MicroRNAs emerge as critical post-transcriptional regulators in bone metabolism. We have previously reported in vitro that miR-21 promotes osteogenesis, while studies have also revealed miR-21 as a regulator of osteoclastogenesis and a promoter of osteoclast differentiation in vitro. However, in vivo data are still lacking in identifying skeletal function of miR-21, particularly its effects on osteoporosis. Here, using miR-21 knockout (miR-21−/−) mice, we investigated effects of miR-21 on bone development, bone remodeling and bone loss. Unexpectedly, miR-21−/− mice demonstrated normal skeletal phenotype in development and maintained osteoblastogenesis in vivo. Besides, miR-21−/− mice showed increased receptor activator of nuclear factor κB ligand (RANKL) and decreased osteoprotegerin (OPG) through miR-21 targeting Sprouty 1 (Spry1). Nevertheless, interestingly, miR-21 deficiency promoted trabecular bone mass accrual physiologically. Furthermore, in pathological states, the protection of bone mass was prominent in miR-21−/− mice. These skeletal effects were attributed to inhibition of bone resorption and osteoclast function by miR-21 deficiency through miR-21 targeting programmed cell death 4 (PDCD4), despite the existence of RANKL. As far as we know, this is the first in vivo evidence of a pro-osteoclastic microRNA. Together, these findings clarified function of miR-21 in bone metabolism, particularly uncovering osteo-protective potential of miR-21 inactivation in osteoporosis.

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Colon cancer is a major health problem worldwide. While chemotherapy remains a main approach for treating late-stage colon cancer patients, most, if not all, of them will develop drug resistance and die of uncontrollable disease progression eventually. Therefore, identification of mechanism of drug resistance and development of overcoming strategy hold great significance in management of colon cancer. In this study, we discovered that activation of the PERK branch of the unfolded protein response (UPR) pathways is required for colon cancer cells to survive treatment of 5-Fluorouracil (5-FU), one of the first-line chemotherapeutics for late-stage colon cancer patients. Genetic and pharmacological inhibition of PERK or its downstream factors greatly sensitize colon cancer cells to 5-FU. Most importantly, in vivo use of PERK inhibitor synergizes with 5-FU in suppressing the growth of colon cancer cells in mouse models. In summary, our findings established a promising way to overcome resistance to chemotherapy in colon cancer.

Type VII secretion systems (T7SSs) are found in many disease related bacteria including Mycobacterium tuberculosis (Mtb). ESX-1 [early secreted antigen 6 kilodaltons (ESAT-6) system 1] is one of the five subtypes (ESX-1∼5) of T7SSs in Mtb, where it delivers virulence factors into host macrophages during infection. However, little is known about the molecular details as to how this occurs. Here, we provide high-resolution crystal structures of the C-terminal ATPase 3 domains of EccC subunits from four different Mtb T7SS subtypes. These structures adopt a classic RecA-like ɑ/β fold with a conserved Mg-ATP binding site. The structure of EccCb1 in complex with the C-terminal peptide of EsxB identifies the location of substrate recognition site and shows how the specific signaling module "LxxxMxF" for Mtb ESX-1 binds to this site resulting in a translation of the bulge loop. A comparison of all the ATPase 3 structures shows there are significant differences in the shape and composition of the signal recognition pockets across the family, suggesting that distinct signaling sequences of substrates are required to be specifically recognized by different T7SSs. A hexameric model of the EccC-ATPase 3 is proposed and shows the recognition pocket is located near the central substrate translocation channel. The diameter of the channel is ∼25-Å, with a size that would allow helix-bundle shaped substrate proteins to bind and pass through. Thus, our work provides new molecular insights into substrate recognition for Mtb T7SS subtypes and also a possible transportation mechanism for substrate and/or virulence factor secretion.

Background We aimed to investigate the functions and underlying mechanism of lncRNA SNHG1 in bone differentiation and angiogenesis in the development of osteoporosis. Methods The differential gene or proteins expressions were measured by qPCR or western blot assays, respectively. The targeted relationships among molecular were confirmed through luciferase reporter, RIP and ChIP assays, respectively. Alkaline phosphatase (ALP), alizarin red S (ARS) and TRAP staining were performed to measure the osteoblast/osteoclast differentiation of BMSCs. The viability, migration and angiogenesis in BM-EPCs were validated by CCK-8, clone formation, transwell and tube formation assays, respectively. Western blot and immunofluorescence detected the cytosolic/nuclear localization of β-catenin. Ovariectomized (OVX) mice were established to confirm the findings in vitro. Results SNHG1 was enhanced and miR-181c-5p was decreased in serum and femoral tissue from OVX mice. SNHG1 directly inhibited miR-181c-5p to activate Wnt3a/β-catenin signaling by upregulating SFRP1. In addition, knockdown of SNHG1 promoted the osteogenic differentiation of BMSCs by increasing miR-181c-5p. In contrast, SNHG1 overexpression advanced the osteoclast differentiation of BMSCs and inhibited the angiogenesis of BM-EPCs, whereas these effects were all reversed by miR-181c-5p overexpression. In vivo experiments indicated that SNHG1 silencing alleviated osteoporosis through stimulating osteoblastogenesis and inhibiting osteoclastogenesis by modulating miR-181c-5p. Importantly, SNHG1 could be induced by SP1 in BMSCs. Conclusions Collectively, SP1-induced SNHG1 modulated SFRP1/Wnt/β-catenin signaling pathway via sponging miR-181c-5p, thereby inhibiting osteoblast differentiation and angiogenesis while promoting osteoclast formation. Further, SNHG1 silence might provide a potential treatment for osteoporosis. Graphic abstract

To compare magnetic resonance (MR) imaging, computed tomography (CT) and radiography for the detection of arthropathies in patients with haemophilia. Forty-one symptomatic joints in 14 men with haemophilia, ages 11-24 years (mean age 17.5 +/- 3.9 years) were examined with radiography, CT and MR. Images of each joint were acquired on the same day. The precontrast MR examination obtained coronal spin-echo T1 images and gradient echo with rephasing T2* images, as well as sagittal, axial gradient echo with rephasing T2* images using a low-field-strength 0.3-T MR imager. For the postcontrast MR examination, coronal, sagittal and axial images were acquired using the same precontrast T1 sequence. Thirteen joints were also examined on enhanced MR. The severity of damage was classified using conventional radiographical staging. Severely affected haemophilic arthropathy (HA) patients (stage 5) were excluded. Findings of soft tissue swelling, osteoporosis, epiphyseal overgrowth, joint erosion, cysts, joint space narrowing, bone marrow oedema, joint effusion, haemorrhage, synovial hypertrophy and widened intercondylar notches as well as anterior and posterior cruciate ligaments (for the knee) were used in all imaging comparisons. The joints were classified by radiographical criteria into stage 0 (n = 5), stage 1 (n = 7), stage 2 (n = 6), stage 3 (n = 8) and stage 4 (n = 15). Soft tissue swelling or joint effusion was observed in 33 joints on radiographs, in 34 on both CT and MR; joint erosions were observed in 34 joints on MR, 33 on CT and 20 on radiographs. Joint cysts appeared in 21 joints on MR, 18 on CT and 9 on radiographs. Significant differences in detection of erosion and cysts were found between radiography and CT (P < 0.05) and radiography and MR imaging (P < 0.05), not between CT and MR (P > 0.05). MR was better for detecting foci of both erosion and cysts than CT and radiography, and CT was better than radiography. MR imaging, CT and radiography were equally effective in showing the changes of epiphyseal overgrowth in 26 joints, joint space narrowing in 14 joints and widened intercondylar notches in 20 knee joints. However, only MR imaging detected tears in 17 anterior and 13 posterior cruciate ligaments in the 20 knee joints with widened intercondylar notches. Bone marrow oedema in 14 joints, haemorrhage in 34 joints and synovial hypertrophy in 27 joints were seen on MR images, but not on CT or radiography. MR imaging is superior to CT and conventional radiography for detecting abnormal changes and should be considered the first choice among imaging modalities in evaluating HAs.

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Our knowledge in how extracellular vesicles (EVs) are secreted from cells remains inadequate due to the limited technologies available for visualizing them in situ. We report a pH-reversible boron dipyrromethene (BODIPY) fluorescent probe for confocal imaging of EVs secreted from living cells without inducing severe cytotoxicity. This probe predominantly assumes a non-fluorescent leuco-BODIPY form under basic conditions, but it gradually switches to its fluorescent parent BODIPY form upon acidification; such pH transition empowers the imaging of acidic EVs (such as CD81-enriched exosomes and extracellular multivesicular bodies) in weakly basic culture medium and intracellular acidic precursor EVs in weakly basic cytoplasm, with minimal false positive signals frequently encountered for “always-on” dyes. Joint application of this probe with plasmid transfection reveals the secretion of some EVs from cellular pseudopodia via microtubule trackways. This probe may provide mechanistic insights into the extracellular transport of EVs and support the development of EV-based nanomedicines.