17β‐Estradiol Maintains Mitochondrial Homeostasis in Osteoblasts by Inhibiting MMP ‐8 and Activating the Ras Signaling Pathway in Postmenopausal Osteoporosis

ABSTRACT 17β‐estradiol is a potent endogenous estrogen used for postmenopausal osteoporosis treatment. Its osteoprotective role correlates with matrix metalloproteinase (MMP) and mitochondrial homeostasis. This research sought to examine the role of 17β‐estradiol on MMP‐8 in mitochondrial homeostasis and elucidate the potential regulatory pathways. We evaluated the effects of 17β‐estradiol on MMP‐8, bone loss, osteogenic differentiation, and mitochondrial homeostasis in bilateral ovariectomy (OVX)‐induced mice and MC3T3‐E1 cells. MMP‐8 was overexpressed to validate its regulatory relationship with 17β‐estradiol. Comprehensive analyses were further conducted to identify the potential pathways associated with MMP‐8. The Ras pathway agonist ML‐099 and inhibitor Lonafarnib were used for pathway validation. 17β‐estradiol treatment attenuated bone loss and increased osteogenic Ca 2+ , osteoprotegerin (OPG), and osteocalcin (OC) levels. It inhibited reactive oxygen species (ROS) and malondialdehyde (MDA), promoted superoxide dismutase (SOD) activity, and restored mitochondrial homeostasis via upregulating the expression of dynamin‐related protein 1 (DRP1), mitofusin 1 (MFN1), and peroxisome proliferator‐activated receptor γ coactivator 1 alpha (PGC‐1α), accompanied by increased adenosine triphosphate (ATP), mitochondrial membrane potential, and mitochondrial oxygen consumption. MMP‐8 overexpression significantly reversed these protective effects. The Ras pathway was identified as a potential pathway associated with MMP‐8‐mediated osteoporosis regulation. ML‐099 administration in 17β‐estradiol + MMP‐8 overexpression cells markedly restored mitochondrial homeostasis and rescued osteogenic differentiation. Conversely, the adverse impacts of MMP‐8 overexpression on osteoblast differentiation, mitochondrial homeostasis, and Ras activation were further aggravated by Lonafarnib treatment. 17β‐estradiol maintains mitochondrial homeostasis in osteoblasts via inhibiting MMP‐8 and activating the Ras pathway, which provides novel potential targets for postmenopausal osteoporosis management.