Mesenchymal Stem Cells Home to Sites of Injury and Inflammation

BACKGROUND: Mesenchymal stem cells (MSCs) have shown significant therapeutic potential in preclinical animal models of wound healing. However, the translation of MSC-based therapeutics to clinical practice has been delayed by questions including the mechanisms of MSC homing, engraftment, and ultimate function. THE PROBLEM: Experimental models of MSC-based wound therapies often involve intravenous injection of cells followed by sacrifice of animals at various time points and detection of MSCs in wounds by histological methods. However, this methodology is limited by its sampling of only specific tissue at a single time point and provides no information about how exogenously transplanted MSCs home to the wound environment. BASIC/CLINICAL SCIENCE ADVANCES: Most systemically injected MSCs initially become entrapped within the lungs before migrating out to the liver and spleen in the normal state. When an injury is present, after the initial lung entrapment, MSCs migrate in response to inflammatory mediators and home to sites of wounding. CLINICAL CARE RELEVANCE: As MSC-based wound therapies continue to advance toward clinical trials, the availability of noninvasive methods to track cells after injection into patients affords the opportunity to monitor stem cell behavior post-transplantation. CONCLUSION: MSCs have demonstrated great promise as an emerging therapeutic for wound management. However, further preclinical studies will be needed to elucidate the reparative mechanisms of these cells and to determine how to optimize their regenerative potential.