Extracellular matrix composition of different spleen compartments of fruit bats.

The distribution and composition of extracellular matrix (ECM) of the spleen in two species of fruit bats, namely Cynopterus titthaecheilus and Rousettus leschenaultii, were examined by histochemistry and immunohistochemistry. Reticular fibres accompanied by laminin were identified to make up the splenic stromal network. Types I and III collagen were identified in various spleen compartments with varying intensities. Thin and short elastin fibres were scattered in several parts of the spleen. Visualization of the ECM of the spleen can better demonstrate spleen compartmentalization. The alleged vascular space structure in the fruit bats spleen was the sinus structure that was strengthened by the presence of reticular fibres that limit the sinus basement membrane. The present study identified periellipsoidal lymphoid sheath (PELS)-like structure in fruit bats spleen that had never been identified in mammals before. In addition to describing the structure, this study highlighted the variations in ECM composition of the spleen between species that can provide new insight into the phylogenetic study of spleen morphology.