Previously, we reported that (−)-epigallocatechin-3-gallate (EGCG), a green tea polyphenol, increased the osteogenic differentiation of murine bone marrow mesenchymal stem cells by increasing the messenger RNA expression of osteogenesis-related genes, alkaline phosphatase activity, and, eventually, mineralization. The present study further investigated the effects of EGCG on bone microstructure change and possible mechanisms in ovariectomy (OVX)–induced osteopenic rats.
Rats subjected to OVX were administered EGCG systemically for 12 weeks. Proximal tibial bone mineral densities before and after treatment were compared between groups. Changes in the microarchitecture of both the proximal tibia and the third lumbar spine were compared between EGCG-treated and nontreated groups using micro-CT (μCT). Bone histology and immunohistochemistry in the proximal tibia were evaluated.
Results showed that EGCG 3.4 mg/kg/day (estimated peak serum concentration, 10 μmol/L) hampered the decrease in bone mineral density (from 7.97% to 3.96%) and improved the parameters of μCT measurements, including bone volume (from 18% to 27%), trabecular thickness (from 0.17 to 0.22 mm), trabecular number (from 1.13 to 1.37 mm−1), and trabecular separation (from 0.91 to 0.69 mm), compared with nontreated ovariectomized rats. Similar improvements in bone volume (from 30% to 49%) and trabecular thickness (from 0.14 to 0.26 mm) were also found in the third lumbar spine. Bone volume in the tibial cortex also increased after EGCG treatment (from 9% to 28%). A higher trabecular number and greater trabecular volume were also seen in histology, further confirming the results of μCT. The immunolocalized bone morphogenetic protein 2 brown-stained area increased from 31% in the OVX group to 53% in the OVX + 10 EGCG group (P < 0.01). Serial biochemistry data revealed no significant systemic toxic effect of EGCG.
Intraperitoneal treatment with EGCG 3.4 mg/kg/day for 3 months can mitigate bone loss and improve bone microarchitecture in ovariectomized rats, and increased expression of bone morphogenetic protein 2 may contribute to this effect.
From the 1Department of Orthopedics, College of Medicine, Faculty of Medicine, 2Orthopedic Research Center, 3Department of Orthopedics, Kaohsiung Medical University Hospital, and 4Graduate Institute of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan; 5Medical Device Innovation Center, 6Skeleton-Joint Research Center, and 7Graduate Institute of Clinical Medicine, College of Medicine, National Cheng Kung University, Tainan, Taiwan; 8Department of Obstetrics and Gynecology, National Cheng Kung University Medical College and Hospital, Tainan, Taiwan; 9Department of Orthopedics, Kaohsiung Municipal Hsiao-Kang Hospital, 10Department of Orthopedics, Kaohsiung Municipal Ta-Tung Hospital, 11Department of Fragrance and Cosmetic Science, and 12Department of Physical Medicine and Rehabilitation, Kaohsiung Municipal Ta-Tung Hospital, Kaohsiung Medical University, Kaohsiung, Taiwan; 13Department of Physical Medicine and Rehabilitation, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan; 14Department of Orthopedic Surgery, University of Virginia, Charlottesville, VA; and 15Department of Physiology, Faculty of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan.
Received July 7, 2012; revised and accepted October 30, 2012.
C.-H.C. and L.K. contributed equally to this work.
Funding/support: This study was supported, in part, by grants (NHRI-EX96-9615EP and NHRI-EX99-9935EI) from the National Health Research Institute of Taiwan.
Financial disclosure/conflicts of interest: None reported.
Address correspondence to: Mei-Ling Ho, PhD, Department of Physiology, College of Medicine, Kaohsiung Medical University, 100 Shih-Chuan First Road, Kaohsiung 807, Taiwan. E-mail: email@example.com; Gwo-Jaw Wang, MD, Skeleton-Joint Research Center, National Cheng Kung University Medical College and Hospital, National Cheng Kung University, 138 Victory Road, Tainan 70428, Taiwan. E-mail: firstname.lastname@example.org