Human Disc Nucleus Properties and Vertebral Endplate Permeability

Abstract

Study of human cadaveric discs quantifying endplate permeability and porosity and correlating these with measures of disc quality: cell density, proteoglycan content, and overall degeneration. Permeability and porosity increased with age and were not correlated with cell density or overall degeneration, suggesting that endplate calcification may not accelerate disc degeneration.Study Design-Experimental quantification of relationships between vertebral endplate morphology, permeability, disc cell density, glycosaminoglycan content and degeneration in samples harvested from human cadaveric spines.Objective-To test the hypothesis that variation in endplate permeability and porosity contribute to changes in intervertebral disc cell density and overall degeneration.Summary of Background Data-Cells within the intervertebral disc are dependent on diffusive exchange with capillaries in the adjacent vertebral bone. Previous findings suggest that blocked routes of transport negatively affect disc quality, yet there are no quantitative relationships between human vertebral endplate permeability, porosity, cell density and disc degeneration. Such relationships would be valuable for clarifying degeneration risk factors, and patient features that may impede efforts at disc tissue engineering.Methods-Fifty-one motion segments were harvested from 13 frozen cadaveric human lumbar spines (32 to 85 years) and classified for degeneration using the MRI-based Pfirrmann scale. A cylindrical core was harvested from the center of each motion segment that included vertebral bony and cartilage endplates along with adjacent nucleus tissue. The endplate mobility, a type of permeability, was measured directly using a custom-made permeameter before and after the cartilage endplate was removed. Cell density within the nucleus tissue was estimated using the picogreen method while the nuclear GAG content was quantified using the DMMB technique. Specimens were imaged at 8 μm resolution using microCT, bony porosity was calculated. Analysis of variance, linear regression, and multiple comparison tests were used to analyze the data.Results-Nucleus cell density increased as the disc height decreased (R 2 =0.13; p=0.01) but was not related to subchondral bone porosity (p>0.5), total mobility (p>0.4) or age (p>0.2). When controlling for disc height however, a significant, negative effect of age on cell density was NIH Public AccessAuthor Manuscript Spine (Phila Pa 1976). Author manuscript; available in PMC 2012 April 1. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript observed (p=0.03). In addition to this, GAG content decreased with age non-linearly (R 2 =0.83, p<0.0001) and a cell function measurement, GAGs/cell decreased with degeneration (R 2 =0.24; p<0.0001). Total mobility (R 2 =0.14; p<0.01) and porosity (R 2 =0.1, p<0.01) had a positive correlation with age.Conclusion-Although cell density increased with degeneration, cell function indicated that GAGs/cell decreased. Since permeability and porosity increase w...

Age- and degeneration-related variations in cell density and glycosaminoglycan content in the human cervical intervertebral disc and its endplates

“…It is well recognized that GAG content decreases with degeneration [34]. Additionally, Rodriguez et al [30] found that endplate porosity increases with age, while GAG content, as in our study, decreases. Collectively, the presented findings support the theory that endplate porosity increases with age, and that this may be an adaptive response to a reduction of nuclear swelling pressure.…”

“…Cranial and caudal endplates exhibited similar cell density and GAG content, as was also found by Rodriguez et al [30]. The endplate presented similar cell density throughout all of its structure, in some cases "matching" IVD regions of low cell density with endplate areas of high cell density (e.g.…”

“…Overall GAG content, in both the IVD and the endplates, followed cell density values. GAG production is considered a measure of IVD/ endplate cell activity [30]. Interestingly, sagittal and coronal variations in IVD GAG content were rather high when compared to previous studies [18].…”

Evaluation of intervertebral disc cartilaginous endplate structure using magnetic resonance imaging

“…While for some subjects 2-3 levels were used from a single spine, consistent with common practice in the literature [32][33][34], these discs were assumed to be independent samples and post hoc statistical analysis confirmed no subject dependence on CEP height. Each whole spine was first scanned with a mid-sagittal T2-weighted turbo spin echo imaging sequence for routine grading of degenerative state [25,26].…”

Endplate calcification and cervical intervertebral disc degeneration: the role of endplate marrow contact channel occlusion

“…In our study, we have not decided to go beyond microCT and histological analysis, even though some studies [1,20,26] reached out for biochemical parameters to supplement their search for the cause of endplate-IVD degeneration. This is something worth exploring in future studies, as different studies [1,20,26] produce conflicting results -especially when it comes to the role of glycosaminoglycans in the interplay between age, endplate bone porosity and IVD degeneration.…”