San Raffaele Telethon Institute for Gene Therapy

HSC-mediated gene therapy strategies for neurometabolic disorders

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Head of Unit

Alessandra Biffi

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Hematopoietic stem cell (HSC) progeny cells in the central nervous system (CNS) of myeloablated and transplanted recipients represent a vehicle for therapeutic molecule delivery across the blood brain barrier. This effect was demonstrated in animal models and patients affected by lysosomal storage disorders (LSDs) and is dependent on the reconstitution of CNS myeloid/microglia-like cells by the transplanted HSCs. Importantly, we recently showed that the therapeutic potential of HSC transplantation for treating LSDs can be enhanced by means of:

  • gene transfer into the transplanted HSCs for increasing the production of therapeutic molecules delivered to the brain by transplanted HSC progeny;
  • the use of a pre-transplant conditioning aimed not only at HSC ablation from the bone marrow, but also at eliminating CNS microglia progenitors;
  • delivery of HSCs within brain lateral ventricles, to further enhance CNS myeloid cell and microglia reconstitution by the transplanted cells.

We are pursuing these strategies in the context of innovative cell and gene therapy applications for neurodegenerative diseases, including LSDs with a prevalent /exclusive CNS involvement.

Research activity

The research activity of our unit is focused mainly in two areas:

  1. Development of innovative approaches to foster and enhance brain myeloid cell and microglia replacement by engineered cells upon transplantation. Starting from our recent finding that new myeloid/microglia cells can be efficiently generated upon intracerebroventricular (ICV) HSC injection in myeloablated mice, we are working on the set up and optimization of different combinatorial HSC based transplant protocols in which standard intravenous (IV) HSC transplantation is coupled to ICV cell administration. In the perspective of validating a novel therapeutic approach for diseases with systemic or preferentially CNS involvement we are modulating the contribution of IV versus ICV transplanted cells to the CNS and to medullar hematopoiesis in terms of population employed at each site and timing of cell delivery. Moreover, we are actively pursuing the characterization of microglia progenitors in the brain in order to develop brain-specific ablative regimens for an exclusive (and safer) microglia reconstitution.
  2. Development of HSC-mediated gene therapy approaches for LSDs with exclusive/ prevalent nervous system involvement. The deliverables of the exploratory research described above are being employed for the development of ad hoc transplantation strategies aiming at engineering microglia to exert therapeutic effects in poorly responsive LSDs as well as neurodegenerative conditions. One of the early targets of our translation research is a LSD primarily affecting the CNS and lacking efficacious curative options named Late Infantile Neuronal Ceroidolipofuscinosis (LINCL). LINCL is an autosomal recessive lysosomal storage disorder caused by mutations in the CLN2 gene that leads to the deficiency of TPP-1, a lysosomal enzyme that is responsible for degrading membrane proteins resulting in progressive and rapid  neurological degeneration with death occurring by the age of 8–12 years. The results obtained on LINCL and other severe LSDs being explored in the laboratory would be preparatory for the application of similar HSC gene therapy strategies to neurodegenerative diseases of greater social impact.