Abstract
We report on the performance of composite nerve grafts with an inner 3D multichannel porous chitosan core and an outer electrospun polycaprolactone shell. The inner chitosan core provided multiple guidance channels for regrowing axons. To analyze the in vivo properties of the bare chitosan cores, we separately implanted them into an epineural sheath. The effects of both graft types on structural and functional regeneration across a 10 mm rat sciatic nerve gap were compared to autologous nerve transplantation (ANT). The mechanical biomaterial properties and the immunological impact of the grafts were assessed with histological techniques before and after transplantation in vivo. Furthermore during a 13-week examination period functional tests and electrophysiological recordings were performed and supplemented by nerve morphometry. The sheathing of the chitosan core with a polycaprolactone shell induced massive foreign body reaction and impairment of nerve regeneration. Although the isolated novel chitosan core did allow regeneration of axons in a similar size distribution as the ANT, the ANT was superior in terms of functional regeneration. We conclude that an outer polycaprolactone shell should not be used for the purpose of bioartificial nerve grafting, while 3D multichannel porous chitosan cores could be candidate scaffolds for structured nerve grafts.
Highlights
Trauma patients are often affected by injuries to the peripheral nervous system [1]
The analysis of the SEM images of the chitosan cores showed that the average pore size and mean minimum pore size only slightly differ when the cooling rate is varied from B = 1–5 K/min and the temperature gradient from G = 1, 1.5, 2.0 K/mm
The average pore size area of these samples could be estimated with reasonable accuracy up to 2,100 μm2, which corresponds to an equivalent circle diameter of 51 μm
Summary
Trauma patients are often affected by injuries to the peripheral nervous system [1]. The associated sensory and motor defects, as well as neuropathic pain syndromes, can lead to devastating life-long functional disability and socioeconomic burden [2]. As complete functional recovery is seldom achieved and autologous nerve transplantation is accompanied by donor-site morbidity and limited availability, treatment using bioengineered nerve guidance channels (NGCs) is a promising therapeutic alternative [3,4,5]. Scaffolds used for nerve reconstruction have to be biocompatible and biodegradable to allow optimal integration into the nervous tissue. Their mechanical solidity should be tailored to match the regeneration progress [6], which is only possible as soon as the regeneration rates have been evaluated for a specific nerve and graft type. Two cell types have to be supported during peripheral nerve regeneration: neurons
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