Impaired bone homeostasis in amyotrophic lateral sclerosis mice with muscle atrophy
Authors: Ke Zhu
Chuanyue Wu
Jianxun Yi
Wei Zheng
Jingsong Zhou
Yumei Lai
Jie Fan
Hongli Jiao
Guozhi Xiao
Di Chen
Pingping Song
Yajuan Xiao
Journal: Journal of Biological Chemistry (2015)
Discipline: BIOLOGY & BIOCHEMISTRY
Keywords: Amyotrophic Lateral Sclerosis (ALS) (Lou Gehrig Disease); Bone; Muscle Atrophy; Osteoblast; Osteoclast.
Affiliations: From the Department of Biochemistry and., Department of Molecular Biophysics and Physiology, Rush University Medical Center, Chicago, Illinois 60612., Department of Surgery and., Department of Pathology, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, and., From the Department of Biochemistry and Department of Biology and Shenzhen Key Laboratory of Cell Microenvironment, South University of Science and Technology of China, Shenzhen 518055, China  .

Abstract:  There is an intimate relationship between muscle and bone throughout life. However, how alterations in muscle functions in disease impact bone homeostasis is poorly understood. Amyotrophic lateral sclerosis (ALS) is a neuromuscular disease characterized by progressive muscle atrophy. In this study we analyzed the effects of ALS on bone using the well established G93A transgenic mouse model, which harbors an ALS-causing mutation in the gene encoding superoxide dismutase 1. We found that 4-month-old G93A mice with severe muscle atrophy had dramatically reduced trabecular and cortical bone mass compared with their sex-matched wild type (WT) control littermates. Mechanically, we found that multiple osteoblast properties, such as the formation of osteoprogenitors, activation of Akt and Erk1/2 pathways, and osteoblast differentiation capacity, were severely impaired in primary cultures and bones from G93A relative to WT mice; this could contribute to reduced bone formation in the mutant mice. Conversely, osteoclast formation and bone resorption were strikingly enhanced in primary bone marrow cultures and bones of G93A mice compared with WT mice. Furthermore, sclerostin and RANKL expression in osteocytes embedded in the bone matrix were greatly up-regulated, and β-catenin was down-regulated in osteoblasts from G93A mice when compared with those of WT mice. Interestingly, calvarial bone that does not load and long bones from 2-month-old G93A mice without muscle atrophy displayed no detectable changes in parameters for osteoblast and osteoclast functions. Thus, for the first time to our knowledge, we have demonstrated that ALS causes abnormal bone remodeling and defined the underlying molecular and cellular mechanisms. 

Retracted: No

PubPeer comments:
 Figure 6J appears to have some repeated and overlapping figures, some with a change in magnification, although scale bars seem to be the same. *** ![file] , 
 Dear Dr. Biskrensis, This is Ke Zhu, the first author of this paper. Thank you so much for identifying and let us know this important issue. After careful examination of our data, you are right that these images (Sclerostin and RANKL IHC results) were taken from the same section. We mistakenly picked up the wrong images (RANKL IHC). We are terribly sorry for making such a mistake. We examined our original data and found that there are no marked differences in expression RANKL between the two groups of calvarial bones (i.e., 4-month-old WT and G93A mice). Thus, this situation does not affect the main conclusion of this study. We will contact the journal and see what they advise for us to fix this problem. Kind regards, Ke Zhu , 
 Dear Dr. Biskrensis, We contacted the journal regarding this issue one month ago. However, we have not received the reply yet. We will keep trying. Many thanks again for letting us know this issue in our paper. Ke Zhu ,