Priming Human Mesenchymal Stromal Cells to Enhance their Regenerative Potential

MSCs show promise for cell therapy due to their immune-suppressive and regenerative properties. Consequently, MSCs have been widely used in an increasing number of clinical trials to treat a variety of pathological conditions including cardiovascular diseases and disorders with dysregulated immune function. The outcome of prospective MSC therapy trials however, has shown marginal benefit warranting further investigation to develop strategies to enhance their therapeutic potential. The latter requires better understanding of the mechanisms by which MSCs exert their effects, and studying MSCs under conditions resembling the in vivo microenvironment will help to develop such understanding. The focus of this thesis is to explore the effect of a collagen-based matrix (successfully used in bioengineering approaches for tissue regeneration including for cardiac repair) and Toll-like receptor (TLR) stimulation (providing an in vitro model of an inflammatory environment and widely used for priming MSCs in vitro) on the regenerative properties of MSCs. The first aim of this study (discussed in Chapter 3) involves a comparative analysis of the regenerative properties of MSCs cultivated as a monolayer or on collagen scaffolds, or activated with TLR3 or TL4 agonists. I found that MSCs developed a more cardioprotective phenotype on scaffolds, although no functional changes were detectable when analyzing MSCs in a bioengineered model of heart tissue. The findings of this chapter provide a mechanistic explanation for the potential contribution of MSCs primed with cardiomyogenic cues or TLR agonists. In the second aim (discussed in Chapter 4), signaling through TLR3 was dissected and the effects on MSC phenotype were investigated. The knowledge created in this aim provide some insight into the dynamics of TLR3 signaling, which can be further used to develop preconditioning strategies. In Aim 3 (discussed in Chapter 5), the effects of TLR3 and TLR4 activation on immunomodulatory function of MSCs were further explored. I discovered that activation of either TLR3 or TLR4 enhanced the capacity of MSCs to generate regulatory T lymphocytes. The findings in this aim are applicable to a variety of settings, including tissue regeneration, organ transplantation and autoimmune disorders in which boosting immune suppression can prevent disease development and/or progression.Ph.D.2018-11-17 00:00:0