A novel osteoporosis model with ascorbic acid deficiency in Akr1A1 gene knockout mice

// Cheng-Wei Lai 1,2,* , Hsiao-Ling Chen 3,* , Min-Yu Tu 1,4,5 , Wei-Yu Lin 1,2 , Theresa Röhrig 1,2 , Shang-Hsun Yang 6 , Ying-Wei Lan 1,7 , Kowit-Yu Chong 7,8 and Chuan-Mu Chen 1,2,9 1 Department of Life Sciences, National Chung Hsing University, Taichung, Taiwan 2 Agricultural Biotechnology Center, National Chung Hsing University, Taichung, Taiwan 3 Department of Bioresources, Da-Yeh University, Changhua, Taiwan 4 Department of Orthopaedic Surgery, Taichung Armed Forces General Hospital, Taichung, Taiwan and National Defense Medical Center, Taipei, Taiwan 5 Department of Biomedical Engineering, Hungkuang University, Taichung, Taiwan 6 Department of Physiology and Institute of Basic Medical Sciences, National Cheng Kung University, Tainan, Taiwan 7 Department of Medical Biotechnology and Laboratory Science, College of Medicine, Chang Gung University, Tao-Yuan, Taiwan 8 Department of Thoracic Medicine, Chang Gung Memorial Hospital at Linkou, Tao-Yuan, Taiwan 9 Rong-Hsing Translational Medicine Center, and iEGG Center, National Chung Hsing University, Taichung, Taiwan * These authors have contributed equally to this study Correspondence to: Chuan-Mu Chen, email: // Kowit-Yu Chong, email: // Keywords : osteoporosis; Akr1A1 gene; ascorbic acid; knockout mice; micro-CT imaging; trabecular bone; cortical bone; Pathology Section Received : August 13, 2016 Accepted : December 07, 2016 Published : January 02, 2017 Abstract The AKR1A1 protein is a member of the aldo-keto reductase superfamily that is responsible for the conversion of D-glucuronate to L-gulonate in the ascorbic acid (vitamin C) synthesis pathway. In a pCAG-eGFP transgenic mouse line that was produced by pronuclear microinjection, the integration of the transgene resulted in a 30-kb genomic DNA deletion, including the Akr1A1 gene, and thus caused the knockout (KO) of the Akr1A1 gene and targeting of the eGFP gene. The Akr1A1 KO mice ( Akr1A1 eGFP/eGFP ) exhibited insufficient serum ascorbic acid levels, abnormal bone development and osteoporosis. Using micro-CT analysis, the results showed that the microarchitecture of the 12-week-old Akr1A1 eGFP/eGFP mouse femur was shorter in length and exhibited less cortical bone thickness, enlargement of the bone marrow cavity and a complete loss of the trabecular bone in the distal femur. The femoral head and neck of the proximal femur also showed a severe loss of bone mass. Based on the decreased levels of serum osteocalcin and osteoblast activity in the Akr1A1 eGFP/eGFP mice, the osteoporosis might be caused by impaired bone formation. In addition, administration of ascorbic acid to the Akr1A1 eGFP/eGFP mice significantly prevented the condition of osteoporotic femurs and increased bone formation. Therefore, through ascorbic acid administration, the Akr1A1 KO mice exhibited controllable osteoporosis and may serve as a novel model for osteoporotic research.