Quantitative analysis of α1(I) and α1(III) procollagen mRNA expression in systemic sclerosis skin tissue – an in situ hybridization study

Abstract Human α1(I) and α1(III) procollagen mRNA expression in skin tissue from 15 systemic sclerosis (SSc) patients and from 7 normal control subjects was quantitatively analyzed using in situ hybridization. The grains accumulating in each area, representing procollagen mRNA expression per cell, were counted. To normalize the results from each subject, the number of cells and the number of grains per cell were divided by the area of the skin specimen (in square millimeters). The number of cells per square millimeter expressing α<1(I) and α1(III) procollagen mRNA in SSc skin was significantly elevated compared with normal control skin (both P < 0.01). The number of grains per cell per square millimeter expressing α1(III) procollagen mRNA in SSc skin was also significantly elevated compared with normal control skin (P < 0.01). The relationship between procollagen mRNA expression and the histological findings in SSc was also studied. The numbers of cells and grains per cell per square millimeter expressing α1(I) procollagen mRNA in fibrotic zone SSc skin were significantly elevated compared with normal control skin (both P < 0.01). The numbers of cells and grains per cell per square millimeter expressing α1(III) procollagen mRNA in SSc skin were significantly elevated compared with normal control skin (both P < 0.01) and with border zone SSc skin (number of cells P < 0.01, number of grains P < 0.05). These results indicate an increase in the number of cells showing elevated expression of α1(I) and α1(III) procollagen mRNA, and a close relationship between α1(I) and α1(III) procollagen mRNA expression and the histological findings in SSc.