Factors regulating viable cell density in the intervertebral disc: blood supply in relation to disc height

Abstract

The intervertebral disc is an avascular tissue, maintained by a small population of cells that obtain nutrients mainly by diffusion from capillaries at the disc-vertebral body interface. Loss of this nutrient supply is thought to lead to disc degeneration, but how nutrient supply influences viable cell density is unclear. We investigated two factors that influence nutrient delivery to disc cells and hence cell viability: disc height and blood supply. We used bovine caudal discs as our model as these show a gradation in disc height. We found that although disc height varied twofold from the largest to the smallest disc studied, it had no significant effect on cell density, unlike the situation found in articular cartilage. The density of blood vessels supplying the discs was markedly greater for the largest disc than the smallest disc, as was the density of pores allowing capillary penetration through the bony endplate. Results indicate that changes in blood vessels in the vertebral bodies supplying the disc, as well as changes in endplate architecture appear to influence density of cells in intervertebral discs.

Alterations in Intervertebral Disc Composition, Matrix Homeostasis and Biomechanical Behavior in the UCD-T2DM Rat Model of Type 2 Diabetes

“…This appears to be inconsistent with the finding that diabetes decreased GAG content, yet obesity alone had no appreciable effect. However, Boubriak et al reported that endplate capillary size and density is increased with disc size [14]. In the current study, obese and diabetic rats had 34% greater disc cross-sectional areas, which could explain their greater RBC density.…”

“…During the pre-diabetic state, increased insulin levels resulting from insulin resistance can have an anabolic effect on bone metabolism [11]. Any increase in bone formation in the endplate (sclerosis) could negatively impact disc health since the disc is avascular and thus, sclerosis could hinder the transport of nutrients and metabolites across the endplates to and from the disc [12][13][14]. Hyperglycemia may also be important.…”

Organ Culture Bioreactors – Platforms to Study Human Intervertebral Disc Degeneration and Regenerative Therapy

“…Torsion angle of failure of coccygeal discs for rat and cattle was found to be very high at ~30° [97,98] in contrast to the human lumbar disc where the failure range is smaller ~10° [52]. Biochemical composition, cell density and the cell population lacking notochordal cells of the bovine tail IVD are highly similar to human lumbar IVD [99,100]. …”

Association Between Intervertebral Disc Degeneration and Cigarette Smoking: Clinical and Experimental Findings

“…The uptake of lactic acid waste from the tissue can also be hindered, leading to a buildup within the intervertebral disc and a subsequent decrease in the pH to detrimental levels. Previous studies have shown that a reduced vertebral blood flow is associated with the presence of disc degeneration 36 and that viable cell density in the disc is related to the density of blood vessels in the adjacent vertebral bodies 37 .…”