The intracellular transport of cholesterol is subject to tight regulation. The structure of the lysosomal integral membrane protein type 2 (LIMP-2, also known as SCARB2) reveals a large cavity that traverses the molecule and resembles the cavity in SR-B1 that mediates lipid transfer. The detection of cholesterol within the LIMP-2 structure and the formation of cholesterol − like inclusions in LIMP-2 knockout mice suggested the possibility that LIMP2 transports cholesterol in lysosomes. We present results of molecular modeling, crosslinking studies, microscale thermophoresis and cell-based assays that support a role of LIMP-2 in cholesterol transport. We show that the cavity in the luminal domain of LIMP-2 can bind and deliver exogenous cholesterol to the lysosomal membrane and later to lipid droplets. Depletion of LIMP-2 alters SREBP-2-mediated cholesterol regulation, as well as LDL-receptor levels. Our data indicate that LIMP-2 operates in parallel with Niemann Pick (NPC)-proteins, mediating a slower mode of lysosomal cholesterol export.

Objective To evaluate cartilage diffusion and isolated chondrocyte association of micelles and liposomes and to determine the effect of cell-penetrating peptide (CPP) surface functionalization and extracellular matrix depletion on chondrocyte association and cartilage diffusion, respectively. Methods Rhodamine-labeled micelles and liposomes were incubated with bovine chondrocytes and cell-associated fluorescence was quantified using flow cytometry. Rhodamine-labeled CPP-modified micelles and liposomes were incubated with chondrocytes and cell-associated fluorescence was compared to unmodified nanocarriers. Rhodamine-labeled micelles and liposomes were incubated with bovine cartilage explants for 1, 2 and 4 hours and cartilage-associated fluorescence was compared across groups. Cartilage explants were treated with interleukin-1 alpha (IL-1α) or with 0.25% trypsin. Rhodamine-labeled micelles and liposomes were incubated with control, IL-1 and trypsin-treated explants and cartilage-associated fluorescence was compared across groups. Results Chondrocyte-associated fluorescence following treatment with micelles was significantly higher (P<0.001) than fluorescence in the cells treated with liposomes while there was no difference between cell-associated fluorescence in the liposomes-treated and untreated controls. CPP-modified nanocarriers exhibited a significant increase in chondrocyte association compared to unmodified nanocarriers (P<0.001). Micelles exhibited a time and concentration-dependent diffusion in cartilage explants while liposomes showed no diffusion. Following IL-1 and trypsin treatments, micelle diffusion in articular cartilage was significantly higher (P<0.001) than their diffusion in untreated explants. Conclusion Micelles exhibit superior association with isolated chondrocytes compared to liposomes. Surface modification with a CPP enhances chondrocyte association of both nanocarriers. 15 nm diameter Micelles are better than 138 nm diameter liposomes in penetrating articular cartilage and extracellular matrix depletion enhances micelle penetration.

Objective. To observe the dynamic changes in oxidative stress and the expression levels of antioxidant and oxidative parameters in the blood and synovial fluid in the osteochondral defects of the rabbit knee joints and to explore the significance. Methods. Thirty New Zealand white rabbits were randomly selected and divided into a blank control group ( n = 10 ), a model control group ( n = 10 ), and an osteochondral defect group ( n = 10 ). The osteochondral defect model of rabbit knee joint was constructed by medial parapatellar arthrotomy. The expression levels of glutathione (GSH), malondialdehyde (MDA), superoxide dismutase (SOD), and 8-hydroxydeoxyguanosine (8-OHdG) in peripheral venous blood and knee synovial fluid of the three groups were measured at the end of the 4th, 8th, and 12th weeks after treatment. Results. The expression levels of GSH and SOD in the blood and synovial fluid in the osteochondral defect group at the end of the 8th and 12th weeks were observably lower than those of the other two groups ( P < 0.05 ); higher expression levels of MDA and 8-OHdG in the blood and synovial fluid of the osteochondral defect group compared with those of the other two groups were obtained ( P < 0.05 ). At the end of the 4th, 8th, and 12th weeks, the expression levels of MDA and 8-OHdG in the blood and synovial fluid of the osteochondral defect group presented an upward trend ( P < 0.05 ). Conclusion. The osteochondral defects initiate the oxidative stress in the body, which is presented as the decrease of GSH and SOD expression, and the upregulation of MDA and 8-OHdG expression.

Random copolymers of poly(d,l-lactide-co-glycolide-co--caprolactone) (PLGC) were synthesized by the ring-opening polymerization of d,l-lactide (DLLA), glycolide (GA), and -caprolactone (CL). The effects of CL on the copolymers were evaluated to prepare suitable copolymers with controlled properties. Our results showed that the CL content significantly influenced the thermal and mechanical properties of the copolymers and that the CL content in compositions could be altered to control properties of random copolymers. The in vitro hydrolytic degradation of the resulting implants showed that the degradation rate of PLGC was lower than that of PLGA, which could markedly reduce acidic degradation products. Finally, we demonstrated that higher CL contents in compositions slowed degradation rates.