Latest advances in intervertebral disc development and progenitor cells

Abstract

This paper is a concise review aiming to assemble the most relevant topics presented by the authors at ORS-Philadelphia Spine Research Society Fourth International Spine Research Symposium. It centers on the latest advances in disc development, its main structural entities, and the populating cells, with emphasis on the advances in pivotal molecular pathways responsible for forming the intervertebral discs (IVD). The objective of finding and emphasizing pathways and mechanisms that function to control tissue formation is to identify and to explore modifications occurring during normal aging, disease, and tissue repair. Thus, to comprehend that the cellular and molecular basis of tissue degeneration are crucial in the study of the dynamic interplay that includes cell-cell communication, gene regulation, and growth factors required to form a healthy and functional tissue during normal development.

Keywords: development; stem cell; tissue‐specific progenitor cells.

Figure 1

Schematic illustration depicting key stages of intervertebral disc development, highlighting the growth factors, morphogens, and transcription factors. Depiction of key stages in axial skeletogenesis, including (A) node formation and elongation in the early embryo; (B) aggregation of the somatic mesenchyme around the notochord to form a continuous perichordal tube with metameric condensation of the axial mesenchyme (depicted by darker blue bands) leading to spine segmentation; and (C) formation of intervertebral discs. Notochord/nucleus pulposus derived structures are colored in red, and structures contributing to the annulus fibrosus are colored in blue. At each stage, selected growth factors, morphogens, and transcription factors (TFs) known to be required for IVD development are indicated, with notochord/nucleus pulposus associated factors indicated in red, and annulus fibrosus associated factors indicated in blue

Figure 2

Identified progenitor cells populating the IVD and the changes in their numbers as a function of time, from development, through homeostasis and to aging. Depiction of cells with MSC properties, low‐cycling cells near the perichondrium of the vertebral body, notochordal and Tie2+/GD2+ and other progenitor cells