Peimine suppresses interleukin­1ß­induced inflammation via MAPK downregulation in chondrocytes.

Osteoarthritis (OA) is the most common type of degenerative joint disease and secreted inflammatory molecules serve a pivotal role in it. Peimine has been reported to have anti­inflammatory activity. In order to investigate the potential therapeutic role of Peimine in OA, mouse articular chondrocytes were treated with IL­1ß and different doses of Peimine in vitro. The data revealed that Peimine not only suppressed IL­1ß­induced production of nitric oxide (NO) and prostaglandin E2, but also reduced the protein levels of inducible NO synthase (iNOS) and cyclooxygenase­2 (COX­2). In addition, Peimine inhibited the IL­1ß­induced mRNA expression of matrix metalloproteinase (MMP)­1, MMP­3, MMP­9, MMP­13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)­4 and ADAMTS­5. Furthermore, Peimine inhibited IL­1ß­induced activation of the mitogen­activated protein kinase (MAPK) pathway. The protective effect of Peimine on IL­1ß­treated chondrocytes was attenuated following activation of the MAPK pathway, as demonstrated by the increased expression levels of MMP­3, MMP­13, ADAMTS­5, iNOS and COX­2 compared with the Peimine group. The in vivo data suggested that Peimine limited the development of OA in the mouse model. In general, the data indicate that Peimine suppresses IL­1ß­induced inflammation in mouse chondrocytes by inhibiting the MAPK pathway, suggesting a promising therapeutic role for Peimine in the treatment of OA.

Corrigendum: Ulinastatin Inhibits Osteoclastogenesis and Suppresses Ovariectomy-Induced Bone Loss by Downregulating uPAR.

[This corrects the article DOI: 10.3389/fphar.2018.01016.].

Ulinastatin Inhibits Osteoclastogenesis and Suppresses Ovariectomy-Induced Bone Loss by Downregulating uPAR.

Recent studies indicate that uPAR acts a crucial part in cell migration and the modulation of bone homeostasis. As a natural serine protease inhibitor, ulinastatin owns the capacity to reduce proinflammatory factors, downregulate the activation of NF-κB and mitogen-activated protein kinases (MAPKs) signaling pathways. Osteoclastogenesis has been demonstrated to be related with low-grade inflammation which involves cell migration, thus we speculate that ulinastatin may have a certain kind of impact on uPAR so as to be a potential inhibiting agent of osteoclastogenesis. In this research, we investigated the role which ulinastatin plays in RANKL-induced osteoclastogenesis both in vivo and in vitro. Ulinastatin inhibited osteoclast formation and bone resorption in a dose-dependent manner in primary bone marrow-derived macrophages (BMMs), and knockdown of uPAR could completely repress the formation of osteoclasts. At the molecular level, ulinastatin suppressed RANKL-induced activation of cathepsin K, TRAP, nuclear factor-κB (NF-κB) and MAPKs, and decreased the expression of uPAR. At the meantime, ulinastatin also decreased the expression of osteoclast marker genes, including cathepsin K, TRAP, RANK, and NFATc1. Besides, ulinastatin prevented bone loss in ovariectomized C57 mice by inhibiting the formation of osteoclasts. To sum up, this research confirmed that ulinastatin has the ability to inhibit osteoclastogenesis and prevent bone loss, and uPAR plays a crucial role in that process. Therefore, ulinastatin could be chosen as an effective alternative therapeutics for osteoclast-related diseases.

Boldine Ameliorates Estrogen Deficiency-Induced Bone Loss via Inhibiting Bone Resorption.

Osteoporosis is an enormous health problem caused by the imbalance between bone resorption and bone formation. The current therapeutic strategies for osteoporosis still have some limitations. Boldine, an alkaloid isolated from Peumus boldus, has been shown to have antioxidant and anti-inflammatory effects in vivo. For the first time, we discover that boldine has a protective effect for the estrogen deficiency-induced bone loss in mice. According to the Micro-CT and histomorphometry assays, boldine conducts this protective effect through inhibiting bone resorption without affecting bone formation in vivo. Moreover, we showed that boldine can inhibit receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclast formation via impairing the AKT signaling pathways, while SC79 (an AKT agonist) partially rescue this effect. In conclusion, our results suggest that boldine can prevent estrogen deficiency-induced osteoporosis by inhibiting osteoclastogenesis. Thus, boldine may be served as a novel therapeutic agent for anti-osteoporotic therapy.

CD146+ skeletal stem cells from growth plate exhibit specific chondrogenic differentiation capacity in vitro.

Skeletal stem cells (SSCs) are a population of progenitor cells which give rise to postnatal skeletal tissues including bone, cartilage and bone marrow stroma, however not to adipose, haematopoietic or muscle tissue. Growth plate chondrocytes exhibit the ability of continuous proliferation and differentiation, which contributes to the continuous physiological growth. The growth plate has been hypothesized to contain SSCs which exhibit a desirable differentiation capacity to generate bone and cartilage. Due to the heterogeneity of the growth plate chondrocytes, SSCs in the growth plate are not well studied. The present study used cluster of differentiation (CD)146 and CD105 as markers to isolate purified SSCs. CD105+ SSCs and CD146+ SSCs were isolated using a magnetic activated cell sorting method. To quantitatively investigate the proliferation and differentiation ability, the colony-forming efficiency (CFE) and multi­lineage differentiation capacity of CD105+ SSCs and CD146+ SSCs were compared with unsorted cells and adipose-derived stem cells (ASCs). It was revealed that CD105+ and CD146+ subpopulations represented subsets of SSCs which generated chondrocytes and osteocytes, however not adipocytes. Compared with CD105+ subpopulations and ASCs, the CD146+ subpopulation exhibited a greater CFE and continuous high chondrogenic differentiation capacity in vitro. Therefore, the present study suggested that the CD146+ subpopulation represented a chondrolineage­restricted subpopulation of SSCs and may therefore act as a valuable cell source for cartilage regeneration.

Iguratimod prevents ovariectomy­induced bone loss and suppresses osteoclastogenesis via inhibition of peroxisome proliferator­activated receptor­Î³.

Iguratimod is known for its anti­inflammatory activities and therapeutic effects in patients with rheumatoid arthritis. It has previously been demonstrated that iguratimod attenuates bone destruction and osteoclast formation in the Walker 256 rat mammary gland carcinoma cell­induced bone cancer pain model. Therefore, it was hypothesized that iguratimod may additionally exhibit therapeutic effects on benign osteoclast­associated diseases including postmenopausal osteoporosis. In the present study, ovariectomized mice were used to investigate the effects of iguratimod in vivo. Bone marrow mononuclear cells were cultured to detect the effects of iguratimod on receptor activator of nuclear factor­κB ligand (RANKL)­induced osteoclastogenesis in vitro and the molecular mechanisms involved. It was demonstrated that iguratimod may prevent ovariectomy­induced bone loss by suppressing osteoclast activity in vivo. Consistently, iguratimod may inhibit RANKL­induced osteoclastogenesis and bone resorption in primary bone marrow mononuclear cells. At the molecular level, peroxisome proliferator­activated receptor­Î³ (PPAR­Î³)/c­Fos pathway, which is essential in RANKL­induced osteoclast differentiation, was suppressed by iguratimod. Subsequently, iguratimod decreased the expression of nuclear factor of activated T cells c1 and downstream osteoclast marker genes. The results of the present study demonstrated that iguratimod may inhibit ovariectomy­induced bone loss and osteoclastogenesis by modulating RANKL signaling. Therefore, iguratimod may act as a novel therapeutic to prevent postmenopausal osteoporosis.

Icariin Regulates the Bidirectional Differentiation of Bone Marrow Mesenchymal Stem Cells through Canonical Wnt Signaling Pathway.

Fat infiltration within the bone marrow is easily observed in some postmenopausal women. Those fats are mainly derived from bone marrow mesenchymal stem cells (BMMSCs). The increment of adipocytes derived from BMMSCs leads to decreased osteoblasts derived from BMMSCs, so the bidirectional differentiation of BMMSCs significantly contributes to osteoporosis. Icariin is the main extractive of Herba Epimedii which is widely used in traditional Chinese medicine. In this experiment, we investigated the effect of icariin on the bidirectional differentiation of BMMSCs through quantitative real-time PCR, immunofluorescence, western blot, and tissue sections in vitro and in vivo. We found that icariin obviously promotes osteogenesis and inhibits adipogenesis through detecting staining and gene expression. Micro-CT analysis showed that icariin treatment alleviated the loss of cancellous bone of the distal femur in ovariectomized (OVX) mice. H&E staining analysis showed that icariin-treated OVX mice obtained higher bone mass and fewer bone marrow lipid droplets than OVX mice. Western blot and immunofluorescence showed that icariin regulates the bidirectional differentiation of BMMSCs via canonical Wnt signaling. This study demonstrates that icariin exerts its antiosteoporotic effect by regulating the bidirectional differentiation of BMMSCs through the canonical Wnt signaling pathway.