Collagen studies in congenital cutis laxa

Collagen dysregulation in the dermis of the Sagg/+ mouse: a loose skin model

The Sagg/+ mouse is an ethylnitrosourea-derived mutant with a dermal phenotype similar to some of the subtypes of Ehlers-Danlos syndrome (EDS) and cutis laxa. The dermis of the Sagg/+ mouse has less dense and more disorganized collagen fibers compared to controls. The size of extracted Type I dermal collagen was the same as that observed in normal skin; however, more collagen could be extracted from Sagg/+ skin, which also showed decreased collagen content and decreased steady-state levels of alpha1(I), alpha2(I), alpha1(V), and alpha2(V) procollagen mRNAs. The biomechanical properties of Sagg/+ skin were significantly decreased relative to normal skin. However, there were no significant differences in the quantities of the major collagen cross-links, that is, dehydrohydroxylysinonorleucine and dehydrohistidinohydroxymerodesmosine between Sagg/+ and normal skin. Electron microscopic evaluation of Sagg/+ skin indicated that the mutation interferes with the proper formation of collagen fibrils and the data are consistent with a mutation in Type V collagen leading to haploinsufficiency with the formation of two sub-populations of collagen fibrils, one normal and one with irregular shape and a larger diameter. Further study of this novel mutation will allow the identification of new mechanisms involved in the regulation of normal and pathologic collagen gene expression.

Regulation of matrix metalloproteinase (MMP) expression in cutis laxa fibroblasts: upregulation of MMP-1, MMP-3 and MMP-9 genes but not of the MMP-2 gene

A major histopathological abnormality in cutis laxa (CL) is a paucity of elastic structures. The aim of this study was to investigate the gene expression levels of the major matrix degrading factors matrix metalloproteinase (MMP) 1, MMP-2, MMP-3 and MMP-9 in CL. The gene expression levels of MMP-1, MMP-2, MMP-3 and MMP-9 in cultured CL fibroblasts were measured by northern blot, immunoblot and gelatin zymographic analysis. Markedly increased mRNA levels of MMP-1 (8.4-fold), MMP-3 (7.2-fold) and MMP-9 (more than 10-fold) were found in CL fibroblasts, whereas MMP-2 mRNA levels in these fibroblasts were unaltered. Increased protein production levels of MMP-1 (4.6-fold) and MMP-3 (5.1-fold) in CL fibroblasts were shown by immunoblot analysis. On gelatin zymographic analysis, the gelatinolytic activities of MMP-9 but not of MMP-2 were increased (2.2-fold). These results suggest that increased gene expression levels of MMP-1, MMP-3 and MMP-9 in CL fibroblasts may contribute to the histopathological abnormality in CL.

Collagenase gene expression in cutis laxa fibroblasts is upregulated by transcriptional activation of the promoter gene through a 12-0-tetradecanoyl-phorbol-13-acetate (TPA)-responsive element

Our previous work demonstrated that collagenase mRNA levels are increased in fibroblasts derived from patients with cutis laxa (CL). To pursue the mechanism of the upregulation of collagenase expression, we investigated transcriptional levels of the collagenase gene in CL fibroblasts. Fibroblasts cultured from the skin of three congenital CL patients were studied. Northern blot hybridization revealed 2.8- to 7.3-fold increases in collagenase mRNA levels in CL fibroblasts compared with normal cells. Nuclear run-off experiments demonstrated that the transcription rate of the collagenase gene in nuclei isolated from the same cells was 5.1- to 10.2-fold higher in the CL fibroblasts than in the controls. Transient transfection of a normal collagenase promoter-CAT construct into the cells further showed significantly enhanced transcriptional activity in CL but not in normal fibroblasts. Experiments of transient transfection of deleted or small substituted collagenase promoter-CAT constructs indicated that collagenase transcription in CL fibroblasts was activated the TPA-responsive element site of the collagenase promoter gene. Although the levels of Jun and Fos gene expression did not differ from those observed in normal fibroblasts, AP-1-binding activity, as measured by the ability to bind to an oligonucleotide containing a TPA-responsive element, was significantly elevated in CL fibroblasts as compared with normal fibroblasts. These data suggest that collagenase expression is upregulated at the transcriptional level by endogenous activation of DNA binding of AP-1 in CL fibroblasts [corrected].

Collagen metabolism in cutis laxa fibroblasts: increased collagenase gene expression associated with unaltered expression of type I and type III collagen

Collagen metabolism was studied in cutis laxa by analyzing collagen and collagenase gene expression in three dermal fibroblast strains from patients with congenital cutis laxa and comparing them with fibroblasts obtained from age-matched healthy subjects. Normal collagen synthetic activity was observed in the cutis laxa fibroblasts. An increased level of collagenase mRNA and unaltered levels of alpha 1(I) and alpha 1(III) collagen mRNA were found in all cutis laxa cell strains by dot blot hybridization. Reduced levels of elastin mRNA were also detected in these strains. However, no qualitative differences in these mRNA transcripts were detected between the control and cutis laxa fibroblasts by Northern blot analysis. Collagenase activity in fibroblast culture supernatants was then measured using fluorescein isothiocyanate (FITC)-labeled type I collagen. Increased collagenolytic activity in cutis laxa fibroblast culture supernatants was also found. These data suggest that increased collagenase expression of fibroblasts is related to the structural abnormality of dermal connective tissue in cutis laxa.

Cutis laxa: autosomal dominant inheritance in five generations

Cutis laxa is described in three cases: a 17-year-old man, his mother and his maternal grandmother. The onset of skin symptoms occurred from puberty to early adulthood. The skin was loose-hanging, wrinkled and without elasticity. X-ray examination showed numerous gastrointestinal diverticulae in the two older patients, and both had been operated on for abdominal hernia and genital prolapse. There were no cardiopulmonary symptoms. Histopathological investigation showed a reduction in the amount of elastic tissue in the dermis, but normally localized and ultrastructurally normal components. The family history revealed clinically similar cases in at least five generations, consistent with autosomal dominant inheritance.