The effects of intervertebral disc degeneration combined with osteoporosis on vascularization and microarchitecture of the endplate in rhesus monkeys

Rui Zhong, Fuxin Wei, Le Wang, Shangbin Cui, Ningning Chen, Shaoyu Liu, Xuenong Zou

To evaluate the influence of osteoporosis on the microarchitecture and vascularization of the endplate in rhesus monkeys with or without intervertebral disc (IVD) degeneration using micro-computerized tomography (micro-CT), and to further analyze the correlation between osteoporosis and IVD degeneration. Twelve rhesus monkeys were randomly divided into the ovariectomy (OVX, n = 6) and the sham group (n = 6). The subchondral bone adjacent to the lumbar IVDs (from L4/5 to L6/7) of each monkey was randomly injected with 4 ml pingyangmycin (PYM) solution (1.5 mg/ml, PYM), or 4 ml phosphate buffered saline (PBS) as vehicle treatment, or exteriorized but not injected anything as control (Cntrl). Degenerative and osteoporotic processes were evaluated at different time points. Micro-CT and histology were performed to analyze microarchitecture, calcification area and vascularization of the endplate. OVX resulted in significant decrease of bone mineral density (BMD). PYM injection induced progressively IVD degeneration, which was more progressive when combined with OVX. There was a negative correlation between BMD and Pfirrmann grade in the subgroups with PYM injection. The micro-CT analysis showed the combination of osteoporosis and IVD degeneration led to more calcification of endplate than any one thereof. The decrease of vascular volume percent in the endplate of the OVX-PYM subgroup was significantly greater than that in the Sham-PYM subgroup, both of which showed significant less vascularization compared to the other subgroups. In conclusion the osteoporosis could accumulate the calcification and decrease the vascularization in the endplates adjacent to the degenerated IVDs, which subsequently exacerbated degeneration of the degenerated IVDs.