Immunohistochemical identification of notochordal markers in cells in the aging human lumbar intervertebral disc

Abstract

The fate of notochord cells during disc development and aging is still a subject of debate. Cells with the typical notochordal morphology disappear from the disc within the first decade of life. However, the pure morphologic differentiation of notochordal from non-notochordal disc cells can be difficult, prompting the use of cellular markers. Previous reports on these notochordal cell markers only explored the occurrence in young age groups without considering changes during disc degeneration. The aim of this study, therefore, was to investigate presence, localization, and abundance of cells expressing notochordal cell markers in human lumbar discs during disc development and degeneration. Based on pilot studies, cytokeratins CK-8, -18 and -19 as well as Galectin-3 were chosen from a broad panel of potential notochordal cell markers and used for immunohistochemical staining of 30 human lumbar autopsy samples (0-86 years) and 38 human surgical disc samples (26-69 years). In the autopsy group, 80% of fetal to adolescent discs (0-17 years) and 100% of young adult discs (18-30 years) contained many cells with positive labeling. These cells were strongly clustered and nearly exclusively located in areas with granular changes (or other matrix defects), showing predominantly a chondrocytic morphology as well as (in a much lesser extent) a fibrocytic phenotype. In mature discs (31-60 years) and elderly discs (≥ 60 years) only 25 and 22-33%, respectively, contained few stained nuclear cells, mostly associated with matrix defects. In the surgical group, only 16% of samples from young adults (≤ 47 years) exhibited positively labeled cells whereas mature to old surgical discs (>47 years) contained no labeled cells. This is the first study describing the presence and temporo-spatial localization of cells expressing notochordal cell markers in human lumbar intervertebral discs of all ages and variable degree of disc degeneration. Our findings indicate that cells with a (immunohistochemically) notochord-like phenotype are present in a considerable fraction of adult lumbar intervertebral discs. The presence of these cells is associated with distinct features of (early) age-related disc degeneration, particularly with granular matrix changes.

The evolutionary importance of cell ratio between notochordal and nucleus pulposus cells: an experimental 3-D co-culture study

“…The search for specific markers to distinguish these two cell populations has just started [13]. Weiler et al [38] found that cells in the human fetal and juvenile nucleus pulposus with the typical morphology of the notochord (physaliferous) express the markers cytokeratin (CK)-8, -18, -19 and galectin-3 [29]. Gilson et al [13] found that pig NP cells, which are phenotypically similar to human infant nucleus pulposus cells, were all CK-8 positive.…”

Evoked thalamic neuronal activity following DRG application of two nucleus pulposus derived cell populations: an experimental study in rats

“…The reduction in evoked thalamic activity after application of notochordal cells was an interesting observation. The clinical relevance of this observation is, however, difficult to assess, since the number of notochordal cells in human adult nucleus pulposus is limited [8,9]. The findings indicate a high complexity of the cellular interactions involved in NPrelated changes in nervous tissue as seen in association with disc herniation, radiculopathy and sciatic pain.…”

“…Viable chondrocyte-like cells have been demonstrated in human NP from individuals of high ages [7] while it has previously been proposed that notochordal cells disappear within the first three decades of life [8]. Weiler et al [9], however, recently observed cells with notochordal phenotype present in elderly human NP. Both notochordal cells and chondrocyte-like cells are present in rat NP after skeletal maturity [10].…”

CK8 phosphorylation induced by compressive loads underlies the downregulation of CK8 in human disc degeneration by activating protein kinase C

“…24,25 In addition, CK8 exists in adult human NP cells and decreases with age or IDD. 7,8 However, the underlying mechanisms of the downregulation of CK8 are still unidentified. Here, we found that CK8 expression decreases in IDD with phosphorylation in degenerate NP cells.…”

“…[4][5][6] Accumulating evidence has shown that cytokeratin 8 (CK8) exists in normal human NP cells and decreases with age. 7,8 We also previously found a downregulated CK8 expression with IDD based upon multiple lines of evidence. 9 CK8 is a member of the cytokeratins family, which belongs to the intermediate filament proteins of epithelial cells.…”