Mesenchymal Stem Cell Functionalization for Enhanced Therapeutic Applications

To date, the therapeutic efficacy of human mesenchymal stem cells (hMSCs) has been investigated in various clinical trials with moderate or, in some cases, inconsistent results. The still elusive reproducibility relates, in part, with constitutive differences in the cell preparation, translated into variable cell potencies. Other factors include poor cell homing and survival, and age-/disease-associated host tissue impairment. It is well accepted that within in vivo niches, MSCs exist as heterogeneous cell populations with different stemness propensities and supportive functions. Phenotype-based MSC purification of homogeneous subsets can result in cell populations with distinct biological functions. In addition, preclinical studies have shown that MSC functionalization in vitro, through cell priming, can boost their immunomodulatory, trophic, and reparative capacities in vivo. Therefore, in this review, we discuss how phenotype-based MSC purification and MSC priming technologies can contribute to an improved MSC-based product for safer and more effective therapeutic applications. Culture expansion of MSCs has detrimental effects on various cell characteristics and attributes (e.g., phenotypic changes and senescence), which, in addition to inherent interdonor variability, negatively impact the standardization and reproducibility of their therapeutic potential. The identification of innate distinct functional MSC subpopulations, as well as the description of ex vivo protocols aimed at maintaining phenotypes and enhancing specific functions have the potential to overcome these limitations. The incorporation of those approaches into cell-based therapy would significantly impact the field, as more reproducible clinical outcomes may be achieved.