Growth factor expression in degenerated intervertebral disc tissue. An immunohistochemical analysis of transforming growth factor beta, fibroblast growth factor and platelet-derived growth factor

Abstract

Degenerated intervertebral disc has lost its normal architecture, and there are changes both in the nuclear and annular parts of the disc. Changes in cell shape, especially in the annulus fibrosus, have been reported. During degeneration the cells become more rounded, chondrocyte-like, whereas in the normal condition annular cells are more spindle shaped. These chondrocyte-like cells, often forming clusters, affect extracellular matrix turnover. In previous studies transforming growth factor beta (TGFbeta) -1 and -2, basic fibroblast growth factor (bFGF) and platelet-derived growth factor (PDGF) have been highlighted in herniated intervertebral disc tissue. In the present study the same growth factors are analysed immunohistochemically in degenerated intervertebral disc tissue. Disc material was obtained from 16 discs operated for painful degenerative disc disease. Discs were classified according to the Dallas Discogram Description. Different disc regions were analysed in parallel. As normal control disc tissue material from eight organ donors was used. Polyclonal antibodies against different growth factors and TGFbeta receptor type II were used, and the immunoreaction was detected by the avidin biotin complex method. All studied degenerated discs showed immunoreactivity for TGFbeta receptor type II and bFGF. Fifteen of 16 discs were immunopositive for TGFbeta-1 and -2, respectively, and none showed immunoreaction for PDGF. Immunopositivity was located in blood vessels and in disc cells. In the nucleus pulposus the immunoreaction was located almost exclusively in chondrocyte-like disc cells, whereas in the annular region this reaction was either in chondrocyte-like disc cells, often forming clusters, or in fibroblast-like disc cells. Chondrocyte-like disc cells were especially prevalent in the posterior disrupted area. In the anterior area of the annulus fibrosus the distribution was more even between these two cell types. bFGF was expressed in the anterior annulus fibrosus more often in chondrocyte-like disc cells than in fibroblast-like disc cells. Control discs showed cellular immunopositivity for only TGFbeta-1 and -2 and TGFbeta receptor type II . We suggest that growth factors create a cascade in intervertebral disc tissue, where they act and participate in cellular remodelling from the normal resting stage via disc degeneration to disc herniation.

Figures

Fig. 1

In all figures the ABC-peroxidase immunostaining method was used. The used AEC chromogen shows the specific immunoreaction in red. All the used antibodies were of polyclonal type and as counterstain we used hematoxylin. a Platelet-derived growth factor (PDGF) immunostaining in posterior annulus fibrosus from a 40 year old male patient. Note the total lack of positive immunoreaction. Arrows mark pale nuclei of disc cells. Original magnification×370. b Transforming growth factor (TGFβ-1) immunopositive chondrocyte-like disc cells (open arrows) in anterior annulus fibrosus. The surgical sample was obtained from a 42-year-old male patient operated for painful degenerative disc disease. The operation level was L5-S1. Original magnification×370. c The TGFβ-receptor type II immunopositivity (open arrows) in cluster of chondrocyte-like posterior annulus fibrosus disc cells from a 40-year-old male patient. The operation level was L4–5. Original magnification×370

Fig. 2

Expression of growth factors (bFGF, TGFβ-1, −2 and TGFβ receptor type II) in different disc regions. (DC chondrocyte-like disc cell, F fibroblast-like disc cell, bFGF basic fibroblast growth factor, TGFβ transforming growth factor β)