Research and application of stem cell-derived exosomes in regenerative medicine

Stem cells are a class of undifferentiated cells with high self-renewal and rapid proliferative capabilities. Undercertain conditions, stem cells can induce differentiation into other tissue cells of the human body, such as skeletal muscle cells, cardiomyocytes, osteoblasts, and nerve-like cells. In recent years, with the development of tissue engineering and regenerative medicine, stem cells have been extensively used in various fields of regenerative medicine as optimal seeded cells; however, there are still some problems, such as the decreased cell survival rate and regenerative capacity after transplantation, immune rejection, and ethical supervision. Therefore, it is difficult to universally and safely use stem cell banks for regeneration applications. The paracrine effect of stem cells has been extensively studied since its discovery. Increasing evidence supports the view that stem cells act in paracrine manner, and the secretion of exosomes plays a vital role in their biological functions. Exosomes are nanoscale extracellular vesicles containing biologically active molecules such as RNA and proteins; they possess similar functions to stem cells and play important roles in cell communication, immune response, and repair of tissue damage. At present, clinical studies on stem cell exosomes in tissue engineering and regenerative medicine have also been carried out in the fields of bone and cartilage repair, nerve tissue regeneration, liver tissue regeneration, skeletal muscle tissue engineering, vascular regeneration, taste bud repair, tooth regeneration, etc. In this paper, the composition, formation, release and identification of exosomes are introduced in detail. The research status of exosomes from different stem cell sources in tissue engineering and regenerative medicine is described, and their broad application prospects are discussed.