Mesenchymal Stem Cells from Different Tissues: Immune Status and Activity

Mesenchymal stem cells (MSCs) have been found in almost all tissues and due to their regenerative properties represent promising tools in cell-based therapy. Role of MSCs in tissue repair is strongly governed by their interplay with immune cells and regulating factors. In addition to the first and most investigated MSCs isolated from bone marrow (BM-MSCs), other tissues were also reported as abundant sources of MSCs, such as peripheral and menstrual blood, fetal and perinatal tissues, adipose and dental tissue. Although BM-MSCs have been shown to be immunosuppressive in both in vitro and in vivo conditions, multiple evidences indicate that these cells have immunogenic properties, making their immune privileged status at least questionable. Besides their similarity with BM-MSCs, MSCs isolated from alternative sources manifest significant differences in their phenotype, functionality, immune status and activity. Complexity of interactions of BM-MSCs with the immune system is also found for MSCs isolated from other tissues. Due to specific conditions present in different tissues, variability in the immune repertoire of resident MSCs is to be expected and must be taken into consideration during experimental or clinical protocol planning.