Two-Chambered Chitosan Nerve Guides With Increased Bendability Support Recovery of Skilled Forelimb Reaching Similar to Autologous Nerve Grafts in the Rat 10 mm Median Nerve Injury and Repair Model

Abstract

Tension-free surgical reconstruction of transected digital nerves in humans is regularly performed using autologous nerve grafts (ANGs) or bioartificial nerve grafts. Nerve grafts with increased bendability are needed to protect regenerating nerves in highly mobile extremity parts. We have recently demonstrated increased bendability and regeneration supporting properties of chitosan nerve guides with a corrugated outer wall (corrCNGs) in the common rat sciatic nerve model (model of low mobility). Here, we further modified the hollow corrCNGs into two-chambered nerve guides by inserting a perforated longitudinal chitosan-film (corrCNG[F]s) and comprehensively monitored functional recovery in the advanced rat median nerve model. In 16 adult female Lewis rats, we bilaterally reconstructed 10 mm median nerve gaps with either ANGs, standard chitosan nerve guides (CNGs), CNGs (CNG[F]s), or corrCNG[F]s ( n = 8, per group). Over 16 weeks, functional recovery of each forelimb was separately surveyed using the grasping test (reflex-based motor task), the staircase test (skilled forelimb reaching task), and non-invasive electrophysiological recordings from the thenar muscles. Finally, regenerated tissue harvested from the distal part of the nerve grafts was paraffin-embedded and cross-sections were analyzed regarding the number of Neurofilament 200-immunopositive axons and the area of newly formed blood vessels. Nerve tissue harvested distal to the grafts was epon-embedded and semi-thin cross-sections underwent morphometrical analyses (e.g., number of myelinated axons, axon and fiber diameters, and myelin thicknesses). Functional recovery was fastest and most complete in the ANG group (100% recovery rate regarding all parameters), but corrCNG[F]s accelerated the recovery of all functions evaluated in comparison to the other nerve guides investigated. Furthermore, corrCNG[F]s supported recovery of reflex-based grasping (87.5%) and skilled forelimb reaching (100%) to eventually significantly higher rates than the other nerve guides (grasping test: CNGs: 75%, CNG[F]s: 62.5%; staircase test: CNGs: 66.7%, CNG[F]s: 83.3%). Histological and nerve morphometrical evaluations, in accordance to the functional results, demonstrated best outcome in the ANG group and highest myelin thicknesses in the corrCNG[F] group compared to the CNG and CNG[F] groups. We thus clearly demonstrate that corrCNG[F]s represent promising innovative nerve grafts for nerve repair in mobile body parts such as digits.

In Vivo and In Vitro Evaluation of a Novel Hyaluronic Acid–Laminin Hydrogel as Luminal Filler and Carrier System for Genetically Engineered Schwann Cells in Critical Gap Length Tubular Peripheral Nerve Graft in Rats

“…When comparing the performance among the CNG groups investigated, two-chambered CNG[F]s generally performed better than hollow CNGs. This underlines our previous findings that CFs effectively guide axonal regrowth, thereby accelerating and improving functional recovery 21 , 22 , 44 . While for the TA muscle, the highest recovery rate was detected in the CNG[F]+HAL group (in 87.5% of the animals), the highest recovery rate for the PL muscle was detected in the CNG[F]+HA group and ranged only at 40% (two of five animals).…”

New basic insights on the potential of a chitosan‐based medical device for improving functional recovery after radical prostatectomy

“…As no standardised pre‐clinical models exist for evaluating the effect of biomaterials to be applied after RP in men, we selected the rat median nerve model as an alternative. The rat median nerve model is a well‐established and valuable model to elucidate effects of an implanted biomaterial on the regeneration of axotomised neurones towards re‐innervation of peripheral target tissue .…”

Appropriate Animal Models for Translational Nerve Research

“…Furthermore, peripheral nerve lesions to the upper limb show a higher prevalence than those to the lower limb in the clinic (Kouyoumdjian et al 2017). Therefore, the rat median nerve injury and repair model is considered to be appropriate for extrapolation toward human upper limb or digital nerve injuries (Jager et al 2014;Muratori et al 2018;Ronchi et al 2018;Dietzmeyer et al 2019). With regard to ethical concerns, this model also represents with the advantage that lesion only partially impairs the upper limb function, because sensitivity and specific motor functions are preserved through innervation by the ulnar and the radial nerve (Bertelli et al 1995;Sinis et al 2006;Jager et al 2014).…”

“…Therefore, studies addressing the question of how to improve peripheral nerve regeneration in the elderly will currently not focus primarily on tissue engineering of nerve grafts but other approaches. For analyzing functional recovery, however, it may be an issue to make sure that performing complex tasks will crucially depend on the animals' learning willingness and ability, and also the completeness of the learning process (Stossel et al 2017;Casal et al 2018;Dietzmeyer et al 2019) prior to starting the experiment should be reflected.…”