The role of nitric oxide in the formation of keloid and hypertrophic lesions

Multimodal roles of transient receptor potential channel activation in inducing pathological tissue scarification

Transient receptor potential (TRP) channels are a class of transmembrane proteins that can sense a variety of physical/chemical stimuli, participate in the pathological processes of various diseases and have attracted increasing attention from researchers. Recent studies have shown that some TRP channels are involved in the development of pathological scarification (PS) and directly participate in PS fibrosis and re-epithelialization or indirectly activate immune cells to release cytokines and neuropeptides, which is subdivided into immune inflammation, fibrosis, pruritus and mechanical forces increased. This review elaborates on the characteristics of TRP channels, the mechanism of PS and how TRP channels mediate the development of PS, summarizes the important role of TRP channels in the different pathogenesis of PS and proposes that therapeutic strategies targeting TRP will be important for the prevention and treatment of PS. TRP channels are expected to become new targets for PS, which will make further breakthroughs and provide potential pharmacological targets and directions for the in-depth study of PS.

Keloid Patient Plasma-Derived Exosomal hsa_circ_0020792 Promotes Normal Skin Fibroblasts Proliferation, Migration, and Fibrogenesis via Modulating miR-193a-5p and Activating TGF-β1/Smad2/3 Signaling

Background

Keloids are fibroproliferative disorders, which seriously affect the quality of life of patients with keloids. Additionally, circRNAs are enriched within exosomes derived from human blood samples, whereas their relationship with keloids remains largely unknown. It has been reported that hsa_circ_0020792 was abnormally upregulated in keloid tissues. However, the role of keloid patient plasma-derived exosomal hsa_circ_0020792 in the formation and development of keloids is not well understood.

Methods

Exosomes were isolated from the peripheral blood plasma of the patients with keloids (keloid patient-Exo) and healthy controls (Healthy control-Exo). The hsa_circ_0020792 and miR-193a-5p levels in keloid patient-Exo and healthy control-Exo, as well as in keloid fibroblasts and normal skin fibroblasts (NFs) were evaluated by RT-qPCR.

Results

The level of hsa_circ_0020792 was remarkably increased in keloid patient-Exo and keloid fibroblasts compared with that in Healthy control-Exo and NFs, respectively. In addition, keloid patient-Exo obviously enhanced the viability, migration, and extracellular matrix (ECM) synthesis, but reduced the apoptosis of NFs. Moreover, keloid patient-Exo notably promoted the fibrogenesis of NFs, as characterized by enhanced TGF-β signaling, increased expressions of phosphorylated Smad2/3. However, downregulation of hsa_circ_0020792 markedly reversed the promoting effects of keloid patient-Exo on cell growth, migration, and myofibroblast activation and fibrogenesis. Furthermore, downregulation of hsa_circ_0020792 significantly reduced the viability, migration, and fibrogenesis in NFs, whereas these phenomena were reversed by miR-193a-5p inhibitor.

Conclusion

Collectively, keloid patient plasma-derived exosomal hsa_circ_0020792 could promote the proliferation, migration, and fibrogenesis of NFs via modulating miR-193a-5p and activating TGF-β1/Smad2/3 signaling.

Synthetic, Natural, and Semisynthetic Polymer Carriers for Controlled Nitric Oxide Release in Dermal Applications: A Review

Nitric oxide (NO•) is a free radical gas, produced in the human body to regulate physiological processes, such as inflammatory and immune responses. It is required for skin health; therefore, a lack of NO• is known to cause or worsen skin conditions related to three biomedical applications- infection treatment, injury healing, and blood circulation. Therefore, research on its topical release has been increasing for the last two decades. The storage and delivery of nitric oxide in physiological conditions to compensate for its deficiency is achieved through pharmacological compounds called NO-donors. These are further incorporated into scaffolds to enhance therapeutic treatment. A wide range of polymeric scaffolds has been developed and tested for this purpose. Hence, this review aims to give a detailed overview of the natural, synthetic, and semisynthetic polymeric matrices that have been evaluated for antimicrobial, wound healing, and circulatory dermal applications. These matrices have already set a solid foundation in nitric oxide release and their future perspective is headed toward an enhanced controlled release by novel functionalized semisynthetic polymer carriers and co-delivery synergetic platforms. Finally, further clinical tests on patients with the targeted condition will hopefully enable the eventual commercialization of these systems.

The Keloid Disorder: Heterogeneity, Histopathology, Mechanisms and Models

Keloids constitute an abnormal fibroproliferative wound healing response in which raised scar tissue grows excessively and invasively beyond the original wound borders. This review provides a comprehensive overview of several important themes in keloid research: namely keloid histopathology, heterogeneity, pathogenesis, and model systems. Although keloidal collagen versus nodules and α-SMA-immunoreactivity have been considered pathognomonic for keloids versus hypertrophic scars, conflicting results have been reported which will be discussed together with other histopathological keloid characteristics. Importantly, histopathological keloid abnormalities are also present in the keloid epidermis. Heterogeneity between and within keloids exists which is often not considered when interpreting results and may explain discrepancies between studies. At least two distinct keloid phenotypes exist, the superficial-spreading/flat keloids and the bulging/raised keloids. Within keloids, the periphery is often seen as the actively growing margin compared to the more quiescent center, although the opposite has also been reported. Interestingly, the normal skin directly surrounding keloids also shows partial keloid characteristics. Keloids are most likely to occur after an inciting stimulus such as (minor and disproportionate) dermal injury or an inflammatory process (environmental factors) at a keloid-prone anatomical site (topological factors) in a genetically predisposed individual (patient-related factors). The specific cellular abnormalities these various patient, topological and environmental factors generate to ultimately result in keloid scar formation are discussed. Existing keloid models can largely be divided into in vivo and in vitro systems including a number of subdivisions: human/animal, explant/culture, homotypic/heterotypic culture, direct/indirect co-culture, and 3D/monolayer culture. As skin physiology, immunology and wound healing is markedly different in animals and since keloids are exclusive to humans, there is a need for relevant human in vitro models. Of these, the direct co-culture systems that generate full thickness keloid equivalents appear the most promising and will be key to further advance keloid research on its pathogenesis and thereby ultimately advance keloid treatment. Finally, the recent change in keloid nomenclature will be discussed, which has moved away from identifying keloids solely as abnormal scars with a purely cosmetic association toward understanding keloids for the fibroproliferative disorder that they are.

Nitric oxide: Is it the culprit for the continued expansion of keloids?

Keloids are characterized by excessive proliferation of fibroblasts and invasion of surrounding healthy skin. High levels of Nitric Oxide (NO) are thought to be the crucial factor within the micro-environment in promoting keloid formation. However, the effects and mechanisms of NO on the proliferation of Keloid Fibroblasts (KDFs) remain unclear. In this study, we investigated the effect of NO on KDFs proliferation by Sodium Nitroprusside (SNP), an NO donor. Our results show that SNP significantly enhanced KDFs proliferation. Moreover, with prolonged treatment with SNP after cell confluence, the growth of KDFs escape contact inhibition and experience significant pile up growth. Furthermore, PTIO, an NO scavenger, attenuated SNP-enhanced cell proliferation effectively. The mechanism involved in SNP-induced KDFs proliferation was soluble Guanylyl Cyclase (sGC) and cGMP independent. ODQ, a specific sGC inhibitor, failed to suppress SNP-enhanced KDFs proliferation. 8-Bromo-c GMP, a cell-permeable cGMP analogue, could not stimulate KDFs proliferation. Erk and Akt provide important signaling for cell growth. U0126 and LY294002, inhibitors of Erk and Akt respectively, block SNP-enhanced KDFs proliferation effectively. As expected, a Western blot showed that SNP up-regulated the phosphorylation levels of Erk and Akt. Moreover, it decreased the expression of p²⁷, a cell cycle inhibitor. Our results reveal that SNP induced KDFs proliferation and loss contact inhibition led to pile up growth via activation of the Erk and Akt pathways, as well as a decreased expression of p²⁷. Thus, we speculate that the pathological feature of continuous expansion in keloids is caused by NO-induced KDFs sustained growth.

Tension enhances cell proliferation and collagen synthesis by upregulating expressions of integrin αvβ3 in human keloid-derived mesenchymal stem cells

AIMS

Keloids are a dermal fibrotic disease whose etiology remains totally unknown and for which there is no successful treatment. Mechanical tension, in addition, is closely associated with the germination and development of keloids. In this study, we investigated the influence of human keloid-derived mesenchymal stem cells (KD-MSCs) on cell proliferation, collagen synthesis, and expressions of integrin αvβ3 under tension.

MAIN METHODS

KD-MSCs and human normal skin-derived mesenchymal stem cells (NS-MSCs) were isolated and cultured in stem cell medium with a gradual increase in the serum concentration. Cell proliferation and collagen synthesis were detected by Cell Counting Kit-8 (CCK-8) assay and hydroxyproline content analysis under tension respectively. We investigated the messenger RNA expressions of nine integrin subunits, including integrin units α2, α3, α5, αv, α8, α10, α11, β1, and β3, in KD-MSCs stimulated with tension. Identification of differentially expressed genes was performed by Western blot analysis and immunocytochemistry staining.

KEY FINDINGS

We obtained high-purity KD-MSCs and NS-MSCs using the culture method of decreasing serum concentration gradient gradually. Furthermore, we found that tension enhances cell proliferation and collagen synthesis and promotes expressions of integrin αvβ3 in KD-MSCs. In addition, blocking experiments showed that increased integrin αvβ3 expression affects cell proliferation and collagen synthesis of KD-MSCs under tension.

SIGNIFICANCE

Our results suggest that integrin αvβ3 receptor may be sensitive molecules of mechanical tension and could contribute to the occurrence and development of keloids. It could lead to novel targets for therapeutic intervention, treatment, and prevention of recurrence for keloid disorders.

High in situ mRNA levels of IL-22, TFG-β, and ARG-1 in keloid scars

Keloid scars are currently considered a chronic inflammatory process and no longer a benign skin tumor. Keloids are defined as highly inflamed, hyperproliferative pathological scars. Growth factors and cytokines have important functions in the keloid inflammatory etiopathogenesis. The aim of this study was to analyze the in situ expression of cytokines and growth factors in keloid scars in comparison with that in normal scars. Among them, we specifically assessed TGF-β, FGF, IL-33, IL-22, ARG-1, ARG-2, iNOS, VIP, VIP-R1, TAC, and TAC-R1. A total of 98 biopsies were evaluated, including of 53 keloid and 45 normal scars. The age of patients with keloids ranged from 11 to 73 years, with a mean age of 28 years and predominance of the female gender (58.5% of the total patients). Around 64.15% of the patients belonged to the black ethnic group. Evaluated keloids were most commonly located in the earlobe because of ear piercing, representing 73.6% of the cases. We found significantly greater expression of TGF-β, IL-22, and ARG-1 in keloids when compared with that in normal scars. As for IL-33, ARG-2, and VIP-R1, despite the higher number of mRNA copies found in keloids, this difference was not significant. Furthermore, FGF, iNOS, VIP, TAC, and TAC-R1 mRNA levels were not detectable, and therefore these results were inconclusive in this study. Considering these results, understanding the cellular and molecular mechanisms that control the inflammatory response during cutaneous healing may promote the development of strategies to improve the treatment of patients with keloids.

Keloid progression: a stiffness gap hypothesis

Keloids are fibroproliferative skin disorders characterised clinically by continuous horizontal progression and post-surgical recurrence and histologically by the accumulation of collagen and fibroblast ingredients. Till now, their aetiology remains clear, which may cover genetic, environmental and metabolic factors. Evidence in the involvement of local mechanics (e.g. predilection site and typical shape) and the progress in mechanobiology have incubated our stiffness gap hypotheses in illustrating the chronic but constant development in keloid. We put forward that the enlarged gap between extracellular matrix (ECM) stiffness and cellular stiffness potentiates keloid progression. Matrix stiffness itself provides organisational guidance cues to regulate the mechanosensitive resident cells (e.g. proliferation, migration and apoptosis). During this dynamic process, the ECM stiffness and cell stiffness are not well balanced, and the continuously enlarged stiffness gap between them potentiates keloid progression. The cushion factors, such as prestress for cell stiffness and topology for ECM stiffness, serve as compensations, the decompensation of which aggravates keloid development. It can well explain the typical shape of keloids, their progression in a horizontal but not vertical direction and the post-surgical recurrence, which were evidenced by our clinical cases. Such a stiffness gap hypothesis might be bridged to mechanotherapeutic approaches for keloid progression.

Influence of sleep deprivation and morphine on the expression of inducible nitric oxide synthase and cyclooxygenase-2 in skin of hairless mice

Skin performs a host of primordial functions that keep the body alive. Morphine is a drug with immunosuppressant properties whose chronic use may lead to increased infection and delayed wound healing. Sleep is a fundamental biological phenomenon that promotes the integrity of several bodily functions. Sleep deprivation adversely affects several systems, particularly the immune system. The aim of this study was to perform an immunohistochemical evaluation on the expression of inducible nitric oxide synthase and cyclooxygenase-2 in skin of sleep-deprived mice and mice chronically treated with morphine. Adult hairless male mice were distributed into the following groups: Control, morphine, sleep-deprived, and morphine + SD. Morphine (10 mg/kg, subcutaneous) was injected every 12 h for 9 days. Morphine induced immunoexpression of cyclooxygenase-2 and nitric oxide synthase. Sleep deprivation did not modulate outcomes induced by morphine. Morphine, not sleep loss, induces cyclooxygenase-2 and nitric oxide synthase immunoexpression in the skin of hairless mice.

Extracorporeal shock wave therapy in pillar pain after carpal tunnel release: a preliminary study

"Pillar pain" is a relatively frequent complication after surgical release of the median nerve at the wrist. Its etiology still remains unknown although several studies highlight a neurogenic inflammation as a possible cause. Pillar pain treatment usually includes rest, bracing and physiotherapy, although a significant number of patients still complain of painful symptoms two or even three years after surgery. The aim of this study was to investigate the efficacy of low-energy, flux density-focused extracorporeal shock wave therapy (ESWT) in the treatment of pillar pain. We treated 40 consecutive patients with ESWT who had pillar pain for at least six months after carpal tunnel release surgery, and to our knowledge, this is the first study that describes the use of ESWT for treating this condition. Our results show that in all of the treated patients, there was a marked improvement: the mean visual analogue scale (VAS) score decreased from 6.18 (±1.02) to 0.44 (±0.63) 120 d after treatment, and redness and swelling of the surgical scar had also decreased significantly.

Oxidative stress in cancer associated fibroblasts drives tumor-stroma co-evolution: A new paradigm for understanding tumor metabolism, the field effect and genomic instability in cancer cells

Loss of stromal fibroblast caveolin-1 (Cav-1) is a powerful single independent predictor of poor prognosis in human breast cancer patients, and is associated with early tumor recurrence, lymph node metastasis and tamoxifen-resistance. We developed a novel co-culture system to understand the mechanism(s) by which a loss of stromal fibroblast Cav-1 induces a "lethal tumor micro-environment." Here, we propose a new paradigm to explain the powerful prognostic value of stromal Cav-1. In this model, cancer cells induce oxidative stress in cancer-associated fibroblasts, which then acts as a "metabolic" and "mutagenic" motor to drive tumor-stroma co-evolution, DNA damage and aneuploidy in cancer cells. More specifically, we show that an acute loss of Cav-1 expression leads to mitochondrial dysfunction, oxidative stress and aerobic glycolysis in cancer associated fibroblasts. Also, we propose that defective mitochondria are removed from cancer-associated fibroblasts by autophagy/mitophagy that is induced by oxidative stress. As a consequence, cancer associated fibroblasts provide nutrients (such as lactate) to stimulate mitochondrial biogenesis and oxidative metabolism in adjacent cancer cells (the "Reverse Warburg Effect"). We provide evidence that oxidative stress in cancer-associated fibroblasts is sufficient to induce genomic instability in adjacent cancer cells, via a bystander effect, potentially increasing their aggressive behavior. Finally, we directly demonstrate that nitric oxide (NO) over-production, secondary to Cav-1 loss, is the root cause for mitochondrial dysfunction in cancer associated fibroblasts. In support of this notion, treatment with anti-oxidants (such as N-acetyl-cysteine, metformin and quercetin) or NO inhibitors (L-NAME) was sufficient to reverse many of the cancer-associated fibroblast phenotypes that we describe. Thus, cancer cells use "oxidative stress" in adjacent fibroblasts (i) as an "engine" to fuel their own survival via the stromal production of nutrients and (ii) to drive their own mutagenic evolution towards a more aggressive phenotype, by promoting genomic instability. We also present evidence that the "field effect" in cancer biology could also be related to the stromal production of ROS and NO species. eNOS-expressing fibroblasts have the ability to downregulate Cav-1 and induce mitochondrial dysfunction in adjacent fibroblasts that do not express eNOS. As such, the effects of stromal oxidative stress can be laterally propagated, amplified and are effectively "contagious"--spread from cell-to-cell like a virus--creating an "oncogenic/mutagenic" field promoting widespread DNA damage.

Human skin keloid fibroblasts display bioenergetics of cancer cells

Cultured human skin keloid fibroblasts (KFs) showed bioenergetics similar to cancer cells in generating ATP mainly from glycolysis as demonstrated by increased lactate production. Activities of hexokinase, glyceraldehyde-3-phosphate dehydrogenase, and lactate dehydrogenase were also significantly higher compared with normal fibroblasts (NFs). Inhibitors of glycolysis decreased the rate of ATP biosynthesis more significantly in KFs suggesting their reliance on glycolysis. In contrast, ATP generation in NFs was derived mainly from oxidative phosphorylation (OXPHOS), which was more compromised by mitochondrial/respiratory inhibitors. However, when fortified with excess exogenous respiratory substrates, ATP production was increased to a similar maximal level in both types of fibroblasts. In spite of this seemingly equal total capacity, ATP biosynthesis and intracellular ATP concentration were significantly higher in KFs, which further increased their ATP production when exposed to hypoxia and hypoxia-mimetics: desferrioxamine and cobalt chloride. This upregulation was again significantly compromised by glycolytic inhibitors. The rate of generation of reactive oxygen species was lower in KFs possibly due to their switch to aerobic glycolysis from mitochondrial OXPHOS. Thus, cultured skin KFs could provide a human cell model to study the de-regulation of bioenergetics of proliferative cells and their response to the HIF (hypoxia-inducible factor) signaling.

Induction of TIMP-1 and HSP47 synthesis in primary keloid fibroblasts by exogenous nitric oxide

BACKGROUND

The excessive accumulation of extracellular matrix is a hallmark of many fibrotic diseases, including the hypertrophic scar and keloid. Recent reports from this research team had shown that exogenous nitric oxide (NO) participates in the keloid formation; however, its role on the synthesis of fibrotic factor (TGF-beta1, TIMP-1 and HSP47) in the keloid fibroblasts (KF) remained unclear.

OBJECTIVE

In this study, to better define the potential effect of exogenous NO on the expression of fibrotic factors in KF, the enhancing effect of exogenous NO, released from a NO donor, on the synthesis of fibrotic factors in KF was investigated.

METHODS

The seven primary KF cultures were set up to measure the effect of exogenous NO on enhancing the expression of fibrotic factor.

RESULTS

Elevation of cellular cGMP levels was observed to be induced by NO or blocked by the hydrolysis activity of phosphodiesterase (PDE) by the PDE inhibitor. The elevated levels of cellular cGMP were noted to enhance the expression of TIMP-1 and HSP47 in KF. Exogenous NO was found to significantly accelerate the production of TIMP-1 and HSP47 in the seven primary KFs with a corresponding increase in the production of TGF-beta1.

CONCLUSION

The results have led to a conclusion, that is: the excess collagen formations in the keloid lesion may be attributed to the NO/cGMP signal pathway by initiating a rapid increase in the expression of TGF-beta1, TIMP-1 and HSP47 in the KF cells.

Exogenous nitric oxide stimulated collagen type I expression and TGF-beta1 production in keloid fibroblasts by a cGMP-dependent manner

Keloids arise from the aberrant wound healing process and nitric oxide (NO) plays an important role in the inflammation stage of wound healing. In order to better define the potential effect of NO/cGMP signal pathway in the keloid pathogenesis, the enhancing effect of exogenous NO (released from NO donor) on collagen expression in the keloid fibroblast (KF) as well as on the induction of collagen type I protein and TGF-beta1 expression in the KF were studied in this investigation. The DETA NONOate, an NO donor, was added to the KF, as the exogenous NO, to release NO in the culture medium. The expression of collagens was then determined by assaying the total soluble collagens and collagen type I in the KF. The cellular concentration of cGMP was measured by EIA in the KF. Exogenous NO was found to enhance the expression of collagens and elevate the cellular levels of cGMP. Moreover, to evaluate the effect of the elevated cellular cGMP levels on the expression of collagen and TGF-beta1, both cGMP and TGF-beta1 were measured by ELISA. The inhibitors for phosphodiesterase (PDE), such as IBMX (3-isobutyl-1-methylxanthine), Vinpocetine, EHNA, Milrinone and Zapriast, which have been reported to reduce the ability of PDE and subsequently produce an increase of cellular cGMP, induce the production of autocrine TGF-beta1 as well as the synthesis of collagen in the KF. In this investigation, the inhibition of the PDE enzyme activity was observed to enhance the effect on the collagen synthesis, and was induced by exogenous NO. Taken together, these results have suggested that the NO/cGMP pathway could positively influence the progression of keloid formation, via the TGF-beta1 expression in the KF.

Keloids and scars: a review of keloids and scars, their pathogenesis, risk factors, and management

PURPOSE OF REVIEW

The precise mechanisms of normal and abnormal scar formation have long remained a mystery despite the extensive literature regarding wound healing. Only recently have researchers begun to delineate the complex biochemical signaling pathways that regulate these processes. This article reviews basic wound healing, while focusing on medicine's latest understanding of the development and treatment of keloids and hypertrophic scars.

RECENT FINDINGS

The importance of the transforming growth factor-beta signaling pathways and the related downstream effector molecules has proven to offer a new detailed view of scar biology. Regulation of scar metabolism with regards to collagen and wound matrix degradation is likewise showing promise in generating alternate therapies to treat abnormal scars.

SUMMARY

Understanding the exact process of normal and abnormal scar formation will help define better ways to successfully manage and potentially prevent abnormal healing like hypertrophic scars and keloids.

Nitric oxide produced by iNOS is associated with collagen synthesis in keloid scar formation

Nitric oxide (NO) has emerged as an important mediator of many physiological functions. Recent reports have shown that NO participates in the wound healing process, however, its role in keloid formation remains unclear. This study aimed to investigate the effect of NO on keloid fibroblasts (KF) and to determine the levels of inducible nitric oxide synthase (iNOS) expression in clinical specimens of keloid. Scar tissue from seven keloid patients with matched perilesion skin tissue controls was studied for inducible nitric oxide synthase expression and location. In addition, primary keloid and normal scar skin fibroblast cultures were set up to investigate the effects of NO in inducing collagen type I expression. Inducible nitric oxide synthase expression, and NO production were elevated in keloid scar tissues but not in matched perilesion skin tissues. Furthermore, exposure of KF to exogenous NO resulted in increased expression of collagen type I in a dose-dependent manner. NO exposure also induced time-course dependent collagen I expression that peaked at 24h in KF. Taken together, these results indicate that excess collagen formations in keloid lesion may be attributed to iNOS overexpression.

Differential expression of nitric oxide synthases in human scalp epidermal and hair follicle pigmentary units: implications for regulation of melanogenesis

BACKGROUND

Nitric oxide (NO) is a ubiquitous gaseous lipophilic molecule generated from the conversion of L-arginine to L-citrulline by the NO synthases (NOSs). Ultraviolet radiation (UVR)-induced NO production appears to stimulate epidermal melanogenesis. However, given their relative protection from UVR, it is unclear whether NO plays a similar role in hair bulb melanocytes.

OBJECTIVES

We aimed to identify the expression profiles of the NOS isoforms endothelial NOS (eNOS), neuronal NOS (nNOS) and inducible NOS (iNOS) and of phosphorylated eNOS and nitrotyrosine within the epidermal and follicular melanin units of normal human haired scalp during the hair growth cycle.

METHODS

This study employed single and double immunohistochemical and immunofluorescence staining techniques using haired scalp from 10 healthy individuals (six women and four men).

RESULTS

Melanocytes in the basal layer of the epidermis expressed eNOS, nNOS and nitrotyrosine. By contrast, melanogenically active melanocytes of the anagen hair bulb were wholly negative for these markers. However, other follicular melanocytes not actively involved in pigment production, including undifferentiated melanocytes located in the outer root sheath and melanocytes surviving the apoptosis-driven hair follicle (HF) regression during catagen/telogen, expressed eNOS, nNOS and nitrotyrosine. While iNOS was only weakly expressed in the basal layer of the human epidermis, it was highly expressed in keratinocytes of the inner root sheath (IRS), where it colocalized with trichohyalin, a differentiation-associated protein of the IRS that requires enzyme-catalysed conversion of arginine to citrulline.

CONCLUSIONS

The NOS isoforms and nitrotyrosine are differentially expressed in different cutaneous melanocyte subpopulations. Results of this study suggest a possible role for eNOS, nNOS, iNOS and nitrotyrosine in melanocyte biology, particularly with respect to melanogenesis and melanocyte survival during HF regression. Another example of possible NO involvement in HF biology is the postsynthetic modification of trichohyalin in differentiating keratinocytes of the IRS. These results suggest that NO may influence several aspects of HF biology.

Wound fluid inhibits wound fibroblast nitric oxide synthesis

BACKGROUND

Fibroblast-derived nitric oxide (NO) is an autocrine stimulator of collagen synthesis by wound fibroblasts. Little is known about the in vivo regulation of wound fibroblast NO synthesis. We investigated the net effect of wound environment on wound fibroblast NO production and characterized a soluble factor mediating this effect.

MATERIALS AND METHODS

Wound fibroblasts and acellular wound fluid (pool of 100 Lewis rats) were isolated from subcutaneously implanted polyvinyl alcohol sponges harvested 10 days post-wounding. Fibroblasts were incubated in the presence of 10% (v/v) wound fluid. Nitrite, an index of NO synthesis, was measured in supernatants by Griess reagent.

RESULTS

Wound fibroblasts spontaneously synthesize large amounts of NO. Spontaneous NO synthesis was further increased by LPS + IFN-gamma (P < 0.001). Wound fluid significantly inhibited both spontaneous and LPS plus IFN-gamma-stimulated NO synthesis (by 88 and 55%, respectively; P < 0.01). Wound fluid from 5- to 35-day-old wounds equally suppressed NO synthesis. Separation by Sephadex G-100 gel filtration identified the active factor in wound fluid to have a molecular weight of about 100 kDa. Characterization of this factor showed it to be a heat-resistant (56 degrees C, 30 min), trypsin-sensitive, and neuraminidase-resistant protein (ammonium sulfate precipitation). The isoelectric point appeared to be 7.0, as determined by ion exchange chromatography. Addition of high arginine did not restore the effect of wound fluid on fibroblast NO synthesis, suggesting that substrate is not a limiting factor.

CONCLUSION

Our data demonstrate that following postoperative day 5 the wound environment contains a high molecular weight protein that inhibits NO synthesis by wound fibroblasts.

Post acne scarring: a review

Historically, post acne scarring has not been well treated. New techniques have been added and older ones modified to manage this hitherto refractory problem. The patient, his or her expectations and overall appearance as well as the morphology of each scar must be assessed and treatment designed accordingly. Upon reaching an understanding of what the pathology of the scar is and where it resides in the skin, the most pertinent treatment for that scar may be devised. Post acne scars are polymorphous and include superficial macules, dermal troughs, ice picks, multi-channelled fistulous tracts and subcutaneous atrophy. The wide variety of new methods includes the latest resurfacing tools such as CO(2) and erbium infrared lasers, dermasanding and possibly some future techniques such as non-ablative and radiofrequency resurfacing. Dermal and subcutaneous augmentation with autologous (including fat and blood transfer) and non-autologous tissue augmentation and the advent of tissue undermining has greatly improved the treatment of atrophic scars. Use of punch techniques for sharply marginated scars (such as ice picks) is necessary if this scar morphology is to be treated well. One should attempt to match each scar against an available treatment as far as possible. Many of these techniques may be performed in a single treatment session but repeat treatments are often necessary. The treatment of hypertrophic acne scarring remains difficult, but silastic sheeting, vascular laser and intralesional cytotoxics are interesting developments. Most often occurring extra-facially and in males, these distressing scars often require multiple treatments and modalities before adequate improvement is achieved.