Epigenetic modifications in spinal ligament aging.

Spinal stenosis is a common degenerative spine disorder in the aged population and the spinal ligament aging is a main contributor to this chronic disease. However, the underlying mechanisms of spinal ligament aging remain unclear. Epigenetics is the study of heritable and reversible changes in the function of a gene or genome that occur without any alteration in the primary DNA sequence. Epigenetic alterations have been demonstrated to play crucial roles in age-related diseases and conditions, and they are recently studied as biomarkers and therapeutic targets in the field of cancer research. The main epigenetic modifications, including DNA methylation alteration, histone modifications as well as dysregulated noncoding RNA modulation, have all been implicated in spinal ligament aging diseases. DNA methylation modulates the expression of critical genes including WNT5A, GDNF, ACSM5, miR-497 and miR-195 during spinal ligament degeneration. Histone modifications widely affect gene expression and obvious histone modification abnormalities have been found in spinal ligament aging. MicroRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) exert crucial regulating effects on spinal ligament aging conditions via targeting various osteogenic or fibrogenic differentiation related genes. To our knowledge, there is no systematic review yet to summarize the involvement of epigenetic mechanisms of spinal ligament aging in degenerative spinal diseases. In this study, we systematically discussed the different epigenetic modifications and their potential functions in spinal ligament aging process.