Mesenchymal stromal cells (MSC) have attracted the attention of scientists and clinicians due to their self-renewal, capacity for multipotent differentiation, and immunomodulatory properties. Some essential problems remain to be solved before the clinical application of MSC. Platelet lysate (PL) has recently been used as a substitute for FBS in MSC amplification in vitro to achieve clinically applicable numbers of MSC. In addition to promising trials in regenerative medicine, such as in the treatment of major bone defects and myocardial infarction, MSC have shown therapeutic effect other than direct hematopoiesis support in hematopoietic reconstruction. It has been confirmed that MSC promote hematopoietic cell engraftment and immune recovery after allogeneic hematopoietic stem cell transplantation, probably through the provision of cytokines, matrix proteins, and cell-to-cell contacts. Their suppressive effects on immune cells, including T cells, B cells, NK cells and DC cells, suggest MSCs as a novel therapy for GVHD and other autoimmune disorders. These cells thus present as promising candidates for cellular therapy in the fields of regenerative medicine, allogeneic hematopoietic stem cell transplantation, and autoimmune disorders.