The toll skeletal muscle injury, resulting in significant muscle mass loss, has on the patient reaches far more than physical and emotional, as the tolls are financial as well. Approximately more than 3 billion dollars is spent on the initial medical costs and on subsequent disability benefits, following a volumetric muscle loss. Skeletal muscle has a robust capacity for self-repair; this propensity for repair is hindered when skeletal muscle loss is larger than 20% of the total mass of the muscle. Previous work in our lab, has shown functional and morphological improvements following the cellular therapy, with mesenchymal stem cells (MSC), as well as with nerve relocation to the extracellular matrix (ECM). To further observe the regenerative properties of the above treatments, a defect weighing approximately 307 ± 3.7 mg wet weight and measuring approximately 1x 1cm² was removed from the lateral gastrocnemius (LGAS) of male Sprague Dawley rats. Additionally, the medial branch of the plantar nerve was then relocated and implanted to the middle of the ECM. Seven days post injury bone-marrow derived mesenchymal stem cells were injected directly into the implant using a PEGylated Fibrin hydrogel (PEG). Following 56 days of recovery, partial functional restoration was observed in the LGAS ECM seeded with MSC and implanted with the plantar nerve. The LGAS produced 86.3 ± 5.8% of the contralateral LGAS, a value that was significantly higher than ECM implantation alone (p <.05). The implanted ECM seeded with MSC and implanted with the plantar nerve showed significant increases in blood vessel density and myofiber content (p <.05). The data suggest that a volumetric injury can be repaired by neurotization of an implanted muscle-derived ECM seeded with MSCs. / text

<p>In living cells, calcium ions (Ca2+) play an important role as an intracellular second messenger. It mediates the regulation of cellular processes such as gene expression, initiation of vesicle fusion in synapses, is used in muscle contraction and is believed to play a fundamental role in synaptic plasticity as a molecular substrate for learning. The Ca2+ signals are created by the fact that the concentration of Ca2+ in the cytosol is four orders of magnitude lower than in the extracellular fluid as well as in cytoplasmic compartments such as the endoplasmic reticulum (ER). This enables fast increments in the cytosol concentration, which is regulated back to normal concentration by different mechanisms. In this project, the connection between Ca2+ signals of different cells was analysed using different correlation techniques: cross-correlation of continuous signals and digitalised signals. Therefore a software tool was developed in MATLAB, which takes Ca2+ recordings from time-lapse fluorescence microscopy as input and calculates the pair wise correlation for all cells. The software was tested by using previous data from experiments with embryonic stem cells from mouse (mES) and human (hES) as well as data from recordings done as part of the project. The study shows that the mathematical method of cross-correlation can successfully be applied to quantitative and qualititative analysis of Ca2+ signals. Furthermore, there exist strongly correlated cells in colonies of mES cells and hES cells. We suggest the synchronisation is achieved by physical coupling implicating a decrease of correlation as the distance increases for strong correlations. In addition, the lag used by the cross-correlation function (an effective phase shift) decreases as the correlation coefficient increases and increases as the intercellular distance increases for high correlation coefficients. Interestingly, the number of cells included in small scale clusters of strongly correlated cells is significantly larger for the differentiating mES cells than for the proliferating mÉS cells. In a broader perspective, the developed software might be usd in for instance analysis of cellular electrical activity and shows the relevance of applying methods from the exact sciences to biology.</p> / QC 20100708

The adaptor protein Shb has been implicated in the signaling of several tyrosine kinase receptors and previous studies have suggested a role for Shb in the signal transduction of T cells. Shb associates with the T cell receptor (TCR) and partakes in the signal propagation of activated T lymphocytes. In order to explore Shb’s influence on TCR signaling in vivo, T cell development and function was studied in a Shb knockout mouse. The loss of Shb led to aberrant TCR signaling in both thymocytes and peripheral CD4+ TH cells, with elevated basal phosphorylation of key components in the signal cascade. Shb was found to be dispensable for thymocyte development, but its absence resulted in a TH2 bias in in vitro stimulated peripheral CD4+ TH cells. As imbalances in TH2 responses are linked to allergic diseases, we further explored Shb’s role in immune regulation in a mouse model of atopic dermatitis. Shb knockout mice exhibit more aggravated signs of atopic dermatitis, including increased immune cell recruitment to the affected areas and elevated mRNA levels of typical TH2 cytokines. The effect of Shb on hematopoiesis in general was determined by examining populations of long-term hematopoietic stem cells (LT-HSCs) and hematopoietic progenitor cells in bone marrow of Shb knockout and wild type mice. Shb deficient bone marrow was found to contain significantly fewer relative numbers of LT-HSCs due to a proliferative defect. The reduced cell cycle activity of Shb LT-HSCs could further be linked to an abnormal regulation of the focal adhesion kinase/Rac1/p21-activated kinase pathway. Since alterations in LT-HSC proliferative abilities may have implications for leukemia development, BCR-Abl induced myeloid neoplasia was investigated in the absence of Shb. Shb deficiency confers a more aggressive progression of BCR-Abl induced myeloid neoplasia characterized by an increased peripheral blood neutrophilia and a deregulated cytokine profile. In addition, focal adhesion kinase and STAT3 signaling is hyperactivated in Shb knockout leukemic cells. In conclusion, Shb appears to be a multifunctional signaling mediator that controls several responses in hematopoietic cells, under homeostatic as well as disease conditions.

Cell-based therapies involving adipose-derived stem cells (ASCs) have shown promise in stimulating cardiovascular regeneration, including in the treatment of myocardial infarction (MI) and ischemic heart disease. However, previous studies involving the delivery of ASCs following MI have indicated that therapeutic efficacy has been limited by low survival and/or poor retention of the transplanted cells at the site of injury. To address these limitations, the goal of this thesis was to develop a more effective delivery strategy incorporating an injectable biomaterial combined with chemotactic growth factor delivery to enhance ASC retention within the gel. Working towards future in vivo analysis in a rat model, multilineage characterization studies confirmed that ASCs isolated from the epididymal fat pad of male Wistar rats could differentiate in vitro along the adipogenic, osteogenic, and chondrogenic lineages. Subsequently, the chemotactic response of the rat ASCs (rASCs) to varying concentrations of stromal derived factor-1 α (SDF-1α) and hepatocyte growth factor (HGF) was analyzed using a modified Boyden chamber assay. The results demonstrated that SDF-1α and HGF, at 20, 50, and 100 ng/mL elicited significant migratory responses under normoxic (21%) and hypoxic (5%) culture conditions. RT-PCR analysis was conducted to assess the expression of the two chemotactic growth factors and their associated receptors in the rASCs, and secreted SDF-1α protein expression was quantified by ELISA. Moving towards the development of the biomaterials-based delivery approach, the viability of rASCs encapsulated by photopolymerization in methacrylated glycol chitosan (MGC) hydrogels modified with various degrees of arginine-glycine-aspartic acid (RGD)-peptide modification was examined. More specifically, rASCs were encapsulated in MGC hydrogels with 0%, 4%, and 7% RGD modification and cultured for up to 14 days. Viability staining results indicated that rASC viability was enhanced in the 4% and 7% RGD-modified MGC hydrogels in comparison to the MGC hydrogels with no peptide modification. Pre-loading the gels with 50 ng/mL of SDF-1α had no significant effects on cell viability over 14 days. Overall, the results demonstrate that peptide modification to promote cell adhesion within the MGC hydrogels is key to improving cell viability and thereby improving the therapeutic potential of ASCs. / Thesis (Master, Chemical Engineering) -- Queen's University, 2012-10-24 23:54:37.126

The mammalian cell cycle and its points-of-entry are well characterized pathways. These points-of-entry are normally regulated via mitogens and include, amongst others, the ERK, JNK and p38 mitogen-activated protein kinase (MAPK) pathways. However, while the restriction point(R-point), the temporal switch-point at which a cell becomes irrevocably committed to division irrespective of mitogenic stimulus, is known among other cell types, its position within the murine myoblast line C2C12 is currently unknown. Similarly, while MAPK pathways, such as JNK and ERK, have been modeled computationally, no model yet exists of p38 MAPK as stimulated by mitogens. The aims of this dissertation, then, were to determine the R-point within the C2C12 cell cycle and construct a computational mitogen-stimulated p38 MAPK model. It was found that a synchronous C2C12 population, when stimulated to divide, took 7 to 9 hours to reach S-phase from G0, consistent with data from the literature. The R-point was determined to lie between 6 and 7 hours post G1-re-entry stimulation,which was consistent with studies in other cell types. Core modeling of the p38 MAPK pathway revealed that ultrasensitivitywas inherent within the pathway structure. Further, a branching/re-converging structure within the pathway imparted greater responsiveness to signal upon the pathway. A realistic p38 MAPK model demonstrated good responsiveness to signal, its output matched that of several other MAPK models, and it was capable of replicating previous in vitro data. This model can be used as a tool for further investigation of the mammalian cell cycle by linking it to other cell cycle models. The predictions by an expanded model may be better suited for understanding the effects of mitogen stimulus on the cell cycle in situ. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Stem cells have great potential value for treating a number of diseases and conditions, including diabetes, Parkinson's, and spinal cord injuries. Applying stem cells for therapeutic purposes will require an in-depth understanding of their biology, not only of the genes they express, but also the functions of the proteins encoded by the genes. The goal of the project presented in this thesis was to develop a method for high-throughput analyses of protein localization in mouse stem cells. Localization information can provide insight into the functions and biological roles of proteins. <br /><br /> One means of studying protein localization involves creating proteins with a green fluorescent protein (GFP) reporter gene and analyzing their localization using fluorescence microscopy. The research outlined in this thesis focused on developing a system to create a large number of GFP-tagged proteins by constructing a cDNA?GFP fusion library. This involved exploring methods for optimizing cDNA synthesis, designing a retroviral vector (pBES23) for the expression of cDNA?GFP fusions in mouse stem cells, and constructing a cDNA?GFP fusion library in this vector using R1 mouse embryonic stem cell mRNA. The library constructed was not successfully delivered to target cells for GFP-tagged protein expression; it was therefore not possible to characterize protein localization in mouse stem cells. Suggestions are given as to how the methods used in this thesis might be optimized further.

The primary aim of the thesis is to contribute to demonstrating how established and emerging science in the regenerative medicine (RM) domain can be translated into profitable commercial practice, and generate clinically- and cost-effective therapies. It achieves this by exploring and assessing underlying economics, including investment readiness and economic assessment, exploring regulatory and reimbursement frameworks, developing stem cell culture systems and assessing fit with clinical practice. The thesis is the first public domain wide-ranging analysis of business trends in the production, manufacturing and supply segments of the RM industry. It analyses the clinical potential of the domain as well as the translational and commercial challenges facing the industry. The industry is at a turning point as big pharmaceutical companies engage with RM in order to explore technologies as potential therapeutics and discovery tools. This unlocks the industry by confirming an exit path for RM based small- and medium-sized enterprises. Translation has come to be recognised as a core issue in the overall space and translation of regenerative therapies into the clinic is presently challenging, high-risk and expensive. This research addresses the question what are the mechanisms required to enable translation of emerging scientific knowledge into commercially viable clinical RM products? These mechanisms are particularly important as their creation involves and requires major investment decisions, which can determine the success or failure of RM developments and indeed of the companies concerned. The lack of well-established business models and the complexity of the domain suggested a conceptual approach drawing upon relevant literature from product and process development, applied business and revenue models, technological evolution and capital market ingenuity. The research was carried out in two phases. The first phase was concerned with identification of key challenges and mapping the overall industry emergence including emergence of related regulations to provide a context and framework for understanding the domain. Based on the emergence mapping a timeline of key parallel factors was identified, and their inherent connections explored to identify transforming events affecting and influencing multiple factors on the journey to clinical success within a business environment. This creates the reference model. The second phase was concerned with manufacturing a stem cell based therapeutic and applying health economic principles to determine available headroom for investment, cost of goods and return on investment, taking hearing disorders as a case exemplar, and exploring the behaviour of the net present value curve to identify key parameters affecting the economic positioning of this novel regime. A key output of the research is the investment readiness reference model. It integrates key RM business issues against reducing uncertainty and increasing value. The model argues that the complex nature of RM products means that the issues affecting industry emergence and development go well beyond the primarily scientific and technological concerns on which much current research focuses. The performance of RM firms ultimately hinges upon the successful clinical application of their developed products, the key step for creating and realising value, and their ability to deal with the fundamental business issues specific to the area. The framework deals with these business issues, which are investment & technology readiness, business models, organisational challenges, public policy and industry emergence. This thesis explores ideas that may bridge the chasm between the promise and reality of RM i.e. mechanisms to enable late stage translation of RM products. It links technological capability and business models for firms in the domain. Furthermore, it offers a unique perspective on the nature and characteristics of investment readiness and financial assessment, specifically identifying key parameters affecting economic positioning. The key contributions are therefore: New insights into the key challenges involved in realising the commercial potential of cell based therapeutics. Technology road mapping to link fundamental enabling technological capability for developing RM products with robust business plans integrating strategy, technology development and the regulatory and reimbursement framework. A generic investment readiness reference model generated from the enabling technology, value and supply chain structures to identify key indicators and characteristics of industry readiness. A novel experimental programme demonstrating expansion, maintenance and differentiation of human embryonic stem cells by manual and automated methods. New insights into economic positioning by mapping net present value, and economic analysis by estimating available headroom, cost of goods and return on investment for a putative hearing therapeutic.

T lymphocytes are considered an essential and advanced component of the immune system, since these cells are able to discriminate self from non-self, start up an immune reaction and further develop into memory cells. However, therapies based on the use of patient derived newly generated T cells reinoculated into humans do not exist. This is due to difficulties in replicating the peculiar conditions required for T cell development in vitro. The systems developed so far are based on the use of animal or unrelated human thymic tissue and therefore they would not be adequate to be used in any clinical application. Having conjectured that human skin cells, rearranged in a threedimensional fashion, would be able to support the development of human T lymphocytes from hematopoietic stem cells, we developed a model consisting of human skin keratinocytes and fibroblasts arrayed on a synthetic matrix so to create a prototype suitable to be translated into the clinic. In this way we were able to induce few hundred cord blood CD34⁺ haematopoietic stem cells to entirely develop into mature CD4⁺ or CD8⁺ T lymphocytes in vitro. However, circulating adult peripheral CD34⁺ precursors failed to survive in the same conditions. Finally we were able to explain our success as consequence of strong induction of the Notch delta ligand Dll-4 by the keratinocytes cultured in the construct. In synthesis, we report here for the first time that skin keratinocytes, in the presence of fibroblasts and reconfigured in a three-dimensional arrangement, are able to induce the differentiation of a minimal amount of cord but not adult blood stem cells into fully differentiated T cells by acting through the Dll-4 Notch signaling pathway in vitro.

Fibroblast growth factor (FGF) signalling plays many fundamentally important roles during the development of the mammalian embryo. However, its effects on pluripotent stem cells derived from mouse and human embryos appear to be markedly different. FGF2 is routinely added to culture medium for propagating undifferentiated human (hES) cells, whereas in mouse (mES) cell cultures FGFs have been described as regulators of their differentiated progeny. To assess the effect of FGF signalling on undifferentiated mES cells, the effects of FGF2 and 4 were analysed in the presence of saturating and sub-saturating levels of the inhibitor of differentiation, leukaemia inhibitory factor (LIF). Mouse ES cell self-renewal was quantified by measuring the expression of the stem cell specific reporter Oct4-LacZ in biochemical and fluorometric assays. Treatment with FGF reduced the expression of the OCT4-LacZ reporter, even under saturating concentrations of LIF and this was mirrored by decreased levels of OCT4 protein. Furthermore, treatment with FGF leads to upregulation of the ectodermal differentiation marker Pax6. These results suggest that FGF signalling has a direct impact on undifferentiated mES cells, and actively promotes their differentiation. To asses the effect of FGF signalling on hES cells without the influence of undefined factors, a feeder and serum free system was developed. Cells growing in this conditions for >20 passages maintained expression of surface (SSEA3 and TRA1-60 and 81) and internal (OCT4) markers specific for undifferentiated hES cells. Expression of these markers was dependant on the continuous presence of FGF2. Indeed, withdrawal of FGF2 resulted in a rapid decrease of in hES cell growth and of the emergence of cell flattened morphology and of the surface marker SSEA1, changes typically associated with differentiation. Two important signals activated by FGF in hES cells are the ERK/MAPK and PI3K pathways. To assess their functional relevance, hES cell cultures were treated with the drugs UO126 and LY294002, inhibitors of the MAPK and PI3K pathways respectively. Drug mediated suppression of the phosphorylation of these pathways, correlated with a reduction in cell growth, flattening of the colonies and reduction in SSEA4 expression. Use of SB431542, specific inhibitor of TGFβ/activin type I receptor kinase (Alk5) also resulted in the flattening of the colonies and the appearance of dispersed cells. Therefore, inhibition of MAPK and PI3K appears to impair growth and self-renewal in hES cells and this may be happening in conjunction with TGFβ/Activin pathway. Taken together, these results suggest that FGF signalling has opposite effects in mouse and human ES cells: inducing differentiation in mES and sustaining self-renewal in hES.

Les affections ostéo-articulaires concernent des millions de personnes. L’ingénierietissulaire osseuse, associant cellules souches mésenchymateuses humaines (CSM) etmatériaux synthétiques, pourrait répondre aux besoins cliniques. Pour cela, les différentescomposantes de cette approche et leur association doivent être mieux étudiées pour la rendreutile cliniquement. Durant cette thèse, une première étude animale proche du cas cliniquenous a permis de définir les points à améliorer pour le traitement des pertes osseuses. Nousavons ainsi pu développer un milieu spécifique induisant une différenciation rapide etterminale des CSM en ostéoblastes. Par la suite, l’utilisation de particules de céramiquescomme support cellulaire nous a permis d’obtenir des hybrides riches en matriceextracellulaire. Cet environnement 3D biomimétique permet l’engagement spontané des CSMvers un phénotype ostéoblastique et l’obtention d’une quantité osseuse importante in vivo.L’ensemble de ces résultats met en évidence l’importance de l’environnement et du stade dedifférenciation cellulaire pour la formation osseuse par ingénierie tissulaire osseuse. / Osteo-articular disorders affect millions of people over the world. Bone tissueengineering, an approach combining human mesenchymal stem cells (MSC) and syntheticmaterials, could potentially fulfill clinical needs. However, the different components of thisapproach and their association should be investigated further to make it clinically useful. Inthis thesis, an initial animal study close to clinical situation allowed us to identify areas thatneed improvement for regenerating bone defect. We were then able to develop a specificmedium which induces a rapid and terminal osteoblastic differentiation of MSC.Subsequently, the use of ceramic particles as cell support has allowed us to obtain hybridmainly composed of extracellular matrix. This biomimetic 3D environment allowsspontaneous osteoblastic commitment of MSC and induces a large bone quantity in vivo.Overall, these results highlight the importance of the environment and the cell differentiationstate for bone formation using bone tissue engineering.