Meeting Abstract

P1.57  Tuesday, Jan. 4  Intervertebral Disc Ontogeny in Land Mammals and Cetaceans MORAN, Meghan M.*; THEWISSEN, JGM; Northeastern Ohio Universities Colleges of Medicine and Pharmacy; Northeastern Ohio Universities Colleges of Medicine and Pharmacy mmoran1@neoucom.edu

This project aims to understand the molecular mechanisms that control mammalian intervertebral disc ontogeny. The mammalian intervertebral disc consists of the nucleus pulposus, the annular fibrosus, and the endplate. In the sacrum of land mammals the disappearance of the intervertebral disc occurs by means of synostosis. Sacral synostosis occurs around 38 days in postnatal mice and starts in the late 20’s and can continue beyond 30 years in humans. To understand these processes, we analyze intervertebal disc ontogeny in the cervical, lumbar, and sacral regions using Safranin-O staining and immunohistochemistry for specific osteoblast markers in an ontogenetic time series of postnatal mice (Day 1, 10, 20, 30, 40, 50, 60 and >1 year old). We compare the non-fused cervical and lumbar regions to the fused sacrum in mice. We record cell type, proteoglycan expression, disc thickness, and overall disc morphology, and compare osteoblast marker expression in the fused and non-fused regions of the vertebral column. Unlike land mammals, the sacrum is never synostosed in cetaceans (whale, dolphins and porpoises). Instead, the cervical vertebrae fuse in some cetaceans (e.g. the bowhead whale, Balaena mysticetus) similar to the sacral region of land mammals. This allows us to compare the non-fused lumbar and sacral regions to the fused neck in whales. Our ultimate goal is to understand the evolution of vertebral synostosis controls and explore the molecular mechanisms responsible for intervertebral disc dissipation and bone formation.