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Blood, 15 June 2007, Vol. 109, No. 12, pp. 5178-5185. Prepublished online as a Blood First Edition Paper on March 1, 2007; DOI 10.1182/blood-2006-12-061382.
GENE THERAPY Hematopoietic stem celltargeted neonatal gene therapy reverses lethally progressive osteopetrosis in oc/oc mice1 Department of Molecular Medicine and Gene Therapy, Lund University, Lund, Sweden; 2 Department of Periodontology and Oral Cell Biology, Academic Center for Dentistry Amsterdam (ACTA), Universiteit van Amsterdam and Vrije Universiteit, Amsterdam, the Netherlands; 3 Department of Pathology, Lund University, Lund, Sweden; 4 Department of Pediatrics, Göteborg University, Gothenburg, Sweden Infantile malignant osteopetrosis (IMO) is a fatal disease caused by lack of functional osteoclasts, and the only available treatment is hematopoietic stem cell (HSC) transplantation. In the majority of patients, the TCIRG1 gene, coding for a subunit of a proton pump essential for bone resorption, is mutated. Oc/oc mice have a deletion in the homologue gene (tcirg1) and die at 3 to 4 weeks, but can be rescued by neonatal transplantation of HSCs. Here, HSC-targeted gene therapy of osteopetrosis in the oc/oc mouse model was developed. Oc/oc fetal liver cells depleted of Ter119-expressing erythroid cells were transduced with a retroviral vector expressing tcirg1 and GFP, and subsequently transplanted intraperitoneally to irradiated neonatal oc/oc mice. Eight of 15 mice survived past the normal life span of oc/oc mice. In vitro osteoclastogenesis revealed formation of GFP-positive osteoclasts and bone resorption, albeit at a lower level than from wild-type cells. The skeletal phenotype was analyzed by X-ray and histopathology and showed partial correction at 8 weeks and almost normalization after 18 weeks. In summary, osteopetrosis in oc/oc mice can be reversed by neonatal transplantation of gene-modified HSCs leading to long-term survival. This represents a significant step toward the development of gene therapy for osteopetrosis.
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