Effects of Lobeglitazone, a New Thiazolidinedione, on Osteoblastogenesis and Bone Mineral Density in Mice

BACKGROUND: Bone strength is impaired in patients with type 2 diabetes mellitus despite an increase in bone mineral density (BMD). Thiazolidinedione (TZD), a peroxisome proliferator activated receptor γ agonist, promotes adipogenesis, and suppresses osteoblastogenesis. Therefore, its use is associated with an increased risk of fracture. The aim of this study was to examine the in vitro and in vivo effects of lobeglitazone, a new TZD, on bone. METHODS: MC3T3E1 and C3H10T1/2 cells were cultured in osteogenic medium and exposed to lobeglitazone (0.1 or 1 µM), rosiglitazone (0.4 µM), or pioglitazone (1 µM) for 10 to 14 days. Alkaline phosphatase (ALP) activity, Alizarin red staining, and osteoblast marker gene expression were analyzed. For in vivo experiments, 6-month-old C57BL/6 mice were treated with vehicle, one of two doses of lobeglitazone, rosiglitazone, or pioglitazone. BMD was assessed using a PIXImus2 instrument at the baseline and after 12 weeks of treatment. RESULTS: As expected, in vitro experiments showed that ALP activity was suppressed and the mRNA expression of osteoblast marker genes RUNX2 (runt-related transcription factor 2) and osteocalcin was significantly attenuated after rosiglitazone treatment. By contrast, lobeglitazone at either dose did not inhibit these variables. Rosiglitazone-treated mice showed significantly accelerated bone loss for the whole bone and femur, but BMD did not differ significantly between the lobeglitazone-treated and vehicle-treated mice. CONCLUSION: These findings suggest that lobeglitazone has no detrimental effects on osteoblast biology and might not induce side effects in the skeletal system.

The Effects of Wnt Protein on Proliferation and Stemness Maintenance of Corneal Limbal Stem Cells (CLSCs)

PURPOSE: To evaluate the effects of the Wnt protein on proliferation and stemness maintenance of cultured corneal limbal stem cells. METHODS: We examined the expression of Wnt proteins by Western blot analysis. We then evaluated the effects of Wnt on cell proliferation by colony forming efficiency. beta-catenin activation using Wnt proteins was examined by immunocytochemistry. We also examined the effects of Wnt on proliferation and stemness maintenance by reverse transcriptase polymerase chain reaction of p63 and connexin43. RESULTS: Wnt has a different effect on corneal epithelial stem cells. Colony forming efficiency was also significantly higher in treated Wnt2 and Wnt4 cells compared with controls. The Wnt2 and Wnt4 treated cells showed nuclear accumulation of beta-catenin. In addition, the limbal stem cell marker p63 was strongly expressed in Wnt2, Wnt4 Wnt5a, and Wnt5b. Connexin43 mRNA was also strongly expressed in Wnt5a, Wnt5b and Wnt7b cells. CONCLUSIONS: We suggest that Wnt2 and Wnt4 could lead to more effective proliferation and stemness maintenance for human corneal epithelial stem cells.