The project is based on collaboration with the laboratory of the Department of Medicine, Division of Endocrinology of the Emory University (Atlanta, USA), directed by Prof. Roberto Pacifici. The project encompasses an outgoing phase (February 2005- December 2006) and a return phase (December 2006- August 2007) Post-menopausal osteoporosis is a bone disease of high prevalence and a cause of substantial morbidity and mortality due to its association with fractures. In the recent years, substantial progresses have been made in the understanding of the regulatory function exerted by immune cells over bone homeostasis. In fact, naïve and activated T cells have been reported to play a key role in the regulation of osteoclasts formation through increased production of RANKL, osteoprotegerin (OPG), IL-6, IFN-. Furthermore, increased antigen presentation has been demonstrated to play a key role as a mechanism of activation of T cells after estrogen depletion in mice. The hypothesis that site-specific initiation of T cell-mediated immune response may take place in the bone marrow (BM) has been recently demonstrated (Feuerer M et al. Nat Medicine 2003), and may constitute a novel concept in the investigation of the mechanisms of bone homeostasis. With the present research project, local activation of immune cells within the bone marrow microenvironment was investigated in murine models of osteoporosis and in human specimens of bone marrow from osteoporotic women, following preliminary observations that dendritic cells (DC) are selectively activated in the BM but not in other tissues in mice. The project will consist in 2 specific aims: Specific Aim 1b, ‘Understanding DC contribution to bone loss’. To investigate in vivo the contribution of increased antigen presentation by DC on bone loss induced by estrogen depletion. Rationale: preliminary data suggest that bone marrow restricted T cell priming by dendritic cells may be a novel mechanism by which ovariectomy induces accelerated bone resorption. However, the relative contribution of this mechanism is unknown. To address this question we will make use of the transgenic mice OT-II, in which T cells are not activated by APC unless mice are treated with ovalbumin. In these mice, ovariectomy fails to induce bone loss (Cenci et al. PNAS 2003). Dendritic cells will be isolated from C57BL/6 mice, pulsed in vitro with OVA, and adoptively transferred into OT-II mice previously ovariectomized or sham operated, according to methods well described (Martin-Fontecha et al. J Exp Med 2003). At the end of the experiment bone mineral density (BMD) and markers of T cell activation will be evaluated (see section methods for further details). In this model, DC will be the only cell type able to optimally interact with T cells inducing activation and proliferation. The expected result is that dendritic cells pulsed with OVA will restore in vivo the ability of ovariectomy to cause bone loss. Specific Aim 3, ‘Translating to humans’: to characterize dendritic cells localization and function in human tissues. Rationale: to clarify if findings based on mouse models can be translated to humans in the perspective of new therapeutic strategies. Dendritic cells, along with chemokines regulated in vivo by estrogen will be investigated in specimens obtained from human biopsies of osteoporotic patients undergoing major surgery (hip sobstitution) for fractures. The purpose of this working package is defining in humans what is the localization and the activation state of dendritic cells in osteoporosis specimens compared to controls (non osteoporotic patients undergoing hip substitution for trauma) Also, the availability of human bone marrow samples will allow an ex-vivo characterization of the main activation markers of dendritic cells .

Denditric cells as possible determinants for bone marrow restricted T cell activation and bone loss in estrogen depleted mice. OSTEODEN €194.763 / Facchini A.. - (2005).

Denditric cells as possible determinants for bone marrow restricted T cell activation and bone loss in estrogen depleted mice. OSTEODEN €194.763

FACCHINI, ANDREA
2005

Abstract

The project is based on collaboration with the laboratory of the Department of Medicine, Division of Endocrinology of the Emory University (Atlanta, USA), directed by Prof. Roberto Pacifici. The project encompasses an outgoing phase (February 2005- December 2006) and a return phase (December 2006- August 2007) Post-menopausal osteoporosis is a bone disease of high prevalence and a cause of substantial morbidity and mortality due to its association with fractures. In the recent years, substantial progresses have been made in the understanding of the regulatory function exerted by immune cells over bone homeostasis. In fact, naïve and activated T cells have been reported to play a key role in the regulation of osteoclasts formation through increased production of RANKL, osteoprotegerin (OPG), IL-6, IFN-. Furthermore, increased antigen presentation has been demonstrated to play a key role as a mechanism of activation of T cells after estrogen depletion in mice. The hypothesis that site-specific initiation of T cell-mediated immune response may take place in the bone marrow (BM) has been recently demonstrated (Feuerer M et al. Nat Medicine 2003), and may constitute a novel concept in the investigation of the mechanisms of bone homeostasis. With the present research project, local activation of immune cells within the bone marrow microenvironment was investigated in murine models of osteoporosis and in human specimens of bone marrow from osteoporotic women, following preliminary observations that dendritic cells (DC) are selectively activated in the BM but not in other tissues in mice. The project will consist in 2 specific aims: Specific Aim 1b, ‘Understanding DC contribution to bone loss’. To investigate in vivo the contribution of increased antigen presentation by DC on bone loss induced by estrogen depletion. Rationale: preliminary data suggest that bone marrow restricted T cell priming by dendritic cells may be a novel mechanism by which ovariectomy induces accelerated bone resorption. However, the relative contribution of this mechanism is unknown. To address this question we will make use of the transgenic mice OT-II, in which T cells are not activated by APC unless mice are treated with ovalbumin. In these mice, ovariectomy fails to induce bone loss (Cenci et al. PNAS 2003). Dendritic cells will be isolated from C57BL/6 mice, pulsed in vitro with OVA, and adoptively transferred into OT-II mice previously ovariectomized or sham operated, according to methods well described (Martin-Fontecha et al. J Exp Med 2003). At the end of the experiment bone mineral density (BMD) and markers of T cell activation will be evaluated (see section methods for further details). In this model, DC will be the only cell type able to optimally interact with T cells inducing activation and proliferation. The expected result is that dendritic cells pulsed with OVA will restore in vivo the ability of ovariectomy to cause bone loss. Specific Aim 3, ‘Translating to humans’: to characterize dendritic cells localization and function in human tissues. Rationale: to clarify if findings based on mouse models can be translated to humans in the perspective of new therapeutic strategies. Dendritic cells, along with chemokines regulated in vivo by estrogen will be investigated in specimens obtained from human biopsies of osteoporotic patients undergoing major surgery (hip sobstitution) for fractures. The purpose of this working package is defining in humans what is the localization and the activation state of dendritic cells in osteoporosis specimens compared to controls (non osteoporotic patients undergoing hip substitution for trauma) Also, the availability of human bone marrow samples will allow an ex-vivo characterization of the main activation markers of dendritic cells .
2005
Denditric cells as possible determinants for bone marrow restricted T cell activation and bone loss in estrogen depleted mice. OSTEODEN €194.763 / Facchini A.. - (2005).
Facchini A.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/38861
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