Current and future applications for stem cell therapies in spine surgery

Spinal surgery involves the bone-cartilage-neural interface. It is a field of surgery that is rapidly changing and evolving; not only through the development of novel techniques, approaches and devices but also through evidence from large clinical trials assessing indications, efficacy and outcomes. The use of biologics in spine surgery has now become widespread. Biologics in the form of autologous or allogeneic stem cells or progenitor cells are not yet in routine clinical use in spine surgery. However it is likely that they will have a significant role in the future, since increasing numbers of preclinical and clinical studies have demonstrated the safety and efficacy of progenitor cells to treat a variety of spinal conditions. Such studies have paved the way to larger clinical trials. Cell therapies encompass a wide range of stem cell and progenitor cell types. Stem cells subtypes differ in their lineage potential often being described as pluripotent or multipotent, some of which have potential application in therapies to treat diseases of the spine having the ability to differentiate into tissues including bone and cartilage and to secrete factors that promote matrix repair and regeneration. Furthermore, studies have shown that some cells, particularly mesenchymal stromal cells, modulate oxidative stress and secrete cytokines and growth factors that have immunomodulatory, antiinflammatory, angiogenic and antiapoptotic effects. It is these combined characteristics that make cell based therapies prime candidates for advancing current techniques in spine surgery and for providing new strategies directed at targeting the underlying causes of spinal diseases and disorders to promote repair and regeneration. This review will explore the characteristics of various stem cells and other progenitor cells derived from different sources. The authors are not suggesting that all these cells are necessarily suitable clinically. The review will thus focus on their application to both current and potentially future areas of spine surgery based on results of the available evidence and clinical trials. This review will not address spinal cord injury.