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International audience; Cohen syndrome (CS) is a rare genetic disorder due to variation in the VPS13B gene. It is characterized by a wide variety of clinical features that includes a typical facial dysmorphism, hypotonia, neutropenia, microcephaly, intellectual disability and severe visual impairments. In their early childhood, CS patients already suffer from myopia and a retinal dystrophy that affects both peripheral and central vision. In addition, long-term outcome studies showed that cataract reaches a high prevalence in adults with CS in their forties. To understand how VPS13B variants lead to these visual impairments and have the possibility to assess therapeutic approaches, we generated the Vps13bΔEx3/ΔEx3 mouse model. Cataract was almost systematic in 2-month-old animals. Eye fundi appeared normal until cataract development, but OCT, ERG and histological data suggest that rod homeostasis may be affected in the few Vps13bΔEx3/ΔEx3 mice without cataract after 5 months of age. Immunostaining of the lens revealed that cataract formation was associated with the appearance of large vacuoles in the cortical area, epithelial-mesenchymal transition and fibrosis. In later stages, cataracts became hypermature, lens capsules ruptured, and sclerotic nuclear parts dissociated. Altogether, our results show that Vps13b has a function in lens homeostasis in mice and that the Vps13bΔEx3/ΔEx3 mouse line is a useful model to study the pathomechanism leading to CS-related cataract.

International audience; The bone microenvironment (e.g. glycosaminoglycans (GAGs), growth factors) plays a major role in bone resorption, especially in the formation of osteoclasts which differentiate from the hematopoietic lineage in the presence of RANKL. Previous studies revealed that GAGs may influence osteoclastogenesis, but data are very controversial, some studies showing an inhibitory effect of GAGs on osteoclastic differentiation whereas others demonstrated a stimulatory effect. To clarify their activities, we investigated the effect of 5 families of GAGs in three different models of human/mouse osteoclastogenesis. The present data revealed that heparin inhibited osteoclastogenesis in these three models, which was confirmed by a decrease in mRNA expression of osteoclastic markers and by an inhibition of the bone resorption capacity. We also demonstrated in RAW 264.7 cells that other families of GAGs different from heparin inhibited RANKL-induced osteoclastogenesis, and that this inhibition was dependent on the length and the level of sulfation of GAGs. In the present work, heparin did not bind to RANKL and did not modulate RANKL signaling. Heparin acted at 2 distinct steps of osteoclastogenesis from human CD14(+) cells: first, heparin strongly decreased the adherence of osteoclast precursors, and secondly inhibited osteoclasts to spread and to be active. Furthermore, the second action of heparin was reversible as the removal of heparin at the end of the culture time allowed the condensed cells to spread out and showed the formation of morphological active osteoclasts. The present work clearly evidences that GAGs inhibit osteoclastogenesis in vitro and strengthens the therapeutic interest of defined GAGs in osteolytic diseases.

International audience; The bone microenvironment (e.g. glycosaminoglycans (GAGs), growth factors) plays a major role in bone resorption, especially in the formation of osteoclasts which differentiate from the hematopoietic lineage in the presence of RANKL. Previous studies revealed that GAGs may influence osteoclastogenesis, but data are very controversial, some studies showing an inhibitory effect of GAGs on osteoclastic differentiation whereas others demonstrated a stimulatory effect. To clarify their activities, we investigated the effect of 5 families of GAGs in three different models of human/mouse osteoclastogenesis. The present data revealed that heparin inhibited osteoclastogenesis in these three models, which was confirmed by a decrease in mRNA expression of osteoclastic markers and by an inhibition of the bone resorption capacity. We also demonstrated in RAW 264.7 cells that other families of GAGs different from heparin inhibited RANKL-induced osteoclastogenesis, and that this inhibition was dependent on the length and the level of sulfation of GAGs. In the present work, heparin did not bind to RANKL and did not modulate RANKL signaling. Heparin acted at 2 distinct steps of osteoclastogenesis from human CD14(+) cells: first, heparin strongly decreased the adherence of osteoclast precursors, and secondly inhibited osteoclasts to spread and to be active. Furthermore, the second action of heparin was reversible as the removal of heparin at the end of the culture time allowed the condensed cells to spread out and showed the formation of morphological active osteoclasts. The present work clearly evidences that GAGs inhibit osteoclastogenesis in vitro and strengthens the therapeutic interest of defined GAGs in osteolytic diseases.

International audience; Factor VIII-von Willebrand factor (FVIII.vWF) complex, a molecule involved in coagulation, can be physically associated with osteoprotegerin (OPG). OPG is an anti-osteoclastic protein and a soluble receptor for the proapoptotic protein TRAIL (tumor necrosis factor-related apoptosis-inducing ligand), suggesting a potential role of FVIII.vWF complex in bone and cancer biology. We, thus, assessed the effects of FVIII.vWF complex on osteoclastogenesis and cell survival. We first evidenced that FVIII.vWF complex inhibited RANKL-induced osteoclastogenesis and enhanced the inhibitory effect of OPG. Interestingly, we revealed by surface plasmon resonance that FVIII.vWF complex bound to RANKL, whereas recombinant FVIII and vWF did not. By modeling, we showed that the OPG binding domain to the A1 domain of vWF was closely located and partially overlapped to its binding site to RANKL. Then, we demonstrated that FVIII.vWF complex cancelled the inhibitory activity of OPG on TRAIL-induced apoptosis and characterized interactions between these molecules. The present work evidenced a direct activity of FVIII.vWF complex on osteoclasts and on induced cell apoptosis, pointing out its potential involvement in physiological bone remodeling or in bone damages associated with severe hemophilia and cancer development.

International audience; Factor VIII-von Willebrand factor (FVIII.vWF) complex, a molecule involved in coagulation, can be physically associated with osteoprotegerin (OPG). OPG is an anti-osteoclastic protein and a soluble receptor for the proapoptotic protein TRAIL (tumor necrosis factor-related apoptosis-inducing ligand), suggesting a potential role of FVIII.vWF complex in bone and cancer biology. We, thus, assessed the effects of FVIII.vWF complex on osteoclastogenesis and cell survival. We first evidenced that FVIII.vWF complex inhibited RANKL-induced osteoclastogenesis and enhanced the inhibitory effect of OPG. Interestingly, we revealed by surface plasmon resonance that FVIII.vWF complex bound to RANKL, whereas recombinant FVIII and vWF did not. By modeling, we showed that the OPG binding domain to the A1 domain of vWF was closely located and partially overlapped to its binding site to RANKL. Then, we demonstrated that FVIII.vWF complex cancelled the inhibitory activity of OPG on TRAIL-induced apoptosis and characterized interactions between these molecules. The present work evidenced a direct activity of FVIII.vWF complex on osteoclasts and on induced cell apoptosis, pointing out its potential involvement in physiological bone remodeling or in bone damages associated with severe hemophilia and cancer development.