Deficiency of the decorin core protein in the variant form of Ehlers-Danlos syndrome with chronic skin ulcer

Alterations of Matrisome Gene Expression in Naturally Aged and Photoaged Human Skin In Vivo

The main component of human skin is a collagen-rich extracellular matrix (ECM), known as the matrisome. The matrisome is essential for maintaining the structural integrity and mechanical properties of the skin. Recently, we reported notable decreases in matrisome proteins in natural aging and photoaging human skin. This study aims to investigate the mRNA expression of the core matrisome proteins in human skin, comparing young versus aged and sun-protected versus sun-exposed skin by quantitative real-time PCR and immunostaining. Our findings reveal a notable decrease in core matrisome transcription in aged skin. The mRNA expression of the core matrisome, such as collagen 1A1 (COL1A1), decorin, and dermatopontin, is significantly reduced in aged skin compared to its young skin. Yet, the majority of collagen mRNA expression levels of aged sun-exposed skin are similar to those found in young sun-exposed skin. This discrepancy is primarily attributable to a substantial decrease in collagen transcription in young sun-exposed skin, suggesting early molecular changes in matrisome transcription due to sun exposure, which preceded the emergence of clinical signs of photoaging. These findings shed light on the mRNA transcript profile of major matrisome proteins and their alterations in naturally aged and photoaged human skin, offering valuable insights into skin matrisome biology.

Age-dependent alterations of decorin glycosaminoglycans in human skin

Proteoglycans, a family of glycosaminoglycan (GAG) conjugated proteins, are important constituents of human skin connective tissue (dermis) and are essential for maintaining mechanical strength of the skin. Age-related alterations of dermal proteoglycans have not been fully elucidated. We quantified transcripts of 20 known interstitial proteoglycans in human skin and found that decorin was the most highly expressed. Decorin was predominantly produced by dermal fibroblasts. Decorin was localized in dermal extracellular matrix with GAG bound to type I collagen fibrils. Analysis of decorin extracted from young (21–30 years) and aged (>80 years) sun-protected human buttock skin revealed that decorin molecular size in aged skin is significantly smaller than in young skin. The average size of decorin protein did not alter, indicating size of GAG chain is reduced in aged, compared to young skin. This age-dependent alteration of decorin GAG may contribute to skin fragility of elderly people.

Thrombospondin-2 and extracellular matrix assembly

BACKGROUND

Numerous proteins and small leucine-rich proteoglycans (SLRPs) make up the composition of the extracellular matrix (ECM). Assembly of individual fibrillar components in the ECM, such as collagen, elastin, and fibronectin, is understood at the molecular level. In contrast, the incorporation of non-fibrillar components and their functions in the ECM are not fully understood.

SCOPE OF REVIEW

This review will focus on the role of the matricellular protein thrombospondin (TSP) 2 in ECM assembly. Based on findings in TSP2-null mice and in vitro studies, we describe the participation of TSP2 in ECM assembly, cell-ECM interactions, and modulation of the levels of matrix metalloproteinases (MMPs).

MAJOR CONCLUSIONS

Evidence summarized in this review suggests that TSP2 can influence collagen fibrillogenesis without being an integral component of fibrils. Altered ECM assembly and excessive breakdown of ECM can have both positive and negative consequences including increased angiogenesis during tissue repair and compromised cardiac tissue integrity, respectively.

GENERAL SIGNIFICANCE

Proper ECM assembly is critical for maintaining cell functions and providing structural support. Lack of TSP2 is associated with increased angiogenesis, in part, due to altered endothelial cell-ECM interactions. Therefore, minor changes in ECM composition can have profound effects on cell and tissue function. This article is part of a Special Issue entitled Matrix-mediated cell behaviour and properties.

Granzyme B cleaves decorin, biglycan and soluble betaglycan, releasing active transforming growth factor-β1

Objective

Granzyme B (GrB) is a pro-apoptotic serine protease that contributes to immune-mediated target cell apoptosis. However, during inflammation, GrB accumulates in the extracellular space, retains its activity, and is capable of cleaving extracellular matrix (ECM) proteins. Recent studies have implicated a pathogenic extracellular role for GrB in cardiovascular disease, yet the pathophysiological consequences of extracellular GrB activity remain largely unknown. The objective of this study was to identify proteoglycan (PG) substrates of GrB and examine the ability of GrB to release PG-sequestered TGF-β1 into the extracellular milieu.

Methods/Results

Three extracellular GrB PG substrates were identified; decorin, biglycan and betaglycan. As all of these PGs sequester active TGF-β1, cytokine release assays were conducted to establish if GrB-mediated PG cleavage induced TGF-β1 release. Our data confirmed that GrB liberated TGF-β1 from all three substrates as well as from endogenous ECM and this process was inhibited by the GrB inhibitor 3,4-dichloroisocoumarin. The released TGF-β1 retained its activity as indicated by the induction of SMAD-3 phosphorylation in human coronary artery smooth muscle cells.

Conclusion

In addition to contributing to ECM degradation and the loss of tissue structural integrity in vivo, increased extracellular GrB activity is also capable of inducing the release of active TGF-β1 from PGs.

Decorin in atherosclerosis

Atherosclerotic cardiovascular disease is a major cause of morbidity and mortality in the Western world. Despite tremendous strides in understandings its pathogenesis, it still remains a challenge because of gaps in our understanding of its initiation, progression and complications leading to the clinical syndromes of angina, acute coronary syndrome, cerebrovascular disease and peripheral vascular disease. Recent studies have provided impetus on the shift from models of atherosclerosis based on cellular interactions to models where the important role of extracellular matrix is recognized. Proteoglycans, especially those belonging to the small leucine-rich proteoglycan family of which decorin is a representative example, have come under close scrutiny for their role in atherogenesis. There is evidence from in vitro and in vivo animal models as well as humans to suggest an important role of decorin in attenuating progression of atherosclerosis. Decorin distribution in different blood vessels has been shown to inversely correlate with the tendency to develop atherosclerosis. Decorin seems to interact closely with different cellular components of the plaque milieu, thereby suggesting its role in influencing atherogenesis at different steps. Here we review the current understanding of the role of decorin in the pathogenesis of atherosclerosis.

Defective glycosylation of decorin and biglycan, altered collagen structure, and abnormal phenotype of the skin fibroblasts of an Ehlers–Danlos syndrome patient carrying the novel Arg270Cys substitution in galactosyltransferase I (β4GalT-7)

The Ehlers-Danlos syndrome (EDS) is a heterogeneous group of connective tissue disorders affecting skin and joint function. Molecular defects in extracellular matrix proteins, including collagen (type I, III, and V) and tenascin X are associated with different forms of EDS. Compound heterozygous mutations in the B4GALT7 gene, resulting in aberrant glycosylation of the dermatan sulfate proteoglycan decorin, had been described in a single patient affected with the progeroid form of EDS. We have studied the molecular phenotype of decorin, biglycan, and collagen type I containing fibrils in skin fibroblasts of a patient carrying the novel homozygous C808T point mutation in the B4GALT7 gene, which causes an Arg270Cys substitution in beta4GalT-7. Compared to control fibroblasts, galactosyltransferase activity in beta4GalT-7(Arg270Cys) cells was approximately three times reduced over a temperature range of 25-41 degrees C. Pulse-chase experiments and confocal microscopy demonstrated that synthesis and secretion of decorin were normal in beta4GalT-7(Arg270Cys) cells. However, about 50% of decorin were synthesized as a protein core in addition to its proteoglycan form. Biglycan was found in a monoglycanated form in addition to its mature form. Glycosaminoglycan chains were of the dermatan/chondroitin sulfate type both in beta4GalT-7(Arg270Cys) and control cells, and epimerization was reduced for decorin and biglycan. Compared to control cells, beta4GalT-7(Arg270Cys) cells showed altered, highly spread or stretched phenotypes and decreased proliferation rates. At the ultrastructural level, an intracellular accumulation of multiple secondary lysosomes and degenerative vacuoles was seen in beta4GalT-7(Arg270Cys) cells. Furthermore, the collagen suprastructures were altered in the beta4GalT-7(Arg270Cys) cells. The reduced beta4GalT-7 activity resulting in defective glycosylation of decorin and biglycan may be responsible for the complex molecular pathology in beta4GalT-7 deficient EDS patients, given the role of these proteoglycans in bone formation, collagen fibrillogenesis, and skeletal muscle development.

Decorina e Condroitim sulfato na remodelação da matriz extracelular do línquen escleroso vulvar

FUNDAMENTOS: O líquen escleroso (LS) apresenta zona de hialinização do colágeno na derme superior característica, que persiste pouco definida do ponto de vista morfológico e cujo significado permanece sem explicação. Já se pôde demonstrar que no LS há profundas modificações da matriz extracelular (MEC), com acúmulo de proteínas colagênicas e de glicosaminoglicanos sulfatados na região hialina. OBJETIVOS: Caracterizar morfologicamente a presença nessa zona de decorina e condroitim sulfato que, ao interagir com as fibrilas colágenas, entre outras proteínas matriciais, poderiam contribuir para essa peculiar apresentação da MEC. MÉTODOS: 31 casos de LS vulvar foram subdivididos segundo a gradação histológica de Hewitt e analisados por imuno-histoquímica utilizando anticorpos contra decorina e condroitim sulfato revelados pela diaminobenzidina. Esses resultados foram comparados aos do grupo controle constituído por fragmentos de retalhos cutâneos excisados durante cirurgias corretivas da região vulvoperineal. RESULTADOS: Ocorreu predomínio da decorina quando a matriz apresentava um aspecto frouxo/edematoso, e o condroitim sulfato foi mais evidente quando a MEC assumia um padrão compacto, parecendo que ambos contribuem para o aspecto hialino, porém em fases diferentes da patogenia dessa doença. CONCLUSÕES: A seqüência observada na síntese desses proteoglicanos/glicosaminoglicanos levou à suposição de que a decorina seja um possível marcador precoce do LS vulvar e de que o condroitim sulfato possa estar relacionado à contenção da alteração matricial no nível da derme média.

Krüppel-like factor 2, a novel immediate-early transcriptional factor, regulates IL-2 expression in T lymphocyte activation

Ag presentation to T lymphocytes and subsequent activation are characterized by a cascade of signaling events, some of which result in the transcriptional activation of a diverse set of genes. An important example is the induction of the IL-2 gene, which is a critical event in the escalation of T cell activation. Previous studies have found that expression of Krüppel-like factor 2 (KLF2), a zinc finger transcription factor, is extinguished after T cell activation. However, the biological role of KLF2 during T cell activation is still unknown. In this study we found that KLF2 protein degradation is delayed, and KLF2 expression is up-regulated during the early stage of T cell activation in primary T cells. Within a few hours, this process is reversed, and KLF2 expression is turned off. Next, we found that the expression of KLF2 significantly increases IL-2 production 4-fold in activated T cells, resulting from activation of the IL-2 promoter. By narrowing down the 2.0-kb IL-2 promoter region, we found that the KLF2 responsive element in the IL-2 promoter is a CACCC element, the KLF consensus binding motif. Moreover, KLF2 binds to this promoter in vivo under different conditions. Our studies show that KLF2 regulates IL-2 promoter activity in the earliest stages of T cell activation, indicating that KLF2 may act as a novel immediate-early transcriptional factor to maximally prime T cell activation.

Asb4, Ata3, and Dcn are novel imprinted genes identified by high-throughput screening using RIKEN cDNA microarray

Genes differentially expressed between parthenogenetic and androgenetic embryos are candidates for the identification of imprinted genes, which are expressed specifically from the maternal or paternal allele. To search for genes differentially expressed between parthenogenetic and androgenetic embryos, we used the RIKEN full-length enriched mouse cDNA microarray. The 25 candidates obtained included 8 known imprinted genes (such as IgfII, Snrpn, and Neuronatin) and 3 new ones--Asb4 (ankyrin repeat and SOCS box-containing protein 4), Ata3 (amino acid transport system A3), and Decorin--which were confirmed by using normal diploid embryos from the reciprocal F1 crosses of B6 and JF1 mice. The 25 candidates also included genes that showed no imprinting-associated expression in normal diploid embryos. We describe a feasible high-throughput method of screening for novel imprinted genes by using the RIKEN cDNA microarray.