Analysis of the age-related composition of human skin collagen and collagens synthesized by fibroblast culture

Increased expression of bone/cartilage-associated genes and core transcription factors in keloids by RNA sequencing

Fibroblasts in keloids undergo cell identity transition with altered transcriptional characteristics. However, the core transcription factors driving this cellular reprogramming remain largely unknown. Here, we report the results of transcriptional profiling from 48 keloid and 24 control dermal tissues. We identified 1187 upregulated differentially expressed genes (foldchange > 2, false discovery rate < 0.05) in keloids, which were mainly enriched in extracellular matrix organization and bone/cartilage development, with significantly increased expression of bone/cartilage-associated collagens (COL5A1, COL10A1, and COL11A1) and glycoproteins (ACAN, COMP, and SPARC). Deconvolution analysis also revealed significantly increased composition of osteoblasts in keloid dermis. A total of 92 upregulated transcription factors were screened out from differentially expressed genes and mainly enriched in transcription process and skeleton development. Additional sequencing of six keloid individuals with multiple regions and intersection further narrow the list with 10 transcription factors. Finally, AEBP1, CREB3L1, RUNX2, and ZNF469 have been identified as candidate core regulators in promoting the gaining of bone/cartilage-like characteristics in keloids. RNA-sequencing of full-skin keloids consolidated the existence of these four transcription factors. Immunohistochemistry was employed to verify the expression of AEBP1, CREB3L1, RUNX2, and ZNF469 in keloid fibroblasts. In conclusion, we bioinformatically discovered the increased expression of bone/cartilage-associated genes and candidate core transcription factors in keloids. Our findings promise to provide molecular clues to develop novel therapeutic modalities against skin fibrosis.

Three-dimensional printing bilayer membranous nanofiber scaffold for inhibiting scar hyperplasia of skin

Hypertrophic scar (HS) is the manifestation of pathological wound healing, which affects the beauty of patients, and even affects the normal physical functions of patients. We aimed to develop a 3D printing layer membranous nanofiber scaffold similar to skin structure. Among them, poly (lactic-co-glycolic acid) copolymer (PLGA) nanofibers were used as the "epidermis" layer above, and a decellular dermis matrix (dECM) nanofiber scaffold was used as the "dermis" layer below. In vitro, experimental results showed that PLGA and dECM nanofiber scaffolds had good biocompatibility. In vivo experiments showed that BLM nanofiber scaffolds could inhibit collagen fiber deposition and angiogenesis, to inhibit the formation of hypertrophic scars. This study shows a simple and effective method for preventing and inhibiting the formation of hypertrophic scars.

Engineering functional skin constructs: A quantitative comparison of three-dimensional bioprinting with traditional methods

Tissue engineering has been successful in reproducing human skin equivalents while incorporating new approaches such as three-dimensional (3D) bioprinting. The latter method offers a plethora of advantages including increased production scale, ability to incorporate multiple cell types and printing on demand. However, the quality of printed skin equivalents compared to those developed manually has never been assessed. To leverage the benefits of this method, it is imperative that 3D-printed skin should be structurally and functionally similar to real human skin. Here, we developed four bilayered human skin epidermal-dermal equivalents: non-printed dermis and epidermis (NN), printed dermis and epidermis (PP), printed epidermis and non-printed dermis (PN), and non-printed epidermis and printed dermis (NP). The effects of printing induced shear stress [0.025 kPa (epidermis); 0.049 kPa (dermis)] were characterized both at the cellular and at the tissue level. At cellular level, no statistically significant differences in keratinocyte colony-forming efficiency (CFE) (p = 0.1641) were observed. In the case of fibroblasts, no significant differences in the cell alignment index (p < 0.1717) and their ability to contract collagen gel (p = 0.851) were detected. At the tissue levels, all the four skin equivalents were characterized using histological and immunohistochemical analysis with no significant differences found in either epidermal basal cell count, thickness of viable epidermis, and relative intensity of filaggrin and claudin-1. Our results demonstrated that 3D printing can achieve the same high-quality skin constructs as have been developed traditionally, thus opening new avenues for numerous high-throughput industrial and clinical applications.

Eclectic characterisation of chemically modified cell-derived matrices obtained by metabolic glycoengineering and re-assessment of commonly used methods

Azide-bearing cell-derived extracellular matrices ("clickECMs") have emerged as a highly exciting new class of biomaterials. They conserve substantial characteristics of the natural extracellular matrix (ECM) and offer simultaneously small abiotic functional groups that enable bioorthogonal bioconjugation reactions. Despite their attractiveness, investigation of their biomolecular composition is very challenging due to the insoluble and highly complex nature of cell-derived matrices (CDMs). Yet, thorough qualitative and quantitative analysis of the overall material composition, organisation, localisation, and distribution of typical ECM-specific biomolecules is essential for consistent advancement of CDMs and the understanding of the prospective functions of the developed biomaterial. In this study, we evaluated frequently used methods for the analysis of complex CDMs. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and (immune)histochemical staining methods in combination with several microscopic techniques were found to be highly eligible. Commercially available colorimetric protein assays turned out to deliver inaccurate information on CDMs. In contrast, we determined the nitrogen content of CDMs by elementary analysis and converted it into total protein content using conversion factors which were calculated from matching amino acid compositions. The amount of insoluble collagens was assessed based on the hydroxyproline content. The Sircol™ assay was identified as a suitable method to quantify soluble collagens while the Blyscan™ assay was found to be well-suited for the quantification of sulphated glycosaminoglycans (sGAGs). Eventually, we propose a series of suitable methods to reliably characterise the biomolecular composition of fibroblast-derived clickECM.

Skin proteomics - analysis of the extracellular matrix in health and disease

INTRODUCTION

The skin protects the human body from external insults and regulates water and temperature homeostasis. A highly developed extracellular matrix (ECM) supports the skin and instructs its cell functions. Reduced functionality of the ECM is often associated with skin diseases that cause physical impairment and also have implications on social interactions and quality of life of affected individuals.

AREAS COVERED

With a focus on the skin ECM we discuss how mass spectrometry (MS)-based proteomic approaches first contributed to establishing skin protein inventories and then facilitated elucidation of molecular functions and disease mechanisms.

EXPERT OPINION

MS-based proteomic approaches have significantly contributed to our understanding of skin pathophysiology, but also revealed the challenges in assessing the skin ECM. The numerous posttranslational modifications of ECM proteins, like glycosylation, crosslinking, oxidation, and proteolytic maturation in disease settings can be difficult to tackle and remain understudied. Increased ease of handling of LC-MS/MS systems and automated/streamlined data analysis pipelines together with the accompanying increased usage of LC-MS/MS approaches will ensure that in the coming years MS-based proteomic approaches will continue to play a vital part in skin disease research. They will facilitate the elucidation of molecular disease mechanisms and, ultimately, identification of new druggable targets.

Monopolar radiofrequency treatment for facial laxity: Histometric analysis

BACKGROUND

A monopolar radiofrequency device can be used in facial tightening. The device targets the dermis and fibrous septae, and the treatment results in immediate collagen contraction and the induction of subsequent collagen remodeling.

AIMS

We aimed to evaluate the histometric change of the subjects treated with a monopolar radiofrequency device using a novel tip.

MATERIALS AND METHODS

Eleven subjects with skin types III and IV participated in the study. They received a single session of a monopolar radiofrequency on the face, and biopsies were performed before treatment, and 2 and 6 months after the treatment. Hematoxylin and eosin, Masson trichome, and Victoria blue stains were used. An image analysis was performed using the Image J software. The dermal density of collagen and elastic fiber, and the coherency of collagen fibers were assessed in the papillary, upper reticular, and lower reticular dermises, respectively.

RESULTS

The monopolar radiofrequency treatments led to improvements in collagen fiber density and coherency. In the Masson trichome staining, the collagen fiber densities were 0.736 ± 0.06 and 0.652 ± 0.063 before treatment and increased to 0.773 ± 0.044 (P = .018) and 0.686 ± 0.05 (P = .045) in the papillary and lower reticular dermises, respectively. The density of the elastic fibers in all parts of the dermis showed a tendency to increase after treatment, though not statistically significantly. The mean coherency was higher after than before treatment.

CONCLUSIONS

In this in vivo study, we found that the collagen and elastic fiber densities and architectural structures were improved after treatment.

Current and upcoming therapies to modulate skin scarring and fibrosis

Skin is the largest organ of the human body. Being the interface between the body and the outer environment, makes it susceptible to physical injury. To maintain life, nature has endowed skin with a fast healing response that invariably ends in the formation of scar at the wounded dermal area. In many cases, skin remodelling may be impaired, leading to local hypertrophic scars or keloids. One should also consider that the scarring process is part of the wound healing response, which always starts with inflammation. Thus, scarring can also be induced in the dermis, in the absence of an actual wound, during chronic inflammatory processes. Considering the significant portion of the population that is subject to abnormal scarring, this review critically discusses the state-of-the-art and upcoming therapies in skin scarring and fibrosis.

Ameliorative effect of tranexamic acid on physiological skin aging and its sex difference in mice

An effective method to protect the skin from natural aging is unknown. Therefore, in this study, we examined the ameliorative effects of tranexamic acid on natural skin aging. In addition, we examined the sex difference in the effect exhibited by tranexamic acid. We bred hairless mice without ultraviolet ray irradiation and physical stress for 2 years. During the study period, mice were orally administered tranexamic acid (12 mg/kg/day) three times per week. Development of signs of skin aging was found to be ameliorated by tranexamic acid. Furthermore, synthetic inhibition of plasmin was observed following tranexamic acid treatment. The synthetic reinforcement of hyaluronic acid by an increase in the number of epidermal cells and the degradative inhibition of extracellular matrix (ECM) by matrix metalloproteinase (MMP) suppression were observed. These results indicate that natural skin aging was ameliorated by tranexamic acid via the regulation of the plasmin/TGF-β/epidermal cells/hyaluronic acid and plasmin/MMPs/ECM signal transmission pathways. Taken together, sex difference was observed for the ameliorative effect of tranexamic acid on skin aging, with a stronger effect observed in females than in males. More importantly, we found that the synthesis of hyaluronic acid was stronger in female mice than in male mice.

Age-related evolutions of the dermis: Clinical signs, fibroblast and extracellular matrix dynamics

Ageing is today a major societal concern that is intrinsically associated with the increase of life expectancy. Outside the context of severe degenerative diseases that affect the elderly populations, normal visible signs of ageing, notably skin sagging and wrinkles, influence the social and individual perception of peoples. Accordingly, there is a strong demand for researches on skin ageing. Deciphering the cellular and molecular processes of skin evolution through ageing is thus an active scientific domain, at the frontier of tissue developmental and ageing biology. The focus of the present article is to provide an overview of the current knowledge concerning the evolution of dermis characteristics at different life stages, from intra-uterine to post-natal life. The description will integrate stage-specific and age-related changes in dermis characteristics at the tissue, cell, and molecular levels.

Radiofrequency for the treatment of skin laxity: mith or truth

The nonablative radiofrequency is a procedure commonly used for the treatment of skin laxity from an increase in tissue temperature. The goal is to induce thermal damage to thus stimulate neocollagenesis in deep layers of the skin and subcutaneous tissue. However, many of these devices haven't been tested and their parameters are still not accepted by the scientific community. Because of this, it is necessary to review the literature regarding the physiological effects and parameters for application of radiofrequency and methodological quality and level of evidence of studies. A literature search was performed in MEDLINE, PEDro, SciELO, PubMed, LILACS and CAPES and experimental studies in humans, which used radiofrequency devices as treatment for facial or body laxity, were selected. The results showed that the main physiological effect is to stimulate collagen synthesis. There was no homogeneity between studies in relation to most of the parameters used and the methodological quality of studies and level of evidence for using radiofrequency are low. This fact complicates the determination of effective parameters for clinical use of this device in the treatment of skin laxity. The analyzed studies suggest that radiofrequency is effective, however the physiological mechanisms and the required parameters are not clear in the literature.

In vitro characteristics of Tenon's fibroblast lines derived from pediatric and adult eyes do not fully explain pediatric glaucoma surgery failure: a preliminary report

PURPOSE

To compare the in vitro characteristics of Tenon's capsule fibroblasts from children and adults that may be relevant to filtration surgery success.

METHODS

Fibroblast cell lines derived from 5 young (median patient age, 2.4 years) and 7 old (median patient age, 71 years) discarded Tenon's capsule surgical specimens were used at early passage (P2-P3). Fibroblasts were plated at "high" (10(4)cells/cm(2)) or "low" density (10(3)cells/cm(2)) and harvested at days 0-14, for growth curve and doubling time comparisons. Migration was measured using a wound model (confluent monolayers ± 5-fluorouracil [5-FU] over 1-96 hours). Collagen synthesis was measured as secreted hydroxyproline/24 hours from confluent monolayers.

RESULTS

At low density, "young" fibroblasts achieved higher cell numbers at confluence (day 14) compared with "old": 158 ± 35 versus 105 ± 12 × 10(3)cells/cm(2) (P = 0.0034). Mean doubling time for young versus old was similar at low density plating: 20.95 ± 1.55 versus 22.37 ± 2.09 hours (P = 0.26). It was shorter, however, for young versus old at high-density plating: 42.11 ± 6.01 versus 54.26 ± 4.24 hours (P = 0.0051). Wound closure rates were similar for young versus old cells (4 lines for each group) with and without 5-FU. Collagen synthesis was similar for young and old (4 lines for each group).

CONCLUSIONS

Although young fibroblasts reached higher density than old at confluence and had shorter doubling times at high-density plating, wound closure/migration and collagen synthesis rates were similar. Despite the preliminary nature of this study (few specimens, limited cell features explored), factors besides those intrinsic to the fibroblasts themselves likely mediate the more rapid healing/scarring after glaucoma filtration surgery in children.

Overhydroxylation of lysyl residues is the initial step for altered collagen cross-links and fibril architecture in fibrotic skin

In fibrotic skin of lipodermatosclerosis a substantial increase of the cross-link hydroxylysylpyridinoline is observed. Hydroxylysylpyridinoline is a typical cross-link of skeletal tissue and is thought to play a major part in the hardening of sclerotic tissue. We investigated whether the increase in hydroxylysylpyridinoline is due to overhydroxylation of lysyl residues in the collagen molecule, which may also be associated with an increase of glycosylated hydroxylysine residues. Furthermore, we determined whether the collagen fibrils in lipodermatosclerosis showed a decrease of the diameter in the tissue as well as in vitro after fibrillogenesis of pepsin-solubilized collagens. Isolated alpha-chains of pepsin solubilized collagen I showed an increase in lysyl hydroxylation (hyl/(hyl + lys)) as compared with normal control [alpha1(I): lipodermatosclerosis 0.18 +/- 0.01; control 0.12 +/- 0.01; alpha2(I): lipodermatosclerosis 0.36 +/- 0.02; control 0. 25 +/- 0.03, p < 0.001]. Furthermore, the content of enzymatic glycosylated hydroxlysine residues increased. This increase is associated with a decrease of fibril diameter of both tissue and fibrils formed in vitro of pepsin-solubilized collagens. In the same pool of collagens an increase in collagen III content was observed as compared with controls (lipodermatosclerosis 14.5% +/- 1.6, control 10.3% +/- 1.6, p < 0.001). Our results showed that the overhydroxylation of lysyl residues, which is required for the generation of hydroxylysylpyridinoline, is not only restricted to the telopeptides but also affects the helical part of the molecule. This process is further associated with an increase of glycosylated hydroxylysyl residues. These changes along with the increase in collagen III content seem to be responsible for the observed alteration in the architecture of collagen fibrils in sclerotic skin.

Applications of reconstructed skin models in pharmaco-toxicological trials

The development of new cosmetic formulations requires precise assessment of their safety and efficacy. Today, legislation demands quality control combined with severe safety measures, as well as a limited use of animals for such testing (European Community directive 93/35/EEC). Consequently, safety assessment protocols are oriented towards in vivo tests on human volunteers and in vitro alternative methods to animal use, especially tissue engineered skin substitutes. In this paper, dermal and skin equivalents developed in the laboratory are described. The applications of reconstructed epidermis and skin substitutes for pharmaco-toxicological trials are also discussed. These tissue models have been shown to be very useful tools to assess cutaneous irritation, phototoxicity, photoprotection and to perform efficacy tests of cosmetic molecules and finished products. In conclusion, the authors are confident that these in vitro models can contribute to reduce animal use for routine toxicity testing.

Abundance of alpha 1(I) and alpha 1(III) procollagen and p21 mRNAs in fibroblasts cultured from fetal and postnatal dermis

The steady-state abundance of alpha 1(I) and alpha 1(III) procollagen mRNAs, p21Sdi1 mRNA, and beta-actin mRNA was determined in 29 skin fibroblast lines established from fetal, young and old donors. Donor ages ranged from 12 gestational weeks to nonagenarian. Adult donors were members of the Baltimore Longitudinal Study of Aging. The abundance of alpha 1(I) procollagen mRNA was decreased in cell lines from both young and old donors compared with fetal lines. Additionally, one alpha 1(I) transcript observed in the fetal lines was not detected in postnatal lines. The abundance of alpha 1(III) procollagen mRNA was decreased in postnatal lines from old donors compared with fetal lines. The abundance of beta-actin mRNA was lower in postnatal lines from both young and old donors compared to fetal lines. These results suggest that cultures of fetal skin fibroblasts exhibit a greater capacity for synthesis of procollagens and beta-actin than postnatal lines. In contrast, the abundance of p21Sdi1 mRNA was elevated in lines established from postnatal donors. These results are consistent with developmental changes in amounts of procollagen, beta-actin and p21.

Altered x-ray diffraction pattern is accompanied by a change in the mode of cross-link formation in lipodermatosclerosis

We studied the molecular packing of collagen fibrils by x-ray diffraction in skin specimens of patients with lipodermatosclerosis and in controls. A difference in the tilt angles of the collagen molecules relative to the fiber axis is suggested by a D-stagger that is 1 nm larger in sclerotic skin than in normal skin. In parallel, the collagen cross-links in the skin specimens were analyzed, and a marked increase of both hydroxylysylpyridinoline and lysylpyridinoline, the trivalent mature cross-links characteristic of skeletal tissues, was found. The content of hydroxylysylpyridinoline and lysylpyridinoline was higher in the deep layer of the affected dermis than in the superficial dermis. This increase was always accompanied by an increase in the hydroxylysylpyridinoline/lysylpyridinoline ratio, suggesting that hydroxylysylpyridinoline is a sclerosis-associated cross-link. In addition, lysyl hydroxylation was increased in affected skin, and this increase was apparently restricted to the collagen telopeptides, which are crucial anchoring structures for lysyl dependent cross-links.

Age-related alterations in collagen and total protein metabolism determined in cultured rat dermal fibroblasts: age-related trends parallel those observed in rat skin in vivo

The cultured fibroblast has been extensively used as a model system to study aging. However, few studies have examined the veracity of observations obtained in cultured fibroblasts aged in vitro to those made in animal tissues in vivo. This paper compares age-related alterations in collagen metabolism measured in cultured cells with previously reported results in the aging rat (Mays et al. (1991) Biochem. J. 276, 307-313). Age-related changes in collagen synthesis in rat skin fibroblasts in vitro over 30 population doublings were determined based on the production of hydroxy-[14C]proline. Degradation of newly synthesized collagen was based on the appearance of free hydroxy-[14C]proline in the culture system. Total protein synthesis rates were based on the incorporation of [14C]proline into proteins. In vitro rates of collagen synthesis decreased 5-fold over 30 population doublings (P < 0.05). Degradation of newly synthesized collagen increased from 33.0 +/- 0.8% (n = 4, SEM) to 45.2 +/- 1.1% (n = 4; P < 0.05) over the same period, with a maximum after 25 population doublings of 55.8 +/- 1.1% (n = 4). Total protein synthesis rates decreased by one-half over 30 population doublings (P < 0.05). The results indicated that collagen production decreased as cells aged in vitro and that this was due to both changes in synthesis and degradation. The results demonstrate that age-related alterations in collagen and total protein metabolism of skin fibroblasts in culture were similar to those reported previously for skin in vivo, suggesting that for studies of these processes, fibroblasts in culture provide an appropriate model.

Collagen synthesis in (sun-) aged human skin and in fibroblasts derived from sun-exposed and sun-protected body sites

Endogenous and sun-induced aging of the skin cause distinct morphological alterations. In this study, we have analysed the ratio of collagen III to collagen III plus I in extracts of sun-exposed (face) and sun-protected (abdomen) aged skin, as well as in collagens synthesized by fibroblasts during in vitro culture derived from actinically damaged and sun-protected skin of other subjects (face, medial aspect of the upper arm vs. abdomen, lateral aspect of the forearm). Furthermore, the amount and extent of post-translational modifications of newly synthesized collagens were determined. Chronic sun exposure of the skin does not have an impact on the quantity of collagenous proteins newly synthesized in cell culture. The proportion of collagen III in pepsin extracts of sun-damaged skin is increased relative to sun-protected skin. However, fibroblasts derived from sun-exposed skin synthesize a lower proportion of collagen III than cells from sun-protected skin. The hydroxylation of lysyl residues in newly synthesized alpha 2(I) and alpha 1(III) collagen chains is reduced by UV irradiation, whereas hydroxylation of lysyl residues in alpha 1(I) chains and of prolyl residues in alpha 1(I), alpha 2(I) and alpha 1(III) chains is unaffected by UV irradiation. These data provide circumstantial evidence to indicate that collagen synthesis is influenced independently by endogenous and sun-induced aging.