Temporal expression and specific localization of tenomodulin with reference to vascular endothelial growth factor A and calcitonin gene-related peptide in developing diaphragm in mice.

Tenomodulin (TNMD) is related to chondromodulin-1, a cartilage-derived growth regulator. It is specifically expressed in hypovascular connective tissues, including tendons and ligaments. Vascular endothelial growth factor A (VEGF-A) and calcitonin gene-related peptide (CGRP) correlate with angiogenesis and neurogenesis, respectively, during development. Because of that the morphological profiles of TNMD, VEGF-A, and CGRP distributions in developing diaphragm are still unclear, we aimed to determine the expression of mRNA and proteins of these 3 markers during the development of the central tendon of the diaphragm (CTD) and the surrounding diaphragm tissue in mice. Male mice from the embryonic and postnatal periods [embryonic day 14.5 (E14.5), E17.5, postnatal day 1 (P1), and P5] were used and their mRNA and protein expressions were assessed using in situ hybridization, immunohistochemistry and quantitative real-time polymerase chain reaction. The results showed that TNMD was preferentially detected in muscle-tendon junction of the CTD at E17.5 and P1, in contrast to scattered distribution of CGRP and VEGF-A throughout the diaphragm from E14.5 to P5. These findings may provide fundamental information concerning the role of the TNMD in the CTD development.