Role of a muscle target organ on the regeneration of motor nerve fibres in long nerve grafts: A synopsis of experimental and clinical data

Abstract

The importance of the muscle target organ as a promoting factor for nerve fibre regeneration in nerve grafts is still a subject of controversial discussion. In the last few years we published uniform results of experimental series in sheep and rabbits in which we investigated the biology of nerve fibre regeneration in long nerve autografts without connection to a target organ. Surprisingly, we found excellent regeneration of myelinated nerve fibres without the influence of a target organ through the whole length of the nerve graft, with an increase in the number of nerve fibres up to fourfold at the distal end. In the sheep series the additional contact with a muscle target organ for 6 months had a variable effect on the fibre population in the distal end of the nerve graft. The results of our planimetric analyses of nerve biopsies in patients with facial paralysis, who were treated by cross-face nerve grafting and free muscle transplantation, are extremely divergent from the results of our experimental series. Instead of an increase, we found a decrease in number of regenerating nerve fibres arriving at the distal end of the cross-face nerve graft down to 20%. Species-specific differences in the biology of nerve regeneration are discussed, together with their implications for the complex clinical situation of nerve grafting with or without the influence of a target organ.

Creation of an Ideal Microenvironment by Reverse Endto-side Coaptation for the Evaluation of Tissue Neurotropism: An Experimental Model

“…In particular, tissue specificity was usually investigated by the Y-chamber experimental model. 7,10,11,14,[20][21][22][23][24] It may be concluded that tropic factors that exert chemiotactic influence on regenerating axons originate from the target tissue (the nervous tissue) and are not modified by blood circulation. It is still unclear whether vascularization of the distal nervous end-organ and/or its connection to the periphery (intact nerve vs nerve graft) influences the maturation of nerve regeneration or not.…”

Augmentation of partially regenerated nerves by end-to-side side-to-side grafting neurotization: experience based on eight late obstetric brachial plexus cases

“…An interesting speculation is the role of the muscle target organ as a promoting factor for nerve fibre regeneration in nerve grafts, whether higher grade muscles are expected to promote axonal growth more than lower grade muscles. This was studied in rabbits, sheep and humans [49]. Excellent regeneration of myelinated nerve fibres was observed without target organ influence through the whole length of the nerve graft, with an increase in the number of nerve fibres up to fourfold at the distal end.…”

Outcomes of Facial Nerve Grafting in 155 Cases

“…Although nerves that are similar to facial nerve in diameter are selected, there are certain inevitable differences between sensory and motor nerves. Sensory nerves contain greater number of fibers than motor nerves; on the other hand, these fibers are lesser in diameter (16). Regeneration through such a graft was shown to create a different neural architecture than the original nerve: many of the regenerated fibers became unmyelinated, and small amount of myelinated fibers were found to be smaller in size than the original (17).…”