Current clinical therapies for critical-sized bone defects (CSBDs) remain far from ideal. Previous studies have demonstrated that engineering bone tissue using mesenchymal stem cells (MSCs) is feasible. However, this approach is not effective for CSBDs due to inadequate vascularization. In our previous study, we have developed an injectable and porous nano calcium sulfate/alginate (nCS/A) scaffold and demonstrated that nCS/A composition is biocompatible and has proper biodegradability for bone regeneration. Here, we hypothesized that the combination of an injectable and porous nCS/A with bone morphogenetic protein 2 (BMP2) gene-modified MSCs and endothelial progenitor cells (EPCs) could significantly enhance vascularized bone regeneration. Our results demonstrated that delivery of MSCs and EPCs with the injectable nCS/A scaffold did not affect cell viability. Moreover, co-culture of BMP2 gene-modified MSCs and EPCs dramatically increased osteoblast differentiation of MSCs and endothelial differentiation of EPCs in vitro. We further tested the multifunctional bone reconstruction system consisting of an injectable and porous nCS/A scaffold (mimicking the nano-calcium matrix of bone) and BMP2 genetically-engineered MSCs and EPCs in a rat critical-sized (8 mm) caviarial bone defect model. Our in vivo results showed that, compared to the groups of nCS/A, nCS/A+MSCs, nCS/A+MSCs+EPCs and nCS/A+BMP2 gene-modified MSCs, the combination of BMP2 gene -modified MSCs and EPCs in nCS/A dramatically increased the new bone and vascular formation. These results demonstrated that EPCs increase new vascular growth, and that BMP2 gene modification for MSCs and EPCs dramatically promotes bone regeneration. This system could ultimately enable clinicians to better reconstruct the craniofacial bone and avoid donor site morbidity for CSBDs.

Lipopolysaccharide (LPS) has been purified from Bacteroides gingivalis. The purity of this LPS is evidenced on ultracentrifugation, immunoelectrophoresis, and chemical analyses. On comparison with LPS from aerobic enteric organisms, LPS from Bacteroides gingivalis exhibits minimal potency when tested for pyrogenicity in rabbits and mitogenicity in mouse spleen cells. On the other hand, purified LPS from Bacteroides gingivalis exhibits high potency in its ability to stimulate 45Ca release from prelabeled fetal rat bones and to inhibit Ca influx into osteoclast‐like cells.

These results demonstrate that this anorganic bovine bone graft material is able to support the attachment and proliferation of osteoblastic cells.

At a concentration of 0.5 mg/ml, CHX and, to a lesser extent, MINO had a cytotoxic effect on osteoblast proliferation in vitro. However, DOXY seemed to enhance maturation and differentiation rather than proliferation. In addition to DOXY's beneficial effect as an adjunctive therapy to mechanical debridement in the treatment of periodontal disease, it may have an effect on periodontal regeneration.

The repair of craniofacial bone defects is surgically challenging due to the complex anatomical structure of the craniofacial skeleton. Current strategies for bone tissue engineering using a preformed scaffold have not resulted in the expected clinical regeneration due to difficulty in seeding cells into the deep internal space of scaffold, and the inability to inject them in minimally invasive surgeries. In this study, we used the osteoconductive and mechanical properties of nano-scale calcium sulfate (nCS) and the biocompatibility of alginate to develop the injectable nCS/alginate (nCS/A) paste, and characterized the effect of this nCS/A paste loaded with bone morphogenetic protein 2 (BMP2) gene-modified rat mesenchymal stem cells (MSCs) on bone and blood vessel growth. Our results showed that the nCS/A paste was injectable under small injection forces. The mechanical properties of the nCS/A paste were increased with an increased proportion of alginate. MSCs maintained their viability after the injection, and MSCs and BMP2 gene-modified MSCs in the injectable pastes remained viable, osteodifferentiated, and yielded high alkaline phosphatase activity. By testing the ability of this injectable paste and BMP2-gene-modified MSCs for the repair of critical-sized calvarial bone defects in a rat model, we found that BMP2-gene-modified MSCs in nCS/A (nCS/A+M/B2) showed robust osteogenic activity, which resulted in consistent bone bridging of the bone defects. The vessel density in nCS/A+M/B2 was significantly higher than that in the groups of blank control, nCS/A alone, and nCS/A mixed with MSCs (nCS/A+M). These results indicate that BMP2 promotes MSCs-mediated bone formation and vascularization in nCS/A paste. Overall, the results demonstrated that the combination of injectable nCS/A paste and BMP2-gene-modified MSCs is a new and effective strategy for the repair of bone defects.

No abstract

The effects of parathyroid hormone (PTH) and cyclic 3',5'-AMP (cyclic AMP) on calcium transport were studied in isolated bone cells. Bone cells were isolated by collagenase digestion of 20-21 day old fetal rat calvaria. Calcium transport was measured with 45Ca. PTH (0.2 mug/ml) increased calcium uptake 30--40% over control values at 37 C. At 4 C, the effects were magnified and 70--170% increases in calcium uptake were observed. The effects were present 1--10 minutes after the simultaneous addition of hormone and 45Ca. PTH had no effect on calcium efflux. Neither dibutyryl cyclic AMP (10(-4)-10(-3)M) nor cyclic AMP (10(-7)-3 X 10(-6)M) had any effect on calcium uptake or efflux. Methylisobutylxanthine (0.1 mM) caused no change in calcium uptake although increase in cyclic AMP were noted. The characteristic PTH-induced increase in cyclic AMP seen at 37 C was not observed at 4 C. It is postulated that PTH increases the permeability of bone cell membranes to calcium. At 4 C the membrane is relatively impermeable so the PTH effect is magnified. The PTH-induced increase does not appear to be mediated through cyclic AMP.

These experiments demonstrate the feasibility of using PDGF-BB in combination with alloplastic materials such as beta-TCP or CaSO(4) to serve as more effective bone graft materials with enhanced osteogenic properties.