Regulation of collagen gene expression was studied in fibroblast cultures established from patients with keloids, fibrotic lesions of the skin. In selected keloid fibroblast cultures, an overproduction of type I procollagen was observed. This increase was accompanied by a parallel increase in type I procollagen-speciflic mRNA levels, as detected by dot-blot and RNA transfer hybridizations, without concomitant change in type I procollagen gene copy number. At the same time, type III procollagen mRNA levels were unaltered, resulting in markedly elevated type I/III procollagen mRNA ratios. Thus, keloid fibroblasts offer a unique model to study the independent regulation of the gene expression of two genetically distinct procollagens, type I and type III.Collagen is a family of closely related, yet genetically distinct, proteins of the extracellular matrix (1, 2). In human skin, collagen comprises 70-80% of the dry weight of the tissue (3). The predominant collagen types in human dermis are types I and III, which together account for >95% of the bulk of the collagen; of this, -85% is type I collagen (3).Cultured human skin fibroblasts, which synthesize type I and type III collagens as precursors, procollagens (4, 5), have provided a useful model to study the modulation of collagen production under carefully controlled tissue culture conditions (6). Indeed, several factors have been shown to alter the production of procollagen in fibroblast cultures (6-8). However, the relative synthesis of type I and type III procollagens appears to be under stringent biological control, since only a few experimental situations have been shown to alter the relative synthesis of these two major procollagens (9-11).Keloids, dermal fibrotic lesions, are histologically and biochemically characterized by excessive accumulation of the extracellular matrix components, most notably collagen (12,13). Previous studies have demonstrated that the production of procollagen by fibroblasts established from keloids is increased when compared to control cells, suggesting an altered regulation of procollagen gene expression (14,15). In the present study, we examined the procollagen gene expression in keloid fibroblasts by determining the cellular steadystate levels of type I and type III procollagen mRNAs. The results indicate that the abundance of type I procollagen mRNA is selectively increased, leading to an altered type I/III procollagen mRNA ratio. No change in type I collagen gene copy number was detected. Thus, the elevated type I procollagen mRNA level reflects either increased transcriptional activity ofthe corresponding gene or increased stability of the mRNA transcripts. A preliminary report of the study has been presented (16). MATERIALS AND METHODSFibroblast Cultures. Keloid tissue specimens were obtained from nine patients by surgical removal under local anesthesia, after obtaining informed consent. The clinical diagnosis was confirmed by histopathologic examination of the lesions, which showed areas of thick, compact, and hyali...

A B S T R A C T Aortae from three patients with classic presentation of Marfan syndrome, who died of vascular complications, were subjected to biochemical analyses of the connective tissue; for comparison, aortae from eight age-matched controls, without evidence of connective tissue abnormalities, were examined. Elastin was prepared from the aortae by two techniques. First, the tissues were extracted with 5 M guanidine-HCI, bacterial collagenase digestion and reduction with dithiothreitol (elastin I preparation). Secondly, this material was further purified by extraction with 0.1 M NaOH at 99°C (elastin II preparation). Amino acid analyses of both elastin preparations indicated that the values for desmosine and isodesmosine were reduced in Marfan cases to approximately onehalf of the control values. A corresponding increase in lysyl residues was noted in elastin II preparations. Also, the concentration of elastin per milligram dry weight of tissue was reduced in Marfan cases. The hydroxyproline content of elastin was increased in two cases with the Marfan syndrome. Recoveries indicated that the alkali treatment solubilized 46.2% of the elastin I preparations in Marfan aortae compared with 23.7% in controls. In contrast to elastin, the concentration and solubility of collagen were unchanged; the amino acid composition and the genetic types of insoluble collagen isolated by limited pepsin proteolysis were the same in both Marfan and control aortae. The results of our study demonstrate that the cross-linking of aortic elastin is reduced in the three patients with A preliminary report of this study was given at the 66th

Previous morphologic observations have suggested abnormalities in the elastic fibers in a number of both inherited and acquired diseases. Recent progress made in understanding of the normal biology of elastin has allowed us to examine these diseases by biochemical means. In this review we are discussing the current status of the research on the elastin diseases with particular emphasis on clinical conditions affecting skin, as for example, cutis laxa, pseudoxanthoma elasticum, and the Buschke-Ollendorff syndrome. In addition, we present new data which appears to be the first demonstration of an elastin abnormality in the Marfan syndrome.

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