Poster Presentation 50th International Society for the Study of the Lumbar Spine Annual Meeting 2024

OSTEOPOROSIS MICE FOLLOWING OVARIECTOMY EXHIBIT BEHAVIOURAL INDICATORS OF OSTEOPOROSIS-RELATED PAIN AND PAIN-RELATED SENSORY INNERVATION IN LUMBAR VERTEBRAE (#157)

Miyako NARITA 1 , Sumihisa ORITA 2 , Kazuhisa INAGE 2 , Yasuhiro SHIGA 2 , Masahiro INOUE 2 , Yawara EGUCHI 2 , Chisato MORI 1 , Seiji OHTORI 2
  1. Department of Bioenvironmental Medicine, Graduate School of Medicine, Chiba University, Chiba City, Chiba, JAPAN
  2. Department of Orthopedic Surgery, Graduate School of Medicine, Chiba University, Chiba City, Chiba, JAPAN

【INTRODUCTION】In clinical practice, osteoporotic patients with no apparent vertebral compression fractures often complain of lower back pain. The involvement of pain-related sensory nerves is suggested in the transmission mechanism of pain caused by this osteoporotic state (osteoporosis-related pain). However, there are few reports regarding pain-related sensory nerve innervation within the vertebral body, especially bone marrow. The purpose of this study was to compare pain behaviours and pain-related sensory innervation in the lumbar vertebral bodies of ovariectomized osteoporotic mice with Sham mice.

【METHODS】Two groups were utilized: the osteoporosis group, in which 6-week-old female C57BL/6 mice had their ovaries removed under general anesthesia, and the sham group, in which only the ovaries were exposed (n=10 in each group). Bone density, hind paw cutaneous hypersensitivity (von Frey test, acetone test, heat test), deep musculoskeletal discomfort (grip force test), and motor function (rotarod assay) were evaluated before and 8 weeks after ovariectomy and sham surgery. Then, the pain sensory nerve fibers (Calcitonin Gene-Related Peptide: CGRP-positive sensory nerve fibers) in the lumbar vertebral body were visualized by perfusion fixation and immunohistochemical staining: DAB(3,3′-Diaminobenzidine) staining. The CGRP-positive sensory nerves in the vertebral bodies were measured and statistically analyzed.

【RESULTS】 Compared to the Sham group, the osteoporosis group had significant hind paw cutaneous hypersensitivity and deep musculoskeletal discomfort (P<0.001), but no significant difference was observed in motor function (P>0.05). Furthermore, the osteoporosis group showed significant outgrowth of CGRP-positive sensory nerves in the lumbar vertebral body compared to the sham group (P<0.001).

【DISCUSSION】It was suggested that significant pain-related sensory innervation within the vertebral body in osteoporotic conditions may be involved in pain transmission of osteoporosis-derived pain.

6556a0e657d15-ISSLS+2024.jpgFigure: (A) von Frey assay: the osteoporosis group had significant hind paw cutaneous hypersensitivity than the Sham group. (B) Acetone test:  the osteoporosis group had significant hind paw cutaneous hypersensitivity than the Sham group. (C) Heat test:  the osteoporosis group had significant hind paw cutaneous hypersensitivity than the Sham group. (D) Grip force test:  the osteoporosis group had significant musculoskeletal discomfort than the Sham group.
(E) Rotarod assay:  there was no significant difference between the OVX group and the Sham group in motor function.
(F) CGRP-ir sensory nerves: the osteoporosis group showed significant outgrowth of CGRP-positive sensory nerves in the lumbar vertebral body compared to the sham group.（Mean ± SEM. p-value,  * * * < 0.001)