Changes in bone density, intraosseous pressure of distal femoral articular cartilage and subchondral bone after proximal femoral medullary cavity cement filling in rabbits.

Bone cement is widely used, particularly in hip replacements, but the potential clinical complications of its use have been largely unrecognized. The purpose of the present study was to investigate the effects of bone cement in the proximal femoral medullary cavity (PFMC) on bone mineral density (BMD), intraosseous pressure (IOP), articular cartilage and subchondral bone in the distal femurs of rabbits. A total of 32 New Zealand white rabbits were randomly numbered and the left hind limb of the odd-numbered rabbits and the right hind limb of the even numbered rabbits were selected as the experimental side. For each rabbit, the non-experimental hind limb was labeled as the control side by the principal investigator. An intramedullary injection of polymethyl methacrylate was made into the experimental hindlimb of each rabbit and the PFMC filled with bone cement. BMD and IOP of the distal femur of the bilateral hindlimb were measured at 4 and 16 weeks after surgery, and histological and ultra-fine structural features were examined by light and transmission electron microscopy, respectively. At week 4 after the operation, IOP in the experimental limb was significantly higher and BMD lower compared with the control limb. At the 16th week after operation, the IOP in the experimental limb was lower than at the 4th week after operation, but still higher compared with controls, and the BMD was significantly higher than the controls. In the controls, IOP and BMD was not significantly different between the 4th and 16th week after operation. Compared with controls, the cartilage in the experimental group was thinner, the chondrocytes partially necrotic and the trabecular structure of the subchondral bone broken. Analysis of ultra-fine structural features in the experimental group showed chondrocytes with necrotic cytoplasm and pyknotic nuclei relative to controls. The results indicated that blockage of the PFMC with bone cement resulted in an increase in the IOP in the distal femur, a change in BMD and damage to the subchondral bone and articular cartilage.

Effects of bone cement filling in rabbit proximal femoral medullary cavity on distal femoral blood flow and metabolism.

OBJECTIVE: A rabbit model was used to evaluate the effects of bone-cemented hip arthroplasty on distal femoral blood flow and metabolism relative to that of the non-cemented contralateral leg. METHODS: The marrow cavity of the right hind femur was filled with bone cement. At each of the following time points, rabbits were randomly selected to receive an injection of one dose of 99mTc-methylene diphosphonate and then immediately scanned using a gamma camera: immediately postoperatively and at 4 and 8 weeks postoperatively. A BL-410 model biofunction experimental system was used to analyze the acquired images and determine the radioactive counts of each hind leg. RESULTS: The X-ray and photographic images of the right femoral bones confirmed successful filling of the marrow cavity with bone cement. The radioactive counts were significantly lower in the experimental than control legs at each time point. The ratio of the radioactive count of the experimental to control leg increased considerably at each time point, but each ratio was <1. CONCLUSION: Blocking the proximal femoral medullary cavity with bone cement was associated with significant lowering of the blood circulation of the femur and marrow, decreasing the distal femoral blood flow and bone metabolic rate.

Long Non-coding RNA-2271 Promotes Osteogenic Differentiation in Human Bone Marrow Stem Cells.

BACKGROUND: Human bone marrow mesenchymal stem cells (BMSCs) are of great significance for bone regeneration and bone formation. Long non-coding RNAs (lncRNAs) may be involved in modulating cell differentiation. This study aimed to investigate the role of lncR-2271 in promoting osteogenic differentiation in human BMSCs. METHODS: Human BMSCs were infected using lncR-2271 overexpression (group A) with lentiviral system or transfected with lncR-2271 siRNA (group B). Cells transfected with scrambled plasmids were used as a negative control (group C). Osteogenesis markers were evaluated using alkaline phosphatase (ALP) activity, RUNX2 and osterix (OSX) at protein levels and calcification by Alizarin Red staining. RESULTS: BMSCs from group A showed significantly higher ALP activity compared to BMSCs in group B and control group (group C) at both days 7 and 14 following osteogenic induction; ALP activity was significantly lower in the group B compared to the group C. RUNX2 and OSX protein expressions were significantly higher in group A and significantly lower in group B, compared to those in group C, respectively. At day 21, calcification in human BMSCs in group A was significantly higher compared to groups B and C as shown by Alizarin Red staining; calcification was significantly lower in group B compared to group C. CONCLUSION: Our data suggested lncR-2271 played a role in promoting osteogenic differentiation in human BMSCs. This study is the first to illustrate the important role of lncR-2271 in bone formation.

Effects of Dermatopontin gene silencing on apoptosis and proliferation of osteosarcoma MG­63 cells.

The present study aimed to investigate the effect of Dermatopontin (DPT) gene silencing on the apoptosis and proliferation of osteosarcoma MG­63 cells. Three eukaryotic expression vectors of short hairpin (sh)RNA fragments targeting different loci of DPT were designed and transfected into an osteosarcoma cell line MG­63. The cells were assigned to a blank, shRNA­control, DPT­shRNA­a, DPT­shRNA­b or DPT­shRNA­c group. The shRNA with the highest silencing efficiency was screened using reverse transcription­quantitative polymerase chain reaction and western blotting. The screened shRNA was transfected into MG­63 cells. The proliferation, cell cycle and apoptosis of MG­63 cells were measured using a Cell Counting Kit­8 assay, flow cytometry and Annexin V­fluorescein isothiocyanate assay. The recombinant plasmids containing DPT shRNA were successfully constructed. DPT gene silencing was able to significantly reduce the proliferation rate of MG­63 cells (P<0.05). The proportion of cells in the G0/G1 phase and in the G2/M phase increased significantly (both P<0.05), while the proportion of cells in the S phase decreased (P<0.05). Furthermore, the cell apoptosis rate increased significantly (P<0.05). These results demonstrate that DPT gene silencing is able to reduce the proliferation of MG­63 cells, slow down cell cycle progression and promote apoptosis, hence may become a novel target for the treatment of osteosarcoma.