Elucidating the significance of osteopetrotic bone marrow niche in hematopoietic stem and progenitor cells, and its implications for stem cell therapy

Autosomal recessive osteopetrosis (ARO) caused by defects in the TCIRG1 gene is a severe inherited bone disease characterized by bone fibrosis, hepatosplenomegaly and progressive pancytopenia leading to increased infection susceptibility and death in the first decade of life. Hematopoietic stem cell transplantation (HSCT) is the treatment of choice; however its success is hampered by the limited availability of donors, conditioning regimen toxicity and transplant related morbidity. We have developed an innovative gene therapy platform coupling transduction with expansion of hematopoietic stem and progenitor cells (HSPC) spontaneously circulating in the peripheral blood of ARO patients thus contributing to extend the therapeutic scenario and offer a cure to the severe forms of osteopetrosis. In the present project, we will address new challenging clinical issues with the final goal of providing instrumental data for the future tuning and implementation of gene therapy osteopetrosis. For this purpose, we will dissect the molecular and cellular heterogeneity of hematopoietic stem and progenitor cells spontaneously circulating in the peripheral blood of the patients and evaluate the effect of repeated infections on hematopoietic stem cell stemness and quiescence. In parallel, we will evaluate the feasibility and efficacy of mobilization procedure and novel conditioning-based biological compound exploiting the mouse model of the disease. Finally, we propose to generate a novel humanized mouse model carrying an osteopetrotic niche to study the dynamics of circulating HSPC. In conclusion, results from this project will allow to develop a more precise correction therapy, further complementing the future clinical translation of ARO gene therapy.