An overview of Mesenchymal stromal cells: biology, functional role and therapeutic potential

Mesenchymal stromal cells (MSCs) are multipotent non-hematopoietic cells able to auto-renewal and differentiate into mesodermal cell lineages. The cells have been attracted for their potential therapeutic roles in different diseases possessing broad spectrum of activities (immunomodulatory, trophic, anti-inflammatory and migratory). Thus, MSCs represent optimal biological “tool" for tissue regeneration approaches both in human and animals. MSCs firstly isolated from bone marrow (BM) (Friedenstein, 1970) can be obtained from different sources and organs in adults like, adipose tissue (AT), Wharton’s jelly, dental pulp, peripheral blood, etc. Upon isolation, MSCs can be characterized by their ability to grow and expand on plastic plates and can differentiate into multiple lineages like osteocytes, chondrocytes, myocytes, adipocytes, and express certain cell surface markers like cluster of differentiation (CD) CD90, CD105, CD73 and are negative for markers like CD45, CD34, CD14, CD11b, CD19. In addition, they express low level of major histocompatibility complex (MHC) class I, CD40, CD80, CD86 and do not express MHC class II molecules, which make these cells immune privileged and an ideal candidate for allogenic transplantation in diseased patients. Recent studies demonstrating the reduced MSCs engraftment revealed that their beneficial regenerative effects primarily derive from paracrine activity (secretome release) rather than differentiation capacity. Today, MSCs are at the forefront of regenerative medicine, offering potential treatments for a wide range of diseases (in primis musculo-skeletal, neurodegenerative and auto-immune) for which MSCs act by reducing inflammation and pain, and promoting the development of hyaline cartilage. Future research is directed towards new and important objectives (optimization of MSC sources and dosage, use of MSC exosomes and/or in combination with other substances/cells) that can allow us to enhance knowledge and increase the number of clinical studies.