Design of biomaterials to enhance stem cell survival when transplanted into the damaged central nervous system

Following injury to the central nervous system (CNS) there is a cascade of events that leads to cell death, tissue loss and consequently functional deficit. In response to injury, the CNS stimulates endogenous stem cell populations. However, this host repair mechanism is insufficient to restore function to the damaged tissue. Stem cells can be transplanted into damaged tissues to replace the lost cells. Although stem cell transplantation is promising, this technique is currently suboptimal. Following transplantation, significant death of the transplanted cells impedes the effectiveness of this technique. In an attempt to improve cell transplantation, groups have used scaffolds to deliver cells. In effect, biomaterials are used to create a niche that provides the appropriate microenvironment to promote survival of transplanted cells. As shown in Fig. 1, this niche includes a biomaterial with the appropriate biochemical and mechanical factors for the cells and tissues studied. In this review, we examine the mechanisms that contribute to the death of transplanted cells. We review both the in vitro data, where biomaterial scaffolds are designed to enhance cell survival, and the in vivo data, where scaffolds are shown to improve cell survival following transplantation into the damaged brain and spinal cord.