Differential effects of hexoses and sucrose, and platelet-derived growth factor isoforms on cyclooxygenase-1 and -2 mRNA expression in keloid, hypertrophic scar and granulation tissue fibroblasts

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.

Immunohistochemical Expression of Cyclooxygenases in Hypertrophic Scars and Keloids

Background:

There are studies demonstrating an increased expression of cyclooxygenase (COX) in keloids and hypertrophic scars, suggesting that anti-inflammatory drugs could be used in their treatment. However, a precise relationship between COX and pathological scarring has not been established in the literature yet. This study aims to evaluate the immunohistochemical expression of COXs in these scars.

Methods:

Prospective study, including 54 patients (aged 18–60 years) undergoing scar excision: 18 normal scars (group 1), 18 hypertrophic scar (group 2), and 18 keloids (group 3). The group classification was performed by clinical criteria. Scars samples were collected and anatomopathological examination (through hematoxylin-eosin method) was performed to confirm the scar type. Immunohistochemistry was performed to assess the expression of COX1 and COX2 in epidermis and dermis. Results were compared among all groups and between group I versus II and III together (abnormal scars).

Results:

For COX1, in the epidermis, there was no significant difference in the immunohistochemical expression when comparing the 3 groups. In the dermis, groups 2 and 3 had greater expression than group 1, with a significant difference being found when comparing all groups (P = 0.014), and in the comparison between normal versus abnormal scars (P = 0.004). For COX2, there was no significant difference between the groups in both the epidermis and dermis.

Conclusions:

The immunohistochemical expression of COX1 was greater in the dermis of abnormal scars when compared with normal scars. Future studies can be performed involving COX blockade as a perspective of these scars treatment.

Growth factor pathways in hypertrophic scars: Molecular pathogenesis and therapeutic implications

Hypertrophic scars represent the most common complication of skin injury and are caused by excessive cutaneous wound healing characterized by hypervascularity and pathological deposition of extracellular matrix (ECM) components. To date, the optimal and specific treatment methods for hypertrophic scars have not been available in the clinic. Current paradigm has established fibroblasts and myofibroblasts as pivotal effector cells in the pathophysiology of wound healing. Their biological properties including origin, proliferation, migration, contraction and ECM regulation have profound impacts on the progression and regression of hypertrophic scars. These complex processes are executed and modulated by a signaling network involving a number of growth factors and cytokines. Of particular importance is transforming growth factor-β, platelet-derived growth factor, connective tissue growth factor, epidermal growth factor, and vascular endothelial growth factor. This review article briefly describes the biological functions of fibroblasts and myofibroblasts during hypertrophic scars, and thereafter examines the up-to-date molecular knowledge on the roles of key growth factor pathways in the pathophysiology of hypertrophic scars. Importantly, the therapeutic implications and future challenges of these molecular discoveries are critically discussed in the hope of advancing therapeutic approaches to limit pathological scar formation.

Immunohistochemical evaluation of COX-1 and COX-2 expression in keloid and hypertrophic scar

Both keloids (KLs) and hypertrophic scars (HSs) are considered as dermal fibroproliferative diseases that differ clinically and histopathologically. Although several factors have been postulated in the etiopathogenesis of these conditions, there has been growing evidence to suggest the role of COXs in the pathogenesis of abnormal wound healing because of the reduction of formation of KL and HS in patients using nonsteroidal anti-inflammatory drugs and a COX-2 inhibitor. The aim of the present work is to evaluate the pattern and localization of COX-1 and COX-2 expression in KL and HS compared with surgical scars. COX-1 and COX-2 were analyzed on skin biopsies of 30 patients who presented with KL (15) and HS (15) and 10 normal surgical scars (controls). Both COX-1 and COX-2 were expressed not only in dermal components (fibroblasts, inflammatory cells, and endothelial cells) but also in keratinocytes of the overlying epidermis in the different studied scar lesions. The percentage of COX-1 expression increased progressively from surgical scar (40%) to HS (53.3%) to KL (100%) with a statistically significant difference (P = 0.002). COX-2 was expressed in 100% of surgical scars, 73.3% of HS and 86.7% of KL with the absence of significant differences (P > 0.05). The significant difference in COX-1 expression between HS and KL may refer to the presence of different pathways for the emergence of these diseases. The expression of COX-2 in all scars (normal or abnormal) indicates its active role as an inflammatory mediator. Keratinocytes play an active role in induction of scarring by up-regulation of inflammatory mediators, such as COX-1 and COX-2.

Genistein inhibits proliferation and functions of hypertrophic scar fibroblasts

Hypertrophic scarring is abnormal proliferation of dermal fibroblasts and excessive deposition of extracellular matrix. To date, despite many studies, treatments have not been satisfactory. Genistein, a potent, specific inhibitor of tyrosine protein kinases (TPKs), has been proved to inhibit many kinds of tumour and some fibrotic diseases. The purpose of this study was to investigate the effects of genistein on the proliferation and functions of hypertrophic scar fibroblasts (HSFBs) and the mechanism by which genistein inhibits TPK signal transduction. The first effect was observed by methyl-thiazol-diphenyl-tetrazolium assay and the second by [gamma-(32)p] adenosine triphosphate incorporation assay. The results demonstrated that genistein inhibits the proliferation and function of HSFBs and changes the TPK signal transduction pathway, which can provide an experimental basis for treating HS with genistein.

Lipid analysis of normal dermis and hypertrophic scars

Hypertrophic scars (HS) are a consequence of abnormal wound healing. We examined fatty acids that are contained within, and participate in, every reaction through the membrane; then, we analyzed the percentage composition of the fatty acids in deepithelialized normal dermis (ND) and HS. In vivo HS samples were obtained from six patients undergoing surgical excision, and ND samples from five patients undergoing skin grafting surgery for excess. In vitro, cultured fibroblasts from HS and ND were also analyzed. The percentage composition of fatty acids extracted from all the samples was analyzed. In vivo, arachidonic acid (20:4) was significantly more abundant in HS than in ND, in the phospholipids from both whole tissue and cell membranes. In vitro, there were no significant differences among ND, HS, and 10% fetal calf serum. The results suggest that HS formation does not necessarily involve simple excess of 20:4; however, there are considerable differences in the percentage composition of 20:4 between ND and HS. Arachidonic acid probably participates in the formation and maintenance of HS, whereas in vitro cultured fibroblasts are affected largely by fetal calf serum.

Prostaglandin E2 inhibition of keloid fibroblast migration, contraction, and transforming growth factor (TGF)-beta1-induced collagen synthesis

Keloid formation has been linked to aberrant fibroblast activity, exacerbated by growth factors and inflammatory mediators. Prostaglandin E2 (PGE2), synthesized from arachidonic acid by cyclooxygenases (COX) and synthases (PGES), acts as both an inflammatory mediator and fibroblast modulator. Although PGE2 has known antifibrotic effects in the lower airway, its role in dermal fibrosis in general, and keloid formation in particular, remains unclear. This study focused on: (1) the effects of PGE2 on keloid fibroblast migration, contraction, and collagen synthesis and (2) endogenous PGE2 synthesis in response interleukin-1beta. PGE2 decreased keloid fibroblast migration and contraction via an EP2/EP4-cAMP mechanism that disrupted actin cytoskeletal dynamics and reversed transforming growth factor-beta1-induced collagen I and III synthesis. Impaired fibroblast PGE2 production has been linked to lower airway fibrosis and recently to keloid formation. Here, we showed that interleukin-1beta stimulation leads to nuclear factor-kappaB translocation to the nucleus, resulting in up-regulation of COX-2 and microsomal PGE2 synthase 1. Up-regulation of COX-2 in, and secretion of PGE2 by keloid fibroblasts are diminished compared with their normal fibroblast counterparts. We suggest that the antifibrotic effects of PGE2 during keloid formation are potentially diminished due to aberrant paracrine fibroblast signaling. Exogenous PGE2 may supplement decreased endogenous levels and inhibit keloid formation or progression.

Inhibition of Pro-Angiogenic Factors by a Lipid-Rich Shark Extract

This study aimed to determine whether a shark muscle oil-olive oil mixture influences activators of human angiogenesis. The mixture completely abolished the stimulation induced by vascular endothelial growth factor (VEGF), fibroblast growth factor-2, transforming growth factor-beta, and platelet-derived growth factor. This suggests that it may compete with these growth factors for their binding sites on the endothelial cell surface either by binding to the growth factor or by blocking the actual receptor. The possibility of the oil binding to the VEGF receptor was studied through the use of soluble forms of the receptors (VEGF-R1 and VEGF-R2). It was found that the shark oil-olive oil inhibited the formation of the complexes of VEGF with both of the receptors. This could have been because the oil bound to either the VEGF or the receptor or both. To determine which is possible, the shark oil-olive oil was mixed with the receptors. The molecular size of the receptors increased, and these larger forms of the receptor had reduced capacity for complexing with VEGF. Therefore, one mode of potential anti-angiogenic action of the shark muscle oil-olive oil is the inhibition of the activity of a number of stimulatory molecules, including VEGF. This study demonstrates that the blend of shark and olive oils antagonizes VEGF activity by binding to at least two receptors for the factor, thereby inhibiting the activation by the growth factor.

Keloid-derived fibroblasts have a diminished capacity to produce prostaglandin E2

Keloids result from pathological wound healing responses. However, the pathogenesis of keloids is still poorly understood. PGE2 was shown to decrease fibroblast proliferation, inhibit collagen synthesis and enhance the expression of matrix-metalloproteinases (MMPs). This study sought to delineate the production of PGE2 by normal and keloid-derived dermal fibroblasts. Human normal and keloid dermal fibroblasts were cultured in vitro. Cell proliferation and viability were determined based on WST-1 assay. IL-1beta-induced PGE2 production and effects of PGE2 on the synthesis of procollagen by culture-derived fibroblasts were determined by using enzyme-linked immunosorbant assay (ELISA) kits. IL-1beta-induced MMP-1 production by culture-derived fibroblasts was determined with an MMP-1 immunoassay kit. Our results showed that normal and keloid-derived fibroblasts exhibited a statistically significant increase (p<0.05) in cell proliferation when the cells were cultured in media with an increase in the concentrations (0%, 2% and 10%) of fetal bovine serum (FBS). In culture medium without FBS, an increase in cell proliferation of keloid-derived fibroblasts was detectable when compared with those of control fibroblasts. IL-1beta (1 ng/ml and 10 ng/ml) stimulated statistically significant production (p<0.01) of PGE2 by both normal and keloid-derived fibroblasts. However, lower levels of PGE2 produced by keloid-derived fibroblasts were detectable compared with those produced by normal-derived fibroblasts (p<0.05). In this study, although not statistically significant, inhibition of procollagen production by PGE2 in a dose-dependent manner was found. In addition, decreased production of MMP-1 by keloid-derived fibroblasts compared with those of control fibroblasts was also observed. In conclusion, keloid-derived fibroblasts produced less PGE2 than those produced by control fibroblasts. The role of diminished capacity of PGE2 production in keloid formation is presently unknown and needs further study.

Cyclooxygenase-2 inhibition selectively attenuates bone morphogenetic protein-6 synthesis and bone formation during guided tissue regeneration in a rat model

OBJECTIVES

Bone formation during guided tissue regeneration is a tightly regulated process involving cells, extracellular matrix and growth factors. The aims of this study were (i) to examine the expression of cyclooxygenase-2 (COX-2) during bone regeneration and (ii) the effects of selective COX-2 inhibition on osseous regeneration and growth factor expression in the rodent femur model.

MATERIAL AND METHODS

A standardized transcortical defect of 5 x 1.5 mm was prepared in the femur of 12 male rats and a closed half-cylindrical titanium chamber was placed over the defect. The expression of COX-2 and of platelet-derived growth factor-B (PDGF-B), bone morphogenetic protein-6 (BMP-6) and insulin-like growth factor-I/II (IGF-I/II) was analyzed at Days 3, 7, 21 and 28 semiquantitatively by reverse transcriptase-polymerase chain reaction and immunohistochemistry. The effects of COX-2 inhibition by intraperitoneal injection of NS-398 (3 mg/kg/day) were analyzed in five additional animals sacrificed at Day 14.

RESULTS

Histomorphometry revealed that new bone formation occurred in the cortical defect area as well as in the supracortical region, i.e. region within the chamber by Day 7 and increased through Day 28. Immunohistochemical evidence of COX-2 and PDGF-B levels were observed early (i.e. Day 3) and decreased rapidly by Day 7. BMP-6 expression was maximal at Day 3 and slowly declined by Day 28. In contrast, IGF-I/II expression gradually increased during the 28-day period. Systemic administration NS-398 caused a statistically significant reduction (P<0.05) in new bone formation (25-30%) and was associated with a statistically significant reduction in BMP-6 protein and mRNA expression (50% and 65% at P<0.05 and P<0.01, respectively). PDGF-B mRNA or protein expression was not affected by NS-398 treatment.

CONCLUSION

COX-2 inhibition resulted in reduced BMP-6 expression and impaired osseous regeneration suggesting an important role for COX-2-induced signaling in BMP synthesis and new bone formation.

Advances in the Modulation of Cutaneous Wound Healing and Scarring

Cutaneous wounds inevitably heal with scars, which can be disfiguring and compromise function. In general, the greater the insult, the worse the scarring, although genetic make up, regional variations and age can influence the final result. Excessive scarring manifests as hypertrophic and keloid scars. At the other end of the spectrum are poorly healing chronic wounds, such as foot ulcers in diabetic patients and pressure sores. Current therapies to minimize scarring and accelerate wound healing rely on the optimization of systemic conditions, early wound coverage and closure of lacerations, and surgical incisions with minimal trauma to the surrounding skin. The possible benefits of topical therapies have also been assessed. Further major improvements in wound healing and scarring require an understanding of the molecular basis of this process. Promising strategies for modulating healing include the local administration of platelet derived growth factor (PDGF)-BB to accelerate the healing of chronic ulcers, and increasing the relative ratio of transforming growth factor (TGF)beta-3 to TGFbeta-1 and TGFbeta-2 in order to minimize scarring.

Mitomycin Does Not Prevent Laryngotracheal Repeat Stenosis After Endoscopic Dilation Surgery: An Animal Study

OBJECTIVES/HYPOTHESIS

Conflicting data exist in the literature regarding the role of mitomycin in the prevention and treatment of laryngotracheal stenosis. The purpose of the study was to assess the value of mitomycin in preventing repeat stenosis after endoscopic dilation surgery of well-established stenoses.

STUDY DESIGN

Prospective controlled animal study.

METHODS

Laryngotracheal stenosis was induced in 16 dogs. After a period of 3 months the dogs underwent endoscopic dilation and were randomly divided into two groups. The control group received immediate topical application of normal saline. Dogs in the mitomycin group received immediate topical application of 0.5 mg mitomycin. The animals were then observed for 3 more months before euthanasia. The laryngeal lumens were measured endoscopically at baseline, before dilation, and before euthanasia. A comparison was made between the two study groups by means of the Wilcoxon rank-sum test for change in the percentage of stenosis attained by the endoscopic dilation.

RESULTS

Nine dogs were included in the control group, and seven in the mitomycin group. Group comparison for initial occlusion before endoscopic dilation using Wilcoxon rank-sum test showed no difference between the two groups (z = 0.16 [P =.87]). Three months after endoscopic dilation, no difference was observed between the two groups regarding the change in the percentage of occlusion (z = -0.21 [P =.83]).

CONCLUSION

Mitomycin exerts a benefit equal to that of normal saline when applied to a well-established laryngotracheal stenosis in dogs and does not prevent repeat stenosis after endoscopic dilation surgery.

The up-regulation of cyclooxygenase-2 expression in human buccal mucosal fibroblasts by arecoline: a possible role in the pathogenesis of oral submucous fibrosis

BACKGROUND

Aberrant and persistent tissue inflammation are believed to play an important role on the occurrence of tissue fibrosis. Cyclooxygenase (COX)-2 is an inducible enzyme responsible for prostaglandin synthesis in certain inflammatory diseases. The purpose of this study was to compare COX-2 expression in normal human buccal mucosa and oral submucous fibrosis (OSF) specimens and further explore the potential mechanism that may lead to induce COX-2 expression.

METHODS

Fifteen OSF specimens and six normal buccal mucosa were examined by immunohistochemistry. Primary human buccal mucosa fibroblasts (BMFs) were established and challenged with arecoline analyzed by reverse transcriptase polymerase chain reaction. Furthermore, to elucidate whether induction of COX-2 is associated with cytotoxicity, aspirin (a non-selective inhibitor of COX enzyme) and NS-398 (a selective COX-2 inhibitor), were added to test their protective effects.

RESULTS

COX-2 expression was significantly higher in OSF specimens and expressed mainly by epithelial cells, endothelial cells, and cells with fibroblast morphology. In vitro studies indicated that BMFs did not express COX-2 constitutively. However, when the cells were treated with 80 micro g/ml arecoline, COX-2 expression was up-regulated as early as half an hour. This indicates that COX-2 expression is an early cellular response and regulated by arecoline at transcriptional level. In addition, pre-treatment with glutathione (GSH) precursor, 2-oxothiazolidine-4-carboxylic acid (OTZ), led to a decrease in induction of COX-2 mRNA by arecoline. GSH synthesis inhibitor, buthionine sulfoximine (BSO), was found to increase arecoline-induced COX-2 mRNA levels. Moreover, both of aspirin and NS-398 at non-cytotoxic doses are not able to prevent arecoline-induced cytotoxicity. This indicates that arecoline cytotoxicity is not directly via the induction of COX-2 expression.

CONCLUSIONS

Taken together, these results suggest that COX-2 expression is significantly up-regulated in OSF tissues from areca quid chewers and arecoline may among other constituents be responsible for the enhanced COX-2 expression in vivo. The regulation of COX-2 expression induced by arecoline is critically dependent on the cellular GSH concentration.

Inhibitory effect of a selective cyclooxygenase-2 inhibitor on liver metastasis of colon cancer

COX-2 overexpression is recognized in various cancers, but the role of COX-2 in the progression of cancer, including the liver metastasis of colon cancer, is not clearly understood. We examined the role of COX-2 in the mechanism of liver metastasis of colon cancer, using a highly metastasizable colon carcinoma cell line, LM-H3. A COX-2 inhibitor, JTE-522, inhibited cell proliferation and invasion of LM-H3 in vitro and clearly reduced the number of metastatic nodules on the surface of nude mouse livers in vivo. We also examined the effects of JTE-522 on the production of growth factors and MMPs through the use of ELISA and gelatin zymography, respectively. JTE-522 downregulated PDGF production by LM-H3 but had no influence on VEGF production. JTE-522 also inhibited MMP-2 secretion by LM-H3. JTE-522 downregulated PGE(2) production, but the associated changes in PGE(2) did not affect PDGF and VEGF production by LM-H3. We conclude that JTE-522 downregulated the cell proliferation and invasive potential of LM-H3 by reducing the production of PDGF and MMP-2 and hypothesize that these inhibitory effects on the production of PDGF and MMP-2 can lead to inhibition of liver metastasis of colon cancer. These data indicate that the COX-2 inhibitor JTE-522 has a high potential for use as a clinical agent for the treatment of liver metastasis of colon cancer.