In vitro expansion of human nasoseptal chondrocytes reveals distinct expression profiles of G1 cell cycle inhibitors for replicative, quiescent, and senescent culture stages

Glucosamine promotes chondrocyte proliferation via the Wnt/β‑catenin signaling pathway

The present study investigated the mechanism underlying the effects of glucosamine (GlcN) on the proliferation of chondrocytes isolated from the knee cartilage of Sprague-Dawley rats. Chondrocytes were treated with various concentrations of GlcN or without GlcN. The effects of GlcN on chondrocyte proliferation were determined using reverse transcription-polymerase chain reaction, western blot analysis and immunohistochemistry. The results indicated that GlcN significantly improved chondrocyte viability, accelerated G₁/S transition during progression of the cell cycle and promoted the expression of cell cycle regulatory proteins, including cyclin D1, cyclin-dependent kinase (CDK)4 and CDK6, thus indicating that GlcN may promote chondrocyte proliferation. Furthermore, GlcN upregulated the expression levels of Wnt-4, Frizzled-2 and β-catenin, and downregulated the expression of glycogen synthase kinase-3. GlcN also promoted β-catenin translocation; β-catenin is able to activate numerous downstream target genes, including cyclin D1. To determine the role of the Wnt/β-catenin signaling pathway in chondrocyte proliferation, the Wnt/β-catenin signaling pathway was inhibited using Dickkopf-1 (DKK-1), after which chondrocytes were treated with GlcN. The results demonstrated that the expression levels of β-catenin and cyclin D1 were decreased in chondrocytes treated with DKK-1 and GlcN. These results suggested that GlcN may promote chondrocyte proliferation via the Wnt/β-catenin signaling pathway.

Piperlongumine decreases cell proliferation and the expression of cell cycle-associated proteins by inhibiting Akt pathway in human lung cancer cells

Piperlongumine (PL) is an alkaloid of a pepper plant found in Southeast Asia. PL is known to induce selective toxicity towards a variety of cancer cell types. To explore the possible anti-lung cancer effects of PL, A549 cells were treated with PL (0-40 μM) for 24 h. Alterations in the expression of cell cycle-associated proteins (cyclin D1, cyclin-dependent kinase 4 (CDK4), CDK6 and retinoblastoma (Rb)) and intracellular signaling molecules (extracellular signal receptor-activated kinase 1/2 (ERK1/2), Akt, p38 and nuclear factor-κB (NF-κB)) were examined in cells following treatment of PL using Western blot analysis. Results showed that proliferation of cells were significantly decreased by PL in a dose-dependent manner. Flow cytometry results demonstrated increased number of cells in G1 phase in PL (40 μM)-treated group. Reactive oxygen species was significantly increased in cells treated with PL at 20-40 μM. The expression of cyclin D1, CDK4, CDK6 and p-Rb were markedly decreased in cells treated with PL at 40 μM. Treatment of cells with PL suppressed phosphorylation of Akt but increased ERK1/2 phosphorylation. Treatment of PL significantly decreased nuclear translocation of NF-κB p65 in cells. These results suggest that PL possesses antiproliferative properties in A549 cells.

Identification and validation of risk loci for osteochondrosis in standardbreds

BACKGROUND

Osteochondrosis (OC), simply defined as a failure of endochondral ossification, is a complex disease with both genetic and environmental risk factors that is commonly diagnosed in young horses, as well as other domestic species. Although up to 50 % of the risk for developing OC is reportedly inherited, specific genes and alleles underlying risk are thus far completely unknown. Regions of the genome identified as associated with OC vary across studies in different populations of horses. In this study, we used a cohort of Standardbred horses from the U.S. (n = 182) specifically selected for a shared early environment (to reduce confounding factors) to identify regions of the genome associated with tarsal OC. Subsequently, putative risk variants within these regions were evaluated in both the discovery population and an independently sampled validation population of Norwegian Standardbreds (n = 139) with tarsal OC.

RESULTS

After genome-wide association analysis of imputed data with information from >200,000 single nucleotide polymorphisms, two regions on equine chromosome 14 were associated with OC in the discovery cohort. Variant discovery in these and 30 additional regions of interest (including 11 from other published studies) was performed via whole-genome sequencing. 240 putative risk variants from 10 chromosomes were subsequently genotyped in both the discovery and validation cohorts. After correction for population structure, gait (trot or pace) and sex, the variants most highly associated with OC status in both populations were located within the chromosome 14 regions of association.

CONCLUSIONS

The association of putative risk alleles from within the same regions with disease status in two independent populations of Standardbreds suggest that these are true risk loci in this breed, although population-specific risk factors may still exist. Evaluation of these loci in other populations will help determine if they are specific to the Standardbred breed, or to tarsal OC or are universal risk loci for OC. Further work is needed to identify the specific variants underlying OC risk within these loci. This is the first step towards the long-term goal of constructing a genetic risk model for OC that allows for genetic testing and quantification of risk in individuals.

Sasanquasaponin from Camellia oleifera Abel. induces apoptosis via Bcl-2, Bax and caspase-3 activation in HepG2 cells

The present study aimed to elucidate the molecular mechanisms underlying the induction of cytotoxic effects by sasanquasaponin (SQS) in HepG2 cells. Following SQS treatment, time- and dose-dependent increases in the apoptotic rate were observed. The induction of cell death by SQS mainly occurs via programmed cell death, as indicated by Annexin V-fluorescein isothiocyanate and propidium iodide staining, where up to 30% apoptotic cells were detected following 12 h SQS treatment. Reverse transcription-polymerase chain reaction analysis demonstrated that SQS treatment upregulated B-cell lymphoma-2 (Bcl-2)-associated x protein and caspase-3 mRNA expression and downregulated Bcl-2 mRNA expression. Greater alterations in Bax, Bcl-2 and caspase-3 expression were observed with increasing treatment duration. The decrease in Bcl-2, increase in Bax and, finally, the activation of caspase-3 in HepG2 cells indicated that the apoptotic process induced by SQS was irreversible. The results of the present study therefore suggested that SQS induced HepG2 cell apoptosis via the activation of mitochondrial apoptotic pathways.

Bushen Zhuangjin Decoction promotes chondrocyte proliferation by stimulating cell cycle progression

Bushen Zhuangjin Decoction (BZD), a well-known formulation in Traditional Chinese Medicine, has been widely used for the treatment of osteoarthritis (OA). Due to the poor intrinsic repair capacity of chondrocytes, promoting the proliferation of chondrocytes is an efficient treatment to delay the progression of cartilage degradation. The present study, therefore, focused on the effect of BZD on chondrocyte proliferation, exploring the mechanism of BZD on the inhibition of cartilage degradation. Chondrocytes isolated from the knee articular cartilage of Sprague Dawley rats were cultured and identified by type II collagen immunohistochemistry. It was found that BZD promoted chondrocyte viability in a dose- and time-dependent manner. To investigate if BZD promoted the chondrocyte viability by stimulating the cell cycle progression a flow cytometer was used, and the results showed that the percentage proportion of G0/G1 cells was significantly lower, and the percentage proportion of S cells was significantly higher, in treated cells compared with that in untreated cells. To gain insight into the mechanism underlying the effect of BZD on the cell cycle progression, the mRNA and protein expression of cyclin D1, cyclin-dependent kinase 4 (CDK4), CDK6 and p21 was measured by reverse transcription-polymerase chain reaction and western blotting, respectively. The mRNA and protein expression of cyclin D1, CDK4 and CDK6 in the BZD-treated chondrocytes was significantly upregulated, while the mRNA and protein expression of p21 was significantly downregulated, compared with that in the untreated chondrocytes. These results suggested that BZD promoted chondrocyte proliferation by accelerating G1/S transition, indicating that BZD is a potential therapeutic agent for the treatment of OA.

Duhuo Jisheng Decoction promotes chondrocyte proliferation through accelerated G1/S transition in osteoarthritis

Duhuo Jisheng Decoction (DHJSD), a well known traditional Chinese folk medicine, is used for eliminating stagnation, removing blood stasis, promoting blood circulation and alleviating pain; it is commonly used for the treatment of various diseases, including osteoarthritis (OA). However, the molecular mechanisms behind the therapeutic effects of OA remain unclear. In the present study, the effects of DHJSD on the morphology of articular cartilage and the G1/S cell cycle progression in chondrocytes, as well as the underlying mechanisms, were investigated. A total of 27 two‑month‑old male Sprague Dawley rats were randomly divided into 3 groups: the control group (no papain-induced OA; received an equivalent amount of saline only), the model group (papain-induced OA; received an equivalent amount of saline only) and the DHJSD group [papain-induced OA; received a clinical oral dose of DHJSD (9.3 g/kg/day)]. After 8 consecutive weeks of treatment, the morphological changes in articular cartilage were observed under an optical microscope and by transmission electron microscopy (TEM) and the mRNA and protein expression levels of cyclin D1, CDK4, CDK6, retinoblastoma protein (Rb) and p16 were measured by RT‑PCR and immunohistochemistry, respectively. Treatment with DHJSD significantly improved the arrangement of collagen fibers in the articular cartilage, as well as its structure and reduced cell degeneration compared with the model group. The mRNA and protein expression levels of cyclin D1, CDK4, CDK6 and Rb in the DHJSD‑treated group were significantly increased compared with those in the model group, whereas p16 expression was significantly downregulated. Taken together, these results indicate that DHJSD treatment promotes chondrocyte proliferation by promoting the G1/S checkpoint transition in the cell cycle and by upregulating the expression of cyclin D1, CDK4, CDK6 and Rb and downregulating the expression of p16 and this may, in part, explain its clinical efficacy in the treatment of osteoarthritis.