We compared the effects of a nitrogen-containing bisphosphonate (N-BP), zoledronic acid (ZA), and an anti-mouse RANKL antibody (anti-mRANKL Ab) on the bone tissue pathology of a transgenic mouse ...model of human fibrous dysplasia (FD). For comparison, we also reviewed the histological samples of a child with McCune–Albright syndrome (MAS) treated with Pamidronate for 3 years. EF1α-Gsα
R201C
mice with FD-like lesions in the tail vertebrae were treated with either 0.2 mg/kg of ZA at day 0, 7, and 14 or with 300 μg/mouse of anti-mRANKL Ab at day 0 and 21. All mice were monitored by Faxitron and histological analysis was performed at day 42. ZA did not affect the progression of the radiographic phenotype in EF1α-Gsα
R201C
mice. FD-like lesions in the ZA group showed the persistence of osteoclasts, easily detectable osteoclast apoptotic activity and numerous “giant osteoclasts”. In contrast, in the anti-mRANKL Ab-treated mice, osteoclasts were markedly reduced/absent, the radiographic phenotype reverted and the FD-like lesions were extensively replaced by newly formed bone. Numerous “giant osteoclasts” were also detected in the samples of the child with MAS. This study supports the hypothesis that osteoclasts per se, independently of their resorptive activity, are essential for development and expansion of FD lesions.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Identifying the molecular networks that underlie Fibrous Dysplasia (FD) is key to understand the pathogenesis of the disease, to refine current diagnostic approaches and to develop efficacious ...therapies. In this study, we used the NanoString nCounter Analysis System to investigate the gene signature of a series of nine Formalin Fixed Decalcified and Paraffin-Embedded (FFDPE) bone biopsies from seven FD patients.
We analyzed the expression level of 770 genes. Unsupervised clustering analysis demonstrated partitioning into two clusters with distinct patterns of gene expression. Differentially expressed genes included growth factors, components of the Wnt signaling system, interleukins and some of their cognate receptors, ephrin ligands, matrix metalloproteinases, neurotrophins and genes encoding components of the cAMP-dependent protein kinase. Interestingly, two tissue samples obtained from the same skeletal site of one patient one year apart failed to segregate in the same cluster. Retrospective histological review of the samples revealed different microscopic aspects in the two groups.
The results of our pilot study suggest that the genetic signature of FD is heterogeneous and varies according to the histology and, likely, to the age of the lesion. In addition, they show that the Nanostring technology is a valuable tool for molecular translational studies on archival FFDPE material in FD and other rare bone diseases.
•We used the NanoString technology to analyze Formalin Fixed Decalcified Paraffin Embedded (FFDPE) Fibrous Dysplasia samples.•We show that Fibrous Dysplasia lesions may have different molecular profiles consistent with its histological heterogeneity.•NanoString technology is a valuable tool for molecular studies on rare bone diseases by using FFDPE archival material.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Gsα/cAMP signaling pathway mediates the effect of a variety of hormones and factors that regulate the homeostasis of the post-natal skeleton. Hence, the dysregulated activity of Gsα due to ...gain-of-function mutations (R201C/R201H) results in severe architectural and functional derangements of the entire bone/bone marrow organ. While the consequences of gain-of-function mutations of Gsα have been extensively investigated in osteoblasts and in bone marrow osteoprogenitor cells at various differentiation stages, their effect in adipogenically-committed bone marrow stromal cells has remained unaddressed. We generated a mouse model with expression of Gsα
driven by the Adiponectin (Adq) promoter. Adq-Gsα
mice developed a complex combination of metaphyseal, diaphyseal and cortical bone changes. In the metaphysis, Gsα
caused an early phase of bone resorption followed by bone deposition. Metaphyseal bone formation was sustained by cells that were traced by Adq-Cre and eventually resulted in a high trabecular bone mass phenotype. In the diaphysis, Gsα
, in combination with estrogen, triggered the osteogenic activity of Adq-Cre-targeted perivascular bone marrow stromal cells leading to intramedullary bone formation. Finally, consistent with the previously unnoticed presence of Adq-Cre-marked pericytes in intraosseous blood vessels, Gsα
caused the development of a lytic phenotype that affected both cortical (increased porosity) and trabecular (tunneling resorption) bone. These results provide the first evidence that the Adq-cell network in the skeleton not only regulates bone resorption but also contributes to bone formation, and that the Gsα/cAMP pathway is a major modulator of both functions.
Fibrous dysplasia of bone (FD) is a crippling skeletal disease associated with postzygotic mutations (R201C, R201H) of the gene encoding the α subunit of the stimulatory G protein, Gs. By causing a ...characteristic structural subversion of bone and bone marrow, the disease results in deformity, hypomineralization, and fracture of the affected bones, with severe morbidity arising in childhood or adolescence. Lack of inheritance of the disease in humans is thought to reflect embryonic lethality of germline-transmitted activating Gsα mutations, which would only survive through somatic mosaicism. We have generated multiple lines of mice that express Gsα(R201C) constitutively and develop an inherited, histopathologically exact replica of human FD. Robust transgene expression in neonatal and embryonic tissues and embryonic stem (ES) cells were associated with normal development of skeletal tissues and differentiation of skeletal cells. As in humans, FD lesions in mice developed only in the postnatal life; a defined spatial and temporal pattern characterized the onset and progression of lesions across the skeleton. In individual bones, lesions developed through a sequence of three distinct histopathological stages: a primary modeling phase defined by endosteal/medullary excess bone formation and normal resorption; a secondary phase, with excess, inappropriate remodeling; and a tertiary fibrous dysplastic phase, which reproduced a full-blown replica of the human bone pathology in mice of age ≥1 year. Gsα mutations are sufficient to cause FD, and are per se compatible with germline transmission and normal embryonic development in mice. Our novel murine lines constitute the first model of FD.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
We recently reported the generation and initial characterization of the first direct model of human fibrous dysplasia (FD; OMIM #174800), obtained through the constitutive systemic expression of one ...of the disease-causing mutations, Gsα(R201C) , in the mouse. To define the specific pathogenetic role(s) of individual cell types within the stromal/osteogenic system in FD, we generated mice expressing Gsα(R201C) selectively in mature osteoblasts using the 2.3kb Col1a1 promoter. We show here that this results in a striking high bone mass phenotype but not in a mimicry of human FD. The high bone mass phenotype involves specifically a deforming excess of cortical bone and prolonged and ectopic cortical bone remodeling. Expression of genes characteristic of late stages of bone cell differentiation/maturation is profoundly altered as a result of expression of Gsα(R201C) in osteoblasts, and expression of the Wnt inhibitor Sost is reduced. Although high bone mass is, in fact, a feature of some types/stages of FD lesions in humans, it is marrow fibrosis, localized loss of adipocytes and hematopoietic tissue, osteomalacia, and osteolytic changes that together represent the characteristic pathological profile of FD, as well as the sources of specific morbidity. None of these features are reproduced in mice with osteoblast-specific expression of Gsα(R201C) . We further show that hematopoietic progenitor/stem cells, as well as more mature cell compartments, and adipocyte development are normal in these mice. These data demonstrate that effects of Gsα mutations underpinning FD-defining tissue changes and morbidity do not reflect the effects of the mutations on osteoblasts proper.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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