The Marsupial Intervertebral Disc: An Anatomical Characterization

Abstract

The intervertebral disc (IVD) functions in the support and movement of the vertebrate body. It is composed of the collagenous annulus fibrosis (AF), which surrounds the inner nucleus pulposus (NP). The NP is primarily water and proteoglycans. Cartilage end plates attach the IVD to the adjacent vertebrae. The IVD undergoes numerous changes with aging (degeneration), which can result in back pain. Unfortunately, few effective options exist to treat back pain caused by disc degeneration. This has highlighted the need for methods to repair, regenerate, or prevent disc degeneration. Before these therapies are realized, basic questions on the genetic and regulatory mechanisms of IVD formation and degeneration need to be answered. The use of a wide variety of mammalian models can provide interesting insights, and much work has been done using the mouse. The goal of this study is to develop the gray short-tailed opossum (Monodelphis domestica) as a new mammalian model for study of the formation, maturation, and degeneration of the IVD. The opossum is born at an early stage of development, equivalent to an E10.5-12.5 mouse. Anterior structures are well-developed, while posterior ones (hindlimbs) are delayed at birth. We hypothesize that the IVDs are not formed in the posterior of the body, giving us a unique opportunity to study and manipulate the formation of the IVDs ex utero (in mice, IVDs are formed prenatally). Using in situ hybridization, histology, and skeletal staining, we are investigating the formation of the IVDs. We will also determine if the opossum undergoes age-related degeneration of its IVDs. Successful completion of this work will provide a baseline for future studies and also assess the viability of the opossum as a model for IVD research. Funding: NSF & IGB.