Altered steady-state ratio of type I/III procollagen mRNAs correlates with selectively increased type I procollagen biosynthesis in cultured keloid fibroblasts.

Abstract

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...

Adenoviral Overexpression and Small Interfering RNA Suppression Demonstrate That Plasminogen Activator Inhibitor-1 Produces Elevated Collagen Accumulation in Normal and Keloid Fibroblasts

“…2,4 Altered expression and regulation of various extracellular matrix (ECM) components by keloid fibroblasts, such a collagen, fibronectin (Fn), elastin, proteoglycans, and matrix-directed protease and protease inhibitors, have been implicated in keloid fibrosis. [5][6][7][8][9][10][11][12] Modifications in growth factor-regulated cell growth and apoptosis, intracellular signal transduction, and epidermis-dermis interactions have been reported. [13][14][15][16][17][18][19][20][21] Changes in the level of genes involved in the above phenomena were also detected in gene profiling studies.…”

Lasers thermiques et cicatrisation cutanée

“…Dans une étude pilote menée sur 15 patients (14 femmes et un homme phototype I à IV), une différence significative a été observée à 12 mois à la dose 80-130 J/cm², basée sur une comparaison de cicatrices traitées et non traitées par laser. Aucune complica- Ces observations sont en accord avec différents travaux qui montrent bien que la valeur du rapport entre les collagènes de type I et de type III joue un rôle déter-minant dans le processus de formation de la cicatrice [37][38][39][40]. Les processus cicatriciels pathologiques sont systématiquement associés à une valeur élevée du rapport type I-type III alors qu'une valeur faible conduit à un processus de régénération (scarless healing dans la littérature anglo-saxonne) [41,42].…”

Modeling Aberrant Wound Healing Using Tissue-Engineered Skin Constructs and Multiphoton Microscopy

“…The data presented are in accord with previous work using conventional methods that have shown that keloid-derived fibroblasts exhibit phenotypic differences resulting in increased collagen production. [1][2][3][4][5][6][7] The advantage of the present system is that it incorporates a biologically active wound model resembling human skin with an imaging device that allows serial measurements of the same specimen over time. Furthermore, since MPM provides a quantitative measurement of collagen second harmonic signal generation, it can be used to estimate matrix collagen density without fixation or exogenous dyes that could cause disruption of the native physiologic environment.…”

“…In vitro studies of keloid-derived fibroblast metabolism have identified increased collagen, fibronectin, elastin, and peptidoglycan production. 1,2 More recent studies have identified phenotypic differences in growth factor production, receptor expression, and intracellular signal transduction between normal, keloid, and hypertrophic scar fibroblasts. [3][4][5][6][7] These investigations have focused on studying fibroblast behavior using cell proliferation assays and biochemical assays such as tririated proline incorporation, procollagen…”

“…This correlates with clinical observations of keloid behavior and findings of other in vitro studies investigating collagen deposition by normal or keloid fibroblasts after wounding. 1,8 In conclusion, we have described a wound-healing model and imaging system that allows the measurement of collagen production in organotypic tissue-engineered constructs resembling human skin in living specimens. Fi- broblasts were observed to aggregate along incision line margins, and MPM SHG images identified enhanced collagen production at this interface.…”