Influence of sensory neuropeptides on human cutaneous wound healing process

Impact of L-Arginine on diabetes-induced neuropathy and myopathy: Roles of PAI-1, Irisin, oxidative stress, NF-κβ, autophagy and microRNA-29a

BACKGROUND

T2DM is a chronic disorder with progressive neuromuscular alterations. L-arginine (ARG) is the most common semi-essential amino acid having several metabolic functions.

AIM

to investigate the impact of L-arginine in combating diabetic-induced neuromyopathy and its possible mechanisms.

MATERIALS & METHODS

24 rats were divided into CON, CON+ARG, DC, DC+ARG. Behavioral tests, Body weight (BW), fasting blood glucose (FBG), insulin, total antioxidant capacity (TAC), malondialdehyde (MDA), plasminogen activator inhibitor-1 (PAI-1), and irisin were done. Creatine kinase-MM (CK-MM), interleukin 4 (IL-4), interleukin 6 (IL-6), TAC, MDA, expression of microRNA-29a mRNA & light chain 3 protein were determined in muscle. Histological and NF-κβ immunohistochemical expression in muscle and nerve were assessed.

RESULTS

ARG supplementation to diabetic rats improved altered behavior, significantly increased BW, insulin, TAC, irisin and Il-4, decreased levels of glucose, microRNA-29a, NF-κβ and LC3 expression, PAI-1, CK-MM and restored the normal histological appearance.

CONCLUSIONS

ARG supplementation potently alleviated diabetic-induced neuromuscular alterations.

Neural dependency in wound healing and regeneration

In response to injury, humans and many other mammals form a fibrous scar that lacks the structure and function of the original tissue, whereas other vertebrate species can spontaneously regenerate damaged tissues and structures. Peripheral nerves have been identified as essential mediators of wound healing and regeneration in both mammalian and nonmammalian systems, interacting with the milieu of cells and biochemical signals present in the post-injury microenvironment. This review examines the diverse functions of peripheral nerves in tissue repair and regeneration, specifically during the processes of wound healing, blastema formation, and organ repair. We compare available evidence in mammalian and nonmammalian models, identifying critical nerve-mediated mechanisms for regeneration and providing future perspectives toward integrating these mechanisms into a therapeutic framework to promote regeneration.

Outcomes Following Total Hip Arthroplasty in Patients Who Have Charcot Neuroarthropathy of the Hip

BACKGROUND

Historically, Charcot neuroarthropathy hip (CNH) was deemed a contraindication for total hip arthroplasty (THA). However, as implant design and surgical techniques advance, THA for CNH has been performed and documented in literature. Information regarding the outcomes of THA for CNH is limited. The objective of the study was to assess outcomes following THA in patients who have CNH.

METHODS

Patients who have CNH underwent primary THA and had at least 2 years of follow-up were identified in a national insurance database. For comparison, a 1:10 matched control cohort of patients who did not have CNH was created based on age, sex, and relevant comorbidities. Eight hundred and ninety-five CNH patients who underwent primary THA were compared to 8,785 controls. Medical outcomes, emergency department visits, hospital readmissions, and surgical outcomes including revisions between cohorts were evaluated using multivariate logistic regressions.

RESULTS

The CNH patients were found to have higher risks of 90-day wound complications (P = .014), periprosthetic joint infection (P = .013) (P = .021), dislocation (P < .001) (P < .001), aseptic loosening (P = .040) (P = .002), periprosthetic fracture (P = .003) (P < .001), and revision (P < .001) (P < .001) at 1-year and 2-year follow-up, respectively.

CONCLUSION

While patients who have CNH are at a higher risk of wound and implant-related complications, they are comparatively lower than previously reported in literature. Orthopaedic surgeons should be cognizant of the increased risk in this population to provide appropriate preoperative counseling and enhanced perioperative medical management.

Emergence of New Concepts in Skin Physiopathology through the Use of in vitro Human Skin Explants Models

BACKGROUND

This review summarizes uses and new applications for dermatological research of in vitro culture models of human skin explants (HSEs). In the last decade, many innovations have appeared in the literature and an exponential number of studies have been recorded in various fields of application such as process culture engineering, stem cell extractions methodology, or cell-to-cell interaction studies under physiological and pathological conditions, wound-healing, and inflammation. Most studies also concerned pharmacology, cosmetology, and photobiology. However, these topics will not be considered in our review.

SUMMARY

A better understanding of the mechanisms driving intercellular relationships, at work in the maintenance of 3D tissue architectures has led to the improvement of cell culture techniques. Many papers have focused on the physiological ways that govern in vitro tissue maintenance of HSEs. The analysis of the necessary mechanical stress, intercellular and cell-matrix interactions, allows the maintenance and prolonged use of HSEs in culture for up to 15 days, regardless of the great variability of study protocols from one laboratory to another and in accordance with the objectives set. Because of their close similarities to fresh skin, HSEs are increasingly used to study skin barrier repair and wound healing physiology. Easy to use in co-culture, this model allows a better understanding of the connections and interactions between the peripheral nervous system, the skin and the immune system. The development of the concept of an integrated neuro-immuno-cutaneous system at work in skin physiology and pathology highlighted by this article represents one of the new technical challenges in the field of in vitro culture of HSE. This review of the literature also reveals the importance of using such models in pathology. As sources of stem cells, HSEs are the basis for the development of new tissue engineering models such as organoids or optical clearing tissues technology. This study identifies the main advances and cross-cutting issues in the use of HSE.

Neuropeptide substance P: A promising regulator of wound healing in diabetic foot ulcers

In the past, neuropeptide substance P (SP) was predominantly recognized as a neuroinflammatory factor, while its potent healing activity was overlooked. This paper aims to review the regulatory characteristics of neuropeptide SP in both normal and diabetic wound healing. SP actively in the regulation of wound healing-related cells directly and indirectly, exhibiting robust inflammatory properties, promoting cell proliferation and migration and restoring the activity and paracrine ability of skin cells under diabetic conditions. Furthermore, SP not only regulates healing-related cells but also orchestrates the immune environment, thereby presenting unique and promising application prospects in wound intervention. As new SP-based preparations are being explored, SP-related drugs are poised to become an effective therapeutic intervention for diabetic foot ulcers (DFU).

Basic mechanisms of itch

Pruritus (or itch) is an unpleasant sensation leading to a desire to scratch. In the epidermis, there are selective C or Aδ epidermal nerve endings that are pruriceptors. At their other ends, peripheral neurons form synapses with spinal neurons and interneurons. Many areas in the central nervous system are involved in itch processing. Although itch does not occur solely because of parasitic, allergic, or immunologic diseases, it is usually the consequence of neuroimmune interactions. Histamine is involved in a minority of itchy conditions, and many other mediators play a role: cytokines (eg, IL-4, IL-13, IL-31, IL-33, and thymic stromal lymphopoietin), neurotransmitters (eg, substance P, calcitonin gene-related peptide, vasoactive intestinal peptide, neuropeptide Y, NBNP, endothelin 1, and gastrin-releasing peptide), and neurotrophins (eg, nerve growth factor and brain-derived neurotrophic factor). Moreover, ion channels such as voltage-gated sodium channels, transient receptor potential vanilloid 1, transient receptor ankyrin, and transient receptor potential cation channel subfamily M (melastatin) member 8 play a crucial role. The main markers of nonhistaminergic pruriceptors are PAR-2 and MrgprX2. A notable phenomenon is the sensitization to pruritus, in which regardless of the initial cause of pruritus, there is an increased responsiveness of peripheral and central pruriceptive neurons to their normal or subthreshold afferent input in the context of chronic itch.

Potential link between the nerve injury-induced protein (Ninjurin) and the pathogenesis of endometriosis

Endometriosis remains a widespread but severe gynecological disease in women of reproductive age, with an unknown etiology and few treatment choices. The menstrual reflux theory is largely accepted as the underlying etiology but does not explain the morbidity or unpleasant pain sensations of endometriosis. The neurological and immune systems are both involved in pain mechanisms of endometriosis, and interlinked through a complex combination of cytokines and neurotransmitters. Numerous pieces of evidence suggest that the nerve injury-inducible protein, Ninjurin, is actively expressed in endometriosis lesions, which contributes to the etiology and development of endometriosis. It may be explored in the future as a novel therapeutic target. The aim of the present review was to elucidate the multifaceted role of Ninjurin. Furthermore, we summarize the association of Ninjurin with the pain mechanism of endometriosis and outline the future research directions. A novel therapeutic pathway can be discovered based on the potential pathogenic variables.

Oral Cancer Cells Release Vesicles that Cause Pain

Oral cancer pain is attributed to the release from cancers of mediators that sensitize and activate sensory neurons. Intraplantar injection of conditioned media (CM) from human tongue cancer cell line HSC-3 or OSC-20 evokes nociceptive behavior. By contrast, CM from noncancer cell lines, DOK, and HaCaT are non-nociceptive. Pain mediators are carried by extracellular vesicles (EVs) released from cancer cells. Depletion of EVs from cancer cell line CM reverses mechanical allodynia and thermal hyperalgesia. CM from non-nociceptive cell lines become nociceptive when reconstituted with HSC-3 EVs. Two miRNAs (hsa-miR-21-5p and hsa-miR-221-3p) are identified that are present in increased abundance in EVs from HSC-3 and OSC-20 CM compared to HaCaT CM. The miRNA target genes suggest potential involvement in oral cancer pain of the toll like receptor 7 (TLR7) and 8 (TLR8) pathways, as well as signaling through interleukin 6 cytokine family signal transducer receptor (gp130, encoded by IL6ST) and colony stimulating factor receptor (G-CSFR, encoded by CSF3R), Janus kinase and signal transducer and activator of transcription 3 (JAK/STAT3). These studies confirm the recent discovery of the role of cancer EVs in pain and add to the repertoire of algesic and analgesic cancer pain mediators and pathways that contribute to oral cancer pain.

Exosomes Derived From Umbilical Cord Mesenchymal Stem Cells Treat Cutaneous Nerve Damage and Promote Wound Healing

Wound repair is a key step in the treatment of skin injury caused by burn, surgery, and trauma. Various stem cells have been proven to promote wound healing and skin regeneration as candidate seed cells. Therefore, exosomes derived from stem cells are emerging as a promising method for wound repair. However, the mechanism by which exosomes promote wound repair is still unclear. In this study, we reported that exosomes derived from umbilical cord mesenchymal stem cells (UC-MSCs) promote wound healing and skin regeneration by treating cutaneous nerve damage. The results revealed that UC-MSCs exosomes (UC-MSC-Exo) promote the growth and migration of dermal fibroblast cells. In in vitro culture, dermal fibroblasts could promote to nerve cells and secrete nerve growth factors when stimulated by exosomes. During the repair process UC-MSC-Exo accelerated the recruitment of fibroblasts at the site of trauma and significantly enhanced cutaneous nerve regeneration in vivo. Interestingly, it was found that UC-MSC-Exo could promote wound healing and skin regeneration by recruiting fibroblasts, stimulating them to secrete nerve growth factors (NGFs) and promoting skin nerve regeneration. Therefore, we concluded that UC-MSC-Exo promote cutaneous nerve repair, which may play an important role in wound repair and skin regeneration.

An agonistic monoclonal antibody targeting cMet attenuates inflammation and upregulates collagen synthesis and angiogenesis in Type 2 diabetic mouse wounds

BACKGROUND

Diabetic wounds account for 25%-50% of total diabetic healthcare costs annually, and present overall healing rates of less than 50%. Since delayed diabetic wound healing is associated with impaired fibroblast function, we hypothesize that tyrosine kinase Met (cMet) agonistic monoclonal antibody (mAb) will promote diabetic wound healing via stable activation of HGF/cMet signaling.

METHODS

Two 6 mm dorsal wounds were created in each mice (6-week-old, male BKS.Cg-Dock7m+/+Leprdb/J, n=5). After subcutaneous injections of agonist (20 mg/kg) at 0 and 72h, the wound sizes were measured at days 0, 1, 3, 6, and 10. Histological and immunohistochemical analyses were performed at day 10 (cMet, α-SMA, CD68, and TGF-β). In vitro cytotoxicity and migration tests with diabetic fibroblasts were performed with/without agonist treatment (1 or 10 nM). cMet pathway activation of fibroblasts was confirmed through p-p44/42MAPK, p-mTOR, p-cMet, and ROCK-1 expression.

RESULTS

cMet agonistic mAb-treated group showed 1.60-fold lower wound area (p=0.027), 1.54-fold higher collagen synthesis (p=0.001), and 1.79-fold lower inflammatory cell infiltration (p=0.032) than the saline-treated control. The agonist increased cMet (1.86-fold, p=0.029), α-SMA (1.20-fold, p=0.018), and VEGF (1.68-fold, p=0.029) expression but suppressed CD68 (1.25-fold, p=0.043), TFG-β (1.25-fold, p=0.022), and MMP-2 (2.59-fold, p=0.029) expression. In vitro agonist treatment (10 nM) of diabetic fibroblasts increased their migration by 8.98-fold (p=0.029) and activated HGF/cMet pathway.

CONCLUSIONS

cMet agonistic mAb treatment improved diabetic wound healing in mice and reduced wound-site inflammatory cell infiltration. These results need to be validated in large animals before piloting human trials.

In Vitro Sensitive Skin Models: Review of the Standard Methods and Introduction to a New Disruptive Technology

The skin is a protective organ, able to decode a wide range of tactile, thermal, or noxious stimuli. Some of the sensors belonging to the transient receptor potential (TRP) family, for example, TRPV1, can elicit capsaicin-induced heat pain or histamine-induced itching sensations. The sensory nerve fibers, whose soma is located in the trigeminal or the dorsal root ganglia, are able to carry signals from the skin’s sensory receptors toward the brain via the spinal cord. In some cases, in response to environmental factors, nerve endings might be hyper activated, leading to a sensitive skin syndrome (SSS). SSS affects about 50% of the population and is correlated with small-fiber neuropathies resulting in neuropathic pain. Thus, for cosmetical and pharmaceutical industries developing SSS treatments, the selection of relevant and predictive in vitro models is essential. In this article, we reviewed the different in vitro models developed for the assessment of skin and neuron interactions. In a second part, we presented the advantages of microfluidic devices and organ-on-chip models, with a focus on the first model we developed in this context.

Spindle-Like Zinc Silicate Nanoparticles Accelerating Innervated and Vascularized Skin Burn Wound Healing

The treatment of severe burn injuries is a crucial challenge in skin tissue engineering. Severe burns are always accompanied with large-area neurovascular networks damage, leading to the lack of excitation functions and difficulty in self-healing. Therefore, it is of great importance to develop biomaterials which can not only promote wound healing but also simultaneously reconstruct cutaneous neurovascular networks. In this study, Zn₂ SiO₄ (ZS) nanoparticles-incorporated bioactive nanofibrous scaffolds are designed for innervated and vascularized skin burn wound healing. ZS nanoparticles with spindle-like morphology are synthesized via a facile hydrothermal method. The incorporation of ZS nanoparticles endows the scaffolds with excellent angiogenic and neurogenic activities in vitro. Additionally, in vivo results show that the ZS nanoparticles-incorporated scaffolds have favorable re-epithelialization, innervation, and vascularization abilities through local release of bioactive Zn and Si ions from ZS nanoparticles, leading to rapid wound healing featuring with newly formed blood vessels and nerve fibers. Taken together, this study suggests that the spindle-like ZS nanoparticles are useful bioactive agents for stimulating vascularization and innervation of functional skin repair. The bioactive inorganic nanoparticles may be used for multifunctional tissue regeneration.

Receptor activity-modifying protein 1 regulates mouse skin fibroblast proliferation via the Gαi3-PKA-CREB-YAP axis

Background

Skin innervation is crucial for normal wound healing. However, the relationship between nerve receptors and wound healing and the intrinsic mechanism remains to be further identified. In this study, we investigated the role of a calcitonin gene-related peptide (CGRP) receptor component, receptor activity‐modifying protein 1 (RAMP1), in mouse skin fibroblast (MSF) proliferation.

Methods

In vivo, Western blotting and immunohistochemical (IHC) staining of mouse skin wounds tissue was used to detect changes in RAMP1 expression. In vitro, RAMP1 was overexpressed in MSF cell lines by infection with Tet-On-Flag-RAMP1 lentivirus and doxycycline (DOX) induction. An IncuCyte S3 Live-Cell Analysis System was used to assess and compare the proliferation rate differences between different treatment groups. Total protein and subcellular extraction Western blot analysis, quantitative real-time-polymerase chain reaction (qPCR) analysis, and immunofluorescence (IF) staining analysis were conducted to detect signalling molecule expression and/or distribution. The CUT & RUN assay and dual-luciferase reporter assay were applied to measure protein-DNA interactions.

Results

RAMP1 expression levels were altered during skin wound healing in mice. RAMP1 overexpression promoted MSF proliferation. Mechanistically, total Yes-associated protein (YAP) and nuclear YAP protein expression was increased in RAMP1-overexpressing MSFs. RAMP1 overexpression increased inhibitory guanine nucleotide-binding protein (G protein) α subunit 3 (Gαi3) expression and activated downstream protein kinase A (PKA), and both elevated the expression of cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB) and activated it, promoting the transcription of YAP, elevating the total YAP level and promoting MSF proliferation.

Conclusions

Based on these data, we report, for the first time, that changes in the total RAMP1 levels during wound healing and RAMP1 overexpression alone can promote MSF proliferation via the Gαi3-PKA-CREB-YAP axis, a finding critical for understanding RAMP1 function, suggesting that this pathway is an attractive and accurate nerve target for skin wound treatment.

Macrophage Polarization and Alveolar Bone Healing Outcome: Despite a Significant M2 Polarizing Effect, VIP and PACAP Treatments Present a Minor Impact in Alveolar Bone Healing in Homeostatic Conditions

Host inflammatory immune response comprises an essential element of the bone healing process, where M2 polarization allegedly contributes to a favorable healing outcome. In this context, immunoregulatory molecules that modulate host response, including macrophage polarization, are considered potential targets for improving bone healing. This study aims to evaluate the role of the immunoregulatory molecules VIP (Vasoactive intestinal peptide) and PACAP (Pituitary adenylate cyclase activating polypeptide), which was previously described to favor the development of the M2 phenotype, in the process of alveolar bone healing in C57Bl/6 (WT) mice. Experimental groups were submitted to tooth extraction and maintained under control conditions or treated with VIP or PACAP were evaluated by microtomographic (µCT), histomorphometric, immunohistochemical, and molecular analysis at 0, 3, 7, and 14 days to quantify tissue healing and host response indicators at the healing site. Gene expression analysis demonstrates the effectiveness of VIP or PACAP in modulating host response, evidenced by the early dominance of an M2-type response, which was paralleled by a significant increase in M2 (CD206+) in treated groups. However, despite the marked effect of M1/M2 balance in the healing sites, the histomorphometric analysis does not reveal an equivalent/corresponding modulation of the healing process. µCT reveals a slight increase in bone matrix volume and the trabecular thickness number in the PACAP group, while histomorphometric analyzes reveal a slight increase in the VIP group, both at a 14-d time-point; despite the increased expression of osteogenic factors, osteoblastic differentiation, activity, and maturation markers in both VIP and PACAP groups. Interestingly, a lower number of VIP and PACAP immunolabeled cells were observed in the treated groups, suggesting a reduction in endogenous production. In conclusion, while both VIP and PACAP treatments presented a significant immunomodulatory effect with potential for increased healing, no major changes were observed in bone healing outcome, suggesting that the signals required for bone healing under homeostatic conditions are already optimal, and additional signals do not improve an already optimal process. Further studies are required to elucidate the role of macrophage polarization in the bone healing process.

Cutaneous innervation in impaired diabetic wound healing

Type 2 diabetes is associated with several potential comorbidities, among them impaired wound healing, chronic ulcerations, and the requirement for lower extremity amputation. Disease-associated abnormal cellular responses, infection, immunological and microvascular dysfunction, and peripheral neuropathy are implicated in the pathogenesis of the wound healing impairment and the diabetic foot ulcer. The skin houses a dense network of sensory nerve afferents and nerve-derived modulators, which communicate with epidermal keratinocytes and dermal fibroblasts bidirectionally to effect normal wound healing after trauma. However, the mechanisms through which cutaneous innervation modulates wound healing are poorly understood, especially in humans. Better understanding of these mechanisms may provide the basis for targeted treatments for chronic diabetic wounds. This review provides an overview of wound healing pathophysiology with a focus on neural involvement in normal and diabetic wound healing, as well as future therapeutic perspectives to address the unmet needs of diabetic patients with chronic wounds.

Extreme ecchymoses in a migraine patient using concomitant treatment with calcitonin gene-related peptide receptor antibodies and fish oil supplements: a case report

Background

Erenumab, a monoclonal antibody against the calcitonin gene-related peptide (CGRP) receptor, is registered for migraine prevention. Compared to other conventional migraine prevention medicines (i.e. topiramate, betablockers and amitriptyline) erenumab has better tolerability. Impaired hemostasis has not been reported previously. Here, we report the first case of an increased tendency to bruise in a migraine patient treated with erenumab.

Case presentation

A 41-year old female migraine patient was treated with erenumab for 12 months, which led to a significant reduction of headache and migraine days. Three months after treatment start, she experienced increased tendency to bruise leading to extreme ecchymosis after 4 months treatment. Platelet counts and aggregation, thromboelastography, activated partial thromboplastin time (APTT) and international normalized ratio (INR) were all normal. Thorough interview revealed intake of fish oil supplements for many years prior to treatment. The increased tendency to bruise subsided after discontinuation of fish oil supplements.

Conclusion

The combination of fish oil supplements and erenumab may cause increased tendency to bruise. Erenumab has no effect on the platelets per se but may cause impaired wound healing by suppression of CGRP. Thus, small and unnoticeable bruises may be aggravated instead in patients with tendency to bruise caused by for instance fish oil supplements.

Key indicators of repetitive overuse-induced neuromuscular inflammation and fibrosis are prevented by manual therapy in a rat model

BACKGROUND

We examined the effectiveness of a manual therapy consisting of forearm skin rolling, muscle mobilization, and upper extremity traction as a preventive treatment for rats performing an intensive lever-pulling task. We hypothesized that this treatment would reduce task-induced neuromuscular and tendon inflammation, fibrosis, and sensorimotor declines.

METHODS

Sprague-Dawley rats performed a reaching and lever pulling task for a food reward, 2 h/day, 3 days/week, for 12 weeks, while simultaneously receiving the manual therapy treatment 3 times per week for 12 weeks to either the task-involved upper extremities (TASK-Tx), or the lower extremities as an active control group (TASK-Ac). Results were compared to similarly treated control rats (C-Tx and C-Ac).

RESULTS

Median nerves and forearm flexor muscles and tendons of TASK-Ac rats showed higher numbers of inflammatory CD68+ and fibrogenic CD206+ macrophages, particularly in epineurium, endomysium and epitendons than TASK-Tx rats. CD68+ and CD206+ macrophages numbers in TASK-Tx rats were comparable to the non-task control groups. TASK-Ac rats had more extraneural fibrosis in median nerves, pro-collagen type I levels and immunoexpression in flexor digitorum muscles, and fibrogenic changes in flexor digitorum epitendons, than TASK-Tx rats (which showed comparable responses as control groups). TASK-Ac rats showed cold temperature, lower reflexive grip strength, and task avoidance, responses not seen in TASK-Tx rats (which showed comparable responses as the control groups).

CONCLUSIONS

Manual therapy of forelimbs involved in performing the reaching and grasping task prevented the development of inflammatory and fibrogenic changes in forearm nerves, muscle, and tendons, and sensorimotor declines.

Neuropeptide Substance P Enhances Skin Wound Healing In Vitro and In Vivo under Hypoxia

Pressure ulcers (PUs) or sores are a secondary complication of diabetic neuropathy and traumatic spinal cord injury (SCI). PUs tend to occur in soft tissues located around bony prominences and may heal slowly or not at all. A common mechanism underlying impaired healing of PUs may be dysfunction of the local neurovascular system including deficiency of essential neuropeptides, such as substance P (SP). Previous studies indicate that disturbance in cutaneous sensory innervation leads to a defect in all stages of wound healing, as is the case after SCI. It is hypothesized that nerve fibers enhance wound healing by promoting initial inflammation via the releasing of neuropeptides such as SP. Therefore, we investigated whether exogenous SP improves skin wound healing using in vitro and in vivo models. For in vitro studies, the effects of SP on keratinocyte proliferation and wound closure after a scratch injury were studied under normoxia (pO₂ ~21%) or hypoxia (pO₂ ~1%) and in presence of normal serum (10% v/v) or low serum (1% v/v) concentrations. Hypoxia and low serum both significantly slowed cell proliferation and wound closure. Under combined low serum and hypoxia, used to mimic the nutrient- and oxygen-poor environment of chronic wounds, SP (10⁻⁷ M) significantly enhanced cell proliferation and wound closure rate. For in vivo studies, two full-thickness excisional wounds were created with a 5 mm biopsy punch on the dorsum on either side of the midline of 15-week-old C57BL/6J male and female mice. Immediately, wounds were treated topically with one dose of 0.5 μg SP or PBS vehicle. The data suggest a beneficial role in wound closure and reepithelization, and thus enhanced wound healing, in male and female mice. Taken together, exogenously applied neuropeptide SP enhanced wound healing via cell proliferation and migration in vitro and in vivo. Thus, exogenous SP may be a useful strategy to explore further for treating PUs in SCI and diabetic patients.

Neuroimmune Regulation of Surgery-Associated Metastases

Surgery remains an essential therapeutic approach for most solid malignancies. Although for more than a century accumulating clinical and experimental data have indicated that surgical procedures themselves may promote the appearance and progression of recurrent and metastatic lesions, only in recent years has renewed interest been taken in the mechanism by which metastasizing of cancer occurs following operative procedures. It is well proven now that surgery constitutes a risk factor for the promotion of pre-existing, possibly dormant micrometastases and the acceleration of new metastases through several mechanisms, including the release of neuroendocrine and stress hormones and wound healing pathway-associated immunosuppression, neovascularization, and tissue remodeling. These postoperative consequences synergistically facilitate the establishment of new metastases and the development of pre-existing micrometastases. While only in recent years the role of the peripheral nervous system has been recognized as another contributor to cancer development and metastasis, little is known about the contribution of tumor-associated neuronal and neuroglial elements in the metastatic disease related to surgical trauma and wound healing. Specifically, although numerous clinical and experimental data suggest that biopsy- and surgery-induced wound healing can promote survival and metastatic spread of residual and dormant malignant cells, the involvement of the tumor-associated neuroglial cells in the formation of metastases following tissue injury has not been well understood. Understanding the clinical significance and underlying mechanisms of neuroimmune regulation of surgery-associated metastasis will not only advance the field of neuro–immuno–oncology and contribute to basic science and translational oncology research but will also produce a strong foundation for developing novel mechanism-based therapeutic approaches that may protect patients against the oncologically adverse effects of primary tumor biopsy and excision.

Possible involvement of neuropeptide and neurotransmitter receptors in Adenomyosis

BACKGROUND

Accumulating data indicate that sensory nerve derived neuropeptides such as substance P and calcitonin gene related-protein (CGRP) can accelerate the progression of endometriosis via their respective receptors, so can agonists to their respective receptors receptor 1 (NK1R), receptor activity modifying protein 1 (RAMP-1) and calcitonin receptor-like receptor (CRLR). Adrenergic β2 receptor (ADRB2) agonists also can facilitate lesional progression. In contrast, women with endometriosis appear to have depressed vagal activity, concordant with reduced expression of α7 nicotinic acetylcholine receptor (α7nAChR). The roles of these receptors in adenomyosis are completely unknown.

METHODS

Adenomyotic tissue samples from 30 women with adenomyosis and control endometrial tissue samples from 24 women without adenomyosis were collected and subjected to immunohistochemistry analysis of RAMP1, CRLR, NK1R, ADRB2 and α7nAChR, along with their demographic and clinical information. The extent of tissue fibrosis was evaluated by Masson trichrome staining.

RESULTS

We found that the staining levels of NK1R, CRLR, RAMP1 and ADRB2 were all significantly elevated in adenomyotic lesions as compared with control endometrium. In contrast, α7nAChR staining levels were significantly reduced. The severity of dysmenorrhea correlated positively with lesional ADRB2 staining levels.

CONCLUSIONS

Our results suggest that SP, CGRP and noradrenaline may promote, while acetylcholine may stall, the progression of adenomyosis through their respective receptors on adenomyotic lesions. Additionally, through the activation of the hypothalamic-pituitary-adrenal (HPA)-sympatho-adrenal-medullary (SAM) axes and the lesional overexpression of ADRB2, adenomyosis-associated dysmenorrhea and adenomyotic lesions may be mutually promotional, forming a viscous feed-forward cycle.

[Tridimensional in vitro models of nervous and immune systems in the skin]

The immune system and the sensory nervous system are responsible for perceiving danger under distinct yet complementary forms. In the last few years, neuroimmune interactions have become an important topic of dermatological research for conditions including wound healing, atopic dermatitis and psoriasis. We present here a selection of tridimensional in vitro models that reproduce skin structure and integrate an immune or a sensory function. Future evolutions of such models are expected to greatly contribute in a better understanding of reciprocal influences between sensory nervous system and immune system.

Reduced vagal tone in women with endometriosis and auricular vagus nerve stimulation as a potential therapeutic approach

Sensory and sympathetic nerves have been shown to promote the progression of endometriosis through the release of neuromediators and the lesional activation of respective receptors. The role of vagus nerves (VN) in lesional progression, however, is completely unclear, despite the signs suggestive of increased sympathetic tone in women with endometriosis. This study was undertaken to investigate whether VN plays any role in the progression of endometriosis. We recruited 45 patients with endometriosis and 42 healthy women, who were given electrocardiogram test and their heart rate variability was evaluated. In addition, three prospective, and randomized mouse experiments were conducted that evaluated, respectively, the effect of vagotomy, the effect of VN stimulation (VNS), and the therapeutic potential of VNS after the endometriosis was well established. All lesions were excised, weighed, and processed for immunohistochemistry and histochemistry analysis of select markers for lesional progression and fibrosis. We found that endometriosis patients exhibited reduced vagal activity as compared with controls, indicative of disrupted autonomic balance. Vagotomy increased while VNS decreased the lesion weight as compared with control mice, concomitant with more progressive and retarded lesion development and fibrogenesis, respectively. In addition, VNS demonstrated promising therapeutic effect, as evidenced by significantly reduced lesion weight, more attenuated lesional progression concomitant with improved hyperalgesia. Taken together, our data indicate that VN activity may play a dampening role in the progression of endometriosis. Consequently, boosting the VN activity may have therapeutic potentials for patients with endometriosis.

Sensory neurons from dorsal root ganglia regulate endothelial cell function in extracellular matrix remodelling

BACKGROUND

Recent physiological and experimental data highlight the role of the sensory nervous system in bone repair, but its precise role on angiogenesis in a bone regeneration context is still unknown. Our previous work demonstrated that sensory neurons (SNs) induce the osteoblastic differentiation of mesenchymal stem cells, but the influence of SNs on endothelial cells (ECs) was not studied.

METHODS

Here, in order to study in vitro the interplay between SNs and ECs, we used microfluidic devices as an indirect co-culture model. Gene expression analysis of angiogenic markers, as well as measurements of metalloproteinases protein levels and enzymatic activity, were performed.

RESULTS

We were able to demonstrate that two sensory neuropeptides, calcitonin gene-related peptide (CGRP) and substance P (SP), were involved in the transcriptional upregulation of angiogenic markers (vascular endothelial growth factor, angiopoietin 1, type 4 collagen, matrix metalloproteinase 2) in ECs. Co-cultures of ECs with SNs also increased the protein level and enzymatic activity of matrix metalloproteinases 2 and 9 (MMP2/MMP9) in ECs.

CONCLUSIONS

Our results suggest a role of sensory neurons, and more specifically of CGRP and SP, in the remodelling of endothelial cells extracellular matrix, thus supporting and enhancing the angiogenesis process. Video abstract.

Quantification of axonal ingrowth and functional recovery in a myocutaneous flap model in rats with strong clinical implications

The process of reinnervation, an important component of functional restoration after flap transfer, is understudied, making it necessary to carry out a further investigation for delineation of the exact timeline. Seventy-six Sprague-Dawley rats were used as the experimental animals. An anatomic study was first conducted to clarify the pattern of nerve distribution in the dorsal skin of 16 rats. Afterward, a myocutaneous flap was harvested on the right flanks of 40 rats, which were then assigned into seven time points. At each time point, skin samples were harvested and immunofluorescent staining was performed using α-Bungarotoxin, and antibodies against NF-200, p75, α-SMA, and TH. One-way analysis of variance was adopted for comparison of nerve density after surgery. For evaluation of functional return, cutaneous trunci muscle reflex (CTMr) test was performed on 10 additional rats, and the Chi-square test was used for comparison of reflex intensity among six time points after surgery. The outcomes revealed that the cutaneous branches from the intercostal nerves and the dorsothoracic nerve from the brachial plexus could be found entering the dorsal skin, distributed in the skin proper and the panniculus carnosus, respectively. After flap surgery, full spontaneous reinnervation of the skin proper and vessels within the flaps could be achieved at day 180. However, if the stumps of cutaneous branches of the intercostal nerves were damaged, the nerve density in the skin proper underwent a 2/3 decline. The panniculus carnosus in the cranial part had a much better reinnervation than that in the caudal part. The CTMr test showed that the flap could regain most of its sensate and motor activity. Our study shows that strong spontaneous reinnervation could be expected after flap surgery. The pattern of the original nerve distribution in both the recipient and donor sites may have a big impact on the reinnervation of the flap.

PAR2, Keratinocytes, and Cathepsin S Mediate the Sensory Effects of Ciguatoxins Responsible for Ciguatera Poisoning

Ciguatera fish poisoning is caused by the consumption of fish contaminated with ciguatoxins (CTXs). The most distressing symptoms are cutaneous sensory disturbances, including cold dysesthesia and itch. CTXs are neurotoxins known to activate voltage-gated sodium channels, but no specific treatment exists. Peptidergic neurons have been critically involved in ciguatera fish poisoning sensory disturbances. Protease-activated receptor-2 (PAR2) is an itch- and pain-related G protein‒coupled receptor whose activation leads to a calcium-dependent neuropeptide release. In this study, we studied the role of voltage-gated sodium channels, PAR2, and the PAR2 agonist cathepsin S in the cytosolic calcium increase and subsequent release of the neuropeptide substance P elicited by Pacific CTX-2 (P-CTX-2) in rat sensory neurons and human epidermal keratinocytes. In sensory neurons, the P-CTX-2‒evoked calcium response was driven by voltage-gated sodium channels and PAR2-dependent mechanisms. In keratinocytes, P-CTX-2 also induced voltage-gated sodium channels and PAR2-dependent marked calcium response. In the cocultured cells, P-CTX-2 significantly increased cathepsin S activity, and cathepsin S and PAR2 antagonists almost abolished P-CTX-2‒elicited substance P release. Keratinocytes synergistically favored the induced substance P release. Our results demonstrate that the sensory effects of CTXs involve the cathepsin S-PAR2 pathway and are potentiated by their direct action on nonexcitable keratinocytes through the same pathway.

[Pathophysiological role of calcitonin gene-related peptide (CGRP) in migraine and cluster headache]

Calcitonin gene-related peptide (CGRP) is released from trigeminal afferents during migraine and cluster headache attacks and can be detected in the jugular plasma. Infusion of CGRP can induce headache attacks in migraine and cluster patients. Inhibition of the CGRP signal system is therapeutic in migraine and cluster headache. CGRP is a potent dilator of intracranial arteries but does not immediately activate the trigeminal pain system. CGRP may act as a signal molecule between different cells in the trigeminal ganglion and enhances nociceptive transmission in the spinal trigeminal nucleus. Peripheral inhibition of the CGRP system reduces these actions. Outside the trigeminovascular system, CGRP is important for maintaining the perfusion of organs in critical situations, promotes growth and repair functions and is an immunomodulatory factor. These actions should be considered when the CGRP system is suppressed for a long time.

Neuroendocrinology and neurobiology of sebaceous glands

The nervous system communicates with peripheral tissues through nerve fibres and the systemic release of hypothalamic and pituitary neurohormones. Communication between the nervous system and the largest human organ, skin, has traditionally received little attention. In particular, the neuro-regulation of sebaceous glands (SGs), a major skin appendage, is rarely considered. Yet, it is clear that the SG is under stringent pituitary control, and forms a fascinating, clinically relevant peripheral target organ in which to study the neuroendocrine and neural regulation of epithelia. Sebum, the major secretory product of the SG, is composed of a complex mixture of lipids resulting from the holocrine secretion of specialised epithelial cells (sebocytes). It is indicative of a role of the neuroendocrine system in SG function that excess circulating levels of growth hormone, thyroxine or prolactin result in increased sebum production (seborrhoea). Conversely, growth hormone deficiency, hypothyroidism, and adrenal insufficiency result in reduced sebum production and dry skin. Furthermore, the androgen sensitivity of SGs appears to be under neuroendocrine control, as hypophysectomy (removal of the pituitary) renders SGs largely insensitive to stimulation by testosterone, which is crucial for maintaining SG homeostasis. However, several neurohormones, such as adrenocorticotropic hormone and α-melanocyte-stimulating hormone, can stimulate sebum production independently of either the testes or the adrenal glands, further underscoring the importance of neuroendocrine control in SG biology. Moreover, sebocytes synthesise several neurohormones and express their receptors, suggestive of the presence of neuro-autocrine mechanisms of sebocyte modulation. Aside from the neuroendocrine system, it is conceivable that secretion of neuropeptides and neurotransmitters from cutaneous nerve endings may also act on sebocytes or their progenitors, given that the skin is richly innervated. However, to date, the neural controls of SG development and function remain poorly investigated and incompletely understood. Botulinum toxin-mediated or facial paresis-associated reduction of human sebum secretion suggests that cutaneous nerve-derived substances modulate lipid and inflammatory cytokine synthesis by sebocytes, possibly implicating the nervous system in acne pathogenesis. Additionally, evidence suggests that cutaneous denervation in mice alters the expression of key regulators of SG homeostasis. In this review, we examine the current evidence regarding neuroendocrine and neurobiological regulation of human SG function in physiology and pathology. We further call attention to this line of research as an instructive model for probing and therapeutically manipulating the mechanistic links between the nervous system and mammalian skin.

Human Wound Healing Ex Vivo Model with Focus on Molecular Markers

Wound healing is a complex, multifactorial process that is divided in sequential and overlapping phases in order to restore the skin barrier. For the study of wound healing, different in vivo, in vitro, and ex vivo models have been used in the past. Here we describe in detail the methodology of the human skin punch-in-a-punch ex vivo wound healing model.

Alteration of Pressure-Induced Vasodilation in Aging and Diabetes, a Neuro-Vascular Damage

Skin is constantly subjected to pressure at different levels. Pressure-induced vasodilation (PIV) is one of the response mechanisms to low pressure that maintains the homeostasis of the skin. PIV results from the interaction of primary afferent nerves and vascular endothelium of skin vessels. Thanks to this cutaneous neuro-vascular interaction, the cutaneous blood flow increase allows the maintenance of an optimal level of oxygenation and minimizes the lack of vascularization of the skin tissue under low pressure. It seems to be associated with the cutaneous protection mechanisms to prevent pressure ulcers. In some contexts, where microangiopathy and neuropathy can occur, such as aging and diabetes, PIV is impaired, leading to a dramatic early decrease in local skin blood flow when low pressure is applied. In aging, PIV alteration is due to endothelial dysfunction, essentially from an alteration of the nitric oxide pathway. In the inflamm-aging context, oxidative stress increases leading to endothelial cell and nerve damages. An age-related sensory neuropathy will exacerbate the alteration of PIV during the aging process. In diabetes, non-controlled hyperglycaemia leads to an increase in several pathological biochemical pathways that involve oxidative stress and can affect PIV. Sorbinil, alagebrium and alpha-lipoic acid are able individually to restore PIV through a possible oxidative stress reduction. Candesartan, an angiotensin II type 1 receptor blocker, is also able to restore PIV and prevent pressure ulcer formation. The possibility of preventing pressure ulcer associated to diabetes and/or aging with the restoration of PIV seems to be a promising research path.

Diverse Role of Biological Plasticity in Low Back Pain and Its Impact on Sensorimotor Control of the Spine

Pain is complex. It is no longer acceptable to consider pain solely as a peripheral phenomenon involving activation of nociceptive neurons. The contemporary understanding of pain involves consideration of different underlying pain mechanisms and an increasing awareness of plasticity in all of the biological systems. Of note, recent advances in technology and understanding have highlighted the critical importance of neuroimmune interactions, both in the peripheral and central nervous systems, and the interaction between the nervous system and body tissues in the development and maintenance of pain, including low back pain (LBP). Further, the biology of many tissues changes when challenged by pain and injury, as reported in a growing body of literature on the biology of muscle, fat, and connective tissue. These advances in understanding of the complexity of LBP have implications for our understanding of pain and its interaction with the motor system, and may change how we consider motor control in the rehabilitation of LBP. This commentary provides a state-of-the-art overview of plasticity of biology in LBP. The paper is divided into 4 parts that address (1) biology of pain mechanisms, (2) neuroimmune interaction in the central nervous system, (3) neuroimmune interaction in the periphery, and (4) brain and peripheral tissue interaction. Each section considers the implications for clinical management of LBP. J Orthop Sports Phys Ther 2019;49(6):389-401. doi:10.2519/jospt.2019.8716.

Subclinical lipopolysaccharide from Salmonella Enteritidis induces neuropeptide dysregulation in the spinal cord and the dorsal root ganglia

Background

Despite increasing evidence that lipopolysaccharide (LPS) affects the biological active substances of dorsal root ganglia (DRG) we have limited knowledge of the influence of a single low dose of LPS, which does not result in any clinical symptoms of disease (subclinical LPS) on neuropeptides connected with the sensory pathway. Accordingly, in this work, we investigated the influence of subclinical LPS from Salmonella Enteritidis on selected neuropeptides: substance P (SP), galanin (GAL), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP) and somatostatin (SOM) in the cervical, thoracic, lumbar and sacral regions of the DRG and spinal cord.

Methods

This study was performed on immature female pigs of the Pietrain × Duroc breed. Seven days after the intravenous injection of saline solution for control animals (n = 5) and 5 μg/kg b.w. LPS from S. Enteritidis for the experimental group (n = 5), the DRG and the spinal cord were collected to extract the neuropeptides using solid-phase extraction technology.

Results

Our results demonstrated that subclinical LPS in DRG was able to change the levels of all studied neuropeptides except SOM, whereas in the spinal cord it down-regulated all studied neuropeptides in the sacral spinal cord, maintaining the concentration of all studied neuropeptides in other regions similar to that observed in the control animals. The significant differences in the intensity and character of observed changes between particular regions of the DRG suggest that the exact functions of the studied neuropeptides and mechanisms of responses to subclinical LPS action depend on specific characteristics and functions of each examination region of DRG.

Conclusions

The mechanisms of observed changes are not fully understood and require further study of the molecular interactions between subclinical LPS from S. Enteritidis and neuronal and non-neuronal cells of DRG and spinal cord. The peripheral and central pain pathways must be analysed with the aspect of unknown long-term consequences of the influence of subclinical LPS from S. Enteritidis on neuropeptides in the spinal cord and the dorsal root ganglia.

Neuropeptides Substance P and Calcitonin Gene Related Peptide Accelerate the Development and Fibrogenesis of Endometriosis

Endometriotic lesions are known to be hyperinnervated, especially in lesions of deep endometriosis (DE), which are frequently in close proximity to various nerve plexuses. DE lesions typically have higher fibromuscular content than that of ovarian endometriomas (OE) lesions, but the underlying reason remains elusive. Aside from their traditional role of pain transduction, however, whether or not sensory nerves play any role in the development of endometriosis is unclear. Here, we show that, thorough their respective receptors neurokinin receptor 1 (NK1R), calcitonin receptor like receptor (CRLR), and receptor activity modifying protein 1 (RAMP-1), neuropeptides substance P (SP) and calcitonin gene related peptide (CGRP) induce epithelial-mesenchymal transition (EMT), fibroblast-to-myofibroblast transdifferentiation (FMT) and further turn stromal cells into smooth muscle cells (SMCs) in endometriotic lesions, resulting ultimately in fibrosis. We show that SP and CGRP, or the rat dorsal root ganglia (DRG) supernatant, through the induction of NK1R and CGRP/CRLR/RAMP-1 signaling pathways, promoted EMT, FMT and SMM in endometriosis, resulting in increased migratory and invasive propensity, cell contractility, production of collagen, and eventually to fibrosis. Neutralization of NK1R and/or CGRP/CRLR/RAMP-1 abrogated these processes. Extended exposure of endometriotic stromal cells to SP and/or CGRP or the DRG supernatant induced increased expression of α-SMA, desmin, oxytocin receptor, and smooth muscle myosin heavy-chain. Finally, we show that DE lesions had significantly higher nerve fiber density, increased staining levels of α-SMA, NK1R, CRLR, and RAMP-1, concomitant with higher lesional fibrotic content than that of OE lesions. The extent of lesional fibrosis correlated positively with the staining levels of NK1R, CRLR, and RAMP-1, as well as the nerve fiber density in lesions. Thus, this study provides another piece of evidence that sensory nerves play an important role in promoting the development and fibrogenesis of endometriosis. It explains as why DE frequently have higher fibromuscular content than that of OE, highlights the importance of lesional microenvironment in shaping the lesional fate, gives more credence to the idea that ectopic endometrium is fundamentally wounds that go through repeated tissue injury and repair, and should shed much needed light into the pathophysiology of endometriosis.

Pituitary adenylate cyclase-activating polypeptide is a potent broad-spectrum antimicrobial peptide: Structure-activity relationships

Pituitary adenylate cyclase-activating polypeptide (PACAP) is a naturally occurring cationic peptide with potent immunosuppressant and cytoprotective activities. We now show that full length PACAP38 and to a lesser extent, the truncated form PACAP27, and the closely related vasoactive intestinal peptide (VIP) and secretin had antimicrobial activity against the Gram-negative bacteria Escherichia coli in the radial diffusion assay. PACAP38 was more potent than either the bovine neutrophil antimicrobial peptide indolicidin or the synthetic antimicrobial peptide ARVA against E. coli. PACAP38 also had activity against the Gram-positive bacteria Staphylococcus aureus in the same assay with comparable potency to indolicidin and ARVA. In the more stringent broth dilution assay, PACAP38 had moderate sterilizing activity against E. coli, and potent sterilizing activity against the Gram-negative bacteria Pseudomonas aeruginosa. PACAP27, VIP and secretin were much less active than PACAP38 in this assay. PACAP38 also had some activity against the Gram-positive bacteria Bacillus cereus in the broth dilution assay. Many exopeptidase-resistant analogs of PACAP38, including both receptor agonists and antagonists, had antimicrobial activities equal to, or better than PACAP38, in both assays. PACAP38 made the membranes of E. coli permeable to SYTOX Green, suggesting a classical membrane lytic mechanism. These data suggest that analogs of PACPAP38 with a wide range of useful biological activities can be made by judicious substitutions in the sequence.

Substance P increases CCN2 dependent on TGF-beta yet Collagen Type I via TGF-beta1 dependent and independent pathways in tenocytes

Transforming growth factor beta 1 (TGFbeta-1) and connective tissue growth factor (CCN2) are important mediators of tissue repair and fibrosis, with CCN2 functioning as a downstream mediator of TGFβ-1. Substance P (SP) is also linked to collagen production in tenocytes. A link between SP, TGFbeta-1 and CCN2 has yet to be established in tenocytes or fibrogenic processes. We sought to determine whether SP induces tenocyte proliferation, CCN2, or collagen production via TGFbeta-1 signaling or independently in rat primary tenocytes. Tenocytes were isolated from rat tendons, cultured and stimulated by SP and/or TGFbeta-1. Cultured cells expressed proteins characteristic of tenocytes (vimentin and tenomodulin) and underwent increased proliferation dose dependently after SP and TGFbeta-1 treatments, alone or combined (more than SP alone when combined). SP induced TGFbeta-1 expression in tenocytes in both dose- and time-dependent manners. SP and TGFbeta-1, alone or combined, stimulated CCN2 expression in tenocytes and their supernatants after both 24 and 48 h of stimulation; a response blocked with addition of a TGFbeta-1 receptor inhibitor. In contrast, SP potentiated collagen type I secretion by tenocytes, a response abrogated by the TGFbeta-1 receptor inhibitor after 48 h of stimulation, but not after the shorter 24 h of stimulation. Our findings suggest that both SP and TGFbeta-1 can stimulate tenocyte fibrogenic processes, albeit differently. TGFbeta-1 pathway signaling was involved in CCN2 production at all time points examined, while SP induced collagen type I production independently prior to the onset of signaling through the TGFbeta-1 pathway.

Comparison of Neurovascular Characteristics of Facial Skin in Patients After Primary and Revision Rhytidectomies

Importance

Wound healing influences both the cosmetic and functional outcomes of facial surgery. Study of cutaneous innervation may afford insight into patients' preoperative wound healing potential and aid in their selection of appropriate surgical procedures.

Objective

To present the quantitative and qualitative differences of epidermal nerve fibers (ENFs), neurotransmitters, vasculature, and mast cells in facial skin among patients after primary and revision rhytidectomies.

Design, Setting, and Participants

This pilot study collected cutaneous specimens from 8 female patients aged 42 to 66 years who underwent primary rhytidectomy (n = 5) and revision rhytidectomy (n = 3) at Centennial Lakes Surgery Center, Edina, Minnesota, from July 2010 to March 2014. Tissue was processed for confocal/epifluorescence microscopy and indirect immunofluorescent localization of several neural and tissue antigens as well as basement membrane and mast cell markers.

Intervention

Primary rhytidectomy vs revision rhytidectomy with selection of a small area of redundant, otherwise disposed of tissue anterior to the tragus for ENF study.

Main Outcomes and Measures

Demographic characteristics included smoking status; 10-point rating scales for facial sensation, pain, and paresthesias; and confocal/epifluorescence microscopy to quantify ENFs, neurotransmitters, vasculature, and mast cells.

Results

Patients in the primary rhytidectomy group had a mean (SD) of 54.4 (31.6) ENFs/mm (range, 14.2-99.2 ENFs/mm), and those in the revision rhytidectomy group had a mean (SD) of 18.6 (5.8) ENFs/mm (range, 13.8-25.0 ENFs/mm). A patient in the primary rhytidectomy group was a 25-pack-year smoker and had 14.2 ENFs/mm, the lowest in both groups. In addition to these structural neural changes, functional neural changes in revision rhytidectomy samples included qualitative changes in normal neural antigen prevalence (substance P, calcitonin gene-related peptide, and vasoactive intestinal peptide). Capillary loops appeared less robust and were less common in dermal papilla among samples from both the primary and revision groups, and mast cells were more degranulated. No differences were found in subjective, self-reported postoperative facial sensation.

Conclusions and Relevance

Previous skin elevation was associated with decreased epidermal nerve fiber density and qualitative changes in dermal nerves, capillaries, and mast cells in a clinical sample of patients undergoing rhytidectomy. Future research is needed to determine whether histological findings predict wound healing and to better understand the effects of surgery on regenerative capacity of epidermal nerve fibers.

Level of Evidence

NA.

Morphological and neurochemical differences in peptidergic nerve fibers of the mouse vagina

The vagina is innervated by a complex arrangement of sensory, sympathetic, and parasympathetic nerve fibers that contain classical transmitters plus an array of neuropeptides and enzymes known to regulate diverse processes including blood flow and nociception. The neurochemical characteristics and distributions of peptide-containing nerves in the mouse vagina are unknown. This study used multiple labeling immunohistochemistry, confocal maging and analysis to investigate the presence and colocalization of the peptides vasoactive intestinal polypeptide (VIP), calcitonin-gene related peptide (CGRP), substance P (SP), neuropeptide tyrosine (NPY), and the nitric oxide synthesizing enzyme neuronal nitric oxide synthase (nNOS) in nerve fibers of the murine vaginal wall. We compared cervical and vulvar areas of the vagina in young nullipara and older multipara C57Bl/6 mice, and identified differences including that small ganglia were restricted to cervical segments, epithelial fibers were mainly present in vulvar segments and most nerve fibers were found in the lamina propria of the cervical region of the vagina, where a higher number of fibers containing immunoreactivity for VIP, CGRP, SP, or nNOS were found. Two populations of VIP-containing fibers were identified: fibers containing CGRP and fibers containing VIP but not CGRP. Differences between young and older mice were present in multiple layers of the vaginal wall, with older mice showing overall loss of innervation of epithelium of the proximal vagina and reduced proportions of VIP, CGRP, and SP containing nerve fibers in the distal epithelium. The distal vagina also showed increased vascularization and perivascular fibers containing NPY. Immunolabeling of ganglia associated with the vagina indicated the likely origin of some peptidergic fibers. Our results reveal regional differences and age- or parity-related changes in innervation of the mouse vagina, effecting the distribution of neuropeptides with diverse roles in function of the female genital tract.

Effects of small-fiber neuropathy induced by resiniferatoxin on skin healing and axonal regrowth after burn

BACKGROUND

Damage to the peripheral nervous system influences wound healing and, after a deep burn, imperfect cutaneous nerve regeneration occurs. A third-degree burn model was developed in rats combined with the use of resiniferatoxin (RTX), known to promote sensory neuropathy.

METHODS

Rats were injected intraperitoneally either with RTX or vehicle. A mechanical sensory assay and the hot plate thermal sensory test were performed. The structural integrity of the sciatic nerve was assessed using transmission electron microcopy. After RTX injection, third-degree thermal burns were performed. Wound closure was monitored and samples were collected for histological analysis, immunohistochemistry and immunoblotting for neuronal markers.

RESULTS

RTX promoted both mechanical and thermal hypoalgesia. This transient RTX-mediated sensory deficit occurred without damaging the integrity of nerve fibers and induced a significant depletion of neuropeptides in both neuronal bodies and intraepidermal nerve fibers. Although wound closure rates were similar in both groups, the kinetic of granulation tissue remodeling was delayed in the RTX group compared with control group. A significant reduction of the peripherin expression in the RTX group was observed indicating impaired axonal regrowth of small fibers within the wound.

CONCLUSION

Our study confirms the important roles of innervation during skin healing and the defect of nerve regeneration after burn.

In-Situ-Generated Vasoactive Intestinal Peptide Loaded Microspheres in Mussel-Inspired Polycaprolactone Nanosheets Creating Spatiotemporal Releasing Microenvironment to Promote Wound Healing and Angiogenesis

Vasoactive intestinal peptide (VIP) was reported to promote angiogenesis. Electrospun nanofibers lead to idea wound dressing substrates. Here we report a convenient and novel method to produce VIP loaded microspheres in polycaprolactone (PCL) nanofibrous membrane without complicated processes. We first coated mussel-inspired dopamine (DA) to nanofibers, then used strong adhesive DA to absorb the functional peptide. PCL membrane was then immersed into acetone to generate microspheres with VIP loading. We employed high pressure liquid chromatography to record encapsulation efficiency of (31.8 ± 2.2)% and loading capacity of (1.71 ± 0.16)%. The release profile of VIP from nanosheets showed a prolonged release. The results of laser scanning confocal microscope, scanning electron microscope and cell counting kit-8 proliferation assays showed that cell adhesion and proliferation were promoted. In order to verify the efficacy on wound healing, in vivo implantation was applied in the full-thickness defect wounds of BALB/c mice. Results showed that the wound healing was significantly promoted via favoring the growth of granulation tissue and angiogenesis. However, we found wound re-epithelialization was not significantly improved. The resulting VIP-DA-coated PCL (PCL-DA-VIP) nanosheets with spatiotemporal delivery of VIP could be a potential application in wound treatment and vascular tissue engineering.

The myofibroblast, a key cell in normal and pathological tissue repair

Myofibroblasts are characterized by their expression of α-smooth muscle actin, their enhanced contractility when compared to normal fibroblasts and their increased synthetic activity of extracellular matrix proteins. Myofibroblasts play an important role in normal tissue repair processes, particularly in the skin where they were first described. During normal tissue repair, they appear transiently and are then lost via apoptosis. However, the chronic presence and continued activity of myofibroblasts characterize many fibrotic pathologies, in the skin and internal organs including the liver, kidney and lung. More recently, it has become clear that myofibroblasts also play a role in many types of cancer as stromal or cancer-associated myofibroblast. The fact that myofibroblasts are now known to be key players in many pathologies makes understanding their functions, origin and the regulation of their differentiation important to enable them to be regulated in normal physiology and targeted in fibrosis, scarring and cancer.

Comparative transcriptomic profiling of hydrogen peroxide signaling networks in zebrafish and human keratinocytes: Implications toward conservation, migration and wound healing

Skin wounds need to be repaired rapidly after injury to restore proper skin barrier function. Hydrogen peroxide (H₂O₂) is a conserved signaling factor that has been shown to promote a variety of skin wound repair processes, including immune cell migration, angiogenesis and sensory axon repair. Despite growing research on H₂O₂ functions in wound repair, the downstream signaling pathways activated by this reactive oxygen species in the context of injury remain largely unknown. The goal of this study was to provide a comprehensive analysis of gene expression changes in the epidermis upon exposure to H₂O₂ concentrations known to promote wound repair. Comparative transcriptome analysis using RNA-seq data from larval zebrafish and previously reported microarray data from a human epidermal keratinocyte line shows that H₂O₂ activates conserved cell migration, adhesion, cytoprotective and anti-apoptotic programs in both zebrafish and human keratinocytes. Further assessment of expression characteristics and signaling pathways revealed the activation of three major H₂O₂–dependent pathways, EGF, FOXO1, and IKKα. This study expands on our current understanding of the clinical potential of low-level H₂O₂ for the promotion of epidermal wound repair and provides potential candidates in the treatment of wound healing deficits.

Chronic sciatic nerve compression induces fibrosis in dorsal root ganglia

In the present study, pathological alterations in neurons of the dorsal root ganglia (DRG) were investigated in a rat model of chronic sciatic nerve compression. The rat model of chronic sciatic nerve compression was established by placing a 1 cm Silastic tube around the right sciatic nerve. Histological examination was performed via Masson's trichrome staining. DRG injury was assessed using Fluoro Ruby (FR) or Fluoro Gold (FG). The expression levels of target genes were examined using reverse transcription-quantitative polymerase chain reaction, western blot and immunohistochemical analyses. At 3 weeks post-compression, collagen fiber accumulation was observed in the ipsilateral area and, at 8 weeks, excessive collagen formation with muscle atrophy was observed. The collagen volume fraction gradually and significantly increased following sciatic nerve compression. In the model rats, the numbers of FR-labeled DRG neurons were significantly higher, relative to the sham-operated group, however, the numbers of FG-labeled neurons were similar. In the ipsilateral DRG neurons of the model group, the levels of transforming growth factor-β1 (TGF-β1) and connective tissue growth factor (CTGF) were elevated and, surrounding the neurons, the levels of collagen type I were increased, compared with those in the contralateral DRG. In the ipsilateral DRG, chronic nerve compression was associated with significantly higher levels of phosphorylated (p)-extracellular signal-regulated kinase 1/2, and significantly lower levels of p-c-Jun N-terminal kinase and p-p38, compared with those in the contralateral DRGs. Chronic sciatic nerve compression likely induced DRG pathology by upregulating the expression levels of TGF-β1, CTGF and collagen type I, with involvement of the mitogen-activated protein kinase signaling pathway.