QUANTITATIVE ASSESSMENT OF MYOCARDIAL COLLAGEN WITH PICROSIRIUS RED STAINING AND CIRCULARLY-POLARIZED LIGHT

Collagen plays a major role in the structural organization of the hear t and therefore direct visualization of collagen fibers is a crucial c omponent of cardiac analysis. Although linearly polarized light has pr oven an effective tool for the examination of myocardial collagen in h istologic sections, the use of circularly polarized light may offer ad vantages and additional possibilities. We examined the potential enhan cement of collagen analysis using circularly polarized light in two wa ys. We first measured the brightness, and hence indirectly assessed th e birefringence, of collagen fibers in scars examined at different tim es after myocardial infarction. Secondly, we measured collagen content in myocardial tissue and compared results obtained from brightfield a nalysis of trichrome stained sections with those obtained from circula rly polarized light analysis of picrosirius red stained sections. We o bserved a progressive increase in the maximum brightness of collagen f ibers in the scar with time, and a time-dependent shift in the relativ e distribution of collagen fiber brightness from lower to higher level s. We found consistently lower values of collagen content in trichrome stained versus picrosirius red stained tissue, and concluded that tri chrome staining underestimated collagen content. The information provi ded by these studies could not be obtained by brightfield analysis and could be only partially obtained from linearly polarized light analys is. Thus, analysis using circularly polarized light has the ability to enhance histologic assessment of tissue and can provide additional in sights into the composition and structure of myocardial collagen.