Cell-Mediated Pathologies in Traumatic Orthopaedic Injuries

Physical trauma is one of the most common mechanisms leading to orthopaedic injury. The trauma and associated inflammatory response initiates the process of tissue regeneration and repair, which includes the recruitment and induction of multipotential cells to participate in the process. Too much inflammation can overwhelm this response to cause scarring. Although stem cells have been extensively studied as therapy for regenerating functional tissues, concerns of ethics, availability, and ease of clinical utility call for investigation into an alternative source of multipotential cells for potential therapeutic use. Here, we describe trauma-derived mesenchymal progenitor cells (MPCs). These cells are morphologically and functionally similar to bone marrow-derived mesenchymal stems cells. MPCs, which are not present in large numbers in untraumatized tissue, but are abundant in injured muscle tissue and after isolation have the potential for clinical application in regenerative medicine. MPCs appear to be activated by injury, enhancing their capability of differentiating into multiple cell lines, generating trophic factors, and producing functional tissue. This cell lineage is now thought to be involved in the pathologic process of heterotopic ossification, whereby inflammation and scarring dominates the local tissue response to injury. The utility of MPCs as a therapeutic arm for regenerative medicine can be further realized when the microenvironment commands that trigger these cells to activate are elucidated. This in turn can create patient-specific resource of nongenetically modified induced multipotent cells for regenerative therapy after orthopaedic injury.