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Cell-based therapies have the potential to revolutionize current treatments for diseases with high prevalence and related economic and social burden. Unfortunately, clinical trials have made only modest improvements in restoring normal function to degenerating tissues. This limitation is due, at least in part, to the death of transplanted cells within a few hours after transplant due to a combination of mechanical, cellular, and host factors. In particular, mechanical stress during implantation, extracellular matrix loss upon delivery, nutrient and oxygen deprivation at the recipient site, and host inflammatory response are detrimental factors limiting long-term transplanted cell survival. The beneficial effect of cell therapy for regenerative medicine ultimately depends on the number of administered cells reaching the target tissue, their viability, and their promotion of tissue regeneration. Therefore, strategies aiming at improving viable cell engraftment are crucial for regenerative medicine. Here we review the major factors that hamper successful cell engraftment and the strategies that have been studied to enhance the beneficial effects of cell therapy. Moreover, we provide a perspective on whether mesenchymal stromal cell-derived extracellular vesicle delivery, as a cell-free regenerative approach, may circumvent current cell therapy limitations. [ABSTRACT FROM AUTHOR]

Regenerative medicine has rapidly evolved, due to progress in cell and molecular biology allowing the isolation, characterization, expansion, and engineering of cells as therapeutic tools. Despite past limited success in the clinical translation of several promising preclinical results, this novel field is now entering a phase of renewed confidence and productivity, marked by the commercialization of the first cell therapy products. Ongoing issues in the field include the use of pluripotent vs. somatic and of allogenic vs. autologous stem cells. Moreover, the recognition that several of the observed beneficial effects of cell therapy are not due to integration of the transplanted cells, but rather to paracrine signals released by the exogenous cells, is generating new therapeutic perspectives in the field. Somatic stem cells are outperforming embryonic and induced pluripotent stem cells in clinical applications, mainly because of their more favorable safety profile. Presently, both autologous and allogeneic somatic stem cells seem to be equally safe and effective under several different conditions. Recognition that a number of therapeutic effects of transplanted cells are mediated by paracrine signals, and that such signals can be found in extracellular vesicles isolated from culture media, opens novel therapeutic perspectives in the field of regenerative medicine. [ABSTRACT FROM AUTHOR]

The success of skeletal muscle reconstruction depends on finding the most effective, clinically suitable strategy to engineer myogenic cells and biocompatible scaffolds. Satellite cells (SCs), freshly isolated or transplanted within their niche, are presently considered the best source for muscle regeneration. Here, we designed and developed the delivery of either SCs or muscle progenitor cells (MPCs) via an in situ photo-cross-linkable hyaluronan-based hydrogel, hyaluronic acid-photoinitiator (HA-PI) complex. Partially ablated tibialis anterior (TA) of C57BL/6J mice engrafted with freshly isolated satellite cells embedded in hydrogel showed a major improvement in muscle structure and number of new myofibers, compared to muscles receiving hydrogel MPCs or hydrogel alone. Notably, SCs embedded in HA-PI also promoted functional recovery, as assessed by contractile force measurements. Tissue reconstruction was associated with the formation of both neural and vascular networks and the reconstitution of a functional SC niche. This innovative approach could overcome previous limitations in skeletal muscle tissue engineering. [ABSTRACT FROM AUTHOR]

Purpose: Wound healing of the cryo-injured bladder can bring about organ remodeling because of incomplete reconstitution of depleted smooth muscle cells. Stem cell transplantation could be beneficial to improve smooth muscle cell regeneration and/or modulate the remodeling process. The repair of bladder injury using adult-type stem cells would be useful for adult urological patients but unsuited for neonatal patients, in whom major benefits are likely to derive from fetal-type stem cells. Materials and Methods: The smooth muscle cell differentiation potential of fetal-type vs adult-type stem cells was evaluated by injecting green fluorescent protein labeled mesenchymal stem cells from rat amniotic fluid or bone marrow, respectively, in cryo-injured rat bladder walls. Results: At 30 days after transplantation only a few fetal-type or adult-type mesenchymal stem cells gave rise to enteric or vascular smooth muscle cells, whereas most mesenchymal stem cells appeared incapable of specific differentiation. In vitro co-culture experiments of smooth muscle cells with fetal-type or adult-type mesenchymal stem cells selectively labeled with distinct fluorochromes showed the presence of hybrid cells, suggesting that some mesenchymal stem cells can undergo cell fusion. Surprisingly the major effect of rat bone marrow or amniotic fluid mesenchymal stem cell transplantation seemed to be preventing cryo-injury induced hypertrophy of surviving smooth muscle cells. Conclusions: In this model stem cell transplantation has a limited effect on smooth muscle cell regeneration. Instead it can regulate post-injury bladder remodeling, possibly via a paracrine mechanism. [Copyright &y& Elsevier]