In vivo haemopoietic stem cell gene therapy enabled by postnatal trafficking.

Area of Science:

• * Molecular Biology
• * Gene Therapy
• * Hematology

Background:

• * Lentiviral vector (LV)-mediated ex vivo gene therapy for hematopoietic stem and progenitor cells (HSPCs) offers a potential cure for genetic diseases.
• * Current ex vivo methods require complex manipulation and patient conditioning, posing significant challenges.
• * An in vivo approach could simplify treatment and overcome existing hurdles.

Purpose of the Study:

• * To investigate the feasibility of in vivo gene delivery to HSPCs via systemic LV administration in newborn mice.
• * To enhance gene transfer efficiency and assess the long-term engraftment and multilineage potential of transduced HSPCs.
• * To evaluate the therapeutic efficacy of in vivo HSPC gene therapy in relevant genetic disease models.

Main Methods:

• * Systemic administration of a phagocytosis-shielded lentiviral vector in newborn mice.
• * Tracking of gene-modified HSPCs from liver to bone marrow and assessment of their engraftment potential via serial transplantation.
• * Clonal tracking analysis to confirm long-term multilineage output of transduced HSPCs.
• * Testing the in vivo strategy in mouse models of adenosine deaminase deficiency, autosomal recessive osteopetrosis, and Fanconi anaemia.

Main Results:

• * Successful in vivo gene delivery to bona fide HSPCs was achieved, facilitated by their trafficking from the liver to the bone marrow.
• * Phagocytosis-shielded LVs improved gene transfer efficiency, enabling long-term multilineage engraftment and output confirmed by clonal tracking.
• * HSPC mobilization enhanced gene transfer, broadening the therapeutic window, though transduction efficiency decreased with age.
• * The strategy demonstrated efficacy in mouse models, notably correcting HSPCs in Fanconi anaemia, preventing bone marrow failure.

Conclusions:

• * In vivo gene transfer to HSPCs is feasible in newborn mice, leveraging natural cell trafficking patterns.
• * The developed method using shielded LVs and mobilization is efficient and supports long-term engraftment.
• * This in vivo approach holds significant translational potential for treating various genetic diseases in humans, mirroring the abundance of circulating HSPCs shortly after birth.