Detection of host and donor cells in sex-mismatched rat nerve allografts using RT-PCR for a Y chromosome (H-Y) marker

A rat model for long-gap peripheral nerve reconstruction

BACKGROUND

The rat model has had limited utility for the study of long nerve gaps because of the small size of the animal. The authors sought to develop a simple, effective rat model for reconstruction of long nerve gap defects.

METHODS

Fifteen rats had a sciatic nerve transection followed by reconstruction. Positive control rats received a 1-cm isograft. Negative control rats received a 3.5-cm hollow silicone conduit, and experimental rats received a 4-cm isograft; these were implanted in a looped configuration to accommodate the long length. Nerves were harvested at 6 weeks (1-cm grafts) and 12 weeks (3.5-cm conduits and 4-cm grafts) for histologic and histomorphometric evaluation.

RESULTS

The 1-cm and 4-cm isograft groups showed robust regeneration in the distal nerve segment. The 3.5-cm hollow conduits showed absolutely no initiation of nerve regeneration. Histomorphometric values were as expected for the specified gap length.

CONCLUSIONS

This study describes a simple and effective long nerve gap rat model for experiments on nerve grafts and nerve conduits. The long nerve graft model can be useful for studying techniques such as processed nerve grafts, which are currently a topic of frequent investigation. The 3.5-cm hollow conduit "no-regrowth" long-gap model is ideal for investigating conduit-based tissue-engineering solutions for long-gap nerve repair. The authors' approach overcomes the size limitation of the small animal while exploiting the features that make the rat the model of choice for preliminary nerve studies.

Successful storage of peripheral nerves using University of Wisconsin solution with polyphenol

We have previously reported that green tea polyphenol can preserve peripheral nerve segments for up to 1 month. In this study, we investigated the effect on peripheral nerve preservation of adding polyphenol to the conventional University of Wisconsin solution (UW solution), which has been widely used for organ storage. Twenty millimeter-long sciatic nerve segments, harvested from Lewis rats, were immersed in UW solution containing polyphenol (1 mg/mL) for 1 week and then in UW solution alone at 4 degrees C for 3 additional weeks before transplantation into recipient Lewis rats. Neural cell viability of the preserved nerve segments was confirmed by vital staining (calcein-AM/ethidium homodimer), electron microscopy, and genomic studies. Morphologically, nerve regeneration was similar to that of fresh isografts and superior to that of grafts stored with UW solution alone. Moreover, the electrophysiological results were equal to those of fresh isografts. Polyphenol has the potential to be used for peripheral nerve storage and could be useful for routine peripheral nerve banking.

Migration of cells into and out of peripheral nerve isografts in the peripheral and central nervous systems of the adult mouse

Peripheral nerve (PN) isografts provide a favourable environment for axon regeneration after peripheral and central nervous system (CNS) injury, but definitive information on the extent of cellular intermixing between donor and host tissues is lacking. We wished to compare migration patterns in fresh and predegenerate PN grafts, and also compare the extent of cell migration after transplantation to peripheral nervous system (PNS) versus CNS. To discern how host and donor cells interact after PN transplantation, sciatic nerve segments were transplanted from inbred adult mice into PN defects (PN-PN grafts) or into lesioned cerebral cortex of opposite gender siblings. Migrating male cells were identified using a Y-chromosome-specific probe and in situ hybridization methods, and characterized immunohistochemically. The extent of donor and host cellular intermixing was similar in fresh and predegenerate PN-PN isografts. There was substantial intermixing of donor and host cells by 8 days. Many host cells migrating into epineurial regions of grafts were immunopositive for F4/80 (macrophages). The endoneurium of grafted PN was also colonized by host cells; some were F4/80+ but many were immunostained with S-100 (Schwann cell marker). Donor S-100+ Schwann cells rapidly migrated out into proximal and distal host PN and by 12 weeks were found at least 2 mm from the grafts. Endoneurial microvessels in grafts were mostly donor-derived. By comparison, in male PN grafts to female CNS, even after 6 weeks few donor cells had migrated out into surrounding host cortex, despite the observation that almost all grafts contained regenerating axons and were thus attached to host CNS tissue.