RANKL Inhibition in fibrous dysplasia of bone: A preclinical study in a mouse model of the human disease

Abstract

Fibrous Dysplasia of bone/McCune-Albright Syndrome (FD/MAS, OMIM#174800) is a crippling skeletal disease caused by gain-of-function mutations of Gs. Enhanced bone resorption is a recurrent histological feature of FD and a major cause of fragility of affected bones. Previous work suggests that increased bone resorption in FD is driven by RANKL and some studies have shown that the anti-RANKL monoclonal antibody, denosumab, reduces bone turnover and bone pain in FD patients. However, the effect of RANKL inhibition on the histopathology of FD and its impact on the natural history of the disease remain to be assessed. In this study, we treated the EF1-Gs R201C mice, which develop an FD-like phenotype, with an anti-mouse RANKL monoclonal antibody. We found that the treatment induced marked radiographic and microscopic changes at affected skeletal sites in twomonth-old mice. The skeletal segments involved became sclerotic due to the deposition of new, highly mineralized bone within developing FD lesions and showed a higher mechanical resistance compared to affected segments from untreated transgenic mice. Similar changes were also detected in older mice with a full-blown skeletal phenotype. The administration of anti-mouse RANKL antibody arrested the growth of established lesions and, in young mice, prevented the appearance of new ones. However, after drug withdrawal, the newly formed bone was remodeled into FD tissue and the disease progression resumed in young mice. Taken together, our results demonstrate that the anti-RANKL antibody significantly affected the bone pathology and natural history of FD in the mouse. Pending further work on the prevention and management of relapse after treatment discontinuation, our pre-clinical study suggests that RANKL inhibition may be an affective therapeutic option for FD patients.

Negative bias for sad imagery in depression: An ERP study

“…The experimental procedure was adapted from the encoding-retrieval paradigm (Bone et al, 2020), which required participants to first memorize and then recall or imagine (see Figure 1). During encoding, each trial started with a 7-word Chinese title presented for 0.5 seconds, followed by the corresponding image displayed for 4 seconds (with the title remaining above the image).…”