Adult mesenchymal stem cells (MSCs) are capable of differentiating into various mesenchymal tissues, including bone, cartilage, muscle, and fat. Recent insights and clinical experiences suggest that MSCs naturally function as pericytes, which are released at injury sites to secrete bioactive factors that modulate the immune response and promote tissue regeneration. These factors inhibit apoptosis and scarring, stimulate angiogenesis, and enhance the mitosis of tissue-specific progenitor cells. Additionally, MSCs can inhibit lymphocyte surveillance of injured tissue, preventing autoimmune reactions and allowing allogeneic MSCs to be used in clinical settings. This has led to a new era of experimentation and clinical trials using xenogeneic and allogeneic MSCs for treating a variety of conditions, such as steroid-resistant graft-versus-host disease (GvHD), Crohn's disease, and myocardial infarction. The trophic effects of MSCs, including their ability to inhibit apoptosis, limit damage, and stimulate angiogenesis and mitosis, are key to their therapeutic benefits. The natural niche of MSCs, as pericytes, further supports their immunomodulatory and trophic functions. This understanding has opened new avenues for cell-mediated therapy, particularly in the context of site-regulated multidrug delivery.Adult mesenchymal stem cells (MSCs) are capable of differentiating into various mesenchymal tissues, including bone, cartilage, muscle, and fat. Recent insights and clinical experiences suggest that MSCs naturally function as pericytes, which are released at injury sites to secrete bioactive factors that modulate the immune response and promote tissue regeneration. These factors inhibit apoptosis and scarring, stimulate angiogenesis, and enhance the mitosis of tissue-specific progenitor cells. Additionally, MSCs can inhibit lymphocyte surveillance of injured tissue, preventing autoimmune reactions and allowing allogeneic MSCs to be used in clinical settings. This has led to a new era of experimentation and clinical trials using xenogeneic and allogeneic MSCs for treating a variety of conditions, such as steroid-resistant graft-versus-host disease (GvHD), Crohn's disease, and myocardial infarction. The trophic effects of MSCs, including their ability to inhibit apoptosis, limit damage, and stimulate angiogenesis and mitosis, are key to their therapeutic benefits. The natural niche of MSCs, as pericytes, further supports their immunomodulatory and trophic functions. This understanding has opened new avenues for cell-mediated therapy, particularly in the context of site-regulated multidrug delivery.