Quantitative analysis of fibrosis formation on the microcapsule surface with the use of picro-sirius red staining, polarized light microscopy, and digital image analysis

Transplantation of microencapsulated cells shows potential to treat a variety of diseases. To improve the quality of microcapsules, efficient methods need to be established and standardized for the evaluation of biocompatibility of microcapsules. To this end, a microscopical method was developed to analyze quantitatively the degree of fibrotic overgrowth (FO), which serves as the index of biocompatibility. In this method, sections were stained with picro‐sirius red and illuminated with a polarized light microscope. The images were digitized with the use of a computer‐video system in which collagenous content was depicted by gray levels 1 to 255. Both the area of collagen and the thickness of FO were examined. The ratio of Type I/Type III collagen and the thickness were used as indexes of the degree of FO. The data showed that the ratio of Type I/Type III collagen and the thickness increased with time, and FO was not significant 4 weeks after transplantation. In comparison, this new method is more efficient to evaluate FO. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res, 2006