On the histological biomorphosis of human heart valves II. Morphometric investigations

Previous polarization-microscopical measurements combined with silver-stain ing methods at histological sections of the bicuspid valve and the tricuspi d valve in the region of fibrosa showed (similar to that of the correspondi ng tendinous cords) for middle-aged persons a distinct difference in the co llagen composition in comparison between high pressure vs. low pressure sys tem. The aim of the current study was the morphometric investigation of the coll agen composition, of the relative content of total collagen (measured as re lative number of total collagen fibers per measuring area), and of the cell -collagen relation in dependence of age and possibly on sex in the high and low pressure system, respectively. Tissue samples of atrioventricular valves of 67 probands of both sexes were available. The probands were healthy with regard to heart and circulation and distributed in 3 age groups (Ist to 2nd decade, 3rd to 5th decade, and 6th to 9th decade). After corresponding preliminary treatment, the histolog ical sections of tissue samples were evaluated by a suitable combination of polarization-microscopical, immuno-histochemical, and morphometrical metho dology. The thickness of the heart valves was measured by microscopic image analysis. A rise of the number of fibers per measuring area (ma) for both sexes and b oth valves was observed with increasing age. The slopes of the linear regre ssion curves and the mean values of the numbers of collagenous fibers/ma (f or each age group) were different between both sexes. They depend upon the valve considered. Analogous to these results, the differentiated statements were possible to the number of fibers/ma and to the percentages of the fib er species by the distinction between the collagen types I and III in the f ibrosa of the heart valves. Whereas the relative numbers of fibers/ma rose with increasing age, the number of cell (fibroblasts, fibrocytes) nuclei fo r both valves and sexes slightly decreased. For the latter, there was no di fference between high and low pressure system in contrast to the collagenou s fibers. The opposite age-dependent behavior of the collagenous fibers and of their producing cells during the biomorphosis of the heart valves could be explained with the collagen turn-over.