Bone Lining Cells Could Be Sources of Bone Marrow Adipocytes

BackgroundRecently, lineage-tracing studies demonstrated that parathyroid hormone and anti-sclerostin antibody (Scl-Ab) can convert bone lining cells (BLCs) into active osteoblasts. However, BLCs might also be differentiated into other lineages. Here we investigated whether BLCs could differentiate into bone marrow adipocytes (BMAds) and whether Scl-Ab could suppress this process.MethodsDmp1-CreERt2:mTmG mice were injected with 0.5 mg of 4-hydroxytamoxifen once weekly from postnatal week 4 to week 8. The mice were treated with either vehicle or rosiglitazone for 8 weeks (weeks 12–20). Moreover, they were administered either vehicle or Scl-Ab (50 mg/kg) twice weekly for 4 weeks (weeks 16–20, N = 4–6/group). We chased the GFP+ cells from the endosteal surface to the bone marrow (BM) of the femur. Using immunohistochemical staining, the numbers of perilipin+ or GFP+/perilipin double+ cells in the BM were quantified. In addition, serum N-terminal propeptide of type I procollagen (P1NP) levels were measured at each time point, and bone mass was analyzed at 20 weeks using micro-computed tomography.ResultsScl-Ab administration significantly reversed the decreases in bone parameters induced by rosiglitazone. Plump GFP+ cells, presumably active osteoblasts, and extremely flat GFP+ cells, presumably BLCs, were present on the endosteal surface of the femur at 8 and 12 weeks, respectively, in line with prior findings. When we chased the GFP+ cells, rosiglitazone significantly increased the number of GFP/perilipin double+ BMAds compared to the effects of the vehicle (P < 0.001), and overlapping Scl-Ab administration decreased the number of GFP/perilipin double + BMAd compared to rosiglitazone alone (P < 0.001). In addition, we found that osteoblast lineage cells such as BLCs might express PPARγ on immunohistochemical staining. When rosiglitazone was administered to Rip-Cre:mTmG mice, GFP+ cells were not present on the endosteal surface or in the BM of the femur; however, they were present in the pancreas.ConclusionBLCs could be sources of BMAds, and rosiglitazone could stimulate the differentiation of osteoblast lineage cells into BMAds. Suppression of the differentiation of osteoblast lineage cells into BMAds might contribute to anabolic effects resulting from the pharmacologic inhibition of sclerostin.

BMP1 is Not Required for Lung Fibrosis in Mice

Bone morphogenetic protein 1 (BMP1) belongs to the astacin/BMP1/tolloid-like family of zinc metalloproteinases, which play a fundamental role in the development and formation of extracellular matrix (ECM). BMP1 mediates the cleavage of carboxyl terminal (C-term) propeptides from procollagens, a crucial step in fibrillar collagen fiber formation. Blocking BMP1 by small molecule or antibody inhibitors has been linked to anti-fibrotic activity in the preclinical models of skin, kidney and liver fibrosis. Therefore, we reason that BMP1 may be important for the pathogenesis of lung fibrosis and BMP1 could be a potential therapeutic target for progressive fibrotic disease such as idiopathic pulmonary fibrosis (IPF). Here, we observed the increased expression of BMP1 in both human IPF lungs and mouse fibrotic lungs induced by bleomycin. Furthermore, we developed an inducible Bmp1 conditional knockout (cKO) mouse strain. We found that Bmp1 deletion does not protect mice from lung fibrosis triggered by bleomycin. Moreover, we found no significant impact of BMP1 deficiency upon C-term propeptide of type I procollagen (CICP) production in the fibrotic mouse lungs. Based on these results, we propose that BMP1 is not required for lung fibrosis in mice and BMP1 may not be considered a candidate therapeutic target for IPF.

Predictive and Prognostic Biomarkers for Lung Cancer Bone Metastasis and Their Therapeutic Value

Lung cancer is the leading cause of cancer-related death worldwide. Bone metastasis, which usually accompanies severe skeletal-related events, is the most common site for tumor distant dissemination and detected in more than one-third of patients with advanced lung cancer. Biopsy and imaging play critical roles in the diagnosis of bone metastasis; however, these approaches are characterized by evident limitations. Recently, studies regarding potential biomarkers in the serum, urine, and tumor tissue, were performed to predict the bone metastases and prognosis in patients with lung cancer. In this review, we summarize the findings of recent clinical research studies on biomarkers detected in samples obtained from patients with lung cancer bone metastasis. These markers include the following: (1) bone resorption-associated markers, such as N-terminal telopeptide (NTx)/C-terminal telopeptide (CTx), C-terminal telopeptide of type I collagen (CTx-I), tartrate-resistant acid phosphatase isoform 5b (TRACP-5b), pyridinoline (PYD), and parathyroid hormone related peptide (PTHrP); (2) bone formation-associated markers, including total serum alkaline phosphatase (ALP)/bone specific alkaline phosphatase(BAP), osteopontin (OP), osteocalcin (OS), amino-terminal extension propeptide of type I procollagen/carboxy-terminal extension propeptide of type I procollagen (PICP/PINP); (3) signaling markers, including epidermal growth factor receptor/Kirsten rat sarcoma/anaplastic lymphoma kinase (EGFR/KRAS/ALK), receptor activator of nuclear factor κB ligand/receptor activator of nuclear factor κB/osteoprotegerin (RANKL/RANK/OPG), C-X-C motif chemokine ligand 12/C-X-C motif chemokine receptor 4 (CXCL12/CXCR4), complement component 5a receptor (C5AR); and (4) other potential markers, such as calcium sensing receptor (CASR), bone sialoprotein (BSP), bone morphogenetic protein 2 (BMP2), cytokeratin 19 fragment/carcinoembryonic antigen (CYFRA/CEA), tissue factor, cell-free DNA, long non-coding RNA, and microRNA. The prognostic value of these markers is also investigated. Furthermore, we listed some clinical trials targeting hotspot biomarkers in advanced lung cancer referring for their therapeutic effects.

Reduced Serum Levels of Bone Formation Marker P1NP in Psoriasis

Psoriasis is a chronic inflammatory disease of the skin and joints. More recent data emphasize an association with dysregulated glucose and fatty acid metabolism, obesity, elevated blood pressure and cardiac disease, summarized as metabolic syndrome. TNF-α and IL-17, central players in the pathogenesis of psoriasis, are known to impair bone formation. Therefore, the relation between psoriasis and bone metabolism parameters was investigated. Two serum markers of either bone formation—N-terminal propeptide of type I procollagen (P1NP) or bone resorption—C-terminal telopeptide of type I collagen (CTX-I)—were analyzed in a cohort of patients with psoriasis vulgaris. In patients with psoriasis, P1NP serum levels were reduced compared to gender-, age-, and body mass index-matched healthy controls. CTX-I levels were indistinguishable between patients with psoriasis and controls. Consistently, induction of psoriasis-like skin inflammation in mice decreases bone volume and activity of osteoblasts. Moreover, efficient anti-psoriatic treatment improved psoriasis severity, but did not reverse decreased P1NP level suggesting that independent of efficient skin treatment psoriasis did affect bone metabolism and might favor the development of osteoporosis. Taken together, evidence is provided that bone metabolism might be affected by psoriatic inflammation, which may have consequences for future patient counseling and disease monitoring.

Genetic regulation of myocardial fibrosis in hypertrophic cardiomyopathy

Background Myocardial fibrosis is a common feature of hypertrophic cardiomyopathy (HCM) but its pathophysiology has yet to be elucidated. Purpose In this study, we used a multiplex approach to examine the genetic regulation of pathways associated with fibrosis in patients undergoing septal myectomy. Methods Myocardial tissue was collected at time of surgical intervention. Control biopsy samples were obtained from the left ventricular free wall from structurally normal hearts during autopsy following non-cardiac related death. Tissue was either snap frozen in liquid nitrogen and subsequently stored at −80 degrees or collected in RNA laterTM and frozen 24 hours later at −80 degrees. Total RNA was extracted from HCM tissue samples using the Qiagen RNeasy fibrous tissues mini kit and from control samples using mirVana isolation kit (Ambion), according to the manufacturer's protocol. Quantitative PCR (qPCR) was performed on the extracted RNA using a RT. Profiler™ Human finrosis PCR Array. Results The study cohort comprised 22 HCM samples and 5 controls. The relative regulation of genes involved in myocardial fibrosis in patients with HCM compared to controls is shown in figure 1. In patients with HCM, there was increased expression of genes involved in collagen synthesis. A significant two-fold upregulation in type III procollagen mRNA was observed relative to controls (p=0.013) with a similar trend identified for type I procollagen (1.5 fold up-regulation, p=0.081). The gene expression of MMP3 (−1.5 fold, p=0.029) and MMP8 (−1.8, p=0.002) which are involved in collaged degradation were downregulated in the HCM group. The gene expression of pro-fibrotic mediators TGF-β2 (4.8 fold, p=0.008) and CCN2 (2.9 fold, p=0.021) was also significantly elevated. Within the HCM group, there was a correlation between the fold regulation of TGF-β1 (r=0.570, p=0.006; r=0.528, p=0.012), TGF-β2 (r=0.569, p=0.006; r=0.514, p=0.014) and TGF-β3 (r=0.738, p<0.001; r=0.496, p=0.019) to gene regulation of type I and III procollagens respectively. The expression of BMP-7 which has been shown to reduce myocardial fibrosis by antagonising TGF- β mediated endothelial – mesothelial transformation of fibroblasts was also down-regulated in HCM (−3.8, p=0.015). Conclusions Genetic expression of procollagen is significantly upregulated in patients with HCM relative to controls. TGF-β and CCN2 mediated signalling appear to be key mediators in promoting collagen expression. FUNDunding Acknowledgement Type of funding sources: Other. Main funding source(s): Heart Hospital Charitable Grant, UK Figure 1. Gene expression in HCM

Low Serum 25-hydroxyvitamin D Level Does Not Adversely Affect Bone Turnover in Prepubertal Children

Both vitamin D and insulin-like growth factor 1 (IGF-1) play essential roles in bone metabolism and may interact during prepubertal bone accrual. We investigated the association of low serum 25-hydroxyvitamin D (25(OH)D) (<20 ng/mL) with the circulating bone turnover markers, when compared to their interaction with IGF-1. Subjects and Methods: Serum 25(OH)D, IGF-I, P1NP (N-terminal propeptide of type I procollagen), and CTX-1 (C-terminal telopeptide of type I collagen) were measured, and the bone turnover index (BTI) was calculated in 128 healthy children, aged 9–11 years. Results: Mean 25(OH)D concentration was 21.9 ± 4.9 ng/mL, but in 30.5% of participants it was <20 ng/mL (<50 nmol/L). We observed a trend for higher P1NP (p < 0.05) and IGF-1 (p = 0.08), towards lower 25(OH)D in tertiles. Levels of P1NP in the lowest 25(OH)D tertile (<20 ng/mL) were the highest, while CTX and BTI remained unchanged. Additionally, 25(OH)D negatively correlated with IGF-1, while the correlation with P1NP was not significant. A strong positive correlation of IGF-1 with P1NP and BTI but weak with CTX was observed. Low 25(OH)D (<20 ng/mL) explained 15% of the IGF-1 variance and 6% of the P1NP variance. Conclusions: Low levels of 25(OH)D do not unfavorably alter bone turnover. It seems that serum 25(OH)D level may not be an adequate predictor of bone turnover in children.

Endoplasmic reticulum tubules limit the size of misfolded protein condensates

The endoplasmic reticulum (ER) is composed of sheets and tubules. Here we report that the COPII coat subunit, SEC24C, works with the long form of the tubular ER-phagy receptor, RTN3, to target dominant-interfering mutant proinsulin Akita puncta to lysosomes. When the delivery of Akita puncta to lysosomes was disrupted, large puncta accumulated in the ER. Unexpectedly, photobleach analysis indicated that Akita puncta behaved as condensates and not aggregates, as previously suggested. Akita puncta enlarged when either RTN3 or SEC24C were depleted, or when ER sheets were proliferated by either knocking out Lunapark or overexpressing CLIMP63. Other ER-phagy substrates that are segregated into tubules behaved like Akita, while a substrate (type I procollagen) that is degraded by the ER-phagy sheets receptor, FAM134B, did not. Conversely, when ER tubules were augmented in Lunapark knock-out cells by overexpressing reticulons, ER-phagy increased and the number of large Akita puncta was reduced. Our findings imply that segregating cargoes into tubules has two beneficial roles. First, it localizes mutant misfolded proteins, the receptor, and SEC24C to the same ER domain. Second, physically restraining condensates within tubules, before they undergo ER-phagy, prevents them from enlarging and impacting cell health.

IGFBP7 and GDF-15, but not P1NP, are associated with cardiac alterations and 10-year outcome in an elderly community-based study

Background Little is known about the clinical value of Insulin-like growth factor-binding protein-7 (IGFBP7), a cellular senescence marker, in an elderly general population with multiple co-morbidities and high prevalence of asymptomatic cardiovascular ventricular dysfunction. Inflammation and fibrosis are hallmarks of cardiac aging and remodelling. Therefore, we assessed the clinical performance of IGFBP7 and two other biomarkers reflecting these pathogenic pathways, the growth differentiation factor-15 (GFD-15) and amino-terminal propeptide of type I procollagen (P1NP), for their association with cardiac phenotypes and outcomes in the PREDICTOR study. Methods 2001 community-dwelling subjects aged 65–84 years who had undergone centrally-read echocardiography, were selected through administrative registries. Atrial fibrillation (AF) and 4 echocardiographic patterns were assessed: E/e’ (> 8), enlarged left atrial area, left ventricular hypertrophy (LVH) and reduced midwall circumference shortening (MFS). All-cause and cardiovascular mortality and hospitalization were recorded over a median follow-up of 10.6 years. Results IGFBP7 and GDF-15, but not P1NP, were independently associated with prevalent AF and echocardiographic variables after adjusting for age and sex. After adjustment for clinical risk factors and cardiac patterns or NT-proBNP and hsTnT, both IGFBP7 and GDF-15 independently predicted all-cause mortality, hazard ratios 2.13[1.08–4.22] and 2.03[1.62–2.56] per unit increase of Ln-transformed markers, respectively. Conclusions In a community-based elderly cohort, IGFBP7 and GDF-15 appear associated to cardiac alterations as well as to 10-year risk of all-cause mortality.

Bone Metabolism and RANKL/OPG Ratio in Rheumatoid Arthritis Women Treated with TNF-α Inhibitors

The aim of this study was to evaluate the effect of anti-tumor necrosis factor α (anti-TNF-α) therapy in combination with methotrexate on bone remodeling and osteoclastogenesis in female patients with RA. Serum levels of bone turnover markers (i.e., C- and N-terminal propeptides of type I procollagen (PICP and PINP), C- and N-terminal cross-linking telopeptides of type I collagen (CTX-I and NTX-I), and soluble receptor activator of nuclear factor κB ligand (sRANKL) and osteoprotegerin (OPG)) were determined by immunoassay at baseline and 15 months after initiation of treatment. Bone mineral density was measured by dual-energy x-ray absorptiometry. We found a significant decrease in serum PINP levels, a biomarker of bone formation, and higher levels of CTX-I and sRANKL indicative of increased bone resorption in RA patients prior to TNFαI treatment compared to the controls. Anti-TNF-α therapy was effective in improving bone metabolism in RA patients as reflected in a decrease in CTX-I (at least partially due to the RANKL/OPG reduction) and a concomitant increase in PINP levels. The bone metabolism changes were independent of the type of TNFαI used. PINP and CTX-I were found to be useful markers of bone metabolism, which may prove the effectiveness of TNF-α therapy earlier than the bone density assessment.