Immunohistochemical Study of 78kDa Glucose-regulated Protein (Grp78) and Cripto in the Spheno-occipital Synchondrosis

Abstract

The synchondroses in the cranial base are important structures in craniofacial growth, and the spheno-occipital synchondrosis (SOS) is representative of a typical growth site. Endoplasmic reticulum (ER) stress is associated with multiple biological processes and is a critical factor in chondrogenesis. It has been reported that 78kDa Glucose-regulated protein (Grp78) plays an important role in suppressing regulators in ER stress-mediated apoptosis in chondrogenesis, and Cripto is the cell surface signaling partner of Grp78 in the transforming growth factor-β (TGF-β) signaling pathway. We attempt to clarify the immunolocalization of Grp78 and Cripto in the SOS. The mice head at embryonic day 17.5 (E17.5) were collected and embedded in paraffin. The serial sections were stained with hematoxylin and eosin, Alcian blue, lectin, and immunostaining. The SOS structure containing the resting, proliferative, and hypertrophic zone were identified with Alcian blue staining, wheat germ agglutinin, and Type II Collagen immunostaining. Immunostaining of Grp78 in the SOS revealed positive immunoreactivity in all the chondrocytes of the SOS. However, the chondrocytes of the proliferating zone were weakly immunopositive to Cripto, while the chondrocytes of the hypertrophic zone were strongly immunopositive. Since the immunolocalization of Grp78 and Cripto was different in cartilage zone, these data suggest that Grp78 and Cripto would be involved in the regulation of hypertrophic chondrocyte differentiation and may be related with ER stress in the SOS.