Pattern Of Reinnervation Research Articles

Free sensate secondary skin flaps: an experimental study on patterns of reinnervation and neovascularisation

The main purposes of the present study were: 1) to compare differences, if any, in the patterns of reinnervation between secondary skin flaps, created either from “innervated skin grafts” or from ordinary denervated skin grafts; 2) to examine the influence of time, and the possible roles of granulation tissue and fibrosis in reinnervation following implantation of a nerve trunk into a secondary skin flap at different stages; and 3) to compare neovascularisation before and after free transfer of these flaps. Neurovascular changes were studied in a rat model by microangiography and by immunohistochemical techniques, using antisera to protein gene product 9.5 (panneural marker), to calcitonin gene-related peptide (sensory neurones) and to von Willebrand Factor (endothelial cell marker). The results indicate a potential clinical role for secondary sensate skin flaps where conventional methods of reconstruction including free neurovascular flap transfers are not available.

NGF can induce a 'young' pattern of reinnervation in transplanted cerebral blood vessels from ageing rats.

Peripheral target tissues can determine age-related changes in their density and pattern of innervation. We have shown previously that middle cerebral arteries from young and old rats transplanted in oculo in young hosts become reinnervated with a density and pattern of innervation that is typical of the age of the donor, i.e., the density of reinnervation on old transplants is 50% lower than on young transplants. The alterations in the target tissues responsible for their decreased innervation in old age are still unknown. We have investigated the possibility that increasing the availability of nerve growth factor (NGF) might restore the pattern and density of perivascular nerves on old blood vessels to levels of innervation typical of young tissues. Old middle cerebral transplants were therefore treated with NGF or vehicle by three weekly transscleral injections. NGF treatment markedly increased the reinnervation of old transplants, restoring the density and pattern of innervation to one characteristic of young animals. NGF produced an equivalent increase in nerve growth on young and old transplants, thus confirming that the receptivity of old blood vessels to reinnervation is not impaired. Control experiments were performed by treating transplants with saline, bovine serum albumin, or cytochrome c. Unexpectedly, bovine serum albumin was shown to promote axonal growth, although to a lesser extent and with a different pattern than NGF.

Axonal Regeneration from Transplanted Sympathetic Ganglia Is Not Impaired by Age

Changes occur with age in several areas of the nervous system, including autonomic ganglia and the target tissues of some sympathetic neurons where signs of neuronal degeneration have been shown in old age. In this study, we have employed an intraocular grafting technique to examine whether age changes occur in sympathetic neurons of the superior cervical (SCG) and stellate ganglia that might explain the reduced innervation of some of their target tissues in old age. Ganglia taken from young and old rats were implanted in oculo for 4 or 6 weeks in young hosts whose irises had been previously sympathetically denervated. The extent, pattern, and time course of reinnervation of the host iris was studied by catecholamine histochemistry followed by image analysis. We did not observe any difference in the pattern and time course of reinnervation between ganglia taken from young and old donors. If anything, the extent of reinnervation was greater in irises implanted with SCG taken from 25-month-old animals. Moreover, we did not observe any difference in ability to reinnervate the host iris between ganglia that normally project to the iris (SCG) and ganglia that normally do not project to the iris (stellate), regardless of the age of the donor animal. Our results suggest that sympathetic neurons from aged rats have unimpaired capability of regeneration and retain plasticity, as shown by their ability to reinnervate an inappropriate target. We hypothesize that the decreased innervation observed in some sympathetic targets in old age might be caused by changes in the target tissues themselves rather than being the result of degenerative changes in the neurons.

REINNERVATION OF TRANSPLANTED PANCREATIC ISLETS

Islets transplanted beneath the kidney capsule become reinnervated during the first 3-4 months after implantation by both afferent and efferent nerve fibers. To evaluate the importance of the implantation organ for this process, the present study compared both the degree and the types of nerve fibers reinnervating islets transplanted into the liver, kidney, and spleen. For this purpose, 150 syngeneic islets were grafted under the kidney capsule of C57BL/6 mice. In addition, the same animals were injected with 150 islets into the spleen or liver. All animals were killed 14 weeks after transplantation, after which the graft-bearing organs were processed for indirect immunofluorescence for neuropeptides and tyrosine hydroxylase (TH), and with acetyl cholinesterase (AchE) staining to visualize nerve fibers. Both afferent (containing substance P and/or calcitonin gene-related peptide) and parasympathetic (containing vasoactive intestinal peptide or AchE) nerve fibers were absent from islets implanted into the spleen; an occasional CGRP fiber was seen in islets implanted into the liver; and all these fibers were regularly seen in islets implanted beneath the renal capsule. The islets implanted into the liver or spleen contained a dense network of sympathetic (containing neuropeptide Y and TH) nerve fibers that was often more dense than in the islet grafts under the kidney capsule. One-fifth of islets implanted into the liver were, however, completely devoid of demonstrable nerve fibers. In conclusion, there are marked differences with regard to the pattern of reinnervation of islets transplanted to different implantation sites.

NGF can reverse age-changes in the pattern and density of reinnervation of transplanted cerebral blood vessels from ageing rats

NGF can reverse age-changes in the pattern and density of reinnervation of transplanted cerebral blood vessels from ageing rats

Misdirected regeneration of injured recurrent laryngeal nerve in the cat

Introduction: Misdirected regeneration (MR) frequently occurs following injury to the recurrent laryngeal nerve (RLN) resulting in neurotmesis or axonotmesis. Physiological and anatomic parameters involved in the functional recovery of the larynx following freezing injury or neurorrhaphy of the RLN were studied. A multi-facilitated approach is undertaken to clarify the functional abnormalities caused by the MR after recurrent laryngeal nerve injury. Materials and Methods: Three groups of adult cats were studied. These included controls, cats with recurrent laryngeal neurorrhaphy, and cats with recurrent laryngeal nerve freeze injuries. From 2 weeks to 9 months after the nerve injury, the animals were studied endoscopically and with electromyography (EMG). Using the same animal, the number and location of motoneurons supplying the ipsilateral posterior cricoarytenoid (PCA) muscle were examined with horseradish peroxidase (HRP). Animals were subsequently sacrificed to study the pattern of reinnervation. Results: Following neurorrhaphy all cats had vocal cord paralysis. After neurorrhaphy, effective motion function did not return in the affected vocal cord and it remained fixed in the paramedian position. Although EMG of the laryngeal muscles of the affected side showed interference voltage, the pattern of activities was markedly different from that of the unaffected side, and reciprocity among the laryngeal muscles was not restored. The number of PCA motoneurons recovered to the normal range, but a considerable number of neuronal bodies were dispersed outside the normal PCA area. This indicates misdirected reinnervation to the PCA muscle by motoneurons that originally served other laryngeal muscles. In the freezing injury, effective vocal cord movement finally recovered after 6 months. At this time, EMG showed a normal pattern, although a relatively small amount of misdirected neurons was observed. Discussion: Functional recovery of vocal cord motion does not occur following neurorrhaphy. Prominently disorganized arrangement of laryngeal motor neurons was observed in the horseradish peroxidase study. This suggests that inappropriate reinnervation develops in spite of reapproximation and suturing. Altered central organization of the motor nucleus is a significant pathogenic factor in the loss of laryngeal muscular coordination following recurrent laryngeal nerve lesions. The degree of recovery is related to the mechanism of injury.

Influence of target tissues on their innervation in old age: a transplantation study.

Age-related changes in the nervous system might be intrinsic to the neurons or secondary to changes in the target tissues they supply. We have investigated this question by transplanting old and young vascular muscle into contact with young host nerves in oculo and observing the reinnervating nerve fibres. The density and pattern of reinnervation were those typical of the age of the target tissue, thus old transplants imposed an 'old' pattern of reinnervation on young host nerves. Our findings strongly support the hypothesis that target tissues determine the pattern and density of their innervation in old age.

Restoration of ascending noradrenergic projections by residual locus coeruleus neurons: compensatory response to neurotoxin-induced cell death in the adult rat brain.

There is clinical and experimental evidence that monoamine neurons respond to lesions with a wide range of compensatory adaptations aimed at preserving their functional integrity. Neurotoxin-induced lesions are followed by increased synthesis and release of transmitter from residual monoamine fibers and by axonal sprouting. However, the fate of lesioned neurons after long survival periods remains largely unknown. Whether regenerative sprouting may contribute significantly to recovery of function following lesions which induce cell loss has been questioned. We have previously analyzed the response of locus coeruleus (LC) neurons to systemic administration of the noradrenergic (NE) neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4) to adult rats. This drug causes ablation of nearly all LC axon terminals within 2 weeks after administration, followed by a profound loss of LC cell bodies 6 months later. The present study was conducted to determine the fate of surviving LC neurons and to characterize their potential for regenerative sprouting during a 16 month period after DSP-4 treatment. The time-course and extent of LC neuron degeneration were analyzed quantitatively in Nissl-stained sections, and the regenerative response of residual neurons was characterized by dopamine-beta-hydroxylase immunohistochemistry. The results document that LC neurons degenerate gradually after DSP-4 treatment, cell loss reaching on average 57% after 1 year. LC neurons which survive the lesion exhibit a vigorous regenerative response, even in those animals in which cell loss exceeds 60-70%. This regenerative process leads progressively to restoration of the NE innervation pattern in the forebrain, with some regions becoming markedly hyperinnervated. In stark contrast to the forebrain, very little reinnervation takes place in the brainstem, cerebellum and spinal cord. These findings suggest that regenerative sprouting of residual neurons is an important compensatory mechanism by which the LC may regain much of its functional integrity in the presence of extensive cell loss. Furthermore, regeneration of LC axons after DSP-4 treatment is region-specific, suggesting that the pattern of reinnervation is controlled by target areas. Elucidation of the factors underlying recovery of LC neurons after DSP-4 treatment may provide insights into the compensatory mechanisms of central neurons after injury and in disease states.

Effects of delayed transplantation of cultured Schwann cells on axonal regeneration from central nervous system cholinergic neurons.

The introduction of transplants consisting of cultured Schwann cells and their associated extracellular matrix (Sc/ECM) into a central nervous system (CNS) lesion cavity facilitates axonal regeneration from injured, adult mammalian neurons with subsequent reinnervation of their appropriate target (Kromer and Cornbrooks: Proceedings of the National Academy of Sciences of the United States of America 82:6330-6334, 1985). In the present study, the effects of a delayed transplantation procedure on the time course of this regenerative response were evaluated. For these experiments, bilateral CNS lesions were created between the septum and hippocampus by removing the fimbria-fornix pathway. Lesion cavities received either no transplants, transplants of collagen, or Sc/ECM transplants at the time the lesion was created or 6 days later. When no transplants or transplants of collagen were used, axonal sprouts extended for very short distances into the lesion cavity. These axons were not preferentially associated with the collagen transplants nor maintained at long post-lesion survival times. In animals that received Sc/ECM transplants, the number of sprouting axons and the progression of axonal growth along the transplants was much more extensive than for the collagen transplants. Although more axons were detected in cavities that received transplants immediately after the fimbria-fornix lesion, axonal regeneration along the transplants was similar regardless of whether there was a delay in transplanting the Schwann cells. By using histochemical techniques to identify acetylcholinesterase (AChE), regenerating AChE-positive axons were first detected in the cavity at 3 days post-transplantation, were associated with the Sc/ECM transplants by 5 days, and crossed the cavity within 8 days post-transplantation. Regenerating, neurofilament-positive axons crossed the CNS-Sc/ECM transplant interfaces in association with laminin-positive, glial fibrillary acidic protein-positive cellular pathways. Upon reaching the caudal end of the Sc/ECM transplant, the cholinergic axons abandoned the transplant and oriented directly toward the adjacent hippocampus. Both the simultaneous and delayed transplantation paradigms demonstrated a similar reinnervation pattern of AChE-positive fibers in the hippocampus, but there was a more rapid penetration and more extensive arborization of fibers in animals receiving the delayed transplants. Cholinergic fibers initially invaded the dentate gyrus molecular layer and hilus between 8 and 14 days post-transplantation. By 45 days post-transplantation, AChE-positive axons were detected throughout the dentate gyrus and regio inferior, but few fibers were present in regio superior of the hippocampus.(ABSTRACT TRUNCATED AT 400 WORDS)

Patterns of reinnervation of denervated cerebral arteries by sympathetic nerve fibers after unilateral ganglionectomy in rats

In order to clarify the manner in which previously denervated cerebral arteries become reinnervated after unilateral excision of the superior cervical ganglion (SCG), we observed directly the reinnervating sympathetic nerve fibers originating in the contralateral SCG by using anterograde labeling with wheat germ aggulutinin-horseradish peroxidase in rats. The nerve fibers sprouted from the nerve fibers in the contralateral anterior cerebral artery and reinnervated the arterial wall of the anterior cerebral artery of the denervated side as early as one week after ganglionectomy. In addition to this sprouting route, three other reinnervating nerve fiber routes were observed in the circle of Willis of the denervated side two weeks after ganglionectomy: the proximal portion of the internal carotid artery, the route passing between bilateral ethmodial arteries, and the posterior communicating artery. Eight weeks after ganglionectomy, these reinnervating nerve fibers formed a fairly dense plexus in a circular pattern in the circle of Willis. However, the reinnervation could not be observed in the arterial branches derived from the circle of Willis (middle cerebral artery and posterior cerebral artery) even 16 weeks after ganglionectomy. The present results clearly demonstrated the time course, distribution pattern and limitation of the reinnervation from the contralateral SCG following unilateral ganglionectomy. The fact that reinnervation could be observed only in the main cerebral arteries of the circle of Willis, in which the nerve plexus appeared to have a circular pattern, suggests a difference between the qualities of sympathetic innervation controlling the cerebral circulation in these arteries and the other arterial branches related to these differences in reinnervation capacity.

Functional role of renal afferents.

Functional role of renal afferents.

Morphological, neurochemical, and behavioral studies on serotonergic denervation and graft-induced reinnervation of the rat hippocampus

A procedure was developed to conduct simultaneously immunocytochemical and neurochemical studies on the serotonergic system in adjacent 300-μm-thick slices of rat hippocampus. This procedure was applied to correlate morphological (innervation pattern and density), neurochemical (5-hydroxytryptamine and 5-hydroxyindolacetic acid levels and [ 3H]5-hydroxytryptamine uptake and release) and behavioral (spatial learning) effects of neurotoxin-induced denervation and reinnervation by grafting fetal mesencephalic raphe cells. Intracerebroventricular injections of a low dose of 5,7-dihydroxytryptamine caused a discrete serotonergic denervation of the hippocampus. Eleven months after lesioning, 5-hydroxytryptamine and 5-hydroxyindolacetic acid levels and [ 3H]5-hydroxytryptamine uptake capacity were decreased by 50–60%. By this time, the residual fibers displayed an enhanced vulnerability towards K +-induced depolarization. Grafting of a fetal raphe cell suspension resulted in a reinnervation of the host hippocampus. The pattern of reinnervation was comparable to control innervation and the density was supranormal at the level of the graft. As observed semiquantitatively, the innervation density decreased with distance from the core of the graft. Neurochemical studies showed that the fibers were capable of synthesizing, metabolizing and releasing 5-hydroxytryptamine. The turnover of 5-hydroxytryptamine in both the denervated and the reinnervated hippocampus was comparable to that in control tissue. Previous behavioral testing of the denervated and of the denervated and implanted animals did not reveal any effect on spatial learning, either in an individual or in a social test paradigm. The latter data substantiate the notion that interference with the hippocampal serotonergic innervation does not hamper adequate spatial learning.

Noradrenergic reinnervation of the rat spleen following chemical sympathectomy with 6-hydroxydopamine: Pattern and time course of reinnervation

The time course and pattern of reinnervation of noradrenergic (NA) sympathetic nerve fibers into the spleen following acute chemical sympathectomy with the catecholamine neurotoxin 6-hydroxydopamine (6-OHDA) was examined in young adult male Fischer 344 rats using glyoxylic acid fluorescence histochemistry and neurochemical measurement of NE. Reinnervation proceeds initially along the splenic artery as it enters the hilus (1–5 days), extends into the hilar region (5–10 days), and later proceeds into the regions distal to the hilus (21–56 days), suggestive of orderly growth from the hilar region to distal regions. In all 6-OHDA-treated spleens, the compartmentation of NA innervation was similar to that observed in saline-injected controls, but the density of NA nerve fibers in these compartments differed according to the distance from the hilus. By 56 days postlesion, regions distal to the hilar blood vessels contained fewer NA profiles than their age-matched controls, suggesting that the anatomical process of reinnervation does not restore the density of fibers in a fashion identical to that of nondenervated controls. In contrast, splenic NE concentration at 56 days postdenervation did not differ from the concentration seen in nondenervated control spleens. We suggest that functional restoration of splenic innervation may involve metabolic and receptor compensation for the lack of complete fiber regrowth into regions of white pulp distal from the hilus.

Accurate reconstruction of three complementary laminar afferents to the adult hippocampus by embryonic neural grafts

The hippocampus receives a complex pattern of afferent nerve fibres, segregated in such a way that the different types of afferent axons terminate in strictly demarcated, contiguous, but non-overlapping territories at different proximo-distal levels on the dendrites. In this paper we have used a mouse allelic marking system to show that the dentate, hippocampal, and entorhinal afferents can all be restored correctly and specifically to their proper terminal territories by axonal projections formed by embryonic transplants placed in direct contact with the appropriate denervated terminal territories in adult host brains, and that incorrect connections are not formed. We conclude that the signals for correct reinnervation are present (or inducible by deafferentation) in the adult hippocampus. The embryo-to-adult transplantation experiments show that neither the temporal nor the spatial aspects of cell-to-cell confrontation which occur in normal development are necessary for the formation of specific laminar patterns of reinnervation in the adult.

Septal transplants ameliorate spatial deficits and restore cholinergic functions in rats with a damaged septo-hippocampal connection

Behavioral effects of septal lesion and fornix-fimbria transection were compared in absence and presence of a septal transplant in the hippocampus. The transplant grew in the hippocampus and projected acetylcholinesterase (AChE)-containing fibers throughout the extent of the denervated hippocampus. There were no differences in graft size or AChE reinnervation pattern after septal lesion or fornix transection. An increase in the density of M1 binding sites seen in hippocampal CA3 region after a cholinergic lesion, was restored back to normal after reinnervation of the hippocampus by the graft. Fornix-transected rats were more impaired in water maze acquisition than septal-lesioned rats which were impaired compared to controls. Septal-grafted rats were not different from lesioned rats in the behavioral tasks. However, an injection of physostigmine improved their performance relative to lesioned non-grafted rats. These experiments indicate that grafts can ameliorate behavioral deficits when the efficacy of acetylcholine of graft origin is enhanced.

Regulation of muscarinic receptors in hippocampus following cholinergic denervation and reinnervation by septal and striatal transplants

The regulation of hippocampal muscarinic M1 and M2 receptors was studied by autoradiographic methods following cholinergic denervation and reinnervation from embryonic septal transplant. In young adult male rats the density of M1 sites, labeled either with 3H-pirenzepine (PZ) or 3H-N-methylscopolamine (NMS, in the presence of excess carbachol), exceeded by 4- to 5-fold the density of M2 sites, labeled with 3H-NMS in the presence of excess PZ. Both receptors appeared to be densest in hippocampal regions lowest in acetylcholinesterase or 3H-hemicholinium-3 binding. The distribution of M1 receptors did differ from the distribution of M2 receptors within subregions of the hippocampus. Along the mediolateral axis from the subiculum to the lateral CA 1, the density of M1 receptors is uniform, but the density of M2 receptors decreases. Also apparent is the relatively small difference in density between the CA1 and dentate gyrus for M1 receptors but a significantly greater difference for M2 receptors. However, the response of M1 and M2 receptors to long-term cholinergic denervation following fimbriafornix transection of the septal cholinergic input and to cholinergic innervation by embryonic septal transplants was similar. Long-term denervation (40-60 d) resulted in a 30-60% increase in both M1 and M2 receptors within regions of the hippocampal formation. Receptor levels were reduced to normal in regions innervated by septal transplants. For both receptors, the changes in the density of sites were due to alterations in the Bmax and not the Kd for the radioligands. The specificity of this regulation is supported by the evidence that (1) the degree and topography of the normalization of muscarinic receptor density was entirely dependent on the degree and pattern of cholinergic reinnervation by the fibers of the septal transplant, (2) cholinergic fiber reinnervation by embryonic striatal grafts also down-regulated the density of M1 and M2 receptors, and (3) successfully surviving transplants (e.g., cerebellar and striatal) that did not provide innervation to the hippocampus did not induce down-regulation of muscarinic receptors. Changes in the density of sites were not related to changes in the width of the hippocampus following denervation and reinnervation. The data support the view that the majority of M1 and M2 receptors are located postsynaptically on neurons within the hippocampus and not presynaptically on cholinergic fibers.

Local Mechanical Effects And Humoral Factors Evoke Degeneration Of Guinea Pig Uterine Innervation

Small porcelain pellets were inserted into one of the uterine horns of virgin guinea pigs. Mating caused pregnancies only in contralateral, non-pellet-containing uterine horns. The number and morphology of uterine nerve structures was studied immunohistochemically. In pellet-surrounding tissues of virgin animals the number of nerves was reduced and remaining nerve structures displayed signs of degeneration. This nerve reduction was further advanced in early to mid-pregnancy when almost no nerve structures could be detected. Myometrial strips were transplanted to the anterior eye chamber and became reinnervated by adrenergic nerves. The pattern and structure of the adrenergic reinnervation did not differ between strips taken from virgin animals, untreated or following chemical sympathectomy, or taken from primiparous animals following pregnancy induced sympathectomy. The adrenergic reinnervation of transplants from virgin animals was not affected by pregnancy of the recipient animal. It is suggested that the uterine innervation can be influenced by local, mechanically-induced effects, which during pregnancy co-operate with conceptus-related humoral factors to cause an almost total uterine nerve degeneration. The ability of uterine adrenergic reinnervation is probably not significantly influenced by local environmental tissue factor(s), but is related rather to extent of nerve damage.

Human fetal basal forebrain neurons grafted to the denervated rat hippocampus produce an organotypic cholinergic reinnervation pattern

The septal/diagonal band (SDB) area, obtained from a 9- to 10-week-old abored human fetus, was grafted to the hippocampal formation of adult, immunosuppressed rats subjected to an aspirative lesion of the fimbria-fornix. Nineteen weeks after transplantation, microscopical analysis revealed large, partly acetylcholinesterase (AChE)-positive grafts in the hippocampus in 3 of the 5 recipients. The AChE-positive grafts gave rise to a reinnervation of the host hippocampus and an AChE-positive lamination of the different hippocampal subfields with the same characteristics as the normal septum-derived innervation. Immunological evaluation of host sera revealed that all rats were immunized by the graft. This indicates that grafted human cholinergic SDB neurons can respond to or interact with factors that regulate and guide the innervation of the rat hippocampus.

Reinnervation pattern of heterotopically transposed lingual flaps

Reinnervation pattern of heterotopically transposed lingual flaps

Patterns of reinnervation and motor unit recruitment in human hand muscles after complete ulnar and median nerve section and resuture.

Following complete ulnar or above-elbow median nerve sections, there was no significant correlation between motor unit size (twitch amplitude) and recruitment threshold, as assessed by spike triggered averaging. This absence of orderly recruitment was attributed to misdirection of motor axons during regeneration. Following median nerve section at wrist level, where the reinnervated muscles have more synergistic actions, orderly recruitment by size appeared to be re-established. Thus, the size principle of motor unit recruitment can be re-established after nerve section in humans, if motor axons innervate their original muscles or ones with closely synergistic functions.