Mammalian cells were successfully transfected with plasmid DNA in vitro using ultrasound transmitted through the walls of cell culture flasks or plates. Primary rat fibroblasts or chondrocytes were exposed to ultrasound in the presence of plasmids containing lacZ or neo genes. The transfection efficiency was evaluated by counting the number of beta-galactosidase (beta-Gal) positive cells or neomycin-resistant colonies. Transfection efficiency was optimized by varying ultrasound conditions, ambient temperatures (room temperature or 37 degrees C), plasmid concentrations, and initial cell populations. Additional experiments were performed performed to elucidate the mechanism of the ultrasound-mediated transfection. Maximal gene transfection was seen with two ultrasound conditions: 1-MHz carrier frequency 411 +/- 189 kPascal continuous wave with 20 or 30 sec of exposure time, and 1 MHz carrier frequency 319 +/- 157 kPascal continuous wave with 40 or 60 sec of exposure time. Gene expression was negligible when transfection procedures were performed at room temperature. The average stable transfection rate was 0.34% of surviving cells with a plasmid concentration of 40 micrograms/ml in primary fibroblasts. The transient transfection rate was 2.4% of surviving cells for primary chondrocytes. Data suggest that increasing plasmid concentration will increase efficiency. Identical treatment with 3.5 MHz produced no transfection, implying that cavitation produced by the ultrasound pressure wave appeared to play a critical role in mediating transfection. Ultrasound-mediated transfection was effective for suspended cells as well as for plated cells. This transfection method is simple, easy to keep sterile, and convenient. Ultrasound-mediated transfection appears to be a promising method for gene transfer into mammalian cells.

No abstract

No abstract

There is no animal model that reflects the histological and radiographical heterogeneity of osteosarcoma. We assessed seven osteosarcoma cell lines for their potential to develop orthotopic tumors and lung metastasis in SCID mice. Whereas radiologically, 143B developed osteolytic tumors, SaOS-LM7 developed osteoblastic primary tumors. The mineralization status was confirmed by assessing the alkaline phosphatase activity and the microarray expression profile. We herein report a xenograft orthotopic osteosarcoma mouse model to assess osteoblastic and osteolytic lesions, which may contribute in the search for new diagnostic and therapeutic approaches.

We examined the time course effects of continuous PTH on cortical bone and mechanical properties. PTH increased cortical bone turnover and induced intracortical porosity with no deleterious effect on bone strength. Withdrawal of PTH increased maximum torque to failure and stiffness with no change in energy absorbed. Introduction:The skeletal response of cortical bone to parathyroid hormone (PTH) is complex and species dependent. Intermittent administration of PTH to rats increases periosteal and endocortical bone formation but has no known effects on intracortical bone turnover. The effects of continuous PTH on cortical bone are not clearly established. Materials and Methods: Eighty-four 6-month-old female Sprague-Dawley rats were divided into three control, six PTH, and two PTH withdrawal (WD) groups. They were subcutaneously implanted with osmotic pumps loaded with vehicle or 40 g/kg BW/day human PTH(1-34) for 1, 3, 5, 7, 14, and 28 days. After 7 days, PTH was withdrawn from two groups of animals for 7 (7d-PTH/7d-WD) and 21 days (7d-PTH/21d-WD). Histomorphometry was performed on periosteal and endocortical surfaces of the tibial diaphysis in all groups. CT of tibias and mechanical testing by torsion of femora were performed on 28d-PTH and 7d-PTH/21d-WD animals. Results and Conclusions: Continuous PTH increased periosteal and endocortical bone formation, endocortical osteoclast perimeter, and cortical porosity in a time-dependent manner, but did not change the mechanical properties of the femur, possibly because of addition of new bone onto periosteal and endocortical surfaces. Additionally, withdrawal of PTH restored normal cortical porosity and increased maximum torque to failure and stiffness. We conclude that continuous administration of PTH increased cortical porosity in rats without having a detrimental effect on bone mechanical properties.