Increased cancellous bone and connectivity in coxarthrosis

Patients with coxarthrosis (cOA) have a reduced incidence of intracapsular femoral neck fracture, suggesting that cOA offers protection. The distribution of bone in the femoral neck was compared in cases of coxarthrosis and postmortem controls to assess the possibility that disease-associated changes might contribute to reduced fragility. Whole cross-section femoral neck biopsies were obtained from 17 patients with cOA and 22 age- and sex-matched cadaveric controls. Densitometry was performed using peripheral quantitated computed tomography (pQCT) and histomorphometry on 10-µm plastic-embedded sections. Cortical bone mass was not different between cases and controls (P > 0.23), but cancellous bone mass was increased by 75% in cOA (P = 0.014) and histomorphometric cancellous bone area by 71% (P <0.0001). This was principally the result of an increase of apparent density (mass/vol) of cancellous bone (+45%, P = 0.001). Whereas cortical porosity was increased in the cases (P <0.0001), trabecular width was also increased overall in the cases by 52% (P <0.001), as was cancellous connectivity measured by strut analysis (P <0.01). Where osteophytic bone was present (n = 9) there was a positive relationship between the amount of osteophyte and the percentage of cancellous area (P <0.05). Since cancellous bone buttresses and stiffens the cortex so reducing the risk of buckling, the increased cancellous bone mass and connectivity seen in cases of cOA probably explain, at least in part, the ability of patients with cOA to resist intracapsular fracture of the femoral neck during a fall.

Chondrogenic Differentiation Alters the Immunosuppressive Property of Bone Marrow-Derived Mesenchymal Stem Cells, and the Effect is Partially due to the Upregulated Expression of B7 Molecules

To investigate the immunosuppressive properties of mesenchymal stem cells (MSCs), in the present study we examined the immunogenicity of undifferentiated and tri-lineage (chondrocytes, osteoblasts and adipocytes) differentiated rat bone marrow-derived MSCs under xenogeneic conditions. After chondrogenic-differentiation, rat bone marrow-derived MSCs stimulated human peripheral blood monocyte-derived DCs (hDCs), leading to 8- and 4-fold higher lymphocyte proliferation and cytotoxicity than that of undifferentiated MSCs. The Chondrogenic-differentiated MSCs were chemotactic to hDCs in Dunn chamber chemotaxis system and were rosetted by hDCs inrosette assays. Flow cytometry analysis revealed that chondrogenic-differentiated MSCs had promoted hDCs maturation causing higher CD83 expression in hDCs, whereas undifferentiated MSCs, osteogenic-and adipogenic-differentiated MSCs showed inhibitory effect on hDCs maturation. The co-stimulatory molecules B7 were up-regulated only in the chondrogenic-differentiated MSCs. After blocking B7 molecules with specific monoclonal antibodies in the chondrogenic-differentiated MSCs, CD83 expression of co-cultured hDCs was greatly reduced. In conclusion, chondrogenic differentiation may increase the immunogenicity of MSCs, leading to stimulation of DCs. The up-regulated expression of B7 molecules on the chondrogenic differentiated MSCs may be partially responsible for this event.

Allogenic Peripheral Blood Derived Mesenchymal Stem Cells (MSCs) Enhance Bone Regeneration in Rabbit Ulna Critical-Sized Bone Defect Model

Mesenchymal stem cells (MSCs) were demonstrated to exist within peripheral blood (PB) of several mammalian species including human, guinea pig, mice, rat, and rabbit. Whether or not the PB derived MSCs (PBMSCs) could enhance the regeneration of large bone defects have not been reported. In this study, rabbit MSCs were obtained from mononuclear cells (MNCs) cultures of both the PB and bone marrow (BM) origin. The number of PBMSCs was relatively lower, with the colony forming efficiency (CFE) ranging from 1.2-13 per million MNCs. Under specific inductive conditions, PBMSCs differentiated into osteoblasts, chondrocytes, and adipocytes, showing multi- differentiation ability similar to BMMSCs. Bilateral 20 mm critical-sized bone defects were created in the ulnae of twelve 6-month old New Zealand white rabbits. The defects were treated with allogenic PBMSCs/Skelite (porous calcium phosphate resorbable substitute), BMMSCs/Skelite, PBMNCs/Skelite, Skelite alone and left empty for 12 weeks. Bone regeneration was evaluated by serial radiography, peripheral quantitative computed tomography (pQCT), and histological examinations. The x-ray scores and the pQCT total bone mineral density in the PBMSCs/Skelite and BMMSCs/Skelite treated groups were significantly greater than those of the PBMNCs/Skelite and Skelite alone groups (p

Osteoclastogenesis induced by sRANKL and M-CSF from the non-adherent cell population of human bone marrow is inhibited by rhBMP-2 alone or together with rhVEGF

During bone development and repair, angiogenesis, osteogenesis and bone remodelling are closely associated processes that share some common mediators. In the present study non-adherent human bone marrow mononuclear cells under the induction of sRANKL and M-CSF, differentiated into osteoclasts with TRAP positive staining, VNR expression, and Ca-P resorptive activity. The effects of various combinations of rhBMP-2 (0, 3, 30, 300 ng/ml) and rhVEGF (0, 25 ng/ml) on osteoclastogenesis potentials were examined in this experimental system. The percentages of TRAP-positive multiple nucleated cells represent osteoclast differentiation potential and the percentages of resorptive areas in the Ca-P coated plates resemble osteoclast resorption capability. The presence of rhBMP-2 at 30 and 300 ng/ml showed inhibitory effects on osteoclast differentiation and their resorptive capability in the human osteoclast culture system. rhVEGF (25 ng/ml) enhanced the resorptive function of osteoclast whenever it was used alone or combined with 3 ng/ml rhBMP-2. However, rhVEGF induced resorptive function was inhibited by 30 ng/ml and 300 ng/ml rhBMP-2 at a dose-dependent manner. Statistical analysis demonstrated that an interactive effect exists between rhBMP-2 and rhVEGF on human osteoclastogenesis. These findings suggested that an interactive regulation may exist between BMPs and VEGF signaling pathways during osteoclastogenesis, exact mechanisms are yet to be elucidated.