Study Design. Study of regional variations in composition in a sample of 9 mildly to moderately degenerated human intervertebral discs.Objective. The aim of this study was to obtain proteoglycan distribution in human lumbar discs with high position resolution in the: 1) sagittal, 2) coronal, and 3) axial directions.Summary of Background Data. Regional variation in disc proteoglycan content has only been reported in coronal sections in a small number of discs and with low spatial resolution in the sagittal direction, and has not been reported in the axial direction.Methods. Each of 9 human L2-L3 or L3-L4 lumbar discs (age, 53-56 years) were dissected into 36 to 41 specimens using a rectangular cutting die, measured for water content and analyzed for glycosaminoglycan content using the dimethylmethylene blue dye binding assay.Results. The intervertebral discs were mildly to moderately degenerated. They had glycosaminoglycan content ranging ϳ40 to 600 g/mg dry tissue, with largest values in the nucleus and lowest in the outer anulus. In general, posterior regions had greater glycosaminoglycan content than anterior regions, although values were not as high as in the nucleus. Small variations in glycosaminoglycan content in the axial direction were observed with the largest values in the center, although this variation was small compared with radial variations. Water content results followed similar trends as glycosaminoglycan content with average values ranging from ϳ66% to 86%.Conclusions. A refined map of proteoglycan content is presented with 3 important findings. First, sagittal variations were distinct from coronal variations. Second, the proteoglycan content was not uniform across the nucleus regions. Third, some specimens had localized variations in proteoglycan and water contents suggestive of focal damage and degeneration.Key words: proteoglycans, aggrecan, glycosaminoglycan content, fixed charge density, intervertebral disc, degeneration. Spine 2007;32: [1493][1494][1495][1496][1497] The distribution of proteoglycan content in the intervertebral disc is functionally important in defining the swelling behaviors, streaming potential, and compressive properties of the tissue.1-4 A loss of proteoglycans in the central nucleus pulposus region is a clear sign of early degeneration. 5,6 The tissue mechanical properties depend on proteoglycan content; therefore, this compositional information is required for mechanical modeling of the disc 1,7-10 and offers promise for improved understanding of disc function and remodeling in healthy and diseased states.Previous reports of proteoglycan content distribution in the disc have provided relatively coarse information on the distribution in the sagittal (front to back) direction on a large number of specimens using sulfated glycosaminoglycan (GAG) measurements 6 or with a higher spatial distribution from a relatively small number of discs using radioactive ion tracers to obtain direct measurements of fixed charge density. 11 The proteoglycan distributions in the coronal ...

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