Athymic rat model for studying acellular human allograft

Advances in tissue engineering of peripheral nerve and tissue innervation - a systematic review

Although various options are available to treat injured organs and peripheral nerves, none is without limitations. Auto- and allografts are the first choice of treatment, but tissue survival or functionality is not guaranteed due to often limited vascular and neural networks. In response, tissue-engineered solutions have been developed, yet clinical translations is rare. In this study, a systematic review was performed on tissue-engineered advancements for peripheral nerves and tissues, to aid future developments in bridging the gap toward the clinic by identifying high-potential solutions and unexplored areas. A systematic search was performed in PubMed, Embase, Web of Science, and Scopus until November 9, 2023. Search terms involved "tissue engineering," "guided," "tissue scaffold," and "tissue graft," together with "innervation" and "reinnervation." Original in vivo or in vitro studies meeting the inclusion criteria (tissue-engineered peripheral nerve/innervation of tissue) and no exclusion criteria (no full text available; written in foreign language; nonoriginal article; tissue-engineering of central nervous system; publication before 2012; insufficient study quality or reproducibility) were assessed. A total of 68 out of 3626 original studies were included. Data extraction was based on disease model, cell origin and host species, biomaterial nature and composition, and external stimuli of biological, chemical or physical origin. Although tissue engineering is still in its infancy, explored innervation strategies of today were highlighted with respect to biomaterials, cell types, and external stimuli. The findings emphasize that natural biomaterials, pre-seeding with autologous cell sources, and solutions for reproductive organs are beneficial for future research. Natural biomaterials possess important cues required for cell-material interaction and closely resemble native tissue in terms of biomechanical, geometrical and chemical composition. Autologous cells induce biomaterial functionalization. As these solutions pose no risk of immunorejection and have demonstrated good outcomes, they are most likely to fulfill the clinical demands.

A Preliminary Assessment of the Utility of Large-Caliber Processed Nerve Allografts for the Repair of Upper Extremity Nerve Injuries

Background: Cabled sensory nerve autografts are the historical gold standard for overcoming gaps in larger diameter nerves as repair utilizing large-diameter autograft risks central graft necrosis. Commercially available processed nerve allograft (PNA) is available in diameters up to 5 mm but represents an acellular 3-dimensional matrix as opposed to viable tissue. The purpose of this study is to specifically evaluate whether similar concerns regarding the use of large-caliber PNA are warranted. Methods: The RANGER Registry is an active database designed to collect injury, repair, safety, and outcomes data for PNAs (Avance® Nerve Graft; AxoGen, Inc, Alachua, Florida) according to an institutional review board-approved protocol. The database was queried for patients presenting with large-caliber nerve allograft repairs in the upper extremity. Identified patients reporting quantitative outcomes with a minimum of 9-month follow-up were included in the data set. Results: The large-caliber PNA subgroup included 13 patients with 15 injuries. The mean ± SD age was 36 ± 22 years. Large-caliber single-stranded repairs included twelve 4- to 5-mm-diameter grafts. Large-caliber cabled repairs included the combined use of 3- to 4-mm and 4- to 5-mm-diameter nerve allografts in 3 repairs. The mean nerve gap was 33 ± 10 mm with a mean follow-up time of 13 months. Available quantitative data reported meaningful recovery of sensory and motor function in 67% and 85% of the repairs, respectively. Conclusion: Although based on a small subset of patients, PNAs of up to 5 mm in diameter appear capable of supporting successful nerve regeneration.

Anatomic variations of brachial and lumbosacral plexus models in different rat strains

PURPOSE

Selection of an appropriate model for preclinical assessment of new methods of peripheral nerve injury management is crucial. This report presents anatomic variations within brachial and lumbosacral plexuses in three selected rat strains Sprague Dawley (Hsd:Sprague Dawley SD), Lewis (LEW/SsNHsd), and Athymic Nude (Hsd:RH-Foxn1^rnu ) rats.

METHODS

Based on their strain eighteen rats were divided into three groups. A total of 90 brachial plexus nerves (axillary, musculocutaneous, median, ulnar, and radial nerves) and 72 lumbosacral plexus nerves (sciatic, tibial, common peroneal, and sural nerves) were analyzed for the length, diameter and correlation with the body weight. A detailed anatomic course of each nerve within the brachial and lumbosacral plexuses was outlined.

RESULTS

The sural nerve was the longest nerve in all studied rat strains, whereas the sciatic nerve had the largest diameter. Comparison of all the nerves' length demonstrated that the Lewis rat sciatic and sural nerves were significantly shorter (P < 0.05). No significant differences in nerve diameters were found among the analyzed rat strain groups. Significant correlation was revealed between the length of sciatic nerve and the rats' weight, which is irrelevant to the rats' genetic background.

CONCLUSIONS

This study confirmed that nerves' length within rat's brachial and lumbosacral plexus depends on the inter-individual variations within the rat strains rather than on the differences in the peripheral nerve development, which is inherent to the specific rat strain. Correlation between the nerve length and body weight, suggests that bigger rats should be considered for studies requiring access to the long nerves. © 2016 Wiley Periodicals, Inc. Microsurgery 37:327-333, 2017.