Neural differentiation potential of human bone marrow-derived mesenchymal stromal cells: misleading marker gene expression

Background: In contrast to pluripotent embryonic stem cells, adult stem cells have been considered to be multipotent, being somewhat more restricted in their differentiation capacity and only giving rise to cell types related to their tissue of origin. Several studies, however, have reported that bone marrow-derived mesenchymal stromal cells (MSCs) are capable of transdifferentiating to neural cell types, effectively crossing normal lineage restriction boundaries. Such reports have been based on the detection of neural-related proteins by the differentiated MSCs. In order to assess the potential of human adult MSCs to undergo true differentiation to a neural lineage and to determine the degree of homogeneity between donor samples, we have used RT-PCR and immunocytochemistry to investigate the basal expression of a range of neural related mRNAs and proteins in populations of non-differentiated MSCs obtained from 4 donors. Results: The expression analysis revealed that several of the commonly used marker genes from other studies like nestin, Enolase2 and microtubule associated protein 1b (MAP1b) are already expressed by undifferentiated human MSCs. Furthermore, mRNA for some of the neural-related transcription factors, e.g. Engrailed-1 and Nurr1 were also strongly expressed. However, several other neural-related mRNAs (e.g. DRD2, enolase2, NFL and MBP) could be identified, but not in all donor samples. Similarly, synaptic vesicle-related mRNA, STX1A could only be detected in 2 of the 4 undifferentiated donor hMSC samples. More significantly, each donor sample revealed a unique expression pattern, demonstrating a significant variation of marker expression. Conclusion: The present study highlights the existence of an inter-donor variability of expression of neuralrelated markers in human MSC samples that has not previously been described. This donor-related heterogeneity might influence the reproducibility of transdifferentiation protocols as well as contributing to the ongoing controversy about differentiation capacities of MSCs. Therefore, further studies need to consider the differences between donor samples prior to any treatment as well as the possibility of harvesting donor cells that may be inappropriate for transplantation strategies

The state of the Martian climate

60°N was +2.0°C, relative to the 1981–2010 average value (Fig. 5.1). This marks a new high for the record. The average annual surface air temperature (SAT) anomaly for 2016 for land stations north of starting in 1900, and is a significant increase over the previous highest value of +1.2°C, which was observed in 2007, 2011, and 2015. Average global annual temperatures also showed record values in 2015 and 2016. Currently, the Arctic is warming at more than twice the rate of lower latitudes

An investigation into the characteristics and potential therapeutic application of human bone marrow-derived mesenchymal stromal cells in experimental spinal cord injury

Transplanted mesenchymal stromal cells (MSC) have been reported to improve functional recovery after spinal cord injury (SCI). The mechanism(s) responsible for this effect are, however, largely unknown. The first studies about MSC transplantation into spinal cord lesions reported differentiation of the donor cells to a neural lineage. This so-called transdifferentiation capacity has aroused great excitement as well as great scepticism. Other studies suggested that the beneficial effects were due to a paracrine mechanism. This thesis was designed to provide insights into the properties of MSC as well as into their fate and function after transplantation into spinal cord lesions. Human MSC (hMSC) were found to constitutively express several neural-related markers, a property which may have led other groups to conclude that hMSC were capable of transdifferentitation to a neural lineage. Interestingly, these markers demonstrated a donor-dependent variability which may have influenced the widely differing opinions about hMSC transdifferentiation. Clinical application of hMSC requires the expansion of isolated cells to relevant numbers without supplementation of animal- or donor-derived serum. Conventional expansion, however, includes the employment of 10% fetal bovine serum (FBS) which might transfer infectous agents or might lead to the immune rejection of transplanted cells. The isolation and expansion of hMSC in the absence of serum supplementation was attempted in the present thesis but could not be accomplished. However, significantly better proliferation could be achieved with supplementation of only 2% FBS and certain growth factors compared to the conventional medium. The multipotent capacity of hMSC was found to be unaffected by the employment of this serum-reduced medium. Since the beneficial effects of hMSC transplantation into SCI were thought to be due to paracrine mechanisms, the expression patterns for several growth factors and cytokines were investigated. A donor-dependent variability of expression could be demonstrated in untreated hMSC as well as in hMSC that had been exposed to lipopolysaccharide (LPS). To investigate the possibility that hMSC could change their specific expression pattern when implanted into debris-laden spinal cord lesions, hMSC were co-cultivated with tissue homogenates from normal and injured rat spinal cords. To determine if this possibility might be tissue specific, homogenates from normal and infarcted rat heart were also applied. None of the above homogenates were found to change the individual donor-dependent patterns of growth factor- or cytokine expression suggesting that indivual hMSC expression patterns remained unaltered following implantation into the lesioned spinal cord. However, such donor-dependent variability might have a profound influence on the degree of subsequent functional recovery and it has to be considered that some donor samples might not have the appropriate growth factor and cytokine expression profiles for optimal tissue repair. A major aspect of the present thesis was the evaluation of an hMSC-based tissue engineering strategy to promote orientated axonal re-growth and functional tissue repair in an experimental animal model of acute SCI. Therefore, cooperation partners transduced hMSC to express green fluorescent protein (GFP) to enable identification of transplanted cells. These cells were seeded into oriented 3D collagen scaffolds and implanted into thoracic spinal cord hemisections. Already 1 week after implantation, animals which received hMSC-seeded scaffolds demonstrated better functional improvement than the control animals, which was even significant after four weeks. This difference, however, was no longer significant at 8 weeks. Immunohistochemistry revealed that only small numbers of transplanted hMSC had survived up to the termination date of 8 weeks after implantation. Nonetheless, animals receiving hMSC-seeded scaffolds demonstrated increased numbers of regenerating axons as well as reduced astrocytic and inflammatory responses. Interestingly, donor hMSC were found to express chondroitin sulphate proteoglycans (CSPG) and although few viable cells could be detected, CSPG deposits could be observed throughout the scaffold. In conclusion, it is likely that hMSC exert their regenerative properties by the expression of growth factors, cytokines and extracellular matrix molecules which are capable of influencing resident and invading cells

An investigation into the characteristics and potential therapeutic application of human bone marrow-derived mesenchymal stromal cells in experimental spinal cord injury

Transplanted mesenchymal stromal cells (MSC) have been reported to improve functional recovery after spinal cord injury (SCI). The mechanism(s) responsible for this effect are, however, largely unknown. The first studies about MSC transplantation into spinal cord lesions reported differentiation of the donor cells to a neural lineage. This so-called transdifferentiation capacity has aroused great excitement as well as great scepticism. Other studies suggested that the beneficial effects were due to a paracrine mechanism. This thesis was designed to provide insights into the properties of MSC as well as into their fate and function after transplantation into spinal cord lesions. Human MSC (hMSC) were found to constitutively express several neural-related markers, a property which may have led other groups to conclude that hMSC were capable of transdifferentitation to a neural lineage. Interestingly, these markers demonstrated a donor-dependent variability which may have influenced the widely differing opinions about hMSC transdifferentiation. Clinical application of hMSC requires the expansion of isolated cells to relevant numbers without supplementation of animal- or donor-derived serum. Conventional expansion, however, includes the employment of 10% fetal bovine serum (FBS) which might transfer infectous agents or might lead to the immune rejection of transplanted cells. The isolation and expansion of hMSC in the absence of serum supplementation was attempted in the present thesis but could not be accomplished. However, significantly better proliferation could be achieved with supplementation of only 2% FBS and certain growth factors compared to the conventional medium. The multipotent capacity of hMSC was found to be unaffected by the employment of this serum-reduced medium. Since the beneficial effects of hMSC transplantation into SCI were thought to be due to paracrine mechanisms, the expression patterns for several growth factors and cytokines were investigated. A donor-dependent variability of expression could be demonstrated in untreated hMSC as well as in hMSC that had been exposed to lipopolysaccharide (LPS). To investigate the possibility that hMSC could change their specific expression pattern when implanted into debris-laden spinal cord lesions, hMSC were co-cultivated with tissue homogenates from normal and injured rat spinal cords. To determine if this possibility might be tissue specific, homogenates from normal and infarcted rat heart were also applied. None of the above homogenates were found to change the individual donor-dependent patterns of growth factor- or cytokine expression suggesting that indivual hMSC expression patterns remained unaltered following implantation into the lesioned spinal cord. However, such donor-dependent variability might have a profound influence on the degree of subsequent functional recovery and it has to be considered that some donor samples might not have the appropriate growth factor and cytokine expression profiles for optimal tissue repair. A major aspect of the present thesis was the evaluation of an hMSC-based tissue engineering strategy to promote orientated axonal re-growth and functional tissue repair in an experimental animal model of acute SCI. Therefore, cooperation partners transduced hMSC to express green fluorescent protein (GFP) to enable identification of transplanted cells. These cells were seeded into oriented 3D collagen scaffolds and implanted into thoracic spinal cord hemisections. Already 1 week after implantation, animals which received hMSC-seeded scaffolds demonstrated better functional improvement than the control animals, which was even significant after four weeks. This difference, however, was no longer significant at 8 weeks. Immunohistochemistry revealed that only small numbers of transplanted hMSC had survived up to the termination date of 8 weeks after implantation. Nonetheless, animals receiving hMSC-seeded scaffolds demonstrated increased numbers of regenerating axons as well as reduced astrocytic and inflammatory responses. Interestingly, donor hMSC were found to express chondroitin sulphate proteoglycans (CSPG) and although few viable cells could be detected, CSPG deposits could be observed throughout the scaffold. In conclusion, it is likely that hMSC exert their regenerative properties by the expression of growth factors, cytokines and extracellular matrix molecules which are capable of influencing resident and invading cells

Leadership is like fine wine: It is meant to be shared, globally

The overwhelming majority of leadership theory and research has been developed in North America. Having said that, it cannot be overstated that we are living in an ever more tightly connected global economy. Appropriately, scholars have been giving more attention to the global context of leadership, particularly focusing on the rise of team-based structures, the need for intra-organizational cooperation across distance, a widening scope of competition, and managing diversity and cultural perspectives

Growth factor and cytokine expression of human mesenchymal stromal cells is not altered in an in vitro model of tissue damage

Background aims. The beneficial effect of human (h) mesenchymal stromal cell (MSC) transplantation in a variety of cell-based intervention strategies is widely believed to be because of paracrine mechanisms. The modification of hMSC cytokine and growth-factor expression patterns were studied following exposure to lipopolysaccharide (LPS) and tissue homogenates (representing tissue debris) from normal and pathologic tissues. Methods. Human bone marrow-derived MSC were stimulated with LPS or exposed to homogenate from normal or pathologic rat spinal cord or heart. The expression profiles of a number of cytokines and growth factors were investigated using quantitative reverse transcription (RT)-polymerase chain reaction (PCR) with human-specific primers. The effects of tissue homogenates on hMSC proliferation and migratory behavior were also investigated. Results. Stimulation of hMSC with LPS resulted in an up-regulation of interleukin (IL)-1 beta, IL-6 and IL-8. However, the pattern of up-regulation varied between donor samples. Furthermore, LPS treatment resulted in a donor-dependent alteration of growth factor expression. Induction of a shift in expression pattern was not observed following exposure to homogenates from either normal or pathologic tissues. Tissue homogenates did stimulate cell proliferation, but not migration. Conclusions. The hMSC expression pattern is apparently stable, even when cells are confronted by debris from different tissue types. However, treatment of hMSC with LPS is able to change the expression of cytokines and growth factors in a donor-dependent manner that may enhance their potential use in regenerative medicine