Age-Correlated Phenotypic Alterations in Cells Isolated From Human Degenerated Intervertebral Discs With Contained Hernias.

STUDY DESIGN: Human intervertebral disc (hIVD) cells were isolated from 41 surgically excised samples and assessed for their phenotypic alterations with age.

OBJECTIVE: Toward the design of novel anti-aging strategies to overcome degenerative disc disease (DDD), we investigated age-correlated phenotypic alterations that occur on primary hIVD cells.

SUMMARY OF BACKGROUND DATA: Although regenerative medicine holds great hope, much is still to be unveiled on IVD cell biology and its intrinsic signaling pathways, which can lead the way to successful therapies for IDD. A greater focus on age-related phenotypic changes at the cell level would contribute to establish more effective anti-aging/degeneration targets.

METHODS: The study was subdivided in four main steps: i) optimization of primary cells isolation technique; ii) high-throughput cell morphology analysis, by imaging flow cytometry (FC) and subsequent validation by histological analysis; iii) analysis of progenitor cell surface markers expression, by conventional FC; and iv) statistical analysis and correlation of cells morphology and phenotype with donor age.

RESULTS: Three subsets of cells were identified on the basis of their diameter: small cell (SC), large cell (LC), and super LC (SLC). The frequency of SCs decreased nearly 50% with age, whereas that of LCs increased nearly 30%. Interestingly, the increased cells size was due to an enlargement of the pericellular matrix (PCM). Moreover, the expression pattern for CD90 and CD73 was a reflexion of age, where older individuals show reduced frequencies of positive cells for those markers. Nevertheless, the elevated percentages of primary positive cells for the mesenchymal stem cells (MSCs) marker CD146 found, even in some older donors, refreshed hope for the hypothetical activation of the self-renewal potential of the IVD.

CONCLUSION: These findings highlight the remarkable morphological alterations that occur on hIVD cells with aging and degeneration, while reinforcing previous reports on the gradual disappearance of an endogenous progenitor cell population.

LEVEL OF EVIDENCE: N/A.