Inhibitory effects of high glucose/insulin environment on osteoclast formation and resorption in vitro.

Patients with type 2 diabetes mellitus (T2DM) exhibit hyperglycemia and hyperinsulinemia and increased risk of fracture at early stage, but they were found to have normal or even enhanced bone mineral density (BMD). This study was aimed to examine the molecular mechanisms governing changes in bone structure and integrity under both hyperglycemic and hyperinsulinemic conditions. Monocytes were isolated from the bone marrow of the C57BL/6 mice, induced to differentiate into osteoclasts by receptor activator of nuclear factor kappa-B ligand (RANKL) and macrophage colony-stimulating factor (M-CSF) and exposed to high glucose (33.6 mmol/L), high insulin (1 µmol/L), or a combination of high glucose/high insulin (33.6 mmol/L glucose and 1 µmol/L insulin). Cells cultured in α-MEM alone served as control. After four days of incubation, the cells were harvested and stained for tartrate resistant acid phosphatase (TRAP). Osteoclast-related genes including RANK, cathepsin K and TRAP were determined by using real-time PCR. The resorptive activity of osteoclasts was measured by using a pit formation assay. Osteoclasts that were derived from monocytes were of multinucleated nature and positive for TRAP, a characteristic marker of osteoclasts. Cell counting showed that the number of osteoclasts was much less in high glucose and high glucose/high insulin groups than in normal glucose and high insulin groups. The expression levels of RANK and cathepsin K were significantly decreased in high glucose, high insulin and high glucose/high insulin groups as compared with normal glucose group, and the TRAP activity was substantially inhibited in high glucose environment. The pit formation assay revealed that the resorptive activity of osteoclasts was obviously decreased in high glucose group and high glucose/high insulin group as compared with normal group. It was concluded that osteoclastogenesis is suppressed under hyperglycemic and hyperinsulinemic conditions, suggesting a disruption of the bone metabolism in diabetic patients.

Purification and characterization of a novel antithrombotic peptide from Scolopendra subspinipes mutilans.

ETHNOPHARMACOLOGICAL RELEVANCE: The centipede has been prescribed for the treatment of cardiovascular diseases in Korea, China and other Far Eastern Asian countries for several hundred years. MATERIALS AND METHODS: A novel antithrombotic peptide was isolated from Scolopendra subspinipes mutilans using a combination of ultrafiltration, Sephadex G-50 column, Source 15Q anion exchange column and RP-HPLC C18 column. RESULTS: The molecular mass of the purified peptide is 346Da measured by Electrospray Ionization Mass Spectrometry (ESI-MS). The primary structure of the peptide is Ser-Gln-Leu (SQL) determined by Edman degradation. SQL potently prolonged the activated partial thromboplastin time (aPTT), and inhibited platelet aggregation. CONCLUSIONS: These results help to clarify the mechanism of the antithrombotic activity of the centipede for effective treatment of cardiovascular and cerebrovascular diseases.

[Immortalization of rat epiphysis cartilage cells induced by simian virus 40 large T antigen gene transfection].

OBJECTIVE: To establish immortalized epiphysis cartilage cell strains in order to provide a stable cell resource for cell substitution and gene therapies of growth retardation. METHODS: Plasmid pEGFP-IRES2-SV40LTag containing simian virus 40 large T antigen gene was transfected into primarily cultured epiphysis cartilage cells of the newborn rat using the lipofectin transfection method. Colonies were isolated by G418 selection and cultured to immortalized cell strains. Fibroblast growth factor receptor-3 (FGFR-3), anti-collagen type II and type X antibodies were used to identify cultured cells and to investigate the capability of differentiation of the transfected cells. SV40LTag expression in expanded cell strains was identified by RT-PCR, Southern blot and immunocytochemistry method. RESULTS: Anti-G418 cell clone was obtained, which was confirmed as FGFR-3 positive epiphysis cartilage cells with the capability of stable proliferation. mRNA and protein of SV40LTag were expressed in transfected cells after stable transfection. The transfected cells were expanded to immortalized cell strains and named as immortalized epiphysis cartilage cells. The immortalized cells were elliptic or triangular, with two or three short axons. The immortalized epiphysis cartilage cell strains had stable biological characters. CONCLUSIONS: SV40LTag gene transfection can immortalize epiphysis cartilage cells. The establishment of FGFR-3 positive immortalized epiphysis cartilage cell strains may provide a stable cell resource for cell substitution and gene therapies of growth retardation.

[Regulation of differentiation and proliferation of epiphysis stem cells by Notch1 signaling system].

OBJECTIVE: To investigate the regulation of differentiation and proliferation of epiphysis stem cells by Notch1 signaling system. METHODS: Costocostal cartilage was taken from a SD rat. Epiphysis stem cells were isolated and cultured. Recombinant human nuclear factor-kappaB (rhNF-kappaB), an activator of the Notch signaling system, and gamma-secretase inhibitor (MW167), an inhibitor of the Notch signaling system, were added into the culture medium respectively. The cells cultured in the medium added with phosphate-buffered saline were used as control group. Then the cultured cells were collected. The expression of the homologous Notch receptors and homologous Notch ligands was detected by RT-PCR. Immunohistochemistry was used to detect the levels of collagen II, collagen X, and proliferating cell nuclear antigen (PCNA). MTT method was used to calculate the growth curve. The cell phase was examined by flow cytometry. The level of alkaline phosphatase (AP) was measured. Western blotting was used to detect the protein expression of collagen II, collagen X, and stathmin, a signaling protein of proliferation. RESULTS: Only 2 the expression of the receptor Notch1 and the ligand Jagged1 was found. The expression of PCNA was stronger in the rhNF-kappaB group than in the other 2 groups. rhNF-kappaB remarkably promoted the expression of collagen II and inhibited the expression of collagen X and MW167 remarkably promoted the expression of collagen X and did not remarkably influence the expression of collagen II. MTT method showed that rhNF-kappaB significantly promote the proliferation of the cells (P = 0.027), and MW167 did not significantly promote the cell proliferation (P > 0.05). The percentage of cells at S phase of the rhNF-kappaB group was 26.54%, significantly higher than those of the MW167 group and control group (8.22% and 6.15%). AP was significantly expressed in the MW167 group, and less expressed in the other groups. Western blotting showed a significantly increased expression of collagen X protein and decreased expression of collagen II protein and stathmin. CONCLUSION: When the Notch signaling system is activated the epiphysis stem cells proliferate, and when the Notch signaling system is suppressed the epiphysis stem cells differentiate.