HSPC biology: in vivo clonal tracking and lineage modeling

Hematopoietic Stem and Progenitor cell gene therapy is based on infusion of gene-modified hematopoietic stem cells collected from bone marrow or mobilized peripheral blood of patients with the aim to correct genetic disorders. This strategy has proven its efficacy in the treatment of several genetic diseases including primary immunodeficiencies (such as Wiskott-Aldrich Syndrome, Adenosine deaminase deficiency), in which affected patients display an impaired immune system and failure to clear viral and bacterial infections, and neurodegenerative disorders (such as Metachromatic leukodystrophy and Mucopolysaccharidosis type I), characterized by progressive loss of cognitive and motor activities. Our project has the main goal to study the fate and the behavior of gene-modified hematopoietic stem cells after infusion into the patients. In particular we are tracking each single hematopoietic stem cell and its progeny directly into the patients thanks to the concept that upon gene-correction, each stem cell became molecularly marked by distinct site, where the therapeutic vector integrated into the DNA of the patients’ cells. We showed that only a fraction of the infused hematopoietic stem and progenitor cells is capable to engraft and to maintain the production of gene-corrected hematopoietic cells. To identify this population we are currently studying: a) the progenitors responsible for the initial reconstitution of the hematopoietic system after gene therapy; b) the progenitors capable of maintaining the hematopoiesis in the long term; c) the dynamics of hematopoietic reconstitution exploiting different hematopoietic stem cell sources, such as bone marrow or mobilized peripheral blood; d) the mechanisms involved in the trafficking of hematopoietic stem cells from the bone marrow to the peripheral blood. The information generated from our studies will allow to increase our knowledge on the hematopoietic stem cell biology ultimately leading to improved gene therapy strategies and to extend this type of treatment to other diseases.