Enhanced proliferation of neural stem cells in a collagen hydrogel incorporating engineered epidermal growth factor

Neural stem cells (NSCs) have received much attention in cell-transplantation therapy for central nervous disorders such as Parkinson's disease. However, poor engraftment of transplanted cells limits the efficacy of the treatments. To overcome this problem, collagen-based hydrogels were designed in this study to provide microenvironments for embedded cells to survive and proliferate. Our approach was to incorporate epidermal growth factor (EGF), known as a mitogen for NSCs, into a collagen hydrogel. For the stable binding of EGF with collagen under mild conditions, EGF was fused with a collagen-binding polypeptide domain by recombinant DNA technology. A cell population containing NSCs was derived from the fetal rat brain and cultured in the composite hydrogels for 7 d followed by analysis for cell proliferation. It was shown that the number of living cells was significantly higher in hydrogels incorporating collagen-binding EGF. This effect is largely owing to the collagen-binding domain that serves to sustain presentation of EGF toward cells within the hydrogel. It is further revealed by gene expression analysis that cells proliferated in the EGF-incorporating collagen hydrogel contained subpopulations expressing the marker of stem cells, neurons, astrocytes, or oligodendrocytes.