The Role of the Neural Crest Derived Periocular Mesenchyme in the Development of the Conjunctival Papillae

Abstract

The periocular mesenchyme that surrounds the optic cup gives rise to the sclera including the scleral cartilage and scleral ossicles of the eye. The scleral ossicles are induced by overlying thickenings in the epithelium known as conjunctival papillae (CP). The CP are induced from Hamburger and Hamilton (HH) stages 30 to 34 in a defined sequence and are transient structures, disappearing after inducing osteogenesis in the underlying mesenchyme. To investigate the involvement of neural crest cells (NCC), we performed surgical ablations of signaling centers as well as DiI labeling of NCC streams. Our results show that surgical ablation of the otic vesicle between HH 16-18 does not affect the patterning of the CP (n=5). However when NCC streams are DiI labeled between the otic vesicle and the eye we find DiI in some CP (n=12). Similarly, when the nasal pit epithelium is ablated between HH 16-19, there is an effect on the patterning of the CP (n=2); this is supported by our DiI injections (n=2). These results indicate that NC streams contribute to the scleral mesenchyme throughout HH stages 16-23 and it is these NCCs that are important in the development of the sclerotic bones. Further research will be required to understand how the NCCs contribute to the development and patterning of the scleral ossicle system. This research was primarily funded by the Natural Sciences and Engineering Research Council of Canada and the Killam Trusts.