Differential fractal dimension is associated with extracellular matrix remodeling in developing bovine corpus luteum

To assist in evaluating and quantifying tissue changes, fractal dimension (FD) is a useful method for assessing the organization in an image from fractals that describes the amount of space and the self-similarity of the structure, once FD detects subtle morphological changes and performs functional quantitative measures. Here, we hypothesized that fractal analysis may be different in functional and regressing bovine corpus luteum (CL) and may be correlated with differential expression of genes involved in extracellular matrix remodeling. CL presents two developmental stages, the functional and regressing CL, according to progesterone levels and morphology. First, we found a lower FD in functional CL using HE staining and picrosirius red approach. Additionally, we found a great amount of total collagen in regressing CL. Regarding gene expression, we showed an up regulation of COL1A1, COL1A2, MMP2, and MMP14 and a down regulation of TIMP1 and TIMP2 in regressing CL compared to the functional one. Thus, we concluded that differential FD observed during luteal regression is an effective method to evaluate the tissue changes observed during luteal development in cattle and is related to differential quantity of genes involved in extracellular matrix remodeling.