Abstract

Infantile malignant osteopetrosis (IMO) is an autosomal recessive disorder characterized by nonfunctional osteoclasts. Approximately 50% of the patients have mutations in the TCIRG1 gene, encoding for a subunit of the osteoclast proton pump. Gene therapy represents a potential alternative treatment to allogeneic stem cell transplantation for IMO. The oc/oc mouse is a model of IMO characterized by a 1500 bp deletion in the TCIRG1 gene, severe osteopetrosis and a lifespan of only 3 weeks. Here we show that the osteopetrotic phenotype in oc/oc mice can be reversed by hematopoietic stem cell-targeted gene therapy with a clinically applicable lentiviral vector expressing a non-mutated form of human TCIRG1 under the mammalian promoter elongation factor 1α short (EFS-hT). oc/oc c-kit+ fetal liver cells transduced with EFS-hT were transplanted into sublethally irradiated oc/oc mice by temporal vein injection one day after birth. 9/12 mice survived long-term (19-25 weeks) with evidence of tooth eruption, uncharacteristic of oc/oc mice. Splenocytes were harvested 19-25 weeks after transplantation and differentiated into osteoclasts on bone slices to assess resorption and on plastic to assess TCIRG1 protein expression. Vector-corrected osteoclasts showed human TCIRG1 expression by Western blot. CTX-I release relative to that mediated by oc/oc-derived osteoclasts increased 8-239 fold. Resorption pits on bone slices were observed for osteoclasts derived from 7/9 surviving transplanted oc/oc mice. Histopathology of the bones of surviving animals showed varying degrees of rescued phenotype, the majority with almost full correction. The average vector copy number per cell in the bone marrow was 1.8 ± 0.5. Overall, 75% of transplanted mice exhibited long-term survival and marked reversal of the osteopetrotic bone phenotype. These findings represent a significant step towards the clinical application of gene therapy for IMO.

Go to full publication

Categories

Please don't hesitate to contact us if you have any questions or other inquiries.

Are you interested in learning more about Nordic Bioscience?
Enter your information in the form and a representative will contact you shortly.

By submitting this form you agree to our terms and conditions.

We use cookies on our site to enable essential services and functionalities, and collect data in regards to visitor information to provide the best possible experience. By using our website, you agree to our Privacy Policy and our cookies usage. Cookie Policy Privacy Statement