Systematic investigation of the skin inChst14−/−mice: A model for skin fragility in musculocontractural Ehlers–Danlos syndrome caused byCHST14variants (mcEDS-CHST14)

Abstract

Loss-of-function variants in CHST14 cause a dermatan 4-O-sulfotransferase deficiency named musculocontractural Ehlers–Danlos syndrome-CHST14 (mcEDS-CHST14), resulting in complete depletion of the dermatan sulfate moiety of decorin glycosaminoglycan (GAG) chains, which is replaced by chondroitin sulfate. Recently, we uncovered structural alteration of GAG chains in the skin of patients with mcEDS-CHST14. Here, we conducted the first systematic investigation of Chst14 gene-deleted homozygote (Chst14−/−) mice. We used skin samples of wild-type (Chst14+/+) and Chst14−/− mice. Mechanical fragility of the skin was measured with a tensile test. Pathology was observed using light microscopy, decorin immunohistochemistry, and electron microscopy (EM) including cupromeronic blue (CB) staining. Quantification of chondroitin sulfate and dermatan sulfate was performed using enzymatic digestion followed by anion-exchange HPLC. In Chst14−/− mice, skin tensile strength was significantly decreased compared with that in Chst14+/+ mice. EM showed that collagen fibrils were oriented in various directions to form disorganized collagen fibers in the reticular layer. Through EM-based CB staining, rod-shaped linear GAG chains were found to be attached at one end to collagen fibrils and protruded outside of the fibrils, in contrast to them being round and wrapping the collagen fibrils in Chst14+/+ mice. A very low level of dermatan sulfate disaccharides was detected in the skin of Chst14−/− mice by anion-exchange chromatography. Chst14−/− mice, exhibiting similar abnormalities in the GAG structure of decorin and collagen networks in the skin, could be a reasonable model for skin fragility of patients with mcEDS-CHST14, shedding light on the role of dermatan sulfate in maintaining skin strength.

Glycosaminoglycans: Sweet as Sugar Targets for Topical Skin Anti-Aging

“… 50 , 51 Mice lacking the Chst14 gene possess very low levels of cutaneous DS, resulting in disorganized collagen bundles and reduced skin tensile strength. 52 Biglycan is expressed at relatively low levels within the dermis, 53 but nevertheless interacts with Type I collagen fibers and when deleted within mouse knockout models results in collagen fibril abnormalities and skin fragility. 21 , 54 Lumican, which primarily expresses the KS-I isoform of KS, is highly expressed in skin and similarly regulates fibril assembly and promotes wound healing by facilitating fibroblast activation and contraction.…”

Myopathy Associated With Dermatan Sulfate-Deficient Decorin and Myostatin in Musculocontractural Ehlers-Danlos Syndrome: A Mouse Model Investigation

“…By electron microscopy staining, rod-shaped linear GAG chains were found to be attached at one end to collagen fibrils and protruded outside the fibrils in the skin of mcEDS- CHST14 , in contrast to those in wild type mice where they surround and wrap the collagen fibrils. The structure of the GAG chain from Chst14 –/– mice also exhibited similar abnormalities of collagen networks in the skin ( Hirose et al, 2021 ). Similar to these findings observed in skin tissue, structural and conformational abnormalities in the GAG chain on decorin may affect the formation of collagen fibrils in the muscle tissue.…”

“…These findings suggest that the decorin-proteoglycan is important for collagen fibril formation, and regulates the space between collagen fibrils as well as bundles, as reported previously ( Scott et al, 1995 ). DS and CS/DS hybrid chains are conformationally more flexible than CS chains ( Casu et al, 1988 ; Hirose et al, 2021 ). Thus, collagen bundles bound by CS chains, instead of DS chains, on decorin in mcEDS- CHST14 patients as well as Chst14 –/– mice may be more fragile than those in healthy and wild-type controls, respectively.…”

“…Collagen fibrils normally aggregate in line and form collagen fibers, which are round and uniform. Although there were no significant differences in the diameter of collagen fibrils as well as the circularity as an index of shape between Chst14 +/+ and Chst14 –/– mice, collagen fibrils were scattered and oriented in various directions ( Hirose et al, 2021 ). Furthermore, irregular shapes and sizes of collagen fibrils were detected in decorin-null mice ( Danielson et al, 1997 ), being partially different from those in Chst14 –/– mice.…”

Congenital Disorders of Deficiency in Glycosaminoglycan Biosynthesis

“…Therefore, alteration of the side chain on decorin from DS to CS caused by loss-of-function in CHST11 results in the spatial disorganization of collagen networks, which may disrupt the appropriate structure of GAG side chains surrounding collagen fibrils (Hirose et al, 2019). Functional analyses of CHST14 using knockout mice are ongoing (Yoshizawa et al, 2018;Hirose et al, 2021;Nitahara-Kasahara et al, submitted).…”