Vascular endothelial growth factor and its receptors are expressed in human nerve grafts.

Vascularization and angiogenicity of human nonvascularized nerve grafts in the second stage of facial reanimation were studied. Immunohistochemistry for endothelial markers (CD-31) and vascular endothelial growth factor (VEGF) and its receptors Flt-1 and Flk-1 was performed on distal end biopsies from 35 cross-facial nerve grafts. In grafted nonvascularized nerve, density of vascular structures (also clearly immunopositive for VEGF and both receptors) showed a mean of 166 vessels (range 78 to 267) per unit area, corresponding to control values. In addition, VEGF was expressed in axons and perineural structures. In control samples, VEGF expression was low and occurred in the myelin sheath. In nerve grafts, expression of Flt-1 and Flk-1 (less intense) was seen in axons and perineural structures. A higher density of vessels was associated with lower VEGF expression (not significant). In short, expression of VEGF and its receptors is described in human nerve grafts and compared with basic histology and p75 nerve growth factor receptor expression of the nerve graft and functional outcome of patients.

P75 nerve growth factor receptor is expressed in regenerating human nerve grafts.

BACKGROUND: The purpose of this study was to elucidate the expression of p75 nerve growth factor receptor (p75NGFR) in human cross-facial nerve grafts and to compare the immunohistological findings with patient data and the functional outcome in facial reanimation. MATERIALS AND METHODS: The study comprised 37 sural nerve graft specimens. All of the patients had long-lasting complete facial paralysis and were operated on by the standard two-stage procedure involving cross-facial nerve grafts and microneurovascular muscle transfer. Nerve biopsies were taken 4 to 20 months (mean, 8 months) after the cross-facial nerve grafting. Immunohistochemistry for p75NGFR as well as for Schwann cells (S-100; Dako, Glostrup, Denmark) and for Neurofilament-200 (NF-200; Boehringer, Mannheim, Germany) was performed. RESULTS: In graft biopsies, the mean number of NF-200-positive axons amounted to 38% (range, 6-81%) of that in control samples. Further, regenerated axons were thinner than in control samples. Morphologically, the grafted nerves were characterized by fibrosis and invasion of inflammatory cells. A longer time between cross-facial nerve grafting and biopsy sampling correlated with a higher number of viable axons (NF-200) (P = 0.002). In all cases, expression of p75NGF receptor was clearly higher at the distal end of the grafted nerve. Expression of p75NGFR was lower in older than in younger patients (P = 0.003). A high expression of p75NGFR was often seen with better function of the transplanted muscle. CONCLUSION: Increased expression of p75NGFR in human nerve grafts was noted, especially in younger patients. We suggest that p75NGFR expression might be a contributing factor in a successful axonal regeneration and eventual recovery of muscle function.

Long-term adaptation of human microneurovascular muscle flaps to the paralyzed face: an immunohistochemical study.

The purpose of this study was to characterize microneurovascular (MNV) muscle transplants immunohistochemically up to 10 years after transfer. Histological data was related to long-term functional outcome. The study comprised 17 patients with a mean age of 41 years suffering from complete unilateral long-lasting facial paralysis. A two-stage procedure was performed between 1986 and 2001. The gracilis, latissimus dorsi, and serratus muscles were used in four, eight, and five patients, respectively. Eighteen biopsy samples were taken from MNV muscle grafts during secondary refinement procedures. In one patient, the tissue samples were collected at two different time points. Immunohistochemistry testing revealed muscle fiber type distribution (anti-myosin fast), proliferating satellite cells (Ki-67), and reinnervation (S-100). Muscle atrophy was assessed histomorphometrically. In a recent study, patient characteristics and the function of the flap were evaluated. Histological data were compared with clinical data and long-term functional outcomes of the patients. In biopsy samples taken 1-10 (mean 31 months) years after MNV muscle transfer, the mean muscle fiber diameter was 38 (range 14-70) microm, indicating a 40% decrease compared with control values. Muscle atrophy was not type-specific and the mean percentage of type II fibers was not altered. Individual variation was, however, considerable. Proliferative activity of satellite cells was seen in 60% of the samples but it tended to decline with an increase in follow-up time. All samples showed intramuscular reinnervation. In statistical analysis severe atrophy correlated with prolonged intraoperative ischemia (P=0.04). The good long-term functional outcome correlated with dominance of fast fibers in muscle grafts (P=0.03). Atrophy tended to be more pronounced in the serratus than in the other muscles (ns). In summary, despite dense muscle reinnervation, morphology of the muscle is not fully restored after muscle transfer. Ischemia time affects muscle morphology. Adaptation of the graft to fast-twitch muscle activity favors better mimic function. The proliferative activity of satellite cells declines with prolonged follow-up time.

Long-term morphometric and immunohistochemical findings in human free microvascular muscle flaps.

Reinnervation, muscle regeneration, density of microvessels, and muscle-type specific atrophy were studied 3-4 years after surgery in surgically nonreinnervated free microvascular muscle flaps to 13 patients transplanted to the upper or lower extremities. Routine histology and immunohistochemistry for PGP 9.5 and S-100 (neuronal markers), Ki-67 (cell proliferation), myosin (muscle fiber types), and CD-31 (endothelium) were carried out, and results were analyzed morphometrically. Three to 4 years after surgery, severe atrophy of predominantly slow-type fibers was seen in 9 cases. In 4 cases, muscle-fiber diameter and fiber-type distribution were close to normal. Long intraoperative muscle ischemia and postoperative immobilization were associated with poor muscle bulk in flaps. The density of microvessels in flaps did not differ from control muscles. PGP 9.5 and S-100 immunopositive nerve fibers were detected in 7 patients. Reinnervation was associated with good muscle bulk. In 4 patients, activation of satellite cells was evident. The results suggest that in some cases, spontaneous reinnervation may occur in free muscle flaps, and that several years after microvascular free flap transfer, the muscle still attempts to regenerate.