In this study, we evaluated the bone regenerative capability of a customizable hydroxyapatite (HA) and tricalcium phosphate (TCP) scaffold using a digital light processing (DLP)-type 3D printing system. Twelve healthy adult male beagle dogs were the study subjects. A total of 48 defects were created, with two defects on each side of the mandible in all the dogs. The defect sites in the negative control group (sixteen defects) were left untreated (the NS group), whereas those in the positive control group (sixteen defects) were filled with a particle-type substitute (the PS group). The defect sites in the experimental groups (sixteen defects) were filled with a 3D printed substitute (the 3DS group). Six dogs each were exterminated after healing periods of 4 and 8 weeks. Radiological and histomorphometrical evaluations were then performed. None of the groups showed any specific problems. In radiological evaluation, there was a significant difference in the amount of new bone formation after 4 weeks (p < 0.05) between the PS and 3DS groups. For both of the evaluations, the difference in the total amount of bone after 8 weeks was statistically significant (p < 0.05). There was no statistically significant difference in new bone between the PS and 3DS groups in both evaluations after 8 weeks (p > 0.05). The proposed HA/TCP scaffold without polymers, obtained using the DLP-type 3D printing system, can be applied for bone regeneration. The 3D printing of a HA/TCP scaffold without polymers can be used for fabricating customized bone grafting substitutes.

OBJECTIVES To investigate the roles of glutathione and glutathione‐S‐transferase (GST) in cisplatin‐resistance mechanisms in human bladder cancer, by using glutathione‐depleting or GST‐blocking agents. MATERIALS AND METHODS Cisplatin‐resistant human bladder cancer cell lines were established by continuous exposure of T24 cells to increasing concentrations of cisplatin. Buthionine sulphoximine (BSO), ethacrynic acid and indomethacin were used to deplete glutathione or block GST. Intracellular glutathione content, GST activity and cisplatin cytotoxicity were determined after exposing parental and drug‐resistant cell lines to these agents. RESULTS Intracellular glutathione content and GST activity were significantly decreased, and cisplatin cytotoxicity significantly enhanced, in both parental and resistant cell lines by glutathione‐depleting or GST‐blocking agents. However, the resistance of cisplatin‐resistant cell lines did not fully recover to that of the parental cells with combined BSO and indomethacin. CONCLUSIONS Both increased glutathione content and GST activity are significant in the cisplatin resistance of human bladder tumour cells. Because BSO, ethacrynic acid and indomethacin caused a partial recovery of resistance in the cisplatin‐resistant cell line, further studies are needed to investigate their efficacy for treating patients with metastatic bladder carcinoma resistant to cisplatin.

This study evaluated the mechanical properties and bone regeneration ability of 3D-printed pure hydroxyapatite (HA)/tricalcium phosphate (TCP) pure ceramic scaffolds with variable pore architectures. A digital light processing (DLP) 3D printer was used to construct block-type scaffolds containing only HA and TCP after the polymer binder was completely removed by heat treatment. The compressive strength and porosity of the blocks with various structures were measured; scaffolds with different pore sizes were implanted in rabbit calvarial models. The animals were observed for eight weeks, and six animals were euthanized in the fourth and eighth weeks. Then, the specimens were evaluated using radiological and histological analyses. Larger scaffold pore sizes resulted in enhanced bone formation after four weeks (p < 0.05). However, in the eighth week, a correlation between pore size and bone formation was not observed (p > 0.05). The findings showed that various pore architectures of HA/TCP scaffolds can be achieved using DLP 3D printing, which can be a valuable tool for optimizing bone-scaffold properties for specific clinical treatments. As the pore size only influenced bone regeneration in the initial stage, further studies are required for pore-size optimization to balance the initial bone regeneration and mechanical strength of the scaffold.