 ng/ml) to observe phosphatase enzymatic activity was used to assess the functional mineralization effects (by alizarin red staining - ARS), cytokine production (IL-1β e TNF-α), besides the gene expression for odontoblast differentiation markers (DSPP and DMP-1). Quantitative data will be statistically analyzed by ANOVA and Tukey's test. Cells in osteogenic medium with different concentrations of LPS showed low ALP activity shortterm compared to those treated with α-MEM. These showed high activity, compared to control. 200 ng/ml of LPS did affect the mineralization process over time, reducing the action of mineralization of the groups that have associated LPS with the IM. There was expression of IL-1β and TNF-α for all groups at all times, additionally, IL-1β for the group that has associated 200 ng/ml of LPS with osteogenic media after 7 days showed higher expression. There was expression of DMP-1 and DSPP genes and the expression in groups treated with IM was greater in DMP-1. These findings suggest that the inflammatory potential of LPS on the pulp progenitor cells contribute to an early mineralization ... / Mestre

O envelhecimento é um processo gradual e intrínseco que ocorre devido a mudanças fisiológicas e fenotípicas com o avanço da idade e que acarreta na diminuição da capacidade de manter a homeostase e reparo tecidual. A perda do controle homeostático e o possível envolvimento de células-tronco e progenitores, provavelmente, é uma das causas das fisiopatologias do sistema hematopoético que acompanham o envelhecimento. O declínio na competência do sistema imune adaptativo, o aumento de doenças mielóides, leucemias e o desenvolvimento de anemias são algumas mudanças significantes e decorrentes do processo de envelhecimento. Durante a transição ontológica, a habilidade de células-tronco hematopoéticas originarem células progenitoras diminui progressivamente, sugerindo perda da capacidade de autorrenovação e diferenciação das células-tronco com o avanço da idade. O microambiente medular se divide em duas áreas distintas: nicho endosteal e nicho vascular, conhecidos por controlar a homeostase das células-tronco hematopoéticas; e é composto por uma mistura heterogênea de células, dentre elas as células-tronco mesenquimais que expressam moléculas que controlam algumas funções das células-tronco hematopoéticas. De acordo com estas observações, este trabalho investiga o papel do envelhecimento das células-tronco mesenquimais no processo de autorrenovação, multipotência e diferenciação das células-tronco hematopoéticas. Neste trabalho, avaliamos a percentagem de células-tronco hematopoéticas Lin-CD34+ e subpopulações em co-cultura com células-tronco mesenquimais derivadas de medula óssea de diferentes idades, bem como sua capacidade de autorrenovação, diferenciação, secreção da quimiocina CXCL-12 e a expressão do receptor CXCR-4. Nossos resultados mostraram diferenças significativas nos parâmetros fenotípicos e funcionais das células-tronco hematopoéticas co-cultivadas com células-tronco mesenquimais de doadores idosos. Estes dados sugerem que o envelhecimento das células-tronco mesenquimais podem influenciar na homeostase do microambiente medular / Certainly, aging is one of the best identified features of the human biology, and is also the least understood. This is largely attributed to the fact that aging is gradual and fundamentally complex, due to all modifications in the physiological and phenotypic aspects occurred during the age advancing. One of the most striking features of aging is the decreased ability to maintain homeostasis and tissue repair. Consistent with those findings, many of the pathophysiological conditions affecting aging, such as anemia, dysplasia, leukemia and anemia suggest an imbalance between cell losses and the ability to self-renew or differentiation. The decline in homeostatic maintenance and regenerative potential of tissues during aging has been associated with changes in stem cells. Increasing evidences point to the stem cells as major accountable for the aging pathophysiology in several tissues. Thus, studies in mammals comprise a careful evaluation of mechanisms connected to stem cells. The increasing age is accompanied by many pathophysiological changes in the hematopoietic system wherein the etiology suggests loss of homeostatic control and a possible involvement of stem and progenitor cells. The clinically relevant changes are related to adaptive immune system diminished competence, the increase of myeloid diseases including leukemia and the onset of anemia in the elderly. The hematopoietic stem cell microenvironment is located in the bone marrow and is divided in two domains: the endosteal niche near to the bone surface and vascular niche associated with the sinusoidal endothelium; the niche consist of several heterogeneous cells types, among them, the mesenchymal stem cells. The mesenchymal stem cells express molecules that control hematopoietic stem cells functions. Therefore, this study investigates the role of mesenchymal stem cells aging in the self-renewal, multipotency and differentiation of hematopoietic stem cells. This study evaluated the percentage of hematopoietic stem cell Lin-CD34+ and subpopulations in co-culture with mesenchymal stem cell bone marrow-derived from donors with different ages, their ability of self-renewal, differentiation, secretion of chemokine CXCL-12 and expression of the CXCR-4 receptor. Our results suggest that the mesenchymal stem cells aging can affect the bone marrow niche homeostasis

It has long been established that the physical properties of the cell’s surrounding microenvironment has the ability to impose its influence on a range of cell processes. Morphology, differentiation, and proliferation have all been shown to be sensitive to the mechanical cues inherent within the extracellular matrix. Although significant advancements in microfabrication and cell mechanics have been made, questions regarding how physical interactions guide biological systems in three dimensions remain unanswered. By utilizing cocultured systems and microfabricated channeled topographies, we reveal that the three dimensional nature of the environment is capable of driving cell patterning. Contact guidance is the phenomenon by which cells will orient themselves along the geometric patterns of a substrate. Much of its research has focused on the nano/micro scale of two dimensional topographies, affecting alignment along grooves. We have revealed that contact guidance has the ability to impose far more complex cellular behaviour in three dimensional systems. Furthermore, by modulating the elements of confinement surrounding cells, we directed the balance of binding forces between cells and substrate leading to significantly different cell type dependent morphologies. By then altering the geometry of the topography, we revealed the ability to induce cell type separation in cocultured systems. These concepts led to the subsequent discovery that confinement induces three dimensional spheroidal growth of embryonic stem cells. These results reveal that the element of confinement not only influences patterning in three dimensions but guides the fundamental early stages processes essential to all life.

The mammary gland contains a subset of cells with regenerative capacity that is able to generate both luminal and myoepithelial mammary epithelial lineages. Those cells are described as mammary epithelial stem cells. The fate of stem cells is tightly controlled by their microenvironment and adhesion receptors on the stem cells play a vital role in the microenvironment–stem cell communication. They facilitate the interaction of stem cells with the extracellular matrix as well as adjacent cells, and they regulate stem cell homing to their niches, as well as stem cell proliferation, self-renewal, and differentiation. Stem cells express high levels of ECM binding adhesion receptors such as β1 and α6-integrins. Those integrins were used to isolate stem cells from the rest of the differentiated epithelial cells within the mammary gland. However, little is known about the role of those integrins in stem cell self-renewal and differentiation. This project aimed to understand how β1-integrin receptors contribute to stem cell behavior. To achieve this, FACS sorting method of stem cells, the organoid assay, and lentivirus knockdown of β1-integrin using shRNA were optimised. The organoid assay was used as an in-vitro test to assess for the frequency of bi-lineage and luminal progenitor cells in a given mammary epithelial population. It is known that bi-lineage cells produce solid organoids in culture while luminal progenitors produce hollow organoids. The frequency of solid and hollow organoids might therefore be an indication of the stem cells and luminal progenitor frequency respectively. My results showed that cells with the highest solid organoid forming ability were within the basal population, which is high for β1- and α6-integrin. The β1-integrin signaling pathway was shown to be important for maintaining the organoid-forming population in basal and luminal populations. Knocking out β1-integrin in MECs resulted in abolishing their solid and hollow organoid-forming activity. Downstream of β1-integrin, I found that Rac1 but not ILK is important in β1-integrin maintenance of solid organoid-forming cells. Active Rac1 was able to rescue solid organoid formation but was not able to rescue hollow organoids in the β1-integrin knockdown cells. β1-integrin and Rac1 deletion resulted in the down regulation of Wnt/β-catenin signaling, which is important for stem cells. This down regulation was rescued using active Rac1. Activating Wnt/ β1-catenin signaling in primary cells (using Wnt3a ligand or GSK3β inhibitor) resulted in an increase in solid organoid and a decrease in hollow organoid formation. When activating Wnt signaling using GSK3I in β1-integrin knockdown cells, the solid organoid activity was rescued. However, Wnt3a did not rescue solid organoid formation in the β1-integrin knockdown cells. When active Rac1 was overexpressed in β1-integrin null cells, Wnt3a was able to activate solid organoid formation. When inhibiting Rac1 in primary MECs, solid but not hollow organoid activity was significantly decreased. Wnt3a or GSK3I addition did not rescue this reduction. Taken these results together, it can be concluded that β1integrin-Rac1 signaling play a role in controlling stem cells and this is might be achieved through controlling Wnt/β-catenin signaling. These studies are important in understanding the role of integrins in mammary stem cells. They will also provide new insight on how integrins might be controlling breast cancer and thereby, help in providing new targets for cancer therapy.

- anglicky This thesis deals with legal aspects of stem cell research, which in the case of the Czech Republic remains quite disregarded by the general public. The text examines and analyzes the legislation regulating the aforementioned field of research at the international, European and Czech national level in a comprehensive manner. Particular emphasis is placed on legal aspects of embryonic stem cell research, which is also closely related to the legal status of embryo and its protection. The thesis also notes what types of regulatory approaches are adopted in various countries with respect to stem cell research and it subsequently demonstrates these conclusions by examples of Slovak Republic and the United Kingdom. Explanation is set in a broader framework through the introductory chapters that deal with biological and ethical aspects of stem cell research.

Hypothermia is potently neuroprotective, but the molecular basis of this effect remains obscure and the practical challenges of cooling have restricted its clinical use. This thesis was borne on the premise that considerable therapeutic potential may lie in a deeper understanding of the neuronal physiology of cooling. Rodent studies indicate that hypothermia can elicit preconditioning wherein a subtoxic stress confers resistance to an otherwise lethal injury. This cooling-induced tolerance requires de novo protein synthesis – a fundamental arm of the cold-shock response, for which data in human neurons is lacking. Since cooling protects the human neonatal brain, experiments herein address the molecular effects of clinicallyrelevant cooling using functional, maturationally-comparable cortical neurons differentiated from human pluripotent stem cells (hCNs). Several core hypothermic phenomena are explored, with particular scrutiny of neuronal tau, since this protein is modified extensively in brains that are resistant to injury. Mild-to-moderate hypothermia produces an archetypal cold-shock response in hCNs and protects them from oxidative and excitotoxic stress. Principal features of human cortical tau development are recapitulated during hCN differentiation, and subsequently reversed by cooling, returning tau transcriptionally and post-translationally to an earlier foetallike state. These findings provide the first evidence of cold-stress-mediated ontogenic reversal in human neurons. Furthermore, neuroprotective hypothermia induces mild endoplasmic reticulum (ER) stress in hCNs, with subsequent activation of the unfolded protein response (UPR). Reciprocal modulation of both tau phosphorylation and the ER-UPR cascade suggests that cold-induced hyperphosphorylation of tau and ER-hormesis (preconditioning) represent significant components of hypothermic neuroprotection. Cooling thus modifies proteostatic pathways in a manner that supports neuronal viability. Historically, hypothermic preconditioning has been limited to the acute injury setting, and tau hyperphosphorylation is an established hallmark of chronic neural demise. More recently however, preconditioning has been proposed as a target for neurodegenerative disease and neuroprotective roles of phospho-tau have emerged. To date, hypothermia has protected hCNs against oxidative, excitotoxic and ER stress, all of which have been implicated in traumatic as well as degenerative processes. This ‘cross-tolerance’ effect places exponential value on the molecular neurobiology of cooling, with the potential to extract multiple therapeutic targets for an unmet need.

Ischaemic heart disease accounts for approximately 7 million deaths worldwide on a yearly basis and this figure is only set to rise as life expectancy in developing countries increases. Although no longer considered a post mitotic organ, the adult heart demonstrates only a very limited capacity for regeneration. Consequently ischaemic injury results in massive loss of contractile cardiomyocytes with damaged myocardium replaced by a non-contractile and poorly conductive collagen scar. This in turn often leads to the development of heart failure. Enhancing or supplementing the myocardial regenerative capacity of the heart is thus a key goal in the development of effective therapies for the treatment of cardiac infarction. Several stem cell populations of non-cardiac origin have been investigated for their capacity to contribute to myocardial repair when therapeutically transplanted into injured hearts. Recent efforts have focused on the “next generation” of donor cells, endogenous cardiac progenitor cells, as these are thought to be better adapted to survival in the cardiac environment and to possess enhanced cardiomyocyte differentiation potential. Pericytes, proposed as the source of the elusive mesenchymal stem cells (MSC) within multiple tissues, are a potential new cell type for use in regenerative medicine. This study tests the hypothesis that pericytes and another perivascular progenitor population, the adventitial cell, from foetal cardiac tissue will positively contribute to the repair of the myocardium post injury. Staining of human foetal ventricular myocardium confirmed the presence of large numbers of both cell types with pericytes tightly associated with capillaries and adventitial cells primarily located in the outer, adventitial layer of muscular arteries. CD146+ CD34- pericytes and CD146- CD34+ adventitial cells were isolated by FACS and expanded in culture. On examination of gene and protein expression both populations stably expressed a similar panel of pericyte markers, MSC markers and cardiac transcription factors as well as c-kit, a cardiac progenitor cell candidate marker. Co-culture with neo-natal rat cardiomyocytes induced expression of an additional cardiac progenitor marker Isl-1 and a mature cardiomyocyte marker ANP in adventitial cells but not pericytes. Labelled, co-cultured, perivascular progenitors readily adhered to rat cells but did not appear to contract independently. De-methylation of perivascular progenitors prior to co-culture resulted in expression of sarcomeric proteins and spontaneous cytoplasmic calcium fluctuations in both populations but more commonly in pericytes. This suggests that cardiac perivascular cells contain a minor sub-population capable of cardiomyocyte differentiation. When these populations were injected into the infarcted hearts of NOD/SCID mice, the animals treated with adventitial cells had significantly reduced cardiac function at 21 days post-surgery on ultrasound examination. An increased scar area and a non-significant trend towards increased scar length and a decreased wall thickness were also observed. Transplanted cells of both groups were detected in low numbers 21 days after injection. Adventitial cells were retained much more readily and in both populations retained cells exhibited three key morphologies: fibroblast type; macrophage type; and cardiomyocyte type. The majority of cells adopted a fibroblast type morphology, lesser numbers a macrophage like morphology and only rare cells a cardiomyocyte like morphology. Both fibroblast and cardiomyocyte type cells had single, human nuclear antigen positive nuclei suggesting true differentiation rather than cell fusion and pericytes exhibited an enhanced ability to differentiate into cardiomyocytes. This supports the in-vitro findings of a minor pro-cardiomyogenic subset within the perivascular cell population. As a result of these findings the starting hypothesis was modified to propose that perivascular cells play a significant role in cardiac fibrosis, largely mediated through expression of surface integrin receptors. This was tested using mice expressing fluorescent proteins under the control of the PDGFR-β promoter and mice in which the αv integrin subunit, common to 5 integrin receptors, had been deleted on the surface of PDGFR-β+ cells. Immunostaining and flow cytometry revealed the PDGFR-β expression to be tightly restricted to perivascular cells and co-expressed with the fibroblast markers, vimentin, PDGFR-α, CD90.2 and CD34 in a subset of cells. Cardiac fibroblasts isolated from reporter mouse hearts revealed strong expression of PDGFR-α and CD34 but PDGFR-β expression in only approximately 20% of the population on flow cytometry. Following angiotensin II induced cardiac hypertrophy and fibrosis approximately 50% of fibroblasts expanding the interstitium were PDGFR-β+. Genetic deletion of the αv integrin subunit on PDGFR-β+ cells resulted in a reduction in cardiac interstitial collagen content of about 50% compared to wild type controls. These findings suggest that the cardiac perivascular PDGFR-β+ population is heterogeneous with a sub-population likely to be fibroblasts or fibroblast progenitors and that the development of cardiac interstitial fibrosis is in part modulated by integrin receptor expression on these cells. In summary this study provides evidence of the existence of a pro-fibrotic progenitor population, which co-express pericyte and MSC markers, within the cardiac perivascular niche. These cells contribute to cardiac fibrosis both on transplantation and endogenously following cardiac injury with the latter mediated via αv integrin expression. Within the perivascular progenitor population however there also appears to be a minor subset of pro-cardiomyogenic cells which are able to adopt a cardiomyocyte phenotype both in-vitro and in-vivo.