Evaluation of an anorganic bovine-derived mineral with P-15 hydrogel bone graft: preliminary study in a rabbit cranial bone model

Authors

Sérgio Matos, Fernando Guerra, Jack T. Krauser, Helena Figueiredo, João Pedro Marcelino, Mariano Sanz

Abstract

The present investigation aimed to assess the bone-regenerative potential of two formulations of anorganic bovine-derived mineral bound to a P-15 (ABM/P-15) bone graft – the particulate and the hydrogel forms – in a delayed healing rabbit cranial defect model. Ten adult male New Zealand White rabbits were used to create two 8 mm transcortical cranial defects per rabbit and each one received randomly the test material (ABM/P-15 carboxymethyl cellulose (CMC)-hydrogel graft), the standard control material (ABM/P-15 particulate graft) or remained empty as a negative control. The defects were allowed to heal for 2 and 4 weeks. Qualitative and quantitative histological outcomes were assessed on undecalcified sections. In the defects grafted with the test material, at both time points, there was a marked random migration of the bone substitute particles. As a consequence, the space maintenance provision was lost and new bone formation was reduced compared with the control particulate graft material. The histomorphometric analysis showed that the control material attained better results, with an average of 13.8 ± 1.9% and 18.2 ± 4.4% of new bone at 2 and 4 weeks, compared with 8.5 ± 2.4% and 13 ± 2.9% for the test material. These differences were significant at 2 weeks (P≤0.05), but not at 4 weeks (P>0.05). Additionally, there was a significant difference in the total area of mineralized tissue (new bone plus particles), favoring the standard control over the test material: 43.2 ± 14.4% vs. 14.2 ± 5.3% at 2 weeks and 56.9 ± 4.2% vs. 24.2 ± 9.6% at 4 weeks, respectively. The test ABM/P-15 CMC-hydrogel graft material behaved in this animal model by migration of the graft particles, what determined an unpredictable osseoconduction and, consequently, a decreased quality and quantity of bone regeneration as compared with the osseopromotive behavior exhibited by the standard particulate form of the ABM/P-15 control graft. It is therefore suggested to restrain the application of the hydrogel graft form in non-contained anatomical bone defects.

Link to Article

http://dx.doi.org/10.1111/j.1600-0501.2011.02179.x

Temporal and spatial expression of osteoactivin during fracture repair

Authors

Samir M. Abdelmagid, Mary F. Barbe, Michael Hadjiargyrou, Thomas A. Owen, Roshanak Razmpour, Saqib Rehman, Steven N. Popoff, Fayez F. Safadi

Abstract

We previously identified osteoactivin (OA) as a novel secreted osteogenic factor with high expression in developing long bones and calvaria, and that stimulates osteoblast differentiation and matrix mineralization in vitro. In this study, we report on OA mRNA and protein expression in intact long bone and growth plate, and in fracture calluses collected at several time points up to 21 days post-fracture (PF). OA mRNA and protein were highly expressed in osteoblasts localized in the metaphysis of intact tibia, and in hypertrophic chondrocytes localized in growth plate, findings assessed by in situ hybridization and immunohistochemistry, respectively. Using a rat fracture model, Northern blot analysis showed that expression of OA mRNA was significantly higher in day-3 and day-10 PF calluses than in intact rat femurs. Using in situ hybridization, we examined OA mRNA expression during fracture healing and found that OA was temporally regulated, with positive signals seen as early as day-3 PF, reaching a maximal intensity at day-10 PF, and finally declining at day-21 PF. At day-5 PF, which correlates with chondrogenesis, OA mRNA levels were significantly higher in the soft callus than in intact femurs. Similarly, we detected high OA protein immunoexpression throughout the reparative phase of the hard callus compared to intact femurs. Interestingly, the secreted OA protein was also detected within the newly made cartilage matrix and osteoid tissue. Taken together, these results suggest the possibility that OA plays an important role in bone formation and serves as a positive regulator of fracture healing.

Link to Article

http://dx.doi.org/10.1002/jcb.22702

Bone biopsy findings and correlation with clinical, radiological and biochemical parameters in children with fractures

Authors

Mervi K Mäyränpää, Inari S Tamminen, Heikki Kröger, Outi Mäkitie

Abstract

In children the diagnosis of osteoporosis is based on fracture history and DXA-derived BMD. Bone biopsy is an invasive but accurate method to study bone characteristics. In this study we evaluated bone biopsy findings and their correlation with non-invasive measures of bone health. Transiliac bone biopsy was performed on 24 consecutive children (17 boys, median age 12 years, range 6-16 years) evaluated for suspected primary osteoporosis. Biopsy findings were compared with normative data and correlated with clinical, radiological, biochemical, and densitometric findings. The patients had sustained altogether 64 non-vertebral fractures (median 2.5) from low- or moderate-energy traumas, and 14 patients (58%) had vertebral fractures. The median lumbar spine BMD Z-score was –1.2 (range -3.1 to +1.0). Hypovitaminosis D was present in 58%. Histomorphometry showed low bone volume in 7 patients and normal bone volume in 17. Bone turnover was high in 7, low in 7, and normal in 10 patients. Histomorphometric findings correlated poorly with fracture history, serum bone turnover markers and DXA findings. Vitamin D deficiency and low lumbar BMD were associated with high bone turnover in the biopsy. These findings underscore the difficulties in diagnosing pediatric osteoporosis. Bone histomorphometry gives additional information and may be useful when considering bisphosphonate treatment in children with suspected primary osteoporosis.

Link to Article

http://dx.doi.org/10.1002/jbmr.373

Temporal and spatial expression of osteoactivin during fracture repair

Authors

Samir M. Abdelmagid, Mary F. Barbe, Michael Hadjiargyrou, Thomas A. Owen, Roshanak Razmpour, Saqib Rehman, Steven N. Popoff, Fayez F. Safadi

Abstract

We previously identified osteoactivin (OA) as a novel secreted osteogenic factor with high expression in developing long bones and calvaria, and that stimulates osteoblast differentiation and matrix mineralization in vitro. In this study, we report on OA mRNA and protein expression in intact long bone and growth plate, and in fracture calluses collected at several time points up to 21 days post-fracture (PF). OA mRNA and protein were highly expressed in osteoblasts localized in the metaphysis of intact tibia, and in hypertrophic chondrocytes localized in growth plate, findings assessed by in situ hybridization and immunohistochemistry, respectively. Using a rat fracture model, Northern blot analysis showed that expression of OA mRNA was significantly higher in day-3 and day-10 PF calluses than in intact rat femurs. Using in situ hybridization, we examined OA mRNA expression during fracture healing and found that OA was temporally regulated, with positive signals seen as early as day-3 PF, reaching a maximal intensity at day-10 PF, and finally declining at day-21 PF. At day-5 PF, which correlates with chondrogenesis, OA mRNA levels were significantly higher in the soft callus than in intact femurs. Similarly, we detected high OA protein immuno-expression throughout the reparative phase of the hard callus compared to intact femurs. Interestingly, the secreted OA protein was also detected within the newly made cartilage matrix and osteoid tissue. Taken together, these results suggest the possibility that OA plays an important role in bone formation and serves as a positive regulator of fracture healing.

Link to Article

http://dx.doi.org/10.1002/jcb.22702

Multiple roles for CCR2 during fracture healing

Authors

Xing, Z. and Lu, C. and Hu, D. and Yu, Y. and Wang, X. and Colnot, C. and Nakamura, M. and Wu, Y. and Miclau, T. and Marcucio, R.S.

Abstract

Bone injury induces an inflammatory response that involves neutrophils, macrophages and other inflammatory cells. The recruitment of inflammatory Ccr2 transcripts and the filtration of macrophages into fracture calluses were most robust during the early phases of fracture healing. We then determined that the number of macrophages at the fracture site was significantly lower in Ccr2–/– mice compared with wild-type controls at 3 days injury. As a result, impaired vascularization, decreased formation of callus, and delayed maturation of cartilage were observed at 7 days after in mutant mice. At day 14, Ccr2–/– mice had less bone in their calluses. At day 21, Ccr2–/– mice had larger calluses and more bone compared with wild-type mice, suggesting a delayed remodeling. In addition, we examined the effect of Ccr2 mutation on osteoclasts. We found that a lack of Ccr2 did not affect the number of osteoclasts within fracture calluses at 21 days after injury. However, Ccr2–/– osteoclasts exhibited a decreased ability to resorb bone compared with wild-type cells, which could contribute to the delayed remodeling of fracture calluses observed in Ccr2–/– mice. Collectively, these results indicate that a deficiency of Ccr2 reduces the infiltration of macrophages and impairs the function of osteoclasts, leading to delayed fracture healing.

Link to Article

http://dmm.biologists.org/content/early/2010/03/25/dmm.003186.full.pdf