Expression of Heparanase Isoforms in Intervertebral Discs Classified According to Pfirrmann Grading System for Disc Degeneration

Study Design. This is a quantitative study of heparanase isoforms expression in degenerative and nondegenerative intervertebral discs (IVDs). Objective. To quantify the expression of both heparanase isoforms (HPSE1 and HPSE2) in IVD tissues as classified by different degeneration grades using the Pfirrmann grading system, and to correlate the expression with the loss of extracellular matrix molecules observed in patients with the disease. Summary of Background Data. The loss of proteoglycans as observed in IVD degeneration may occur due to the enhanced expression of matrix degrading enzymes, such as heparanase. However, the heparanase function in IVD degeneration remains unclear. Methods. This study comprised 53 surgical samples of degenerative discs obtained from patients with lumbar disc degeneration and 12 control samples collected from healthy individuals without any degenerative lumbar disc alterations who had accidental spine fractures. All patients underwent magnetic resonance imaging based on the Pfirrmann grading system for disc degeneration. Only the specimens that were classified according to magnetic resonance imaging evaluations as Pfirrmann grades I, II, III, and IV were analyzed. The tissue sections of the disc samples were subject to immunohistochemical staining with antibodies against the heparanase isoforms and to quantitative real time PCR to amplify heparanase isoforms cDNA. Protein and mRNA expressions were quantified. Analysis of variance and Student t test were used to compare the means of the study populations. Results. The data demonstrated a gradual increase in both the heparanase isoform protein expression and disc degeneration progression. Besides, mRNA expression of both heparanase isoforms were significantly higher in degenerative than nondegenerative IVDs. Conclusion. The overexpression of HPSE1 and HPSE2 in the intervertebral degenerated discs suggests a role for these factors in mediating extracellular matrix remodeling in degenerative discs during disease development. (AU)