Dermal Nerve Research Articles

Neuropeptide-containing C-fibres and wound healing in rat skin. Neither capsaicin nor peripheral neurotomy affect the rate of healing.

Wound healing in rat skin was studied in standardized wounds inflicted on both hind legs after unilateral sciatic nerve sectioning and/or capsaicin-induced depletion of sensory nerve (C-fibre) neuropeptide content. Daily visual inspection, histological examination and immunohistochemistry with antibodies against substance P, calcitonin gene-related peptide (CGRP), vasoactive intestinal peptide, neuropeptide Y and a pan-neuronal marker, protein gene product 9.5 (PGP 9.5) were used to assess wound healing and determine the distribution of dermal nerve fibres. In controls, nerve fibre density in the wound tissue was low during the first few days after wound infliction, but started to increase on day 4, reaching a peak on day 7 when 25% of medial wounds and 70% of lateral wounds were healed. All wounds were healed on day 11, a scar appearing on day 14 followed by a decrease in nerve fibre density. Capsaicin treatment and/or sciatic nerve sectioning reduced the density of CGRP-immunoreactive nerve fibres by 70% and that of PGP 9.5-immunoreactive fibres by 50%. The capsaicin-induced reduction in PGP 9.5-immunoreactive nerve fibre density is attributable to partial destruction of peripheral nerve fibres. CGRP-immunoreactive and PGP 9.5-immunoreactive nerve fibre density was restored both in capsaicin-treated and denervated groups, reaching a maximum, corresponding to the original level, by days 4-10. Neither the reduction in nerve fibre density following sciatic nerve sectioning nor the impairment of sensory nerve functional capacity following capsaicin treatment affected the rate of wound healing, all wounds being closed on day 11. The study shows that it is difficult to knock out all cutaneous sensory innervation. Thirty per cent of C-fibre innervation seems enough to ensure a normal wound healing.

Primary Macular Amyloidosis: An Ultrastructural Approach to Diagnosis

Seven cases of primary macular amyloidosis were studied on skin biopsies. The Congo red stain was positive only in three cases, whereas the ultrastructural observation allowed for the detection of amyloid deposits in all biopsies. Fibrillary degeneration of basal keratynocytes was occasionally observed, and regressive changes of keratynocytes and dermal nerve bundles presumably related to the intensity of the scratch trauma were detected in one case. In six biopsies mast cell profiles exhibiting various degrees of degranulation were detected in the dermis. Melanosome aggregates were also observed consistently in dermal macrophages and occasionally in Schwann cells. A variable degree of structural alteration was observed in dermal unmyelinated nerve fibers. Even if the intimate mechanism of amyloid deposition was not explained by the ultrastructural study, this approach is a useful instrument in the differential diagnosis of cutaneous macular hyperpigmented lesions.

Neural spectrum: palisaded encapsulated neuroma and verocay body poor dermal schwannoma.

We examined 25 palisaded encapsulated neuromas (PEN) of the skin and used peripherin antibody as an immunohistochemical label for axons. Quantitative analysis of the axon to schwann cell nuclear ratio for each PEN was determined by examining cross-sectioned neuroid fascicles. This revealed that 120 of the 253 cross-sectioned fascicles in PEN lacked axon and only 5% of the fascicles had an axon to schwann cell nuclear ratio greater than 1:2. In contrast, all fascicles in 40 dermal nerves adjacent to PENs as well as 35 traumatic neuromas in surgical scars had an axon to schwann cell nuclear ratio of at least 1:2 and the majority a ratio of 1:1 or higher. These results suggest that there is a spectrum between PENs which are axon rich to a form of schwannoma with an identical histopathology which lacks significant axonal content and that not all PENs are true neuromas.

Intradermal Injection of Capsaicin in Humans Produces Degeneration and Subsequent Reinnervation of Epidermal Nerve Fibers: Correlation with Sensory Function

The ability of capsaicin to excite and subsequently to desensitize a select group of small sensory neurons has made it a useful tool to study their function. For this reason, application of capsaicin to the skin has been used for a variety of painful syndromes. We examined whether intradermal injection of capsaicin produced morphological changes in cutaneous nerve fibers that would account for its analgesic properties by comparing cutaneous innervation in capsaicin-treated skin with psychophysical measures of sensation. At various times after capsaicin injection, nerve fibers were visualized immunohistochemically in skin biopsies and were quantified. In normal skin the epidermis is heavily innervated by nerve fibers immunoreactive for protein gene product (PGP) 9.5, whereas fibers immunoreactive for substance P (SP) and calcitonin gene-related peptide (CGRP) are typically associated with blood vessels. There was nearly complete degeneration of epidermal nerve fibers and the subepidermal neural plexus in capsaicin-treated skin, as indicated by the loss of immunoreactivity for PGP 9.5 and CGRP. The effect of capsaicin on dermal nerve fibers immunoreactive for SP was less obvious. Capsaicin decreased sensitivity to pain produced by sharp mechanical stimuli and nearly eliminated heat-evoked pain within the injected area. Limited reinnervation of the epidermis and partial return of sensation occurred 3 weeks after treatment; reinnervation of the epidermis was approximately 25% of normal, and sensation improved to 50-75% of normal. These data show that sensory dysfunction after capsaicin application to the skin results from rapid degeneration of intracutaneous nerve fibers.

Neuropathological alterations in diabetic truncal neuropathy: evaluation by skin biopsy

OBJECTIVESTo describe the neuropathological features in skin biopsies from patients with diabetic truncal neuropathy.METHODSThree patients with diabetic truncal neuropathy underwent skin biopsies from both symptomatic and asymptomatic regions of the...

BDNF overexpression induces differential increases among subsets of sympathetic innervation in murine back skin.

Besides their recognized dependence on nerve growth factor (NGF) during development, the dependence of mature sympathetic ganglion neurons on other neurotrophins is still unclear. Here, we have investigated the sympathetic innervation of back skin in mice overexpressing brain-derived neurotrophic factor (BDNF) under the alpha-myosin heavy-chain promoter, as well as in BDNF knockout (-/-) mice. Compared with wild-type controls, the dorsal skin of BDNF overexpressing mice displayed a significantly enhanced number of adrenergic, tyrosine hydroxylase-immunoreactive (IR) nerve fibres, while cholinergic or peptidergic sensory nerve fibres appeared unaltered. The adrenergic hyperinnervation in dorsal skin of BDNF overexpressing mice was most pronounced in the arrector pili muscle of hair follicles, while no increase of tyrosine hydroxylase-or neuropeptide Y-IR fibres associated with subcutaneous blood vessels was found. Instead, back skin of BDNF knockout (-/-) mice contained significantly fewer tyrosine hydroxylase-IR dermal nerve fibres than wild-type animals. This suggests that BDNF plays an important role in the control of different subsets of adrenergic innervation in murine back skin, and indicates that paravertebral sympathetic ganglia display a previously unrecognized differential BDNF-dependence in vivo.

Morphological assessment of the effects of cyclosporin A on mast cell--nerve relationship in atopic dermatitis.

There is considerable clinical and experimental evidence that cyclosporin A has powerful therapeutic effects on severe, therapy-resistant atopic dermatitis. To further clarify the mechanism of beneficial action of cyclosporin A for atopic dermatitis, we assessed its effects on mast cell morphology and on the topographical relationship between mast cells and cutaneous nerves in lesional skin of atopic dermatitis. The ultrastructural features of mast cell-specific granules in cyclosporin A-treated skin compared with those in the pretreated skin included an increase in the stable granule population and the disappearance of signs of granule exocytosis. The close apposition of mast cells to peripheral nerve fibres in the upper dermis and an invasion of mast cells into nerve bundles in the lower dermis were immunohistochemically noted, and an intimate association between mast cells and unmyelinated dermal nerves or Schwann cells was observed ultrastructurally in the pretreated lesional skin. After cyclosporin A therapy, the close interrelation of mast cells and cutaneous nerves was not seen. These findings suggest that cyclosporin A may exert its therapeutic efficacy by inhibiting mast cell activation, and by affecting the interaction between mast cells and nerves, which may explain the beneficial therapeutic action of cyclosporin A in the management of the disease.

Light and Electron Microscopic Demonstration of the p75 Nerve Growth Factor Receptor in Normal Human Cutaneous Nerve Fibers: New Vistas

The nerve growth factor and its receptor are important in nerve growth, differentiation, maturation, and maintenance. In order to explore the exact distribution of p75 low-affinity nerve growth factor receptor (p75 NGFr) expression in cutaneous nerve fibers, p75 NGFr and neuron-specific enolase double immunofluorescence and immunoelectron microscopic studies were conducted on normal human skin samples. After p75 NGFr and neuron-specific enolase immunofluorescence double staining, the dermal nerves were strongly p75 NGFr-immunoreactive (IR); however, very few p75 NGFr-IR nerve fibers were found in the epidermis. p75 NGFr immunoreactivity was found mainly in the peripheral part of cutaneous nerve trunks and fibers, whereas neuron-specific enolase immunoreactivity was mainly seen within the axons. After ultrastructural immunostaining, the Schwann cell membrane was strongly p75 NGFr-IR. The Schwann cell membrane facing the connective tissue was more strongly p75 NGFr-IR than the part of the membrane close to the axon; the Schwann cell cytoplasm nearest to the membrane sometimes also showed a high p75 NGFr immunoreactivity, whereas the rest of the cytoplasm was generally more weakly p75 NGFr-IR; however, the axon itself seldom showed any such immunoreactivity; actually, only a few parts of the axonal membrane revealed a weak staining, leaving most of the membrane unstained. The axoplasm was not p75 NGFr-IR. The results--that in human cutaneous nerves it is mainly the Schwann cells that express p75 NGFr immunoreactivity--further stress the active role of the glial ensheathment in the control and maintenance of a normal target innervation.

Innervation of developing human taste buds. An immunohistochemical study.

Morphological changes in developing human gustatory papillae during the 6th to the 23rd postovulatory week have been studied. The general innervation pattern of taste papillae and taste bud primordia was revealed immunohistochemically using antibodies against protein gene product 9.5 (PGP9.5), neurofilament H (NFH), neurofilament L (NFL), neurone-specific enolase (NSE), and tubulin. The autonomic and somatosensory nerve supply has been investigated using antibodies against substance P (SP), calcitonin gene-related peptide (CGRP), tyrosine hydroxylase (TH), neuropeptide Y (NPY), the neuronal form of nitric oxide synthase (n-NOS), and, enzyme histochemically, NADPH-diaphorase. Nerve fibers approach the basal membrane of the lingual epithelium around the 7th postovulatory week and invade the epithelium of papilla-like structures at the 8th week, but some also penetrate the basal membrane of the non-papillary epithelium. They are in close contact with slender epithelial cells that are considered to be the taste bud's progenitor cells. Early human taste buds situated at the anterior part of the tongue do not necessarily require a dermal (later fungiform) papilla. The NADPH-diaphorase reaction revealed positive results in dermal nerve fibers, but the immunohistochemical reaction against n-NOS was negative. Immunohistochemical detection of neuropeptides and vasoactive substances rendered negative results for developmental stages of 7-18 postovulatory weeks. By the 18th week, only SP was detected in dermal papillae, but not in the vicinity of taste buds' primordia. Thus, autonomic and somatosensory nerves seem not to play a key role in formation and maintenance of early human taste buds.

Histological studies in primary neuritic leprosy: changes in the apparently normal skin.

The visually normal skin of 196 patients diagnosed clinically to have primary neuritic leprosy was studied histologically to determine whether there were any specific changes due to the disease in this site. Histological changes due to leprosy were seen in 32.1% of the patients, and included, indeterminate leprosy in 19.4%, borderline tuberculoid leprosy in 6.6% and borderline lepromatous leprosy in 6.1%. The remaining biopsies showed mild non-specific dermal inflammation, mild nerve changes or no significant lesion. The nerve inflammation and/or granulomas were mostly in the deep dermal nerves or neurovascular complexes. This study shows that there is a cutaneous component to primary neuritic leprosy and the disease is not totally confined to nerves. The absence of visible hypopigmented patches in these patients is probably related to the deep location of the dermal inflammation.

Pathogenicity of experimental caryosporosis

Pathogenicity of the coccidia C. bigenetica and C. simplex was studied in experimentally inoculated pigs, goat kids (untreated and immunosuppressed) and severe combined immunodeficient (SCID) mice. The major pathological changes of caryosporosis were similar in all inoculated animals. In pigs and goat kids, caryosporosis was self-limiting, with clinical responses that included focal swelling and erythema of the muzzle, snout, jaws, cheeks, eyelids, bases of the ears, backs of the necks, scrotum, external genitalia of females, legs and footpads. Histopathological changes were characterized by involvement of the cutaneous mononuclear phagocyte system with an inflammatory exudate containing numerous macrophages, especially around the root sheaths, sensory nervous corpuscles of the hair follicles and surrounding dermal free nerve endings. The tactile hair follicles in the muzzle, snout and upper jaw were most severely changed. In SCID mice, inoculation with C. bigenetica or C. simplex caused a severe, fatal, systemic disease characterized by dissemination of numerous caryosporan developmental stages into the host mononuclear phagocyte system. This study presents evidence that both caryosporan species tested caused similar clinical signs and lesions of dermal coccidiosis in the mammalian secondary hosts.

Comparison of Immunohistochemical and Functional Reinnervation of Skin and Muscle after Peripheral Nerve Injury

In order to investigate the usefulness of immunohistochemical detection of regenerating axons as a correlate of functional recovery, reinnervation of mouse foot pads, hairy skin, and muscle were studied at several intervals along 3 months after sciatic nerve crush using immunohistochemical markers PGP 9.5 and CGRP. These histological results were compared with functional recovery of sweat glands (SGs), plantar muscles, and pain sensibility. One week after nerve injury all neural functions were abolished in the operated hindpaw of all mice, no CGRP-immunoreactive (-ir) fibers were seen in the samples studied, while PGP 9.5 immunofluorescence remained at dim levels within nerve trunks, but disappeared from terminal innervation. The first PGP 9.5- and CGRP-ir regenerating fibers were seen at 15–16 days postoperation (dpo) in dermal nerve trunks of dorsal hairy skin and some days later in dermal trunks of foot pads. Regenerating nerve fibers progressed along the periphery of the dermis reinnervating the different dermal appendages. At 25 dpo all target organs were reinnervated. The first SGs activated by pilocarpine reappeared by 16 dpo and increased in number to 88% of control counts. Nociceptive responses reappeared at 17 dpo and reached 100% of control values. The first PGP immunofluorescence in neuromuscular junctions was seen at 16 dpo, while the first muscle action potentials were recorded at 19 dpo, and the potentials amplitude increased to 66% of controls. Good correlations were found between morphological and functional results of reinnervation. However, the density and distribution of nerve profiles in the tissues studied did not reach normal levels, while neural functions conveyed by small fibers reached levels similar to controls.

Immunohistochemical study of skin reinnervation by regenerative axons

The time sequence of sensory and sudomotor nerve regeneration to the mouse footpad was studied between one and seven weeks after crush or section of the sciatic nerve. Protein gene product 9.5, vasoactive intestinal peptide, substance P, and calcitonin gene-related peptide were localized in thick sections by using indirect immunofluorescence techniques and imaged by confocal microscopy. Nerve regeneration was visually assessed in all nerves and quantified in sweat glands. After denervation, protein gene product 9.5 immunoreactivity remained as dim fluorescence within thick fibers of dermal nerve trunks, whereas thin nerve fibers to sweat glands and to epidermis disappeared. By 14 days postcrush and 35 days postsection, the first protein gene product 9.5 immunoreactive regenerating axons appeared in large nerve trunks, quickly extending to epidermis and sweat glands. Reinnervation of Meissner's corpuscles occurred nearly simultaneous with return of epidermal free nerve endings and sudomotor network. Calcitonin gene-related peptide, vasoactive intestinal peptide, and substance P immunoreactivity disappeared completely one week after denervation, then reappeared at 17-18 days postcrush and 35 days postsection. Fewer nerve fibers were immunoreactive to these peptides than to protein gene product 9.5. The overall density of reinnervation, although reduced, more closely resembled normal in the sweat glands and Meissner's corpuscles than in the epidermis. Reinnervation was more successful after crush than after nerve section. The time course for functional return of sweating paralleled the return of protein gene product 9.5 immunoreactivity, whereas appearance of vasoactive intestinal peptide was delayed by several days.

Histopathology of peripheral nerves in cutaneous herpesvirus infection.

Cutaneous herpesvirus infection is a common viral disorder manifest by epidermal and/or mucosal vesicle formation. Though it is believed that the virus most likely resides in regional sensory ganglia following primary infection and that cutaneous involvement represents reactivation of a latent infection, the histopathology of cutaneous nerves in sites of disease has not been well characterized. In order to assess and characterize the pathologic changes of these nerves, we retrospectively examined 54 cases of cutaneous and mucosal herpesvirus infection as defined by the presence of diagnostic multinucleate epithelial giant cells that demonstrated viral cytopathic effect. Dermal nerves were evaluable in 48 of 54 cases. All cases showed perineural inflammation that consisted of a dense mixed lymphocyte-polymorphonuclear cell infiltrate. Twenty-six cases exhibited intraneural infiltrations accompanied by Schwann cell hypertrophy with nuclear eosinophilia and pyknosis. Frank neuronal necrosis was present in 21 cases, with viral cytopathic effect evident within neurons of four cases. The degree of peri- and intraneural inflammation correlated with the severity of the inflammatory response within the dermis in most cases; however, in eight cases there was inflammatory involvement of neurovascular structures distant from and out of proportion to dermal and epidermal changes. Immunoperoxidase staining using a polyvalent antibody to human herpesvirus was performed in two cases and demonstrated viral antigen within nerve twigs. This pattern of peripheral nerve twig inflammation, along with the occurrence of more distant neural involvement, may prove to have diagnostic implications and serve as a clue in the recognition of cutaneous herpesvirus infection, particularly in cases with subtle or absent epidermal alteration. Furthermore, the presence of inflammation within and around nerves as well as degenerative changes suggest that nerve twigs are not passive conduits for viral spread but may be directly involved in infection.

Histopathological and bacteriological findings in prurigo nodularis.

Prurigo nodularis is a chronic disease with unknown aetiology. Biopsy specimens of 43 patients with prurigo nodularis were taken for histopathological and mycobacteriological analyses. By conventional histopathology, 25 (58%) samples, and by immunostaining for S100 protein, 31 (72%) samples had changes relevant to prurigo nodularis. Twelve (28%) of the samples were positive for acid fast bacilli in tissue staining by Ziehl-Neelsen technique, including 4 of the 6 samples also positive for mycobacteria in cultivation. The results verified the usefulness of S100 staining in detection of neural hyperplasia in dermal nerves, a feature regarded as diagnostic for prurigo nodularis. They also indicated that atypical mycobacteria may be a contributing factor in prurigo nodularis.

Ultrastructural study of the dermal nerves in the cutaneous macular lesions of patients with early leprosy

Thirteen biopsies of macular lesions of early leprosy patients were studied ultrastructurally with transmission electron microscopy (TEM). All of the biopsies displayed at least one dermal nerve partially or completely encircled by mononuclear cells in the conventional histopathological study with light microscopy The patients'diagnosis varied from indeterminate leprosy to borderline tuberculoide (BT). In the ultrastructural study,twenty-seven dermal nerve branches were found in the thirteen biopsies. Twenty dermal nerve branches in eleven biopsies were found to display no inflammatory involvement Seven nerves in seven biopsies were morphologically associated with mononuclear leukocytic cells. Four biopsies exhibited nerves with and without inflammatory involvement concomitantly. Three nerves showed morphological evidence of endoneurial fibrosis, not morphologically associated with the inflammatory process at least in the sections examined. No detectable axional andSchwann cell ultra strutural changes even in the twenty-seven nerveswere found. The sensorial loss exhibited by the patients before the institution of treatment was completely reversed in eight patients after the end of multidrug therapy regimen. These findings suggest that sensory loss in the early stages of leprosy may be caused by reversible pathological mechanisms, rather than anatomical damage. It is also possible, concerning the mechanisms of nerve damage in leprosy, to speculate on the existence of a pathological process which may precede the inflammation.

Hypomelanosis of Ito: electron microscopical observations on two new cases

An ultrastructural study on two new cases of Ito's hypomelanosis is reported. According with previous studies on this pathological condition, a marked reduction of melanocytes is detected in the hypopigmented areas. In the proximity of preserved melanocytes, a nearly normal content of melanosomes is detected in basal keratinocytes. Melanocyte profiles are frequently located in close relationship with the basal lamina. An apparent increase of nerve endings is demonstrated at the dermo-epidermal edge. Nerve fibres show no pathological alterations. A functional impairement of the melanocytes is hypothesized, involving regressive changes and a tendence towards a round shape of their profiles. This could in part account for the prevalent basal location of the melanocytes. The role of the dermal nerve endings in the pathogenesis of the hypopigmented lesions is discussed.

Immunohistochemical Analysis of Dermal Nerves Using Skin Biopsy Material from Diabetic Patients

Immunohistochemical Analysis of Dermal Nerves Using Skin Biopsy Material from Diabetic Patients

Toxicology of topical local anesthetics.

Topical anesthesia of the skin, nowadays performed for various indications from pruritus over postherpetic neuralgia to minor surgery, has been under investigation for more than 30 years. Due to low water solubility, the active base form of most of the local anesthetics on the market is poorly absorbed through the skin. Hence, the most challenging target was to develop galenic preparations which provide a good skin penetration in order to reach the dermal nerve endings and thereby lead to sufficient local anesthesia. On the other hand good skin penetration also results in a distribution of the drug in the circulation. Since local anesthetic agents are known to have an impact on the heart and central nervous system, unwanted side effects following topical application onto the skin are worth discussing. This article reviews the current topical local anesthetics with particular accent on their pharmacological and toxicological data.

MORPHOLOGIC OBSERVATIONS ON THE DERMAL NERVES IN VITILIGO: AN ULTRASTRUCTURAL STUDY

Vitiligo is a common idiopathic skin disorder. The etiology is unknown, although various hypotheses have been advanced. These include the neuronal hypothesis, where neuronal factors are thought to play a role in the pathogenesis of this disease. Skin biopsies were taken from marginal and central parts of four vitiligo patients. Biopsies were also taken from nonvitiliginous skin of each patient and from four normal control subjects. Sections were examined under the electron-microscope. Nerve fibers in the superficial dermis were examined. Subtle ultrastructural changes, including regeneration and degeneration, were consistently found in dermal nerves of vitiligo lesions. The most consistent feature, seen in all four vitiligo patients studied (in both lesional and marginal areas), was an increased thickness of the basement membrane of Schwann cells. This change was found in approximately three-quarters of all dermal nerves in vitiligo biopsies, but in only about one-quarter of dermal nerves in normal control skin. About half the abnormal dermal nerves in vitiligo skin showed minor axonal damage, although indicators of regeneration (increased mitochondria and rough endoplasmic reticulum) predominated. The dermal nerves in vitiligo showed no difference in fiber diameter or fiber density in comparison with controls. In vitiligo both axonal degeneration and nerve regeneration may occur, with the latter possibly being a reactive change to earlier axonal damage. These findings support the hypothesis that there is a neuronal component to this disease.