Abstract

P 288

Biofunctionalized silk fibers drive axonal regeneration in retinal ganglion cells.

Corinne Wittmer1, Thomas Claudepierre2, Frank Pfrieger3, Peter Wiedemann2, David Kaplan1, Christophe Egles4
1Tufts University, Department of Biomedical Engineering, Medford, MA, United States; 2Department of Ophthalmology and Eye Hospital, Faculty of Medicine, University of Leipzig, Leipzig, Germany; 3CNRS UPR 3212, Institute of Cellular and Integrative Neurosciences (INCI), Strasbourg, France; 4Division of Cancer Biology and Tissue Engineering, Tufts School of Medicine, Tufts University, Boston, United States

Objective
Traumatic optic neuropathy is a severe complication of a head or face trauma. Impairment or loss of vision due to optic nerve injury occurs in about 10% of patients with cranio-facial fractures and are irreversible in case of axotomy. Glial scar, inflammatory response, cell death are some of the many surrounding factors barring the growth cone to cross the lesion site; in addition to the fact that axotomized retinal ganglion cells (RGCs) are unable to switch to a regenerative state and degenerate. To circumvent this cascade of events, we aim to develop a physical guide that will topically deliver molecules of interest, helping to restore the regenerative state of RGCs and could be use to promote vision recovery after optic nerve lesion.
Methods
We selected silk fibers prepared from silkworm (Bombyx Mori) for their biocompatibility and test, in different culture conditions, regenerative abilities of purified RGCs at the contact of this biomaterial.
Results
In a first step we used our model of pure primary RGCs culture to identify factors that promote axon regeneration in vitro. We analyzed the effect of different growth factors (GF) on survival and neurite elongation of pure retinal ganglion cells (RGCs) preparation from post natal rat retina. Among all factors tested, we demonstrated that brain derived neurotrophic factor (BDNF) promote survival of RGCs whereas cilliary neurotrophic factor (CNTF) act both on survival and axon elongation. We then tested the ability of silk fibers to serve as a support for growth cones and showed that neurites elongate preferentially on silk fibers. Moreover, direction of growth was influenced by the silk network. Silk fibers were then biofunctionalized with GF and orientated in order to obtain a directing path of silk fibers loaded with BDNF and CNTF. In a minimal culture medium we then observed that RGCs exhibit strong survival and axonal growth along silk fibers loaded with CNTF.
Conclusions
Our results demonstrate the properties of silk fibers to serve as a guide and a reservoir for therapeutic molecules that can be released topically at lesion site. CNTF is the most promising factor we tested so far. Development of a 3 dimensional silk guide to study the neuroregenerative properties of CNTF in vivo would be of main interest in the treatment of optic nerve lesions after facial trauma.

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