Comparison of the effects of dexamethasone and 13-cis-retinoic acid on connective tissue biosynthesis in human skin fibroblasts

Elastogenesis in Focus: Navigating Elastic Fibers Synthesis for Advanced Dermal Biomaterial Formulation

Elastin, a fibrous extracellular matrix (ECM) protein, is the main component of elastic fibers that are involved in tissues' elasticity and resilience, enabling them to undergo reversible extensibility and to endure repetitive mechanical stress. After wounding, it is challenging to regenerate elastic fibers and biomaterials developed thus far have struggled to induce its biosynthesis. This review provides a comprehensive summary of elastic fibers synthesis at the cellular level and its implications for biomaterial formulation, with a particular focus on dermal substitutes. The review delves into the intricate process of elastogenesis by cells and investigates potential triggers for elastogenesis encompassing elastin-related compounds, ECM components, and other molecules for their potential role in inducing elastin formation. Understanding of the elastogenic processes is essential for developing biomaterials that trigger not only the synthesis of the elastin protein, but also the formation of a functional and branched elastic fiber network.

Calcipotriol counteracts betamethasone-induced decrease in extracellular matrix components related to skin atrophy

The calcipotriol/betamethasone dipropionate fixed-combination gel is widely used for topical treatment of psoriasis vulgaris. It has been hypothesized that calcipotriol counteracts glucocorticoid-induced skin atrophy which is associated with changes in the extracellular matrix (ECM). To elucidate the combined effects of calcipotriol and betamethasone on key ECM components, a comparative study to the respective mono-treatments was carried out. The effect on collagen I synthesis, matrix metalloproteinase (MMP) secretion, and hyaluronic acid (HA) production was investigated in primary human fibroblast and keratinocyte cultures as well as in a human skin explant model. We show that calcipotriol counteracts betamethasone-induced suppression of collagen I synthesis. Similarly, calcipotriol and betamethasone have opposing effects on MMP expression in both fibroblasts and keratinocytes. Moreover, calcipotriol is able to restore betamethasone-impaired HA synthesis in keratinocytes and prevent betamethasone-induced epidermal thinning in minipigs upon treatment with the calcipotriol/betamethasone gel. In summary, our results show for the first time in primary human skin cultures that calcipotriol reduces early signs of betamethasone-induced skin atrophy by modulation of key ECM components. These results indicate that the calcipotriol component of the fixed-combination gel counteracts the atrophogenic effects of betamethasone on the skin.

Action of topical thyroid hormone analogue, triiodothyroacetic acid in reversing glucocorticoid-induced skin atrophy in humans

The present study concerns the effect of topical treatment with a cream formulation of triiodothyroacetic acid (TRIAC) in comparison with a placebo preparation in producing a reversal of skin atrophy induced by long-term employment of topical glucocorticoid therapy in humans. A total of 39 patients with clinically verified skin atrophy due to long-term use of topical potent glucocorticoids were randomized. The changes in skin thickness, elastic fibers, and hyaluronic acid were evaluated by means of sonography and histology. After 8 weeks' treatment, the skin thickness measured by sonography increased by 16% in the epidermis, 8% in the dermis, and epidermis + dermis in the placebo group. In the TRIAC 0.1% group, the corresponding values were 24% ( p=0.063) in the epidermis, 28% ( p=0.042) in the dermis, and 25% ( p=0.039) in the epidermis + dermis. After 8 weeks, in the placebo group, the skin thickness measured by biopsy increased by 5% in the epidermis, epidermis + dermis, and 6% in the dermis. In the TRIAC 0.1% group, the corresponding values were 31% ( p=0.041) in the epidermis, 46% ( p=0.041) in the dermis and 44% ( p=0.043) in the epidermis + dermis. After 8 weeks, the elastic fibers of moderately irregular and thickened fibers increased by 56% in the placebo group and 100% ( p=0.043) in the TRIAC 0.1 group. This study indicates that topical treatment with TRIAC appears to reverse glucocorticoid-induced skin atrophy under the narrow conditions tested.

Glucocorticoid therapy-induced skin atrophy

Glucocorticoids (GCs) are highly effective for the topical treatment of inflammatory skin diseases. Their long-term use, however, is often accompanied by severe and partially irreversible adverse effects, with atrophy being the most prominent limitation. Progress in the understanding of GC-mediated molecular action as well as some advances in technologies to determine the atrophogenic potential of compounds has been made recently. It is likely that the detailed mechanisms of GC-induced skin atrophy will be discovered and in vitro models for the reliable prediction of atrophy will be established in the foreseeable future. This knowledge will not only facilitate safety profiling of established drugs but will also foster further drug discovery by improving compound characterization processes. New insights into GC modes of action will guide optimization strategies aiming at novel GC receptor ligands with improved effect/side effect profile.

Molecular basis of the alteration in skin collagen metabolism in response to in vivo dexamethasone treatment: effects on the synthesis of collagen type I and III, collagenase, and tissue inhibitors of metalloproteinases

BACKGROUND

Glucocorticoids are widely used for the treatment of various diseases, despite known side-effects such as skin atrophy. Many studies have shown that the status of collagen fibres in the skin is affected by glucocorticoid treatment. However, the molecular mechanism underlying the alteration of collagen metabolism in the skin by glucocorticoid treatment remains unknown.

OBJECTIVES

To characterize the molecular mechanisms related to the deterioration of the dermis in response to glucocorticoids, the status of two major types of collagen, collagenase, and tissue inhibitors of metalloproteinases (TIMPs) in the dorsal skin of rats was studied at the protein and mRNA levels.

METHODS

Samples of rat dorsal skin were obtained after daily (1 mg kg-1) subcutaneous injections of dexamethasone (DEX) for 8 days. mRNA levels of two types of collagen and of TIMPs were measured by a lysate RNase protection assay. mRNA levels of collagenase were measured by a quantitative polymerase chain reaction. Protein levels of collagen and collagenase were measured by an immunoblot analysis.

RESULTS

Levels of type I tropocollagen and type III tropocollagen were drastically reduced in response to DEX. The effects of DEX treatment were more severe on type III than type I collagen: it also produced a significant decrease in fibril collagen of type III collagen. DEX treatment was found to decrease both active and latent forms of collagenase as well as its mRNA levels. Among TIMPs, mRNA levels of TIMP-1 and TIMP-2 were decreased in response to DEX treatment, whereas those of TIMP-3 were not affected.

CONCLUSIONS

These results suggest that DEX treatment strongly interferes with both the synthesis and degradation of type I collagen and, more drastically, type III collagen, the molecule that is known to play a major role in the initiation of wound healing. The present study may provide a molecular basis for the deterioration of skin function, impaired wound healing, and skin atrophy caused by glucocorticoid treatment.

The molecular basis of glucocorticoid-induced skin atrophy: topical glucocorticoid apparently decreases both collagen synthesis and the corresponding collagen mRNA level in human skin in vivo

The effects of topical betamethasone-17-valerate on collagen propeptide levels, collagen mRNA level, lysyl oxidase mRNA and matrix metalloproteinase (MMP)-1 and MMP-2 mRNA levels were studied in human skin. Three days' treatment of healthy skin with topical betamethasone caused a 70-80% decrease in type I and III collagen propeptides in suction blister fluid. A similar decrease was found in type I collagen mRNA when assayed by either slot-blot hybridization or a quantitative polymerase chain reaction method, indicating that the decrease in collagen synthesis after topical glucocorticoid treatment is apparently due to a decrease in corresponding mRNA. mRNA of lysyl oxidase, which is an important enzyme catalysing the cross-linking of collagen chains, and collagen-degrading enzyme MMP-1 and MMP-2 mRNAs were not decreased in the same skin samples. This suggests that in vivo, glucocorticoids modulate variably the genes involved in collagen synthesis and degradation. Our study provides a solid molecular basis for glucocorticoid-induced dermal atrophy, which results from the decrease in functional collagen mRNA in the skin.

The pathogenesis of cutaneous fibrosis

Cutaneous fibrosis is an integral component of a variety of human disorders including keloids, hypertrophic scar, and most notably, scleroderma. Each has its own etiology and unique clinical characteristics, but all involve the dysregulation of connective tissue metabolism, in particular, the activation of dermal fibroblasts. In this review, we examine various molecular events in scleroderma that may lead to fibroblast activation, and propose a new model to explain the persistence of such activation by scleroderma fibroblasts in the apparent absence of exogenous stimuli.

Topical tretinoin enhances corticosteroid-induced inhibition of tumorigenesis in hairless mice previously exposed to solar simulating radiation

The role of retinoids in hairless mouse photocarcinogenesis has been studied extensively but remains controversial. By contrast, the role of corticosteroids has hardly been investigated. Many findings indicate an antagonism between the action of these two drugs. To examine these issues, we irradiated hairless mice thrice weekly for 10 weeks with 1.5 minimal erythema doses of solar simulating radiation (UVB + UVA). In the post-UV period, groups of mice were treated topically for 30 weeks with tretinoin, corticosteroid or emollient vehicle alone or with a sequential combination of corticosteroid and tretinoin. A control group remained topically untreated. All three agents, when used alone, significantly inhibited tumorigenesis. The sequential combination produced the greatest inhibition.

Effects of retinoids on glycosaminoglycan synthesis by human skin fibroblasts grown as monolayers and within contracted collagen lattices

Fibroblasts grown within contracted collagen lattices synthesize substantially less glycosaminoglycans than fibroblasts grown as monolayers on a plastic substrate. [3H]glucosamine incorporation into hyaluronate was reduced by 70%, and incorporation into sulphated glycosaminoglycans was reduced by 40%. However, incorporation into heparan sulphate and chondroitin sulphates was reduced by 14 and 49%, respectively, resulting in a substantial change in the proportions of the individual glycosaminoglycans. On the basis of [3H]glucosamine incorporation, hyaluronate constituted 80% of the total glycosaminoglycans synthesized in monolayer cultures, but only 67% in collagen lattice cultures. Incorporation of 35SO4 into chondroitin sulphates was reduced by 22%, whereas no change was observed in heparan sulphates following culture within collagen lattices. Exposure of the fibroblast cultures to retinoic acid (10(-6) mol/l) and retinyl propionate (2 x 10(-6) mol/l) resulted in a decrease in the incorporation of [3H]glucosamine into hyaluronate by up to 41% in monolayer cultures, and 25% in collagen lattice cultures. The retinoids stimulated the incorporation of [3H]glucosamine into heparan sulphate by up to 72%, and chondroitin sulphates by up to 30%, whereas 35SO4 incorporation remained essentially unaltered. Only modest changes in the incorporation of both isotopes into fibroblast sulphated glycosaminoglycans were observed following exposure to the retinoids in lattice cultures. Q-Sepharose ion-exchange chromatography at pH 2.0 revealed that there was no change in the degree of polymer sulphation of either chondroitin sulphate or heparan sulphate isolated from collagen lattice cultures compared with monolayer cultures. Retinoic acid (10(-6) mol/l) treatment did, however, reduce the degree of polymer sulphation of heparan sulphates and chondroitin sulphates in both monolayer and lattice cultures.(ABSTRACT TRUNCATED AT 250 WORDS)

Etretinate administration reduces serum propeptide of type I procollagen level in patients with psoriasis

The serum carboxyterminal propeptide of type I procollagen (PICP) level in 26 patients with psoriasis was significantly lower than in control subjects (124 +/- 47 and 224 +/- 78 ng/ml, respectively; P < 0.001). The patients were divided into two groups, those treated with etretinate and untreated patients. PICP levels in the treated group were significantly lower than those in the untreated group (P < 0.001), but there was no difference between the control and untreated groups. In addition, there was a negative correlation between PICP levels and the serum etretinate concentration in treated patients (r = -0.622, P < 0.05). There was no difference between procollagen type III aminoterminal propeptide (PIIIP) levels in patients and controls, nor was there any significant difference between etretinate-treated and untreated patients. In cell culture studies, etretinate dose-dependently (from 10(-9) to 10(-5) M) decreased the PICP concentration in the medium of fibroblasts from both healthy subjects and patients. In osteoblast cell culture, PICP levels were reduced only in a high concentration of etretinate (10(-5) M). However, no change was observed in preadipose cells. Our in vivo and in vitro observations indicated that psoriasis per se did not affect either serum PICP or PIIIP levels, but that etretinate had an inhibitory effect on collagen synthesis by fibroblasts. Hence, the administration of etretinate to psoriatic patients is, at least in part, responsible for the reduction of serum PICP levels in these patients.

In vivo prevention of corticosteroid-induced skin atrophy by tretinoin in the hairless mouse is accompanied by modulation of collagen, glycosaminoglycans, and fibronectin

In an earlier study we showed that tretinoin could prevent corticosteroid-induced skin atrophy in hairless mice. In this study, we examined the histochemical, biochemical, and immunochemical changes that accompanied the atrophy and its prevention. Mice were treated dorsally for 3 weeks in the morning and afternoon (AM:PM) as follows: 1) vehicle:vehicle, 2) steroid:vehicle, 3) steroid:tretinoin. Tretinoin concentration was 0.05% in an ethanol:propylene glycol vehicle. The steroid was clobetasol propionate (0.05%). The normally sparse dermal glycosaminoglycans were further reduced by steroid:vehicle treatment and increased to greater than vehicle:vehicle amounts by steroid:retinoid. Mast cells were similarly affected. Biochemical quantification of glycosaminoglycans confirmed the histochemical findings. Collagen, non-collagenous protein, and total protein content were reduced by the steroid. The latter two were returned to more normal levels by tretinoin whereas with collagen there was only a trend toward normal levels. Fibronectin, which was increased by the steroid:vehicle treatment, was reduced to more normal levels by steroid:tretinoin. We conclude that tretinoin has the ability to prevent the major steroid-induced biomechanical changes in hairless mouse dermal connective tissue that contribute to atrophy.

Collagen synthesis in fibroblasts from human colon: regulatory aspects and differences with skin fibroblasts

The purpose of this study was to examine regulation of collagen synthesis in human colon fibroblasts and compare the results from colon fibroblasts with those obtained in fibroblasts from human skin. The effects of interleukin-1 beta, tumour necrosis factor alpha, interferon gamma, transforming growth factor-beta, dexamethasone, and the calcium ionophore A23187 were investigated. All compounds were tested both in the absence and in the presence of fetal calf serum in the culture medium. The process of collagen synthesis in fibroblasts from colon and skin appears to be affected differently by these regulatory compounds. The most pronounced differences were that the relative collagen synthesis increased in dermal fibroblasts and decreased in colon fibroblasts upon addition of serum. In the presence of serum, interleukin-1 beta inhibited collagen synthesis in skin fibroblasts but not in colon fibroblasts. Dexamethasone suppressed the relative collagen synthesis in skin fibroblasts but not in colon fibroblasts. Transforming growth factor-beta stimulated the collagen synthesis in dermal fibroblasts in the presence of serum, but inhibited the process in colon fibroblasts. Because fibroblasts are the primary sources of collagen needed during wound repair, these results may offer (part of) the explanation why wounds in skin and intestine appear to behave differently under certain conditions.

Systemic glucocorticoid treatment decreases serum concentrations of carboxyterminal propeptide of type I procollagen and aminoterminal propeptide of type III procollagen

The effect of systemic glucocorticoid treatment on collagen synthesis in patients with various dermatoses was studied by measuring the carboxyterminal propeptide of type I procollagen (PICP) and the aminoterminal propeptide of type III procollagen (PIIINP) in serum. Changes in the propeptide concentrations were compared with those of osteocalcin, which reflects osteoblastic activity, and tartrate resistant acid phosphatase (TRAP), which reflects osteoclastic activity. The treatment caused significant decreases in levels of PICP, PIIINP and osteocalcin of 38, 34 and 49%, respectively (P less than 0.001). For TRAP, both increases and decreases were seen. The effects on PICP and PIIINP were evident 2-4 days after the onset of steroid therapy. The decrease in PICP was dose-related (r = 0.470, P less than 0.005) but even relatively small doses (0.1 mg of prednisone/kg/1 day) caused a significant reduction in PICP. After cessation of treatment, the levels of PICP returned to the pretreatment level in 1 week. The present study demonstrates that systemic glucocorticoid therapy in humans suppresses the synthesis of type I and III collagens and also non-collagenous bone matrix proteins.

A new method to measure type I and III collagen synthesis in human skin in vivo: demonstration of decreased collagen synthesis after topical glucocorticoid treatment

Collagen is synthesized as procollagen and large extra domains known as propeptides are cleaved off enzymatically. In the present study we have measured the carboxyterminal propeptide of type I collagen (PICP) and the aminoterminal propeptide of type III collagen (PIIINP) in blister fluids of human skin. High concentrations of PICP were found in the spontaneous blisters of patients with bullous pemphigoid, erysipelas, or erythema multiforme. Detectable amounts were also found in suction blisters induced on healthy skin. Because the concentrations in suction blisters were several times higher than in corresponding serum, most of PICP and PIIINP was derived from the underlying dermis. This method was used for assessing type I and type III collagen synthesis after topical glucocorticoid treatment. Clobetasol-17-propionate (CP) decreased the concentrations of PICP by 75% after 1 d of treatment, the maximum inhibition (92%) being found after 2 d treatment. PIIINP was also affected. Hydrocortisone and hydrocortisone-17-butyrate also decreased the concentrations of PICP and PIIINP, but less markedly than CP. Partial recovery was seen 3 d after stopping the treatment. Thus measurement of collagen type specific propeptides in suction blisters can be used as an estimate of collagen synthesis in vivo, avoiding both local anesthesia and skin biopsing. With radioimmunoassays for PICP and PIIINP a large number of samples can also be processed simultaneously.

Dexamethasone modulates alpha 2-macroglobulin and apolipoprotein E gene expression in cultured rat liver fat-storing (Ito) cells

Fat-storing (Ito) cells are perisinusoidal liver cells thought to play a central role in vitamin A metabolism and fibrongenesis. Glucocorticoids have been shown to be beneficial in the treatment of certain types of liver diseases by delaying the development of cirrhosis. To study the regulatory effects of dexamethasone on Ito cell gene expression, Ito cells were isolated from normal rat liver and primary cultures were established. The effect of dexamethasone on the synthesis of alpha 2-macroglobulin, apolipoprotein E, fibronectin and actin was examined. Protein synthesis was studied both at the protein level and at the RNA level by means of biosynthetic labeling, immunoprecipitation followed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and by Northern blot analysis of total RNA. After exposure to dexamethasone for 20 hr, alpha 2-macroglobulin protein synthesis was increased threefold, whereas apolipoprotein E expression was decreased 80%. Biosynthesis of fibronectin remained unaffected by hormone treatment. The dexamethasone effect became detectable 5 hr after beginning the exposure. Deinduction kinetic experiments showed that the glucocorticoid effect was detectable more than 12 hr after the replacement of the dexamethasone-containing culture medium by medium without the hormone. Corresponding to the data obtained at the protein level, dexamethasone increased the steady-state levels of alpha 2-macroglobulin-specific messenger RNA and reduced apolipoprotein E-specific transcripts, whereas fibronectin and actin messenger mRNA remained unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

New aspects of the mechanism of corticosteroid-induced dermal atrophy

Glucocorticoids are effective for the treatment of various inflammatory skin diseases, but their long-term use may lead to serious side-effects such as osteoporosis and skin atrophy. The incidence of skin atrophy following application of potent corticosteroids is especially high among children and the elderly. During recent years the effects of glucocorticoids on connective tissue have been elucidated, and it is evident that skin atrophy is mostly due to a decrease in collagen synthesis. Since collagen is the most abundant protein in the skin, the inhibition of its synthesis leads to atrophy. This review discusses the molecular mechanisms of glucocorticosteroid-induced skin atrophy and therapeutic possibilities.

Topical all-trans retinoic acid stimulates collagen synthesis in vivo

Histochemical and ultrastructural studies demonstrate that topical all-trans retinoic acid (RA) stimulates the deposition of a subepidermal band of collagen in photoaged hairless mice. The aim of this study was to examine the effect of RA treatment on collagen synthesis using biochemical and immunochemical techniques. Albino hairless mice were irradiated three times a week for 10 weeks with four minimal erythema doses of UVB from Westinghouse FS-40 bulbs. In the post-UV period, mice were either nontreated or treated with 0.05% RA or the ethanol-propylene glycol vehicle for up to 10 weeks. Antibodies against the aminopropeptide (AP) of type III procollagen were used in immunofluorescence microscopy and radioimmunoassay techniques. The AP of type III collagen is normally present throughout the dermis and in areas of active collagen synthesis (i.e., the dermal-epidermal junction). In this study, a similar distribution was seen in all untreated and vehicle-treated mice, and in mice treated with RA for 2, 4, and 6 weeks. However, increased staining, in a subepidermal band, was detected in the 8-week RA-treated skin. This region became intensely fluorescent to a depth of 100 mu in the 10-week RA-treated skins. As determined by radioimmunoassay, the content of the AP of type III procollagen increased twofold with 10-week RA treatment. Because the ratio of type I to type III collagens remained constant in treated and untreated skins, it is reasonable to assume that the content of type I collagen increased in proportion to type III collagen in RA-treated skins.

Comparison on collagen gene expression in the developing chick embryo tendon and heart. Tissue and development time-dependent action of dexamethasone

Glucocorticoids modulate various cellular functions such as proliferation, energy metabolism and the synthesis of proteins. In the present study, the response of collagen genes to dexamethasone in different stages of chick embryo development was studied in tendon and heart using Northern blot analysis and specific cDNA probes. The changes in collagen gene expression were compared to alterations in two reference mRNAs: actin and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). The levels of specific mRNAs measured per ribosomal RNA in tendon and heart varied markedly during normal development. In tendon the relative levels of alpha 1(I), alpha 2(I) and alpha 1(III) collagen mRNAs were highest between days 14-16 when also the synthesis of matrix proteins is most active. In heart the levels of these mRNAs peaked at day 12. In addition, qualitative differences were observed in the expression of actin genes between tendon and heart. Dexamethasone in high dose decreased collagen mRNA levels in tendons, while in heart a stimulatory effect was noted. Dexamethasone also decreased GAPDH mRNA levels in tendons. The alterations in gene expression after dexamethasone treatment in tendon and heart did not correlate with the level of specific glucocorticoid receptors, which varied markedly during the development of chick embryos. The cDNA for pro alpha 1(I) collagen hybridized to two transcripts corresponding to 6.2 and 5.1 kb in tendon and heart. During normal development of chick embryos the ratio of 6.2/5.1 kb mRNAs decreased markedly in heart, but no such change was observed in tendons. Dexamethasone, however, decreased the ratio of 6.2/5.1 kb transcripts in tendons. There was a significant correlation between the ratio 6.2/5.1 kb transcripts and total alpha 1(I) mRNA both in tendon and heart, suggesting that the 6.2 kb transcript may be associated with the rate of synthesis of type I collagen.

Retinoic acid receptor gene expression in human skin

Human skin exhibits a characteristic, pleiotypic response to topical retinoic acid. In attempting to understand this response at the molecular level, we have used fast protein liquid chromatography (FPLC) and RNA blot hybridization to characterize the expression of the nuclear retinoic acid receptor (RAR) alpha, beta, and gamma genes in adult human epidermis. Size exclusion FPLC of 0.6 M NaCl nuclear extracts prepared from keratome biopsies revealed two peaks of specific [3H] retinoic acid (RA) binding at Mr 45 and 18 kDa, in agreement with the expected sizes of RAR and cellular RA binding protein. Blot hybridization analysis of total RNA extracted from keratome biopsies revealed that RAR-gamma was the predominant RAR species expressed in human epidermis, as RAR-alpha transcripts were detectable only at low levels and RAR-beta transcripts were undetectable. RAR transcripts were not induced by topical treatment with 0.1% RA cream under occlusion for 4 h or 4 d. Moreover, there was no significant difference in RAR-gamma transcript levels in normal and psoriatic epidermis. RAR-gamma transcripts were constitutively expressed not only in cultured human keratinocytes, but also in human dermal and lung fibroblasts. RAR-beta was induced by RA in dermal fibroblasts, but not in keratinocytes. RA induced IL-1 beta transcripts in keratinocytes rapidly (2 to 4 h) and at low concentrations (3 x 10(-10) M), consistent with activation of the IL-1 beta gene via RAR. These results demonstrate constitutive expression of RAR-gamma in human epidermis, and suggest that RAR-gamma is a molecular target of RA action in adult human skin.