Abstract. The present study aimed to investigate the effect and underlying mechanism of microRNA (miR)-4262 in the development of osteoarthritis (OA) in rats. Primary chondrocytes were separated from Sprague-Dawley rats and then treated with tumor necrosis factor-α (TNF-α). The level of miR-4262 was detected in TNF-α-treated chondrocytes, and then the miR-4262 or its target gene sirtuin type 1 (SIRT1) level was overexpressed, or knocked down. Furthermore, cell viability, cell apoptosis, cell autophagy and matrix synthesis, as well as the expressions of proteins associated with the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT)/mammalian target of rapamycin (mTOR) signaling pathway were detected. miR-4262 was significantly overexpressed in TNF-α-treated chondrocytes compared with untreated cells (P<0.05). TNF-α treatment or miR-4262 overexpression significantly decreased cell viability, autophagy-related proteins levels and matrix synthesis-related proteins levels, as well as increased the apoptotic rate in chondrocytes (P<0.05). Overexpression of SIRT1 significantly increased cell viability, autophagy-related proteins levels and matrix synthesis-related proteins levels, as well as decreased the apoptotic rate in TNF-α-treated chondrocytes (P<0.05). In addition, the effects of miR-4262 on cell viability, cell apoptosis, cell autophagy and matrix synthesis were inhibited by SIRT1 (P<0.05). Furthermore, upregulated miR-4262 remarkably increased the expressions of phosphorylated (p)-PI3K, p-AKT and p-mTOR (P<0.05) in TNF-α treated chondrocytes. The present study revealed that the upregulation of miR-4262 may promote the occurrence and development of OA in rats by regulating cell viability, cell apoptosis, cell autophagy, and matrix synthesis. Furthermore, these roles of miR-4262 may be associated with PI3K/AKT/mTOR signaling pathway.

Estradiol (E2) is a first-line drug for osteoporosis (OP) treatment via promotion of osteoblastic proliferation and differentiation. However, a long-term use of E2 would produce side effects thus, it is imperative to discover safer and more effective drugs. Pinoresinol (PINO) has a similar chemical structure to E2. The present study aimed to investigate whether PINO could promote osteoblastic proliferation and differentiation and the potential mechanisms. After treatment with 0.1 µg/l PINO for 2 days, MC3T3-E1 cell migration was assessed by wound healing assay. Estrogen (E2) treatment served as a positive control. RT-qPCR and western blotting were used for mRNA and protein expression analyses. Alkaline phosphatase (ALP) activity assay and Alizarin red staining were performed to investigate the calcification and mineralization, and the cyclic AMP (cAMP) level was detected by enzyme-linked immunosorbent assay (ELISA). H89, an inhibitor of protein kinase A (PKA), was introduced to verify the role of cAMP/PKA in the effect of PINO on MC3T3-E1 cells. Cell viability was the highest under 48 h of 0.1 µg/l PINO treatment. After treatment with PINO, a significant increase was observed in the migration rate and the expression of collagen type I (Col-I), ALP, osteopontin (OPN), runt-related transcription factor 2 (Runx2) and bone morphogenetic protein-2 (BMP-2) (P<0.01). The ALP activity and Alizarin red size in PINO and E2 groups were notably increased. The increased cAMP, PKA and phosphorylated cAMP response element-binding protein (CREB) levels were also observed in the PINO group. Furthermore, H89 co-treatment abolished the positive effects of PINO on cell viability and migration. PINO had similar effects to E2 on the osteoblastic proliferation and differentiation, and these positive effects may be attributed to the regulation of the cAMP/PKA signaling pathway.

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A variety of gadolinium (Gd) based nanoparticles (NPs) were synthesized due to the unique magnetic properties of Gd-containing rare earth compounds and the particularity of micro/nano-materials, which were then incorporated into hydroxyapatite (HA) to obtain inorganic-organic composite materials. Then, HA/Gd NPs containing slow-release transforming growth factor (TGF-β1) were harvested. Adipose-derived stem cells (ADSCs) were extracted from the adipose tissue of a four-month-old New Zealand white rabbit. HA/Gd NPs were attached to absorbable gelatin sponge to obtain HA/Gd NPs/gelatin sponge composite scaffold. In addition, the third generation ADSCs were taken and cultured in the composite scaffold, so that ADSCs-HA/Gd bio-nanocomposites were obtained. The in vitro culture test of osteoblast MC3T3-E1 showed that Gd-containing NPs had good biocompatibility. The prepared HA/Gd NPs loaded with TGF-β1 were spherical, with an average particle size of (9.16 ± 3.16) μm. The NPs were easy to aggregate and adherent. Enzyme-linked immunosorbent assay (ELISA) test results showed that TGF-β1 in NPs was sustained and released continuously for 29 days. HA/Gd NPs/gelatin sponge composite scaffold combined with ADSCs were co-cultured for three days, and the electron microscope showed that the HA/Gd NPs were dispersed, and the cells could adhere and grow well. Then, animal models of rabbit knee articular cartilage defects were established and were rolled into three groups (ADSCs-HA/Gd nano group, HA/Gd nano scaffold group, and blank control). The repair area of the rabbit knee of ADSCs-HA/Gd nano group was smooth and flat, the scaffold was absorbed, the toluidine blue stain was positive, and the type II collagen immunohistochemical stain was positive. In general, ADSCs-HA/Gd nanomaterials were helpful for chondrogenic cell differentiation and had certain adoption prospects in the field of tissue engineering to repair cartilage defects.

Bone marrow mesenchymal stem cells (BMSCs) have characteristics of self-renewal and multidirectional differentiation. LncRNA UCA1 regulates BMSCs differentiation. Whether LncRNA UCA1 plays a role in bone defects remains unclear. BMSCs were randomly divided into control group, radiation group (6Gy), radiation + UCA1 group followed by analysis of the expression of LncRNA UCA1, RUNX2 and OPN by real time PCR, BMSCs proliferation by MTT assay as well as ALP activity. Healthy Sprague-Dawley rats were randomly divided into control group; bone defect group; UCA1 group, in which UCA1-transfected BMSCs were infused into bone defect rats followed by analysis of bone mineral density, ALP activity as well as the formation of type II collagen by ELISA. LncRNA UCA1 expression was significantly decreased in BMSCs of irradiated group, with decreased BMSCs proliferation, reduced expression of RUNX2 and OPN as well as decreased ALP activity (P < 0.05). Transfection of UCA1 significantly up-regulated LncRNA UCA1 expression in BMSCs, promoted BMSCs proliferation, increased the expression of RUNX2 and OPN, and the activity of ALP (P < 0.05). In addition, UCA1 promoted bone mineral density, increased ALP activity and type II collagen formation in rats with bone defect. LncRNA UCA1 promotes osteogenic differentiation of BMSCs, and targeting it might be a novel approach to promote bone remodeling at the bone defect site.