Topical substance P increases inflammatory cell density in genetically diabetic murine wounds

A Narrative Review of Diabetic Macroangiopathy: From Molecular Mechanism to Therapeutic Approaches

Diabetic macroangiopathy, a prevalent and severe complication of diabetes mellitus, significantly contributes to the increased morbidity and mortality rates among affected individuals. This complex disorder involves multifaceted molecular mechanisms that lead to the dysfunction and damage of large blood vessels, including atherosclerosis (AS) and peripheral arterial disease. Understanding the intricate pathways underlying the development and progression of diabetic macroangiopathy is crucial for the development of effective therapeutic interventions. This review aims to shed light on the molecular mechanism implicated in the pathogenesis of diabetic macroangiopathy. We delve into the intricate interplay of chronic inflammation, oxidative stress, endothelial dysfunction, and dysregulated angiogenesis, all of which contribute to the vascular complications observed in this disorder. By exploring the molecular mechanism involved in the disease we provide insight into potential therapeutic targets and strategies. Moreover, we discuss the current therapeutic approaches used for treating diabetic macroangiopathy, including glycemic control, lipid-lowering agents, and vascular interventions.

The neuropeptide substance P/neurokinin-1 receptor system and diabetes: From mechanism to therapy

Diabetes is a significant public health issue known as the world's fastest-growing disease condition. It is characterized by persistent hyperglycemia and subsequent chronic complications leading to organ dysfunction and, ultimately, the failure of target organs. Substance P (SP) is an undecapeptide that belongs to the family of tachykinin (TK) peptides. The SP-mediated activation of the neurokinin 1 receptor (NK1R) regulates many pathophysiological processes in the body. There is also a relation between the SP/NK1R system and diabetic processes. Importantly, deregulated expression of SP has been reported in diabetes and diabetes-associated chronic complications. SP can induce both diabetogenic and antidiabetogenic effects and thus affect the pathology of diabetes destructively or protectively. Here, we review the current knowledge of the functional relevance of the SP/NK1R system in diabetes pathogenesis and its exploitation for diabetes therapy. A comprehensive understanding of the role of the SP/NK1R system in diabetes is expected to shed further light on developing new therapeutic possibilities for diabetes and its associated chronic conditions.

Research status and hot topics of the effects of skin innervation on wound healing from 1959 to 2022: A bibliometric analysis

Background

Skin innervation plays an important role in wound healing by either direct contact with or indirect secretions that impact skin cells. Many studies in this field have been published; however, there is a lack of bibliometric analyses focusing on the effect of skin innervation on skin wound healing. In this study, we aimed to analyse the research trends, status, and hotspots in this field.

Methods

Reviews and articles published in English were extracted from the Web of Science Core Collection (WoSCC) database based on subject term searches. Microsoft Office Excel, VOSviewer, and CiteSpace were used to analyse publication date, country or region, institution, author, and author keywords.

Results

A total of 368 papers published between 1959 and 2022 were included in the analysis. Although there was a pulsation during this period, there was an overall upward trend in studies related to the effect of skin innervation on wound healing. The United States, particularly the University of Washington, and Gibran, Nicole S. from the University of Washington, was the most active in this field. Wound Repair and Regeneration published the most relevant literature, and “Calcitonin gene-related peptide: physiology and pathophysiology” had the highest total number of citations. “Diabetic foot ulcer,” “epidermal stem cells,” “mesenchymal stem cells,” and “mast cells” are current and potential future research hotspots.

Conclusion

This bibliometric analysis will inform the overall trends in research related to the effect of skin innervation on wound healing, summarise relevant research hotspots, and guide future work.

The impact of sensory neuropathy and inflammation on epithelial wound healing in diabetic corneas

Diabetic peripheral neuropathy (DPN) is the most common complication of diabetes, with several underlying pathophysiological mechanisms, some of which are still uncertain. The cornea is an avascular tissue and sensitive to hyperglycemia, resulting in several diabetic corneal complications including delayed epithelial wound healing, recurrent erosions, neuropathy, loss of sensitivity, and tear film changes. The manifestation of DPN in the cornea is referred to as diabetic neurotrophic keratopathy (DNK). Recent studies have revealed that disturbed epithelial-neural-immune cell interactions are a major cause of DNK. The epithelium is supplied by a dense network of sensory nerve endings and dendritic cell processes, and it secretes growth/neurotrophic factors and cytokines to nourish these neighboring cells. In turn, sensory nerve endings release neuropeptides to suppress inflammation and promote epithelial wound healing, while resident immune cells provide neurotrophic and growth factors to support neuronal and epithelial cells, respectively. Diabetes greatly perturbs these interdependencies, resulting in suppressed epithelial proliferation, sensory neuropathy, and a decreased density of dendritic cells. Clinically, this results in a markedly delayed wound healing and impaired sensory nerve regeneration in response to insult and injury. Current treatments for DPN and DNK largely focus on managing the severe complications of the disease. Cell-based therapies hold promise for providing more effective treatment for diabetic keratopathy and corneal ulcers.

The Regenerative Potential of Substance P

Wound healing is a highly coordinated process which leads to the repair and regeneration of damaged tissue. Still, numerous diseases such as diabetes, venous insufficiencies or autoimmune diseases could disturb proper wound healing and lead to chronic and non-healing wounds, which are still a great challenge for medicine. For many years, research has been carried out on finding new therapeutics which improve the healing of chronic wounds. One of the most extensively studied active substances that has been widely tested in the treatment of different types of wounds was Substance P (SP). SP is one of the main neuropeptides released by nervous fibers in responses to injury. This review provides a thorough overview of the application of SP in different types of wound models and assesses its efficacy in wound healing.

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.

Annexin A1-derived peptide Ac2-26 facilitates wound healing in diabetic mice

Impaired wound healing is a common complication of diabetes. In diabetic wounds, macrophages present dysfunctional efferocytosis and abnormal phenotypes, which could result in excessive neutrophil accumulation and prolonged inflammation, thereby eventually hindering wound repair. ANXA1 N-terminal peptide Ac2-26 exhibits a high potential in mitigating inflammation and improving repair; however, its efficacy in diabetic wound repair remains unclear. In this study, a cutaneous excisional wound model was built in genetically diabetic mice. Ac2-26 or a vehicle solution was employed locally in wound sites. Subsequently, wound zones were measured and sampled at different time intervals post-wounding. Using hematoxylin-eosin and Masson's trichrome staining, we observed the histopathological variations and collagen deposition in wound samples. Based on immunohistochemistry and immunofluorescence, the numbers of neutrophils, macrophages, and CD206-positive macrophages in the wound samples were determined. Cytokine expression in wound samples was studied by immunoblot assay. Results showed that Ac2-26 treatment could facilitate diabetic wound closure, down-regulate the number of neutrophils, and improve angiogenesis and collagen deposition. In addition, Ac2-26 application expedited macrophage recruitment and up-regulated the percentage of macrophages expressing CD206, which is a marker for M2 macrophages. Moreover, Ac2-26 inhibited the expressions of TNF-α and IL-6 and up-regulated the expressions of IL-10, TGF-β, and VEGFA during diabetic wound healing. Hence, based on the aforementioned findings, Ac2-26 application in diabetic wounds could exert anti-inflammatory and pro-repair effects by reducing neutrophil accumulation and facilitating M2 macrophage development.

Autonomic nerve dysfunction and impaired diabetic wound healing: The role of neuropeptides

Lower extremity ulcerations represent a major complication in diabetes mellitus and involve multiple physiological factors that lead to impairment of wound healing. Neuropeptides are neuromodulators implicated in various processes including diabetic wound healing. Diabetes causes autonomic and small sensory nerve fibers neuropathy as well as inflammatory dysregulation, which manifest with decreased neuropeptide expression and a disproportion in pro- and anti- inflammatory cytokine response. Therefore to fully understand the contribution of autonomic nerve dysfunction in diabetic wound healing it is crucial to explore the implication of neuropeptides. Here, we will discuss recent studies elucidating the role of specific neuropeptides in wound healing.

Controlled-release neurotensin-loaded silk fibroin dressings improve wound healing in diabetic rat model

Diabetic foot ulcers (DFU), which may lead to lower extremity amputation, is one of the severe and chronic complications of diabetic mellitus. This study aims to develop, and use dressings based on Silk fibroin (SF) as the scaffold material, gelatin microspheres (GMs) as the carrier for the neurotensin (NT), a neuropeptide that acts as an inflammatory modulator in wound healing and NT as accelerate wound healing drug to treat DFU. We evaluated the wound healing processes and neo-tissue formation in rat diabetic model by macroscopic observation, histological observation (H&E staining and Masson's trichrome staining) and immunofluorescence analysis at 3, 7, 14, 21 and 28 post-operation days. Our results show that the NT/GMs/SF group performance the best not only in macroscopic healing and less scars in 28 post-operation days, but also in fibroblast accumulation in tissue granulation, collagen expression and deposition at the wound site. From release profiles, we can know the GMs are a good carrier for control release drugs. The SEM results shows that the NT/GMs/SF dressings have an average pore size are 40–80 μm and a porosity of ∼85%, this pore size is suit for wound healing regeneration. These results suggest that the NT/GMs/SF dressings may work as an effective support for control release NT to promote DFU wound healing.

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This study aims to develop, and use dressings based on Silk fibroin (SF) as the scaffold material, gelatin microspheres (GMs) as the carrier for the Neurotensin (NT), a neuropeptide that acts as an inflammatory modulator in wound healing and NT as accelerate wound healing drug to treat DFU.

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The NT/GMs/SF dressings stimulated fibroblast accumulation in tissue granulation, collagen expression and deposition at the wound site, which lead to the production of a more organized collagen matrix.

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This treatment effectively accelerating wound regeneration and re-epithelialization.

Mechanistic insight into diabetic wounds: Pathogenesis, molecular targets and treatment strategies to pace wound healing

Wound management in diabetic patient is of an extreme clinical and social concern. The delayed and impaired healing makes it more critical for research focus. The research on impaired healing process is proceeding hastily evident by new therapeutic approaches other than conventional such as single growth factor, dual growth factor, skin substitutes, cytokine stimulators, cytokine inhibitors, matrix metalloproteinase inhibitors, gene and stem cell therapy, extracellular matrix and angiogenesis stimulators. Although numerous studies are available that support delayed wound healing in diabetes but detailed mechanistic insight including factors involved and their role still needs to be revealed. This review mainly focuses on the molecular cascades of cytokines (with growth factors) and erstwhile factors responsible for delayed wound healing, molecular targets and recent advancements in complete healing and its cure. Present article briefed recent pioneering information on possible molecular targets and treatment strategies including clinical trials to clinicians and researchers working in similar area.

Substance P combined with epidermal stem cells promotes wound healing and nerve regeneration in diabetes mellitus

Exogenous substance P accelerates wound healing in diabetes, but the mechanism remains poorly understood. Here, we established a rat model by intraperitoneally injecting streptozotocin. Four wounds (1.8 cm diameter) were drilled using a self-made punch onto the back, bilateral to the vertebral column, and then treated using amniotic membrane with epidermal stem cells and/or substance P around and in the middle of the wounds. With the combined treatment the wound-healing rate was 100% at 14 days. With prolonged time, type I collagen content gradually increased, yet type III collagen content gradually diminished. Abundant protein gene product 9.5- and substance P-immunoreactive nerve fibers regenerated. Partial nerve fiber endings extended to the epidermis. The therapeutic effects of combined substance P and epidermal stem cells were better than with amniotic membrane and either factor alone. Our results suggest that the combination of substance P and epidermal stem cells effectively contributes to nerve regeneration and wound healing in diabetic rats.

Inhibitors of endopeptidase and angiotensin-converting enzyme lead to an amplification of the morphological changes and an upregulation of the substance P system in a muscle overuse model

Background

We have previously observed, in studies on an experimental overuse model, that the tachykinin system may be involved in the processes of muscle inflammation (myositis) and other muscle tissue alterations. To further evaluate the significance of tachykinins in these processes, we have used inhibitors of neutral endopeptidase (NEP) and angiotensin-converting enzyme (ACE), substances which are known to terminate the activity of various endogenously produced substances, including tachykinins.

Methods

Injections of inhibitors of NEP and ACE, as well as the tachykinin substance P (SP), were given locally outside the tendon of the triceps surae muscle of rabbits subjected to marked overuse of this muscle. A control group was given NaCl injections. Evaluations were made at 1 week, a timepoint of overuse when only mild inflammation and limited changes in the muscle structure are noted in animals not treated with inhibitors. Both the soleus and gastrocnemius muscles were examined morphologically and with immunohistochemistry and enzyme immunoassay (EIA).

Results

A pronounced inflammation (myositis) and changes in the muscle fiber morphology, including muscle fiber necrosis, occurred in the overused muscles of animals given NEP and ACE inhibitors. The morphological changes were clearly more prominent than for animals subjected to overuse and NaCl injections (NaCl group). A marked SP-like expression, as well as a marked expression of the neurokinin-1 receptor (NK-1R) was found in the affected muscle tissue in response to injections of NEP and ACE inhibitors. The concentration of SP in the muscles was also higher than that for the NaCl group.

Conclusions

The observations show that the local injections of NEP and ACE inhibitors led to marked SP-like and NK-1R immunoreactions, increased SP concentrations, and an amplification of the morphological changes in the tissue. The injections of the inhibitors thus led to a more marked myositis process and an upregulation of the SP system. Endogenously produced substances, out of which the tachykinins conform to one substance family, may play a role in mediating effects in the tissue in a muscle that is subjected to pronounced overuse.

Sensory neurons accelerate skin reepithelialization via substance P in an innervated tissue-engineered wound healing model

Keratinocytes are responsible for reepithelialization and restoration of the epidermal barrier during wound healing. The influence of sensory neurons on this mechanism is not fully understood. We tested whether sensory neurons influence wound closure via the secretion of the neuropeptide substance P (SP) with a new tissue-engineered wound healing model made of an upper-perforated epidermal compartment reconstructed with human keratinocytes expressing green fluorescent protein, stacked over a dermal compartment, innervated or not with sensory neurons. We showed that sensory neurons secreted SP in the construct and induced a two times faster wound closure in vitro. This effect was partially reproduced by addition of SP in the model without neurons, and completely blocked by a treatment with a specific antagonist of the SP receptor neurokinin-1 expressed by keratinocytes. However, this antagonist did not compromise wound closure compared with the control. Similar results were obtained when the model with or without neurons was transplanted on CD1 mice, while wound closure occurred faster. We conclude that sensory neurons play an important, but not essential, role in wound healing, even in absence of the immune system. This model is promising to study the influence of the nervous system on reepithelialization in normal and pathological conditions.

Chitosan-based dressings loaded with neurotensin--an efficient strategy to improve early diabetic wound healing

One important complication of diabetes mellitus is chronic, non-healing diabetic foot ulcers (DFUs). This study aims to develop and use dressings based on chitosan derivatives for the sustained delivery of neurotensin (NT), a neuropeptide that acts as an inflammatory modulator in wound healing. Three different derivatives, namely N-carboxymethyl chitosan, 5-methyl pyrrolidinone chitosan (MPC) and N-succinyl chitosan, are presented as potential biomaterials for wound healing applications. Our results show that MPC has the best fluid handling capacity and delivery profile, also being non-toxic to Raw 264.7 and HaCaT cells. NT-loaded and non-loaded MPC dressings were applied to control/diabetic wounds to evaluate their in vitro/in vivo performance. The results show that the former induced more rapid healing (50% wound area reduction) in the early phases of wound healing in diabetic mice. A NT-loaded MPC foam also reduced expression of the inflammatory cytokine TNF-α (P<0.001) and decreased the amount of inflammatory infiltrate on day 3. On day 10 MMP-9 was reduced in diabetic skin (P<0.001), significantly increasing fibroblast migration and collagen (COL1A1, COL1A2 and COL3A1) expression and deposition. These results suggest that MPC-based dressings may work as an effective support for sustained NT release to reduce DFUs.

Neurotensin-loaded collagen dressings reduce inflammation and improve wound healing in diabetic mice

Impaired wound healing is an important clinical problem in diabetes mellitus and results in failure to completely heal diabetic foot ulcers (DFUs), which may lead to lower extremity amputations. In the present study, collagen based dressings were prepared to be applied as support for the delivery of neurotensin (NT), a neuropeptide that acts as an inflammatory modulator in wound healing. The performance of NT alone and NT-loaded collagen matrices to treat wounds in streptozotocin (STZ) diabetic induced mice was evaluated. Results showed that the prepared dressings were not-cytotoxic up to 72h after contact with macrophages (Raw 264.7) and human keratinocyte (HaCaT) cell lines. Moreover, those cells were shown to adhere to the collagen matrices without noticeable change in their morphology. NT-loaded collagen dressings induced faster healing (17% wound area reduction) in the early phases of wound healing in diabetic wounded mice. In addition, they also significantly reduced inflammatory cytokine expression namely, TNF-α (p<0.01) and IL-1β (p<0.01) and decreased the inflammatory infiltrate at day 3 post-wounding (inflammatory phase). After complete healing, metalloproteinase 9 (MMP-9) is reduced in diabetic skin (p<0.05) which significantly increased fibroblast migration and collagen (collagen type I, alpha 2 (COL1A2) and collagen type III, alpha 1 (COL3A1)) expression and deposition. These results suggest that collagen-based dressings can be an effective support for NT release into diabetic wound enhancing the healing process. Nevertheless, a more prominent scar is observed in diabetic wounds treated with collagen when compared to the treatment with NT alone.

Role of neuropeptides, neurotrophins, and neurohormones in skin wound healing

Due to the close interactions between the skin and peripheral nervous system, there is increasing evidence that the cutaneous innervation is an important modulator of the normal wound healing process. The communication between sensory neurons and skin cells involves a variety of molecules (neuropeptides, neurohormones, and neurotrophins) and their specific receptors expressed by both neuronal and nonneuronal skin cells. It is well established that neurotransmitters and nerve growth factors released in skin have immunoregulatory roles and can exert mitogenic actions; they could also influence the functions of the different skin cell types during the wound healing process.

Recent advances on the development of wound dressings for diabetic foot ulcer treatment--a review

Diabetic foot ulcers (DFUs) are a chronic, non-healing complication of diabetes that lead to high hospital costs and, in extreme cases, to amputation. Diabetic neuropathy, peripheral vascular disease, abnormal cellular and cytokine/chemokine activity are among the main factors that hinder diabetic wound repair. DFUs represent a current and important challenge in the development of novel and efficient wound dressings. In general, an ideal wound dressing should provide a moist wound environment, offer protection from secondary infections, remove wound exudate and promote tissue regeneration. However, no existing dressing fulfills all the requirements associated with DFU treatment and the choice of the correct dressing depends on the wound type and stage, injury extension, patient condition and the tissues involved. Currently, there are different types of commercially available wound dressings that can be used for DFU treatment which differ on their application modes, materials, shape and on the methods employed for production. Dressing materials can include natural, modified and synthetic polymers, as well as their mixtures or combinations, processed in the form of films, foams, hydrocolloids and hydrogels. Moreover, wound dressings may be employed as medicated systems, through the delivery of healing enhancers and therapeutic substances (drugs, growth factors, peptides, stem cells and/or other bioactive substances). This work reviews the state of the art and the most recent advances in the development of wound dressings for DFU treatment. Special emphasis is given to systems employing new polymeric biomaterials, and to the latest and innovative therapeutic strategies and delivery approaches.

Topically applied substance P enhanced healing of open excision wound in rats

Significant social and financial burden due to wounds need newer drugs/formulations to speed up the healing process. Substance P (SP), a neuropeptide, is associated with release of various cytokines and growth factors from inflammatory, epithelial and endothelial cells. In the present study, temporal effects of topically applied SP (10(-7)M in normal saline) were evaluated in the modulation of various cytokines and growth factors that participate in cutaneous wound healing. Gross examination of full thickness open excision wound in rats revealed that once daily topical application of SP significantly increased the wound closure, as compared to control group. SP treatment significantly increased tumor necrosis factor-α (TNF-α) and decreased interleukin 10 (IL-10) levels on day 3. On the contrary, on day 7 level of TNF-α decreased and that of IL-10 increased. The mRNA and protein expressions of vascular endothelial growth factor (VEGF) and transforming growth factor-β1 (TGF-β1) increased on days 3 and 7, and decreased on day 14 in SP-treated wounds. Histopathological evaluation of hematoxylin and eosin stained wound sections showed that SP treatment produced increased early leukocytes infiltration, fibroblast proliferation, angiogenesis, collagen deposition and re-epithelialization. Results of the present study demonstrate that topical application of SP enhanced wound healing by modulating cytokines, growth factors and cells. Based on the results, it is suggested that SP could be of beneficial use in diabetic wounds where levels of VEGF, TGF-β1 and SP decrease along with impairment of inflammatory reaction.

Alternatives for animal wound model systems

In this chapter a review of animal model systems already being utilized to study normal and pathologic wound healing is provided. We also go into details on alternatives for animal wound model systems. The case is made for limitations in the various approaches. We also discuss the benefits/limitations of in vitro/ex vivo systems bringing everything up to date with our current work on developing a cell-based reporter system for diabetic wound healing.

Residual substance P levels after capsaicin treatment correlate with tendon repair

The aim of the study was to assess healing after capsaicin-induced substance P (SP) depletion during rat Achilles tendon repair by biomechanical testing. Capsaicin treatment reduced the concentrations of SP by ∼60% and calcitonin gene-related peptide by ∼40% as compared with the control group, as assessed by radioimmunoassay in the dorsal root ganglia, at 1 and 4 weeks post-tendon rupture. Also, the peripheral neuronal presence of SP and calcitonin gene-related peptide, as assessed by immunohistochemistry, was lower at both weeks 1 and 4. The decreased peripheral neuronal presence of SP at week 1 correlated with the corresponding levels in the dorsal root ganglia (r = 0.54, p = 0.018). The reduced presence of SP/calcitonin gene-related peptide after capsaicin treatment was verified by a decreased sensitivity to painful mechanical and thermal stimuli (p < 0.05). Correlation analyses between individual residual SP levels and biomechanical tissue properties were performed because of differences in failure mode between the groups and high individual variations in the SP levels after capsaicin treatment. Thus, the residual SP levels in the dorsal root ganglia correlated with transverse area, ultimate tensile strength, and stress at failure (r = 0.39, p = 0.036; r = 0.53, p = 0.005; and r = 0.43, p = 0.023, respectively). Furthermore, individual pain sensitivity at week 2 correlated with peripheral occurrence of SP and was correlated with tensile strength and stress at failure (r = 0.89, p = 0.006 and r = 0.78, p = 0.015) at week 4. In conclusion, rats with higher residual SP levels after capsaicin-induced neuropathy develop improved tensile strength and stress at failure in the healing of Achilles tendon.

Cutaneous manipulation of vascular growth factors leads to alterations in immunocytes, blood vessels and nerves: Evidence for a cutaneous neurovascular unit

BACKGROUND

Skin cells produce soluble factors which influence keratinocyte proliferation, angiogenesis, nerve innervation and immunocyte response.

OBJECTIVE

To test the hypothesis that epidermal-dermal interactions influence neural outgrowth, vascular survival, immunocyte recruitment and keratinocyte proliferation.

METHODS

We genetically manipulated the epidermis to express excess vascular endothelial growth factor (VEGF) and/or angiopoietin-1 (Ang1) and then examined the epidermal and dermal phenotypes. We compared these findings with those occurring following overexpression of the Ang1 receptor Tie2 in endothelial cells or keratinocytes.

RESULTS

Keratinocyte-overexpression of Ang1 resulted in increased epidermal thickness compared to control littermates. Keratinocyte-specific overexpression of Ang1 or VEGF increased dermal angiogenesis compared to control animals and combined Ang1-VEGF lead to further increases. Cutaneous leukocyte examination revealed increases in CD4(+) T cell infiltration in mice with keratinocyte-specific overexpression of Ang1, VEGF and Ang1-VEGF combined; in contrast only keratinocyte-specific Ang1 overexpression increased cutaneous F4/80(+) macrophage numbers. Interestingly, combined keratinocyte-derived Ang1-VEGF overexpression reduced significantly the number of F4/80(+) and Cd11c(+) cells compared to mice overexpressing epidermal Ang1 alone. Endothelial cell-specific Tie2 overexpression increased dermal angiogenesis but failed to influence the epidermal and immune cell phenotypes. Keratinocyte-specific Tie2 expressing mice had the highest levels of CD4(+), CD8(+) and CD11c(+) cell numbers and acanthosis compared to all animals. Finally, increases in the number of cutaneous nerves were found in all transgenic mice compared to littermate controls.

CONCLUSION

These findings demonstrate that change to one system (vascular or epidermal) results in change to other cutaneous systems and suggest that individual molecules can exert effects on multiple systems.

Spinal tumor necrosis factor alpha neutralization reduces peripheral inflammation and hyperalgesia and suppresses autonomic responses in experimental arthritis: a role for spinal tumor necrosis factor alpha during induction and maintenance of peripheral inflammation

OBJECTIVE

In addition to the sensitization of pain fibers in inflamed tissues, the increased excitability of the spinal cord is an important mechanism of inflammatory pain. Furthermore, spinal neuronal excitability has been suggested to play a role in modulating peripheral inflammation. This study was undertaken to test the hypothesis that spinal actions of the proinflammatory cytokine tumor necrosis factor alpha (TNFalpha) add significantly to both hyperalgesia and maintenance of peripheral inflammation.

METHODS

Rats with antigen-induced arthritis (AIA) were treated intrathecally with the TNFalpha-neutralizing compound etanercept continuously during the complete time course of AIA, which was 3 days for the acute phase and 21 days for the chronic phase. During this time, inflammation and pain-related behavior were monitored. Since a role for autonomic control of inflammation was proposed, measures from heart rate time series were obtained in the acute phase. Findings were compared with those in vehicle-treated animals and in animals receiving etanercept intraperitoneally.

RESULTS

Spinally administered etanercept acutely reduced pain-related behavior, attenuated both the development and the maintenance of inflammation, and was superior to systemic administration. Parameters indicating autonomic modulation showed a shift toward a sympathetically dominated state in vehicle-treated animals, which was prevented by intrathecal etanercept.

CONCLUSION

Our findings indicate that spinal TNFalpha plays an important role in both pain signaling and modulation of peripheral inflammation. Thus, neutralizing this cytokine at the spinal site not only represents a putative therapeutic option for different pain syndromes, but may be directly used to attenuate peripheral inflammation.

Evaluation of cellular wound healing using flow cytometry and expanded polytetrafluroethylene implants

In wound healing studies that investigate therapeutic interventions, it is important to characterize cellular responses. In a randomized trial enrolling patients at risk for surgical infection, one goal is to phenotype cells within a polytetrafluoroethylene implant using flow cytometry and immunohistochemistry, together with standard hematoxylin- and eosin-based histology. Subcutaneous implants are removed 8-9 days postoperatively. To obtain single cells associated with the mechanism of wound healing, we initially used a mouse skin digestion protocol. We optimized this to increase the cell yield and isolate sufficient cells for flow cytometry. The modifications increased the total cells recovered per subject from an average of 5.3 x 10(4)-41 x 10(4) with an average viability of 80%. The immunoflourescent staining assay was verified for our samples, which have smaller cell sample numbers than tissue biopsies. Thirty-two samples were stained. Cells from the polytetrafluoroethylene tubes were isolated and stained positively with fluorescent-labeled antibodies to CD3, CD20, CD31, CD34, CD68, CD133, and VEGF receptor type 2. Flow cytometry data correlated with immunohistochemistry data especially with respect to CD68. This antigen was the most prevalent in both the cell analysis methods. Our findings demonstrate that flow cytometry can be used with polytetrafluoroethylene samples as an additional evaluation method to document and describe cellular wound healing responses.

Spinally applied ketamine or morphine attenuate peripheral inflammation and hyperalgesia in acute and chronic phases of experimental arthritis

Inflammation causes sensitization of peripheral and central nociceptive neurons. Pharmacological modulation of the latter has successfully been used for clinical pain relief. In particular, inhibitors of the NMDA glutamate receptor such as ketamine and agonists at the mu-opioid receptor such as morphine are broadly used. Besides driving the propagation of pain signals, spinal mechanisms are also discussed to modulate inflammation in the periphery. Here, we tested the hypothesis that intrathecally applied ketamine or morphine not only reduce pain-related behavior, but also attenuate induction and maintenance of the inflammatory response in a model of chronic antigen-induced arthritis (AIA). Ketamine, morphine or vehicle was applied to the spinal cords of anesthesized animals with AIA. Swelling and histopathological changes were assessed after 6h (acute phase). Intrathecal catheters were implanted in another set of animals with AIA and substances were applied continuously. During the observation period of 21 days, inflammation and pain-related behavior were assessed. Ketamine and morphine significantly reduced arthritis severity as indicated by reduced joint swelling, but even more intriguingly by reduced infiltration with inflammatory cells and joint destruction in the acute and the chronic phase of arthritis. Morphine showed strong antinociceptive effects in the acute phase only, while the newly established effective dose for ketamine in a continuous application design reduced hyperalgesia in the acute and the chronic stage. In conclusion, both compounds exhibit anti-inflammatory effects during induction and maintenance of arthritis when applied intrathecally. These data thus propose a role of spinal NMDA- and opioid-receptors in the neuronal control of immune-mediated inflammation.