Mesenchymal stem cells (MSCs) have the potential to differentiate into various cell types, possess potent immunomodulatory properties and can influence various functions of immune cells. Since the immunomodulatory properties of MSCs can be modified by cytokines, we compered the effect of unstimulated MSCs and MSCs pretreated with interleukin (IL)-1, interferon (IFN)- , transforming growth factor (TGF)- and IL-10 on the development of regulatory T cells (Treg) and T helper 17 (Th17) cells in vitro and on the inflammatory environment in the eye. MSCs can produce significant levels of TGF- and IL-6. These cytokines represent the key factors that reciprocally regulate the development of naive T cells into Treg and Th17 cells. Unstimulated MSCs produce TGF- , but not IL-6, and the production of TGF- can be further enhanced by IL-10 or TGF- . In the presence of IL-1, MSCs secrete significant levels of IL-6, in addition to spontaneous production of TGF- . MSC producing TGF- induced preferentially expression of Foxp3 and activation of Treg lymphocytes, whereas MSCs supernatants containing TGF- together with IL-6 supported ROR t expression and development of Th17 cells. We demonstrated that MSCs and their products effectively control the development of Tregs and Th17 cells in a population of...

Current treatment options are limited for patients with myocardial infarction or heart failure. Cellular cardiomyoplasty is a promising therapeutic strategy being investigated as a potential treatment, which aims to deliver exogenous cells to the infarcted heart, for the purpose of restoring healthy myocardial mass and mechanical cardiac function. While several cell types have been studied for this application, only bone marrow cells and human mesenchymal stem cells (hMSCs) have been shown to be safe and effective for improving cardiac function in clinical trials. In both human and animal studies, the delivery of hMSCs to infarcted myocardium decreased inflammatory response, promoted cardiomyocyte survival, and improved cardiac functional indices. While the benefits of using hMSCs as a cell therapy for cardiac repair are encouraging, the desired expectation of cardiomyoplasty is to increase cardiomyocyte content that will contribute to active cardiac mechanical function. Delivered cells may increase myocyte content by several different mechanisms such as differentiating to a cardiomyocyte lineage, secreting paracrine factors that increase native stem cell differentiation, or secreting factors that increase native myocyte proliferation. Considerable work suggests that hMSCs can differentiate towards a cardiomyocyte lineage based on measured milestones such as cardiac-specific marker expression, sarcomere formation, ion current propagation, and gap junction formation. However, current methods for cardiac differentiation of hMSCs have significant limitations. Current differentiation techniques are complicated and tedious, signaling pathways and mechanisms are largely unknown, and only a small percentage of hMSCs appear to exhibit cardiogenic traits. In this body of work, we developed a simple strategy to initiate cardiac differentiation of hMSCs in vitro. Incorporating environmental cues typically found in a myocardial infarct (e.g. decreased oxygen tension and increased concentrations of cell-signaling factors), our novel in vitro conditioning regimen combines reduced-O2 culture and hepatocyte growth factor (HGF) treatment. Reduced-O2 culturing of hMSCs has shown to enhance differentiation, tissue formation, and the release of cardioprotective signaling factors. HGF is a pleiotropic cytokine involved in several biological processes including developmental cardiomyogenesis, through its interaction with the tyrosine kinase receptor c-Met. We hypothesize that applying a combined conditioning treatment of reduced-O2 and HGF to hMSCs in vitro will enhance cardiac-specific gene and protein expression. Additionally, the transplantation of conditioned hMSCs into an in vivo infarct model will result in differentiation of delivered hMSCs and improved cardiac mechanical function. In testing our hypothesis, we show that reduced-O2 culturing can enhance hMSC growth kinetics and total c-Met expression. Combining reduced-O2 culturing with HGF treatment, hMSCs can be conditioned to express cardiac-specific genes and proteins in vitro. Using small-molecule inhibitors to target specific effector proteins in a proposed HGF/c-Met signaling pathway, treated reduced-O2/HGF hMSCs show a decrease in cardiac gene expression. When implanted into rat infarcts in vivo, reduced-O2/HGF conditioned hMSCs increase regional cardiac mechanics within the infarct region at 1 week and 1 month. Further analysis from the in vivo study showed a significant increase in the retention of reduced-O2/HGF conditioned hMSCs. Immunohistochemistry showed that some of the reduced-O2/HGF conditioned hMSCs express cardiac-specific proteins in vivo. These results suggest that a combined regimen of reduced-O2 and HGF conditioning increases cardiac-specific marker expression in hMSCs in vitro. In addition, the implantation of reduced-O2/HGF conditioned hMSCs into an infarct significantly improves cardiac function, with contributing factors of improved cell retention and possible increases in myocyte content. Overall, we developed a simple in vitro conditioning regimen to improve cardiac differentiation capabilities in hMSCs, in order to enhance the outcomes of using hMSCs as a cell therapy for the diseased heart.

Cell therapy, including human mesenchymal stem cell (hMSC) therapy, has the potential to treat different pathologies, including myocardial infarctions (heart attacks). Biological sutures composed of fibrin have been shown to effectively deliver hMSCs to infarcted hearts. However, hMSCs rapidly degrade fibrin making cell seeding and delivery time sensitive. To delay the degradation process, we propose using aprotinin, a proteolytic enzyme inhibitor that has been shown to slow fibrinolysis. This project investigated the effects of aprotinin on hMSCs and suture integrity. Viability of hMSCs incubated with aprotinin, examined using a LIVE/DEAD stain, was similar to controls. No differences in proliferation, as determined by Ki-67 presence, and were observed. hMSCs incubated in aprotinin differentiated into adipocytes, osteocytes, and chondrocytes, confirming multipotency. CyQuant assays were used to determine the number of cells adhered to fibrin sutures. The number of adhered cells was increased through aprotinin supplementation at Days 2, 3, and 5 time points. To examine the effect of aprotinin on suture integrity, sutures were loaded to failure to determine ultimate tensile strength (UTS) and modulus (E). Sutures exposed to aprotinin had higher UTS and E when compared to sutures exposed to standard growth media. Degradation of fibrin was quantified using an ELISA to quantify fibrin degradation products (FDP) and by measuring suture diameter. Fibrin sutures incubated in aprotinin had larger diameters and less FDP compared to the controls, confirming decreased fibrinolysis. These data suggest that aprotinin can reduce degradation of biological sutures, providing a novel method for extending the implantation window and increasing the number of cells delivered for hMSC seeded biological sutures.

Mesenchymal stem cells (MSCs) are promising candidates for treating diverse inflammatory disorders due to their capacity to be immunosuppressive. This phenotype is not present at baseline but develops in response to instructive cues. To date, clinical trials use cells grown in basic culture conditions, anticipating the cells will acquire a useful phenotype in response to in vivo cues. This strategy has failed to produce any FDA approved therapies, based on inconsistent efficacy. This thesis explores whether priming MSCs prior to administration can lead to a more uniformly therapeutic phenotype, and it details the design of an optimal in vitro priming regimen. Because interferon gamma (IFN-γ) is known to induce an anti-inflammatory state in MSCs, hypoxia can confer survival benefits, and both cues coexist in known situations of immune tolerance, we hypothesized dual IFN-γ/hypoxia priming would yield a superior immunosuppressive MSC therapy. We show that priming MSCs with hypoxia or IFN-γ alone improves their ability to inhibit T-cells in vitro, but combining these cues results in additive improvements. We next characterize the proteomic and metabolomic changes MSCs undergo when exposed to single or dual IFN-γ/hypoxia priming. While IFN-γ induces MSCs to suppress inflammation and fibrosis, hypoxia leads to cell adaptations to low oxygen, including upregulation of proteins involved in anaerobic metabolism, autophagy, angiogenesis, and cell migration. Dual priming results in additive effects, with many instances of synergy. Finally, we show initial evidence that dual primed MSCs are better able to inhibit disease progression in a mouse model of acute graft-vs-host disease (GvHD).

Human umbilical cord perivascular cells (HUCPVCs) derived from regions surrounding the umbilical cord vessels represent an attractive cell source for cellular therapies, given their proliferative potential and the accessibility of donor material compared with human bone marrow-derived mesenchymal stem cells (hBM-MSCs). However, these cells remain poorly characterised. Using flow cytometry, HUCPVCs were shown to express conventional MSC markers CD29, CD44, CD73, CD90, CD105, CD146, CD166 and integrins alpha1 to -5, alphaV, alphaVβ3, alphaVβ5, β1 and β3, but not CD14, CD34, CD45, STRO-1 or integrin alphaVβ6. HUCPVC marker profiles were consistent between three donors and at different passage numbers. Immunostaining for smooth muscle cell (SMC) markers; alpha-SMA, SM22alpha and smoothelin revealed that HUCPVCs shared expression of these markers with SMCs. However, in comparison with SMCs, HUCPVCs deposited more extensive fibronectin-rich matrices. When compared with hBM-MSCs, HUCPVCs differentiated along adipogenic and osteogenic lineages more slowly and did not progress to terminal phenotypes. mRNA expression of recently identified mesenchymal progenitor cell markers, ROR2, EPHA2, PLXNA2, CDH13 and CD9, was confirmed in HUCPVCs from two donors. In addition, all these markers (except EPHA2) were detected in the umbilical cord vessel wall cells of three donors, confirming their expression in both cultured HUCPVCs and cells of the primary tissue. To determine the roles of these markers in HUCPVCs, they were depleted individually using siRNA. Knockdown (KD) efficiencies of 90-97% were achieved. CD9 KD cells appeared elongated compared to cells treated with control siRNA, and these cells along with ROR2, EPHA2 and PLXNA2 KD cells exhibited larger cell areas than controls. All KD cells also showed decreased proliferative potential by day 6 compared with control siRNA or lipofectamine treated cells. A decrease in total β1 integrins was detected in the CD9 KD cells. Up-regulation of ROR2 and PLXNA2 mRNA expression was detected in HUCPVCs from two donors, when they underwent osteogenic differentiation. ROR2 and PLXNA2 knockdown resulted in increases in PLXNA2 and ROR2 mRNAs respectively, when cells were cultured in osteogenic medium compared with basal conditions. In addition, each individual knockdown revealed that the KD cells showed trends in increasing RUNX2 mRNA expression after 13-16 days in osteogenic medium. These data suggest that ROR2 and PLXNA2 may co-operate in promoting an osteogenic phenotype. Culturing HUCPVCs on non-mineralised BVSMC-derived matrices had very little impact on their differentiation status. In contrast, when HUCPVCs were cultured on mineralised BVSMC-derived matrices in osteogenic medium, their ability to further deposit mineralised matrix was enhanced by 7 days; no accompanying changes in RUNX2, ROR2 or PLXNA2 mRNA expression were detected. Taken together, early up-regulation of RUNX2, ROR2 and PLXNA2 appears to be important in driving osteogenic differentiation in HUPCVCs, whilst subsequent down-regulation of these markers may be required for mineralisation to occur. HUCPVCs express ROR2, PLXNA2, CDH13 and CD9 in vitro and in situ; these markers have distinct roles in regulating cell proliferation, shape and differentiation which may be regulated via changes in β1 integrins. It is not known why HUCPVCs might differentiate along adipogenic and osteogenic lineages more incompletely than hBM-MSCs. Further comparative characterisation of HUCPVCs and hBM-MSCs is a prerequisite for exploiting their vast clinical potential.

Orientador: Fernanda da Cruz Landim e Alvarenga / Banca: Sony Dimas Bicudo / Banca: Nereu Carlos Prestes / Banca: José Antonio Visintin / Banca: Claudia Barbosa Fernandes / Resumo: 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... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: 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 / Doutor

Hypoxia (low tissue oxygenation) is an important signalling cue for many cell types. The study of its effects has direct relevance to surgery since hypoxic gradients are generated with every cut. On a cellular level, changes in molecular oxygen are sensed by the Hypoxia-Inducible Factors (HIFs). The HIFs are a family of transcription factors that are master regulators of over 100 genes and can effect changes in multiple cellular processes including migration, survival and differentiation. The broad nature of the response to hypoxia means that study of the HIF system is also important in cancer; where many tumour cells have found ways of subverting the HIF response to ensure their continued growth and survival. This thesis explores the role of hypoxia and the HIF system in the regulation of migration, survival and differentiation in both cancer and stem cells. The first experimental chapter examines the role of hypoxia and the HIF system in the regulation of migration and three-dimensional organisation in several cancer cell lines. Using biochemical and functional assays, the HIF system is shown to exert a pleiotropic effect across a panel of cancer cell lines. In particular, HIF 1α is shown to activate proliferation in a prostate cancer cell line in findings that may be useful to inform future clinical strategies for the management of this disease. In the second experimental chapter, the first epigenetic mechanism involving histone modification for the specific regulation of HIF 2α expression is characterised. Here the family with sequence similarity 60, member A (Fam60a) protein is shown to repress expression of the HIF 2α gene through its association with the class 1 Sin3-HDAC co-repressor complex, achieving specificity by co-operation with the SP1 transcription factor. This novel mechanism is demonstrated to be important in the regulation of the basal expression of HIF 2α. Modification of HIF 2α expression through this mechanism is shown to alter cell migration, three dimensional organisation and angiogenesis in vitro. The clinical importance of these findings is demonstrated in a series of 45 patients suffering from colorectal cancer of known stage. In this cohort, the reciprocal relationship between Fam60a and HIF 2α is maintained, and both are identified as potential novel biomarkers for the development of this disease. In the final experimental chapter, the role of hypoxia in the regulation of differentiation is explored. These effects are documented in mesenchymal progenitors primarily derived from human fat. Here, hypoxia is shown to regulate differentiation in a context-dependent manner, promoting osteogenic and retarding adipose and neural differentiation in-vitro. The roles of Fam60a and HIF 2α are explored in this system. These data may be useful in optimising future surgical engraftment of these cells for regenerative purposes.

Background: Exosomes have great potential in regenerative medicine through the transfer of their bioactive cargos, such as RNA. tRF RNA and tiRNA are tRNAderived non-coding RNA. Here, we sought to identify the tRF/tiRNA profile in human mesenchymal stem cell (hMSC) exosomes. Methods: Bone marrow hMSCs were cultured with/without osteogenic differentiation medium and exosomes were harvested. RNA was extracted from: 1) control cells (Cell-NT); 2) control exosomes (EXO-NT); 3) differentiated cells (Cell-OM); 4) exosomes produced by differentiated cells (EXO-OM). RNA was sequenced to profile the small RNA with a focus on tRF/tiRNA. Results: tRF/tiRNA was highly enriched in hMSC exosomes. Less diversity was seen in the tRF/tiRNA profile in exosomes than that in parent cells. Selective tRF/tiRNA were packed into MSC exosomes and their profile is dependent on the cell maturation status. Conclusions: Our results suggest that tRF/tiRNA may play a role in mediating the function of exosomes in tissue regeneration.

Osteoarthritis (OA) is a disease that has significant individual, social, and economic impact worldwide. Although many etiologies lead to the eventual development of OA, one potentially treatable cause is the acute articular cartilage (AC) injury. These injuries are common and have a poor inherent healing capacity, leading to the formation of OA. In an effort to repair AC injuries several treatment strategies have been developed but none have proven completely successful. Studies examining AC tissue-engineering strategies have suggested that those with the most potential for success involve the introduction of autogenous or allogenous cells to the site of injury. These strategies are designed to encourage creation of a matrix with the appropriate characteristics of normal AC. However, development of a completely successful repair method has proven difficult because the biomechanical properties of normal AC are not easy to replicate, a cell source with the appropriate functional characteristics has not been optimized, and the problem of effective incorporation of a repair construct into the host tissue remains unresolved. In an effort to more fully understand the cartilage repair process, this work first focused on the development and utilization of an in vitro human explant model of AC to study the ability of seeded human chondrocytes to integrate into an AC defect. Further work elucidated the gene expression patterns of cultured adult human chondrocytes and human mesenchymal stem cell (MSC)-derived chondrocytes. Results from this work determined that cultured human chondrocytes were able to adhere to articular cartilage defects in a viable in vitro explant model and produce a matrix containing collagen type II. However, further work with the in vitro expanded chondrocytes revealed that these cells have increased expression of collagen type I which promotes the formation of a less durable fibrocartilagenous tissue. This unfavorable expression persisted despite placing the chondrocytes in an environment favoring a chondrocytic phenotype. Further work with MSC-derived chondrocytes demonstrated a similar and unfavorable production of collagen type I. This work represented an important first step towards a treatment for acute AC lesions but it is clear that further work to optimize the culture microenvironment is still required. / Experimental Surgery

Amyotrophic lateral sclerosis (ALS) is a progressive, lethal, degenerative disorder of the CNS. The hallmark of this disease is the premature and selective death of upper and lower motor neurons (MNs) in the brain and spinal cord, leading to fatal paralysis. Although the archetypal vision of neurotoxicity in neurodegenerative diseases is based on the idea that a specific neuronal population is particularly vulnerable to a cumulative toxic event (protein aggregation, mitochondria dysfunction, compromised axonal transport etc…), experimental evidence illustrate that ALS possibly does not arise strictly from damage within MNs. There is now convincing data supporting a non-cell autonomous mechanism in which neurodegeneration is influenced by the toxicity of non-neuronal cells in the vicinity of neurons such as astrocytes and microglia. Considering the accumulation of data implicating astrocytes in the pathogenesis of ALS (loss of GLT-1, secretion of toxic factor, enhanced inflammation, etc…), approaches aiming at replacing astrocytes at site of lesions constitute promising therapeutic strategies. Rapid progresses in the characterization of adult stem cell biology have generated considerable enthusiasm for the development of therapeutic strategies for CNS insults. Several observations support the hypothesis that stem cells may display a valuable influence on diseased host tissues by exerting a protective “chaperone” effect to neurons after differentiation in glial cells. Hence, we decided to study the neuroprotective potential of adult mesenchymal stem cells (MSCs) in ALS. In contrast to neural stem cells (NSCs) which localization in the central nervous system complicates their isolation, MSCs are easily isolated from the bone marrow. The relevance of using on MSCs in stem cell therapies of neurodegenerative disorders is also justified by their capacity to (trans)differentiate into neural cells. For this purpose, we exposed MSCs to growth factors involved in the astroglial differentiation of NSCs. The differentiation of MSCs was characterized by the acquisition of astrocyte morphology in addition to an increased expression of gene related to NSCs (nestin) and astrocytes (glutamine synthetase). The astroglial differentiation of MSCs is associated with the acquisition of a glial-like specific regulation of the production of GDNF, a potent neurotrophic factor for neurons. Then, we characterized the glutamate uptake in differentiated MSCs, a critical function of astrocytes. Our data demonstrate that the differentiation of MSCs is associated with an increased expression of the high affinity glutamate transporter, GLT-1. Thus, our in vitro results confirm the astrocytic differentiation potential of MSCs and we decided to use then in stem cell therapy of ALS. Indeed, we demonstrated that mechanism of stem cell recruitment is present in the spinal cord during the development of the disease by the secretion of stem cell factor (SCF). We injected MSCs derived from healthy animals into the cerebrospinal fluid of a transgenic rat model of familial ALS (expressing a mutated form of the human superoxide dismutase-1, hSOD1G93A) at disease onset. MSCs were found to infiltrate the nervous parenchyma and migrate substantially into the ventral grey matter by interacting with the SCF. At the site of lesion, MSCs differentiated massively into astrocytes around MNs. The intrathecal delivery of MSCs preserved motor functions and extended the survival of hSOD1G93A rats. Investigation of the lumbar spinal cord 35 days after graft demonstrated that the generation of healthy astrocytes from MSCs decreased motor neuron loss. However, this beneficial effect is not related to a decreased excitotoxicity by the rescue of GLT-1 expression but rather a decreased inflammation around MNs. Together, the data presented in this thesis highlight the protective capacity of adult MSC-derived astrocytes in the treatment of ALS.