Suppression of Sclerostin Alleviates Radiation‐Induced Bone Loss by Protecting Bone‐Forming Cells and Their Progenitors Through Distinct Mechanisms

Focal radiotherapy is frequently associated with skeletal damage within the radiation field. Our previous in vitro study showed that activation of Wnt/β‐catenin pathway can overcome radiation‐induced DNA damage and apoptosis of osteoblastic cells. Neutralization of circulating sclerostin with a monoclonal antibody (Scl‐Ab) is an innovative approach for treating osteoporosis by enhancing Wnt/β‐catenin signaling in bone. Together with the fact that focal radiation increases sclerostin amount in bone, we sought to determine whether weekly treatment with Scl‐Ab would prevent focal radiotherapy‐induced osteoporosis in mice. Micro‐CT and histomorphometric analyses demonstrated that Scl‐Ab blocked trabecular bone structural deterioration after radiation by partially preserving osteoblast number and activity. Consistently, trabecular bone in sclerostin null mice was resistant to radiation via the same mechanism. Scl‐Ab accelerated DNA repair in osteoblasts after radiation by reducing the number of γ‐H2AX foci, a DNA double‐strand break marker, and increasing the amount of Ku70, a DNA repair protein, thus protecting osteoblasts from radiation‐induced apoptosis. In osteocytes, apart from using similar DNA repair mechanism to rescue osteocyte apoptosis, Scl‐Ab restored the osteocyte canaliculi structure that was otherwise damaged by radiation. Using a lineage tracing approach that labels all mesenchymal lineage cells in the endosteal bone marrow, we demonstrated that radiation damage to mesenchymal progenitors mainly involves shifting their fate to adipocytes and arresting their proliferation ability but not inducing apoptosis, which are different mechanisms from radiation damage to mature bone forming cells. Scl‐Ab treatment partially blocked the lineage shift but had no effect on the loss of proliferation potential. Taken together, our studies provide proof‐of‐principle evidence for a novel use of Scl‐Ab as a therapeutic treatment for radiation‐induced osteoporosis and establish molecular and cellular mechanisms that support such treatment. © 2016 American Society for Bone and Mineral Research.     

Notch signalling suppresses regulatory T‐cell function in murine experimental autoimmune uveitis

Autoimmune uveitis is an intraocular inflammatory disorder in developed countries. Understanding the mechanisms underlying the development and modulation of immune reaction in uveitic eyes is critical for designing therapeutic interventions. Here we investigated the role of Notch signalling in regulatory T‐cell (Treg cell) function during experimental autoimmune uveitis (EAU). Using the Foxp3‐GFP reporter mouse strain, the significance of Notch signalling for the function of infiltrating Treg cells was characterized in an EAU model. We found that infiltrating Treg cells substantially expressed Notch‐1, Notch‐2, JAG1 and DLL1 in uveitic eyes. Activation of Notch signalling, represented by expression of HES1 and HES5, was enhanced in infiltrating Treg cells. Treatment with JAG1 and DLL1 down‐regulated Foxp3 expression and immunosuppressive activity of isolated infiltrating Treg cells in vitro, whereas neutralizing antibodies against JAG1 and DLL1 diminished Notch ligand‐mediated negative effects on Treg cells. To investigate the significance of Notch signalling for Treg cell function in vivo, lentivirus‐derived Notch short hairpin RNAs were transduced into in vitro expanded Treg cells before adoptive transfer of Treg cells into EAU mice. Transfer of Notch‐1‐deficient Treg cells remarkably reduced pro‐inflammatory cytokine production and inflammatory cell infiltration in uveitic eyes. Taken together, Notch signalling negatively modulates the immunosuppressive function of infiltrating Treg cells in mouse EAU.     

The prevalence and characteristics of obstructive sleep apnea in hospitalized patients with type 2 diabetes in China

Data on the prevalence of obstructive sleep apnea in subjects with type 2 diabetes mellitus in China is scarce. We conducted a multi‐centre, cross‐sectional study involving 12 hospitals from six regional cities to investigate the prevalence of obstructive sleep apnea in hospitalized patients with type 2 diabetes mellitus and to explore the association between obstructive sleep apnea and related risk factors, diabetic complications and comorbidities in China. Each hospital recruited at least 70 consecutive patients with type 2 diabetes mellitus who were admitted to the endocrinology ward. A total of 880 participants were enrolled and administered overnight sleep monitoring with a portable monitor (ApneaLink^?, ResMed, San Diego, CA, USA); other information was collected from medical charts and a standardized questionnaire. In this study, 60.0% (95% confidence interval: 56.8%, 63.2%) of hospitalized patients in China with type 2 diabetes mellitus had comorbid obstructive sleep apnea (apnea–hypopnea index ≥ 5). Only 1.5% (eight of 528) of the patients with both conditions had been diagnosed previously with obstructive sleep apnea. The prevalence of moderate–severe (apnea–hypopnea index ≥ 15) and severe obstructive sleep apnea (apnea–hypopnea index ≥ 30) was estimated to be 25.6% (22.7, 28.5%) and 10.3% (8.3, 12.4%), respectively. Age, sex, body mass index, snoring, reported breath‐holding in sleep or gasping or choking arousal, sleepiness, diabetes duration, hypertension, diabetic nephropathy and cardiovascular diseases history were correlated significantly with the severity of obstructive sleep apnea. In China, the prevalence of obstructive sleep apnea in hospitalized patients with type 2 diabetes mellitus is high. Routine screening for and treatment of obstructive sleep apnea is an important, but often neglected, part of the management of diabetes.     

The spectrum of BRCA mutations and characteristics of BRCA‐associated breast cancers in China: Screening of 2,991 patients and 1,043 controls by next‐generation sequencing

To characterize the prevalence of BRCA mutations and characteristics of BRCA carriers in China and to update the clinical recommendations for BRCA testing, we conducted a wide screen for BRCA mutations using next‐generation sequencing (NGS). A total of 4,034 Chinese subjects were screened for germline BRCA1/2 mutations, including 2,991 breast cancer patients and 1,043 healthy individuals from the community enrolled as controls. We developed an NGS‐based approach to perform BRCA1/2 screening. BRCA mutations were identified in 9.1% (232/2,560) of cases with at least one risk factor, in 3.5% (15/431) of sporadic patients and in 0.38% (4/1,043) of healthy controls. The mutation frequency ranged from 8.9 to 15.2% in cohorts with a single risk factor to 16.6–100% in groups with multiple risk factors. We identified 70 novel BRCA mutations. A high frequency of BRCA1 c.5470_5477del was detected, accounting for 13.9% (16/115) of the BRCA1 mutations detected in our study. Clinical characteristics such as family history, invasive carcinoma, negative human epidermal growth factor receptor 2 (HER2), high Ki67 index, lymph node status, and high tumour grade were closely related to BRCA mutations. BRCA2 carriers had poorer disease‐free survival among HER2‐ or hormone receptor‐positive patients (hazard ratio = 1.892; 95% confidence interval: 1.132–3.161; p = 0.013). This study shows that BRCA mutation carriers could be frequently identified among breast cancer patients with multiple risk factors. Importantly, we established an NGS‐based pipeline for BRCA1/2 testing in clinical practice and strongly suggest that breast cancer patients of premier‐ and moderate‐grade risks receive BRCA1/2 mutations testing in China.