Combination of engineered neural cell adhesion molecules and GDF-5 for improved neurite extension in nerve guide concepts

Current therapeutical approaches for the treatment of severe lesions in the peripheral nervous system rely on the use of autologous tissue or the body's own Schwann cells. However, these approaches are limited and alternative strategies for peripheral nerve regeneration are required. Here we evaluate combinations of a variety of neuronal regeneration factors including engineered cell adhesion molecules and growth factors in embryonic model neurons to test the possible improvement of artificial nerve guides by cooperative mechanisms. Cell adhesion molecules L1 and neurofascin synergistically promote neurite elongation. The outgrowth promoting properties of both proteins can be combined and further increased within one chimeric protein. Addition of growth and differentiation factor 5 (GDF-5) further enhances neurite outgrowth in a substrate-independent manner. This effect is not due to a protective mode of action of GDF-5 against pro-apoptotic stimuli. Consequently, the study supports the idea that different modes of action of pro-regenerative factors may contribute synergistically to neurite outgrowth and emphasizes the applicability of combinations of proteins specifically involved in development of the nervous system for therapeutical approaches.