Activating-mutations in NOD-like receptor (NLR) family, pyrin domain-containing 3 (NLRP3) cause neonatal-onset multisystem inflammatory disease. However, the ontogeny of skeletal anomalies in this disorder is poorly understood. Mice globally expressing the D301N mutation in Nlrp3 (D303N in human) model the human phenotype, including systemic inflammation and skeletal deformities. To gain insights into the skeletal manifestations, we generated mice in which the expression of D301N Nlrp3 (Nlrp3( D301N)) is restricted to myeloid cells. These mice exhibit systemic inflammation and severe osteopenia (∼ 60% lower bone mass) similar to mice globally expressing the knock-in mutation, consistent with the paradigm of innate immune-driven cryopyrinopathies. Because systemic inflammation may indirectly affect bone homeostasis, we engineered mice in which Nlrp3( D301N) is expressed specifically in osteoclasts, the cells that resorb bone. These mice also develop ∼ 50% lower bone mass due to increased osteolysis, but there is no systemic inflammation and no change in osteoclast number. Mechanistically, aside from its role in IL-1β maturation, Nlrp3( D301N) expression enhances osteoclast bone resorbing ability through reorganization of actin cytoskeleton while promoting the degradation of poly(ADP-ribose) polymerase 1, an inhibitor of osteoclastogenesis. Thus, NLRP3 inflammasome activation is not restricted to the production of proinflammatory mediators but also leads to cytokine-autonomous responses.

Interaction between parathyroid hormone/parathyroid hormone-related peptide receptor 1 (PTHR1) and low density lipoprotein receptor-related protein 6 (Lrp6) is important for parathyroid hormone (PTH) signaling and anabolic action. Since N-cadherin has been shown to negatively regulate canonical Wnt/β-catenin signaling, we asked whether N-cadherin alters PTH signaling and stimulation of bone formation. Ablation of the N-cadherin gene (Cdh2) in primary osteogenic lineage cells resulted in increased Lrp6/PTHR1 interaction in response to PTH1–34, associated with enhanced PTH-induced PKA signaling and PKA-dependent β-catenin C-terminus phosphorylation, which promotes β-catenin transcriptional activity. β-catenin C-terminus phosphorylation was abolished by Lrp6 knockdown. Accordingly, PTH1–34 stimulation of Tcf/Lef target genes, Lef1 and Axin2, was also significantly enhanced in Cdh2 deficient cells. This enhanced responsiveness to PTH extends to the osteo-anabolic effect of PTH, as mice with a conditional Cdh2 deletion in Osx+ cells treated with intermittent doses of PTH1–34 exhibited significantly larger gains in trabecular bone mass relative to control mice, the result of accentuated osteoblast activity. Therefore, N-cadherin modulates Lrp6/PTHR1 interaction, restraining the intensity of PTH-induced β-catenin signaling, and ultimately influencing bone formation in response to intermittent PTH administration.

SummaryCanonical Wnt (cWnt) signaling through b-catenin regulates osteoblast proliferation and differentiation to enhance bone formation. We previously reported that osteogenic action of b-catenin is dependent on BMP signaling. Here, we further examined interactions between cWnt and BMP in bone. In osteoprogenitors stimulated with BMP2, b-catenin localizes to the nucleus, physically interacts with Smad4, and is recruited to DNA-binding transcription complexes containing Smad4, R-Smad1/5 and TCF4. Furthermore, Tcf/Lef-dependent transcription, Ccnd1 expression and proliferation all increase when Smad4, 1 or 5 levels are low, whereas TCF/Lef activities decrease when Smad4 expression is high. The ability of Smad4 to antagonize transcription of Ccnd1 is dependent on DNA-binding activity but Smad4-dependent transcription is not required. In mice, conditional deletion of Smad4 in osterix + cells increases mitosis of cells on trabecular bone surfaces as well as in primary osteoblast cultures from adult bone marrow and neonatal calvaria. By contrast, ablation of Smad4 delays differentiation and matrix mineralization by primary osteoblasts in response to Wnt3a, indicating that loss of Smad4 perturbs the balance between proliferation and differentiation in osteoprogenitors. We propose that Smad4 and Tcf/Lef transcription complexes compete for b-catenin, thus restraining cWnt-dependent proliferative signals while favoring the matrix synthesizing activity of osteoblasts.

BackgroundSince 2012, The World Health Organization and UNICEF have advocated for community health workers (CHWs) to be trained in Integrated Community Case Management (iCCM) of common childhood illnesses, such as pneumonia. Despite the effectiveness of iCCM, CHWs face many barriers to accessing training. This pilot study compares traditional training with using locally made videos loaded onto low-cost Android tablets to train CHWs on the pneumonia component of iCCM.MethodsWe conducted a pilot randomised controlled trial with CHWs in the Mukono District of Uganda. The unit of randomisation was the sub-county level, and the unit of analysis was at the level of the individual CHW. Eligible CHWs had completed basic iCCM training but had not received any refresher training on the pneumonia component of iCCM in the preceding 2 years. CHWs in the control group received training in the recognition, treatment, and prevention of pneumonia as it is currently delivered, through a 1-day, in-person workshop. CHWs allocated to the intervention group received training via locally made educational videos hosted on low-cost Android tablets. The primary outcome was change in knowledge acquisition, assessed through a multiple choice questionnaire before and after training, and a post-training clinical assessment. The secondary outcome was a qualitative evaluation of CHW experiences of using the tablet platform.ResultsIn the study, 129 CHWs were enrolled, 66 and 63 in the control and intervention groups respectively. CHWs in both groups demonstrated an improvement in multiple choice question test scores before and after training; however, there was no statistically significant difference in the improvement between groups (t = 1.15, p = 0.254). There was a statistically significant positive correlation (Pearson’s r = 0.26, p = 0.03) linking years of education to improvement in test scores in the control group, which was not present in the intervention group. The majority of CHWs expressed satisfaction with the use of tablets as a training tool; however, some reported technical issues (n = 9).ConclusionTablet-based training is comparable to traditional training in terms of knowledge acquisition. It also proved to be feasible and a satisfactory means of delivering training to CHWs. Further research is required to understand the impacts of scaling such an intervention.Trial registrationRegistered on 23/11/2016 at clinicaltrials.gov (NCT02971449).Electronic supplementary materialThe online version of this article (10.1186/s12960-018-0315-7) contains supplementary material, which is available to authorized users.

IMPORTANCE Previous studies suggest that race or ethnicity may be associated with risk for developing retinopathy of prematurity (ROP). Little is known about how socioeconomic factors mediate the relationship between race or ethnicity and ROP outcomes.OBJECTIVE To evaluate how socioeconomic factors, in the context of race and ethnicity, are associated with ROP outcomes. DESIGN, SETTING, AND PARTICIPANTSThis retrospective cohort study used US Census Bureau income data and electronic medical records from neonatal intensive care units at 4 hospitals,