Cell-Free Fat Extract Prevents Tail Suspension-Induced Bone Loss by Inhibiting Osteocyte Apoptosis

Mingming Xu; Jingke Du; Junqi Cui; Shuangyan Zhang; Shuhong Zhang; Mingwu Deng; Wenjie Zhang; Hanjun Li; Zhifeng Yu

doi:10.3389/fbioe.2022.818572

Cell-Free Fat Extract Prevents Tail Suspension-Induced Bone Loss by Inhibiting Osteocyte Apoptosis

Front Bioeng Biotechnol. 2022 Jan 28:10:818572. doi: 10.3389/fbioe.2022.818572. eCollection 2022.

Authors

Mingming Xu¹, Jingke Du^{1

2}, Junqi Cui³, Shuangyan Zhang¹, Shuhong Zhang¹, Mingwu Deng⁴, Wenjie Zhang⁴, Hanjun Li^{1

5}, Zhifeng Yu¹

Affiliations

¹ Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth Peoples Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
² Knee Surgery Department of the Institute of Sports Medicine, Beijing Key Laboratory of Sports Injuries, Peking University Third Hospital, Beijing, China.
³ Department of Pathology, Shanghai Ninth Peoples Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
⁴ Shanghai Key Laboratory of Tissue Engineering, Department of Plastic and Reconstructive Surgery, Shanghai Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.
⁵ Clinical Stem Cell Research Center, Ren Ji Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China.

Abstract

Introduction: As the space field has developed and our population ages, people engaged in space travel and those on prolonged bed rest are at increasing risk for bone loss and fractures. Disuse osteoporosis occurs frequently in these instances, for which the currently available anti-osteoporosis agents are far from satisfactory and have undesirable side effects. CEFFE is a cell-free fraction isolated from nanofat that is enriched with a variety of growth factors, and we aim to investigate its potential therapeutic effects on disuse osteoporosis. Methods: A tail suspension-induced osteoporosis model was applied in this study. Three weeks after tail suspension, CEFFE was intraperitoneally injected, and PBS was used as a control. The trabecular and cortical bone microstructures of the tibia in each group were assessed by μCT after 4 weeks of administration. Osteocyte lacunar-canalicularity was observed by HE and silver staining. In vitro, MLO-Y4 cell apoptosis was induced by reactive oxygen species (ROSUP). TUNEL staining and flow cytometry were used to detect apoptosis. CCK-8 was used to detect cell proliferation, and Western blotting was used to detect MAPK signaling pathway changes. Results: CEFFE increased the bone volume (BV/TV) and trabecular number (Tb.N) of the trabecular bone and increased the thickness of the cortical bone. HE and silver staining results showed that CEFFE reduced the number of empty lacunae and improved the lacuna-canalicular structure. CEFFE promoted osteocyte proliferative capacity in a dose-dependent manner. CEFFE protected MLO-Y4 from apoptosis by activating the serine/threonine-selective protein kinase (ERK) signaling pathways. Conclusion: CEFFE attenuated immobilization-induced bone loss by decreasing osteocyte apoptosis. CEFFE increased the survival of osteocytes and inhibited osteocyte apoptosis by activating the ERK signaling pathway in vitro.

Keywords: ERK signaling pathway; apoptosis; cell-free fat extract; hind limb; lacunar-canalicular system; osteocyte; osteoporosis.