Effects of Vector Potential Irradiation on Rat Femur Histological Analysis

Abstract

Calcified cartilage trabecular, called calcified cartilage matrix when embedded in cortical bone, are responsible for bone rigidity. Bone strength depends on the balance between the calcified cartilage matrix and the less calcified bone matrix. Recently, the effects of vector potential (VP) generators on the organism have become clearer. It is reported that VP suppressed bone resorption and maintained bone strength in rat hindlimb suspension. For the purpose of this study, experiments were conducted to histologically clarify the effects of VP irradiation on the femur of normally reared rats.In this study, Wistar rats（7-week-old male、n=24） were classified into two groups: normal rearing group (CO, n=12) and group exposed to VP during normal rearing (VP, n=12) The VP condition was 200 kHz frequency and the experimental intervention was 30 min/day, 5 days/week, for 3 weeks.Bone strength tests showed increased deformation and increased bone strength in VP; cortical bone in VP showed a decreased percentage of calcified cartilage matrix in the cortical bone and increased vascular cavity. In addition, many TRAP-positive areas were observed around the vascular cavity. Polychrome staining showed many fibers with collagen oriented vertically, suggesting that the 3-week energization period decreased the amount of calcified cartilage matrix in the cortical bone and changed the collagen orientation, resulting in increased cortical bone deformation and increased bone strength.VP was understood to increase deformation and bone strength by decreasing cortical bone calcified cartilage matrix and increasing vascular cavity and altering collagen orientation to rat femur.

Note:
Funding declaration: This research was supported in part by the JSPS Grant-in-Aid for Scientific Research (Grant No. 24K14409). This study was also funded by the Sumida Electric Co.

Conflict of Interests: This study was funded by the Sumida Electric Co. Wataru Minamizono and Masafumi Osako received research funding and VP equipment from Sumida Electric Co.

Ethical Approval: The experimental protocol was approved by the Toyo University Experimental Panel and conducted at the Toyo University Asaka Campus (approximately 7 m above sea level). The approval number is No. 2022-36.

Keywords: electrical stimulation, bone strength, osteoclasts, osteoblast, bone mass, cortical bone