EXPRESSION OF FIBRILLAR TYPE-I AND TYPE-III AND BASEMENT-MEMBRANE COLLAGEN TYPE-IV GENES IN MYOCARDIUM OF TIGHT SKIN MOUSE

Study objective - The aim was to study the expression of fibrillar collagen types I and III and basement membrane type IV collagen in the heart of the tight skin mouse, a genetic mutant with collagen overproduction in various organs.Design - Collagen gene expression was measured in the ventricular tissues of the heart of the tight skin mouse and the age matched homozygous (+/+) litter mates by the use of cDNA probes to α2 (I), α1 (III) and α2 (IV) procollagen and northern and dot blot analysis. Collagen deposition was examined by immunofluorescent light microscopy using monospecific antibodies to types I, III and IV collagens.Experimental material - Heterozygous male (TSK/+) and normal (+/+) mice, 1.5-2 months old of the C57BL/6 strain were used. The animals were anaesthetised and the hearts were rapidly excised and processed for RNA extraction and antibody staining.Measurements and results - The results of northern and dot blot analyses showed a 41% increase in mRNA level for collagen type I, a 63% increase in mRNA level for type III and a 33% increase in type IV collagen in the ventricular myocardium (right and left ventricles) of the tight skin mouse compared to its counterpart in age matched homozygous (+/+) litter mates. mRNA levels for β actin showed no significant increase. Immunofluorescent light microscopy and monospecific antibodies to types I, III and IV collagens were used to examine collagen deposition. The results showed that collagen type I fibres are thicker and denser in perivascular areas of the tight skin mouse heart compared to normal heart. No abnormal accumulation of type III fibres was observed.Conclusions - The heart of the tight skin mouse may be an appropriate model for studying the up regulation of cardiac collagen gene expression and its potential contribution to myocardial diseases.