Variations in gap junctional intercellular communication and connexin expression in fibroblasts derived from keloid and hypertrophic scars

Connexin 37, 40, 43 and Pannexin 1 Expression in the Gastric Mucosa of Patients with Systemic Sclerosis

Systemic sclerosis (SSc) is an autoimmune disease characterized by fibrosis of the skin and internal organs. Although its pathogenesis is not fully understood, connexins (Cxs) and pannexins (Panx) could be involved in the process of fibrosis. We analyzed the protein expression of Cx37, Cx40, Cx43, and Panx1 in the gastric mucosa of patients with SSc and healthy volunteers, using immunofluorescence staining. Protein levels of Cx37 were slightly increased, while the levels of Cx40 were significantly decreased in the lamina propria of the gastric mucosa of SSc patients compared to the controls. The changes were proportional to SSc severity, with the most prominent changes found in patients with severe diffuse cutaneous SSc. No differences in Cx43 or Panx1 levels were found between the analyzed groups of samples. The lack of changes in Cx43 expression, which has been previously associated with fibrosis, could be due to the weak expression of Cx43 in the gastric mucosa in general. Further studies on full-thickness gastric biopsies containing muscle layers and animal SSc models are needed to fully elucidate the role of Cxs and Panxs in SSc-associated fibrosis.

Molecular Features of Hypertrophic Scars After Thermal Injury: Is There a Biologic Basis for Laser Therapy?

Significance: Hypertrophic scars (HTS) and keloids are common after thermal injuries and other trauma to deep regions of dermis of the skin. These abnormal scars can cause contractures and the thick masses of scar tissue that result in functional and cosmetic impairment. Management of these dermal fibrotic conditions includes a wide range of medical and surgical treatments, which can be time consuming, only partially effective, and often uncomfortable for patients. Recent Advances: The molecular pathophysiology of HTS has become more understood over the past two decades, where thermal injury to the reticular dermis results in an inflammatory response, fibrogenic growth factor release, and the formation of a dermal scar with increased collagen and proteoglycan composition in an abnormal morphology. Lasers are becoming a widely used form of treatment for these types of scars; however, the evidence for the beneficial effects of laser treatments and the understanding of their mechanism of action are still evolving. Critical Issues: Paradoxically, laser delivery of thermal energy to the skin is suggested to improve scar remodeling and wound healing, yet HTS is a well-recognized complication of excessive thermal energy delivered by laser treatments. This review aims to examine the current evidence for the use of lasers for HTS, and to investigate the molecular mechanisms where re-injury of a burn scar from laser treatment could result in overall improvements in scar quality. Future Directions: Improved design of clinical trials for the treatment of scarring in the future will evolve from new methodology and models of HTS in animals and humans.

Hypertrophic scars and keloids: Overview of the evidence and practical guide for differentiating between these abnormal scars

Although hypertrophic scars and keloids both generate excessive scar tissue, keloids are characterized by their extensive growth beyond the borders of the original wound, which is not observed in hypertrophic scars. Whether or not hypertrophic scars and keloids are two sides of the same coin or in fact distinct entities remains a topic of much debate. However, proper comparison between the two ideally occurs within the same study, but this is the exception rather than the rule. For this reason, the goal of this review was to summarize and evaluate all publications in which both hypertrophic scars and keloids were studied and compared to one another within the same study. The presence of horizontal growth is the mainstay of the keloid diagnosis and remains the strongest argument in support of keloids and hypertrophic scars being distinct entities, and the histopathological distinction is less straightforward. Keloidal collagen remains the strongest keloid parameter, but dermal nodules and α-SMA immunoreactivity are not limited to hypertrophic scars alone. Ultimately, the current hypertrophic scars-keloid differences are mostly quantitative in nature rather than qualitative, and many similar abnormalities exist in both lesions. Nonetheless, the presence of similarities does not equate the absence of fundamental differences, some of which may not yet have been uncovered given how much we still have to learn about the processes involved in normal wound healing. It therefore seems pertinent to continue treating hypertrophic scars and keloids as separate entities, until such a time as new findings more decisively convinces us otherwise.

Smooth Muscle Alpha Actin Immunoexpression (α-Sma) and CD-117 Antibody (C-Kit) in Capsules Formed by Polyurethane Foam-Coated Silicone Implants and with Textured Surface: A Study on Rats

BACKGROUND

One of the undesirable complications that might occur after breast augmentation with silicone implants is capsular contracture. In its etiology, the relations between mast cells and myofibroblasts play an important role in collagen synthesis. Mast cells are able to activate fibroblasts into myofibroblasts, through paracrine secretions, inducing collagen production. The objectives of this study were to analyze the myofibroblast concentration through the α-SMA immunomarker and evaluate the intensity of mast cell expression against the C-Kit immunomarker.

MATERIAL AND METHOD

Sixty-four Wistar rats were used, divided into two groups (polyurethane foam and textured surface) with 32 animals in each. The animals received silicone implants on the back, below the panniculus carnosus, and after the determined period, they were killed and the capsules formed around the implants were studied. The capsules were analyzed employing the immunohistochemical technique, with the α-SMA and C-Kit immunomarkers in subgroups of 30, 50, 70 and 90 days.

RESULTS

The myofibroblast concentration was higher in the polyurethane group when compared to the textured group (30 days p = 0.105; 50 days p = 0.247; 70 days p = 0.014 and 90 days p = 0.536). The intensity of mast cell expression was more pronounced in the polyurethane group when compared to the textured group (30 days p = 0.798; 50 days p = 0.537; 70 days p = 0.094 and 90 days p = 0.536).

CONCLUSIONS

Polyurethane-coated implants induced higher concentrations of myofibroblasts and higher expression of mast cells, when compared to the textured surface implants.

NO LEVEL ASSIGNED

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Expression Profile of Long Noncoding RNAs in Human Earlobe Keloids: A Microarray Analysis

Background. Long noncoding RNAs (lncRNAs) play key roles in a wide range of biological processes and their deregulation results in human disease, including keloids. Earlobe keloid is a type of pathological skin scar, and the molecular pathogenesis of this disease remains largely unknown. Methods. In this study, microarray analysis was used to determine the expression profiles of lncRNAs and mRNAs between 3 pairs of earlobe keloid and normal specimens. Gene Ontology (GO) categories and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed to identify the main functions of the differentially expressed genes and earlobe keloid-related pathways. Results. A total of 2068 lncRNAs and 1511 mRNAs were differentially expressed between earlobe keloid and normal tissues. Among them, 1290 lncRNAs and 1092 mRNAs were upregulated, and 778 lncRNAs and 419 mRNAs were downregulated. Pathway analysis revealed that 24 pathways were correlated to the upregulated transcripts, while 11 pathways were associated with the downregulated transcripts. Conclusion. We characterized the expression profiles of lncRNA and mRNA in earlobe keloids and suggest that lncRNAs may serve as diagnostic biomarkers for the therapy of earlobe keloid.

A Multicenter Randomized Controlled Trial Evaluating a Cx43-Mimetic Peptide in Cutaneous Scarring

The transmembrane protein Cx43 has key roles in fibrogenic processes including inflammatory signaling and extracellular matrix composition. aCT1 is a Cx43 mimetic peptide that in preclinical studies accelerated wound closure, decreased inflammation and granulation tissue area, and normalized mechanical properties after cutaneous injury. We evaluated the efficacy and safety of aCT1 in the reduction of scar formation in human incisional wounds. In a prospective, multicenter, within-participant controlled trial, patients with bilateral incisional wounds (≥10 mm) after laparoscopic surgery were randomized to receive acute treatment (immediately after wounding and 24 hours later) with an aCT1 gel formulation plus conventional standard of care protocols, involving moisture-retentive occlusive dressing, or standard of care alone. The primary efficacy endpoint was average scarring score using visual analog scales evaluating incision appearance and healing progress over 9 months. There was no significant difference in scar appearance between aCT1- or control-treated incisions after 1 month. At month 9, aCT1-treated incisions showed a 47% improvement in scar scores over controls (Vancouver Scar Scale; P = 0.0045), a significantly higher Global Assessment Scale score (P = 0.0009), and improvements in scar pigmentation, thickness, surface roughness, and mechanical suppleness. Adverse events were similar in both groups. aCT1 has potential to improve scarring outcome after surgery.

Keloids and Hypertrophic Scars: A Spectrum of Clinical Challenges

Since their earliest description, keloids and hypertrophic scars have beleaguered patients and clinicians alike. These scars can be aesthetically disfiguring, functionally debilitating, emotionally distressing, and psychologically damaging, culminating in a significant burden for patients. Our current understanding of keloid pathophysiology has grown and continues to advance while molecular biology, genetics, and technology provide ever-deepening insight into the nature of wound healing and the pathologic perturbations thereof. Greater understanding will lead to the development and application of refined therapeutic modalities. This article provides an overview of our current understanding of keloids, highlighting clinical characteristics and diagnostic criteria while providing a comprehensive summary of the many therapeutic modalities available. The proposed mechanism, application, adverse events, and reported efficacy of each modality is evaluated, and current recommendations are summarized.

The Multi-Domain Fibroblast/Myocyte Coupling in the Cardiac Tissue: A Theoretical Study

Cardiac fibroblast proliferation and concomitant collagenous matrix accumulation (fibrosis) develop during multiple cardiac pathologies. Recent studies have demonstrated direct electrical coupling between myocytes and fibroblasts in vitro, and assessed the electrophysiological implications of such coupling. However, in the living tissues, such coupling has not been demonstrated, and only indirect coupling via the extracellular space is likely to exist. In this study we employed a multi-domain model to assess the modulation of the cardiac electrophysiological properties by neighboring fibroblasts assuming only indirect coupling. Numerical simulations in 1D and 2D human atrial models showed that extracellular coupling sustains a significant impact on conduction velocity (CV) and a less significant effect on the action potential duration. Both CV and the slope of the CV restitution increased with increasing fibroblast density. This effect was more substantial for lower extracellular conductance. In 2D, spiral waves exhibited reduced frequency with increasing fibroblast density, and the propensity of wavebreaks and complex dynamics at high pacing rates significantly increased.

Connexins, Pannexins, and Their Channels in Fibroproliferative Diseases

Cellular and molecular mechanisms of wound healing, tissue repair, and fibrogenesis are established in different organs and are essential for the maintenance of function and tissue integrity after cell injury. These mechanisms are also involved in a plethora of fibroproliferative diseases or organ-specific fibrotic disorders, all of which are associated with the excessive deposition of extracellular matrix components. Fibroblasts, which are key cells in tissue repair and fibrogenesis, rely on communicative cellular networks to ensure efficient control of these processes and to prevent abnormal accumulation of extracellular matrix into the tissue. Despite the significant impact on human health, and thus the epidemiologic relevance, there is still no effective treatment for most fibrosis-related diseases. This paper provides an overview of current concepts and mechanisms involved in the participation of cellular communication via connexin-based pores as well as pannexin-based channels in the processes of tissue repair and fibrogenesis in chronic diseases. Understanding these mechanisms may contribute to the development of new therapeutic strategies to clinically manage fibroproliferative diseases and organ-specific fibrotic disorders.

Connexin 43 deficiency accelerates skin wound healing and extracellular matrix remodeling in mice

BACKGROUND

Cellular channels composed of connexin 43 are known to act as key players in the life cycle of the skin and consequently to underlie skin repair.

OBJECTIVE

This study was specifically set up to investigate the suite of molecular mechanisms driven by connexin 43-based channels on wound healing.

METHODS

To this end, a battery of parameters, including re-epithelialization, neovascularization, collagen deposition and extracellular matrix remodeling, was monitored over time during experimentally induced skin repair in heterozygous connexin 43 knockout mice.

RESULTS

It was found that connexin 43 deficiency accelerates re-epithelialization and wound closure, increases proliferation and activation of dermal fibroblasts, and enhances the expression of extracellular matrix remodeling mediators.

CONCLUSION

These data substantiate the notion that connexin 43 may represent an interesting therapeutic target in dermal wound healing.

miRNA expression profiles in keloid tissue and corresponding normal skin tissue

BACKGROUND

Because the molecular mechanism behind keloid pathogenesis is still largely unknown, the clinical management of keloids remains problematic. miRNA (microRNA) is a novel class of small regulatory RNA that has emerged as post-transcriptional gene repressors and participants in diverse pathophysiological processes of skin disease. In the present study we aimed to investigate expression profiles of miRNA in keloid tissue and to develop a further understanding of the molecular mechanism involved in the pathogenesis of keloids.

METHODS

miRNA expression profiles in 12 pairs of keloid tissue and corresponding normal skin tissue were analyzed through a mammalian miRNA microarray containing established whole human mature and precursor miRNA sequences. Real-Time quantitative PCR was performed to confirm the array results. The putative targets of differentially expressed miRNA were functionally annotated by bioinformatics approaches.

RESULTS

miRNA microarray analysis identified 32 differentially expressed miRNAs, and a total of 23 miRNAs exhibited higher expression, while 9 miRNAs demonstrated lower expression in keloid tissue than in normal skin tissue. Functional annotations of differentially expressed miRNA targets revealed that they were enriched in several signaling pathways important for scar wound healing.

CONCLUSION

This study showed that the expressions of many miRNAs were altered in keloid tissue, and their expression profiling may provide a useful clue for exploring the pathogenesis of keloids. miRNAs might partly contribute to the etiology of keloids by affecting several signaling pathways relevant to scar wound healing.

Morphological and molecular pathology of CCL4-induced hepatic fibrosis in connexin43-deficient mice

Gap junction channels, formed by connexins (Cx), are involved in the maintenance of tissue homeostasis, cell growth, differentiation, and development. Several studies have shown that Cx43 is involved in the control of wound healing in dermal tissue. However, it remains unknown whether Cx43 plays a role in the control of liver fibrogenesis. Our study investigated the roles of Cx43 heterologous deletion on carbon tetrachloride (CCl(4))-induced hepatic fibrosis in mice. We administered CCl(4) to both Cx43-deficient (Cx43(+/-)) and wild-type mice and examined hepatocellular injury and collagen deposition by histological and ultrastructural analyses. Serum biochemical analysis was performed to quantify liver injury. Hepatocyte proliferation was analyzed immunohistochemically. Protein and messenger RNA (mRNA) expression of liver connexins were evaluated using immunohistochemistry as well as immunoblotting analysis and quantitative real-time PCR. We demonstrated that Cx43(+/-) mice developed excessive liver fibrosis compared with wild-type mice after CCl(4) -induced chronic hepatic injury, with thick and irregular collagen fibers. Histopathological evaluation showed that Cx43(+/-) mice present less necroinflammatory lesions in liver parenchyma and consequent reduction of serum aminotransferase activity. Hepatocyte cell proliferation was reduced in Cx43(+/-) mice. There was no difference in Cx32 and Cx26 protein or mRNA expression in fibrotic mice. Protein expression of Cx43 increased in CCl(4)-treated mice, although with aberrant protein location on cytoplasm of perisinusoidal cells. Our results demonstrate that Cx43 plays an important role in the control and regulation of hepatic fibrogenesis.

Connexins: sensors and regulators of cell cycling

It is nowadays well established that gap junctions are critical gatekeepers of cell proliferation, by controlling the intercellular exchange of essential growth regulators. In recent years, however, it has become clear that the picture is not as simple as originally anticipated, as structural precursors of gap junctions can affect cell cycling by performing actions not related to gap junctional intercellular communication. Indeed, connexin hemichannels also foresee a pathway for cell growth communication, albeit between the intracellular compartment and the extracellular environment, while connexin proteins as such can directly or indirectly influence the production of cell cycle regulators independently of their channel activities. Furthermore, a novel set of connexin-like proteins, the pannexins, have lately joined in as regulators of the cell proliferation process, which they can affect as either single units or as channel entities. In the current paper, these multifaceted aspects of connexin-related signalling in cell cycling are reviewed.

Keloids: pathogenesis, clinical features, and management

Cutaneous wound healing is a complex response to skin injury. Deregulation of this process can lead to excessive scar formation, as seen in keloids. Keloids are common skin lesions that are difficult to treat and are associated with high recurrence rates despite the large number of available treatment options. With increased knowledge of the disease process and further scientific advancements, future approaches will hopefully improve keloid treatment. In this article, we review the epidemiology, genetic basis, etiology, clinical features, pathogenesis, and management of keloids.

Potential cellular and molecular causes of hypertrophic scar formation

A scar is an expected result of wound healing. However, in some individuals, and particularly in burn victims, the wound healing processes may lead to a fibrotic hypertrophic scar, which is raised, red, inflexible and responsible for serious functional and cosmetic problems. It seems that a wide array of subsequent processes are involved in hypertrophic scar formation, like an affected haemostasis, exaggerated inflammation, prolonged reepithelialization, overabundant extracellular matrix production, augmented neovascularization, atypical extracellular matrix remodeling and reduced apoptosis. Platelets, macrophages, T-lymphocytes, mast cells, Langerhans cells and keratinocytes are directly and indirectly involved in the activation of fibroblasts, which in turn produce excess extracellular matrix. Following the chronology of normal wound healing, we unravel, clarify and reorganize the complex molecular and cellular key processes that may be responsible for hypertrophic scars. It remains unclear whether these processes are a cause or a consequence of unusual scar tissue formation, but raising evidence exists that immunological responses early following wounding play an important role. Therefore, when developing preventive treatment modalities, one should aim to put the early affected wound healing processes back on track as quickly as possible.

Alternating synchronizability of complex clustered networks with regular local structure

Small network distance and homogeneous degree distribution have been found to be critical to efficient network synchronization. In this paper, we investigate the synchronizability of clustered networks with regular subnetworks and report a counterintuitive phenomenon: As the density of intracluster links is increased, the network exhibits strong and weak synchronizability in an alternating manner. A theory based on analyzing the eigenvalues and eigenvectors of the coupling matrix is provided to explain this phenomenon. The relevance of the network model to tissue organization for intercellular communication in biological systems is discussed. An implication is that, in order to achieve synchronization, local coupling density in the network needs to be tuned properly.

Effects of gap junction intercellular communication in rat liver on the proliferation of hepatic oval cells in vivo

AIM: To investigate the effect of gap junction intercellular communication (GJIC) in rat liver on the proliferation of hepatic oval cells (HOC) in vivo.

METHODS: Male Wistar rats were randomized into control group (n = 6), model group and phenobarbital (PB) group. HOC proliferation was induced in the rats of model group: 9 days of treatment with 2-AAF, 20 mg/kg per day by gavage, interrupted on day 5 to perform a 70% hepatectomy (2-AAF/PH). The rats in PB group were administered with PB (0.8 g/L, till the end of experiment) in drinking water, and on the 8^th day they received the same treatment as model group. The rats in model and PB group were sacrificed and necropsied at the 4^th hour, on the 4^th, 8^th, 12^th and 16^th day (6 rats at each time point) followed hepatectomy. The morphological changes of liver tissues were observed by pathological examination and the proliferation of HOC was counted using immunohistochemistry and morphological recognition. GJIC was confirmed by incision loading/dye transfer (IL/DT), and the levels of CX32 protein and mRNA were detected by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR), respectively. The expression of CX43 protein and mRNA were determined by immunohistochemistry, Western blot and RT-PCR, respectively.

RESULTS: No HOC proliferation was seen in the rat liver of control, 4-hour model and PB group. HOC appeared at portal area in model group on day 4, increased to the peak on day 8, intensely proliferated from the portal spaces and invaded the liver parenchyma on day 12, and decreased on day 16 as compared with day 12. HOC proliferation had a significant increase in PB group (from day 4 to 16) as compared with that in model group. The distance of dye transfer in model group (4 h, 4, 8, 12, 16 d) was significantly reduced in comparison with that in control group, and moreover, it was further decreased in PB group. The signal number of CX32 in the rat liver of model and PB groups were reduced as compared with that in control group (P < 0.05), and there was also significant differences between model and PB group (P < 0.05 or P < 0.01). The expression of CX32 mRNA in model group at the 4^th hour, on the 4^th, 8^th, 12^th and 16^th day was 0.82 ± 0.13, 0.33 ± 0.11, 0.51 ± 0.13, 0.68 ± 0.14 and 1.12 ± 0.18 folds of that in control group, respectively. As compared with that in model group, the level of CX32 mRNA expression in PB group had no statistical difference at the 4^th hour (P > 0.05), but had a significant increase on day 4 to 16 (P < 0.05). The expression of CX43 protein in the liver of model group at the 4^th hour, on the 4^th, 8^th, 12^th and 16^th day was 1.14 ± 0.17, 3.87 ± 0.35, 5.28 ± 0.48, 2.96 ± 0.33 and 2.12 ± 0.19 folds of that in control group, respectively. As compared with that in model group, the quantity of CX43 protein in PB group had no statistical difference at the 4th hour (P > 0.05), but had a significant decrease on day 4 to 16 (P < 0.05). The level of CX43 mRNA expression in model group at the 4^th hour, on the 4^th, 8^th, 12^th and 16^th day was 1.09 ± 0.16, 2.82 ± 0.23, 5.46 ± 0.58, 3.34 ± 0.64 and 0.91 ± 0.11 folds of that in control group, respectively. As compared with that in model group, the level of CX43 mRNA in PB group was increased (P < 0.05).

CONCLUSION: The GJIC of hepatocyte and HOC can be decreased by altering the spatial and temporal expression patterns of CX in rat liver after 2-AAF/PH, which leads to the acceleration of HOC proliferation.

Function and significance of gap junction intercellular communication in rat liver for hepatic oval cell proliferation in vivo

AIM: To study the expression of connexin 32 (CX32) and connexin 43 (CX43) and function of gap junction intercellular communication (GJIC) in rat liver during 2-acetylaminofluorene/partial hepatectomy (2AAF/PH) for hepatic oval cell (HOC) proliferation, and explore the potential mechanism of HOC proliferation in vivo.

METHODS: Male Wistar rats were randomized into normal control group (n = 6) and model group. Rats in model group were used to induce HOC proliferation: 9 days of treatment with 2-AAF, 20 mg/kg per day by gavage, interrupted on day 5 to perform a 70% hepatectomy (2-AAF/PH). At the 4^th hour, 4^th, 8^th, 12^th and 16^th day, 6 rats of model group were sacrificed respectively. The morphological changes of liver tissues were observed by pathological examination and the proliferation of HOC was counted using immunohistochemistry and morphological recognition. GJIC was confirmed by incision loading/dye transfer (IL/DT), and the levels of CX32 protein and mRNA were detected by immunohistochemistry and reverse transcription-polymerase chain reaction (RT-PCR), respectively. The expression of CX43 protein and mRNA were determined by immunohistochemistry, Western blot and RT-PCR, respectively.

RESULTS: No HOC proliferation was seen in the rat liver of control and 4-hour model group. Pathologic examination revealed that HOC appeared at portal area in model group on day 4, increased to the peak on day 8, intensely proliferated from the portal spaces and invaded the liver parenchyma on day 12, and decreased on day 16 as compared with day 12. In comparison with that in control group, the distance of dye transfer in model groups (4 h, 4, 8, 12, 16 d) was significantly reduced (84.5 ± 3.4, 60.6 ± 3.3, 108.6 ± 4.2, 150.6 ± 2.6, 199.6 ± 3.7 μm vs 250.0 ± 5.0 μm, P < 0.01). The signal number of CX32 in the rat liver of model groups began to decrease at the 4th hour, reached to the minimum (2.85 ± 0.39) on day 4, and recovered starting from day 8, and it was markedly reduced as compared with that in control group (P < 0.05). CX32 mRNA in model groups was decreased at the 4^th hour, reached the lowest level (0.33 ± 0.11) on day 4 and started to recover on day 8. On day 16, CX32 mRNA expression was also higher than that in control group, but the difference was not significant (P > 0.05). Western blot analysis showed an increased CX43 protein expression at the 4^th hour (P > 0.05), on day 4, 8, 12 and 16 (P < 0.01). In comparison with that in control group, the level of CX43 mRNA in model group had a slight increase at the 4^th hour (P > 0.05), an obvious increase on day 4, reached the peak on day 12 (5.46 ± 0.58), and started to decrease on day 16 (P > 0.05).

CONCLUSION: Satisfactory rat model of HOC proliferation is successfully obtained using AAF/PH, and this method is convenient, stable and repeatable. Inhibition of GJIC function, which may activate the proliferation of HOC, is regulated by CX expression patterns.