Immunohistological analysis of transglutaminase factor XIIIA expression in mouse embryonic growth plate.

Previously we demonstrated the expression of Factor XIIIA (FXIIIA), a coagulation transglutaminase, in avian embryonic growth plate. To explore whether FXIIIA is also expressed by chondrocytes of the mammalian cartilage anlagen of bones, we analyzed the mouse embryonic growth plate by immunostaining using anti-FXIIIA antibodies developed against human and chicken proteins. We revealed the expression of FXIIIA in the epiphyseal growth plate, where FXIIIA appears first intracellularly in the zone of proliferation/maturation, and remains intra- and extracellularly throughout the hypertrophic zone. Externalization of FXIIIA occurs before mineralization. Transglutaminase activity was assayed in organ cultures using rhodamine-labeled synthetic substrate Pro-Val-Lys-Gly. Enzymatic activity shows a restricted distribution in cartilage and correlates with FXIIIA expression pattern, suggesting that cartilagenous transglutaminase activity is due, at least partially, to the FXIIIA isoform. We conclude, that coagulation factor FXIIIA is expressed by chondrocytes of embryonic mouse long bone cartilages in a strictly regulated pattern, which correlates with chondrocyte differentiation and matrix mineralization.