The effect of vitamin D insufficiency significantly impairing the establishment of Ti6Al4V implant osseointegration in vivo was unexpectedly profound. The outcome of Ti-based endosseous implants may be confounded by the increasing prevalence of vitamin D insufficiency in our patient population.

A fine balance between bone resorption by osteoclasts and bone formation by osteoblasts maintains bone homeostasis. In patients with cherubism, gain-of-function mutations in 3BP2, which is encoded by SH3-domain binding protein 2 (SH3BP2), cause cystic lesions with activated osteoclasts that lead to craniofacial abnormalities. However, little is known about the function of wild-type 3BP2 in regulating bone homeostasis. Here we have shown that 3BP2 is required for the normal function of both osteoblasts and osteoclasts. Initial analysis showed that Sh3bp2 -/-mice developed osteoporosis as a result of reduced bone formation despite the fact that bone resorption was impaired. We demonstrated using reciprocal bone marrow chimeras, a cellintrinsic defect of the osteoblast and osteoclast compartments in vivo. Further, Sh3bp2 -/-osteoblasts failed to mature and form mineralized nodules in vitro, while Sh3bp2 -/-osteoclasts spread poorly and were unable to effectively degrade dentine matrix in vitro. Finally, we showed that 3BP2 was required for Abl activation in osteoblasts and Src activation in osteoclasts, and demonstrated that the in vitro defect of each cell type was restored by the respective expression of activated forms of these kinases. These findings reveal an unanticipated role for the 3BP2 adapter protein in osteoblast function and in coordinating bone homeostatic signals in both osteoclast and osteoblast lineages. Introduction3BP2 is an adapter protein that contains an N-terminal pleckstrin homology (PH) domain, a proline-rich stretch that binds to Src homology 3 (SH3) domain-containing proteins, and a C-terminal SH2 domain that binds to phosphotyrosine residues (1). 3BP2 was initially identified as a binding protein of the tyrosine kinase Abl (2). Work from our lab and others has identified the Src family kinases (SFKs), Syk, and the Vav family of Rho guanine nucleotide exchange factors (GEFs) as 3BP2-binding partners (1), all of which are known to play important roles in osteoclast function (3-5). Cherubism is a dominantly inherited syndrome characterized by excessive maxillary and mandibular bone resorption that is associated with activated osteoclasts and inflammatory cells creating interosseous cystic lesions (6). Single missense mutations in the gene encoding the adapter protein 3BP2 result in a gain-of-function alteration in the protein and is associated with the majority of cherubism patients (7). A mouse model that harbors 2 copies of a cherubism allele develops severe osteoporosis associated with highly activated osteoclasts (8).In order to elucidate the role of the wild-type form of 3BP2 in bone homeostasis, we analyzed loss-of-function mutant mice. As distinct from the osteoporotic phenotype of mice expressing the cherubism gain-of-function form of 3BP2 associated with active osteoclasts, we uncovered a complex bone phenotype in mice lacking 3BP2 characterized by loss-of-function in both the osteoclast and osteoblast lineages resulting in net decreased bone mineral density and reduced mechanical ...

Craniometaphyseal dysplasia (CMD) is a monogenic human disorder characterized by thickening of craniofacial bones and flaring metaphyses of long bones. Mutations for autosomal dominant CMD have been identified in the progressive ankylosis gene ANKH. Previous studies of Ank loss-of-function models, Ank null/null and Ank ank/ank mice, suggest that Ank plays a role in the regulation of bone mineralization. However, the mechanism for Ank mutations leading to CMD remains unknown. We generated the first knockin (KI) mouse model for CMD expressing a human mutation (Phe377 deletion) in ANK. Homozygous Ank knockin mice (Ank KI/KI ) replicate many typical features of human CMD including hyperostosis of craniofacial bones, massive jawbones, decreased diameters of cranial foramina, obliteration of nasal sinuses, fusion of middle ear bones, and club-shaped femurs. In addition, Ank KI/KI mice have increased serum alkaline phosphatase and TRACP5b, as reported in CMD patients. Biochemical markers of bone formation and bone resorption, N-terminal propeptide of type I procollagen and type I collagen cross-linked C-terminal telopeptide, are significantly increased in Ank KI/KI mice, suggesting increased bone turnover. Interestingly, Ank KI/KI bone marrow-derived macrophage cultures show decreased osteoclastogenesis. Despite the hyperostotic phenotype, bone matrix in Ank KI/KI mice is hypomineralized and less mature, indicating that biomechanical properties of bones may be compromised by the Ank mutation. We believe this new mouse model will facilitate studies of skeletal abnormalities in CMD at cellular and molecular levels.

This investigation provides a detailed histological and molecular analysis of thrombus organization in the swine aneurysm model. The companion study will describe the effect of embolic bioabsorbable polymers on this process.

Cherubism is an autosomal dominant disorder in children characterized by unwarranted symmetrical bone resorption of the jaws with fibrous tissue deposition. Mutations causing cherubism have been identified in the adaptor protein SH3BP2. Knock-in mice with a Pro416Arg mutation in Sh3bp2 exhibit a generalized osteoporotic bone phenotype. In this study, we examined the effects of this "cherubism" mutation on spectroscopic indices of "bone quality" and on osteoblast differentiation. Fourier-transform infrared imaging (FTIRI) analysis of femurs from wild-type and Sh3bp2 knockin mice showed decreased mineral content, decreased mineral crystallinity/crystal size, and increased collagen maturity in homozygous mutants. To assess osteoblast maturation in vivo, knock-in mice were crossed with transgenic mice over-expressing GFP driven by 3.6-kb or 2.3-kb Col1a1 promoter fragments. Reduced numbers of mature osteoblasts were observed in homozygous mice. Neonatal calvarial cultures, which were enriched for osteoblasts by depletion of hematopoietic cells (negative selection for Ter119-and CD45-positive cells) were investigated for osteoblast-specific gene expression and differentiation, which demonstrated that differentiation and mineralization in homozygous osteoblast cultures was impaired. Co-cultures with calvarial osteoblasts and bone marrow macrophages showed that mutant osteoblasts appear to increase osteoclastogenesis resulting in increased bone resorption on bone chips. In summary, the Sh3bp2 mutation in cherubism mice alters bone quality, reduces osteoblast function, and may contribute to excessive bone resorption by osteoclasts. Our data, together with previous osteoclast studies, demonstrate a critical role of Sh3bp2 in bone remodeling and osteoblast differentiation.

Degradation speed was not the only factor determining the strength of the biological response. Polysorb induced an early, unique granulation tissue that conferred greater mechanical strength to the intraaneurysmal coilthrombus complex. Enhancing the formation of this polymer-induced granulation tissue may provide a new direction for improving long-term anatomical outcomes in cases involving aneurysms embolized with detachable coils.

Introduction Cherubism is a human genetic disorder that causes bilateral symmetrical enlargement of the maxilla and mandible in children. It is caused by mutations in SH3BP2. The exact pathogenesis of the disorder is an area of active research. Sh3bp2 knock-in mice were developed by introducing a Pro416Arg mutation (Pro418Arg in humans) in the mouse genome. The osteoclast phenotype of this mouse model was recently described. Methods We examined the bone phenotype of the cherubism mouse model, the role of Sh3bp2 during bone formation, osteoblast differentiation and osteoblast function. Results We observed delays in early postnatal development of homozygous Sh3bp2KI/KI mice. Sh3bp2KI/KI mice exhibit increased growth plate thickness and significantly decreased trabecular bone thickness and reduced bone mineral density. Histomorphometric and μ-CT analyses reveal bone loss in cranial and appendicular skeleton. Sh3bp2KI/KI mice also exhibit a significant decrease in osteoid formation that indicates a defect in osteoblast function. Calvarial osteoblast cell cultures exhibit a decrease in alkaline phosphatase expression and mineralization suggesting reduced differentiation potential. Gene expression of osteoblast differentiation markers like collagen type-I, alkaline phosphatase and osteocalcin are decreased in osteoblast cultures from Sh3bp2KI/KI mice. Conclusions These data suggest that Sh3bp2 function regulates bone homeostasis not only through osteoclast-specific effects but also through effects on osteoblast differentiation and function.

Extended follow-up demonstrates that despite SRT failure, PCSS remains high in select patients. Early failure (≤1 y after SRT) predicted for significantly worse outcome and may represent a subgroup with more aggressive disease that may be considered for further prospective clinical studies.