Spatial distribution and correlation of adipocytes and mast cells in superficial fascia in rats

Superficial fascia has abundant preadipocytes capable of spontaneous and induced differentiation and is thought to be a novel origin of adipocytes. This study aimed to quantitatively evaluate the spatial distribution and correlation of adipocytes and mast cells in rat superficial fascia. Panoramic images were obtained from whole-mounted fascia stained by toluidine blue. Adipocytes increased gradually in superficial fascia of growing rats. Abundant mast cells, with the degranulation and exocytosis of abundant secretory granules, appeared in fascia where partially differentiating adipocytes and mature adipocytes occurred. Quantitative histological analysis by variance-mean ratio and Morisita index of dispersion indicated that both mast cells and adipocytes in fascia were distributed individually in cluster, but not random or uniform. Spearman's correlation coefficient revealed that the spatial cluster distributions of mast cells and adipocytes positively correlated with each other and correlated with increased number and size of adipocytes and adipogenic areas in fascia. Morphometry analysis indicated the strong correlation between fascial adipocytes and mast cells during the periods of rat growth. The correlation coefficient increased significantly at 8 weeks compared to 4 weeks, consistent with the increasing trend of the number and size of fascia adipocytes in growing rats. This finding provided the first quantitative histological analysis for the spatial distribution and correlation of fascia adipocytes and mast cells, which could be the histocytological basis for further exploring spatial and functional interactions between fascial mast cells and adipocytes. Also, the present data were informative for the research on physiologies and pathologies of fascia and fascia-related connective tissues.