| 1. |
- Thudium, Christian Schneider, et al.
(författare)
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Regulation and Function of Lentiviral Vector-Mediated TCIRG1 Expression in Osteoclasts from Patients with Infantile Malignant Osteopetrosis : Implications for Gene Therapy
- 2016
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Ingår i: Calcified Tissue International. - : Springer Science and Business Media LLC. - 0171-967X .- 1432-0827. ; 99:6, s. 638-648
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Tidskriftsartikel (refereegranskat)abstract
- Infantile malignant osteopetrosis (IMO) is a rare, recessive disorder characterized by increased bone mass caused by dysfunctional osteoclasts. The disease is most often caused by mutations in the TCIRG1 gene encoding a subunit of the V-ATPase involved in the osteoclasts capacity to resorb bone. We previously showed that osteoclast function can be restored by lentiviral vector-mediated expression of TCIRG1, but the exact threshold for restoration of resorption as well as the cellular response to vector-mediated TCIRG1 expression is unknown. Here we show that expression of TCIRG1 protein from a bicistronic TCIRG1/GFP lentiviral vector was only observed in mature osteoclasts, and not in their precursors or macrophages, in contrast to GFP expression, which was observed under all conditions. Thus, vector-mediated TCIRG1 expression appears to be post-transcriptionally regulated, preventing overexpression and/or ectopic expression and ensuring protein expression similar to that of wild-type osteoclasts. Codon optimization of TCIRG1 led to increased expression of mRNA but lower levels of protein and functional rescue. When assessing the functional rescue threshold in vitro, addition of 30 % CB CD34+ cells to IMO CD34+ patient cells was sufficient to completely normalize resorptive function after osteoclast differentiation. From both an efficacy and a safety perspective, these findings will clearly be of benefit during further development of gene therapy for osteopetrosis.
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| 2. |
- Askmyr, Maria, et al.
(författare)
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Low-dose busulphan conditioning and neonatal stem cell transplantation preserves vision and restores hematopoiesis in severe murine osteopetrosis.
- 2009
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Ingår i: Experimental Hematology. - : Elsevier BV. - 1873-2399 .- 0301-472X. ; 37, s. 302-308
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Infantile malignant osteopetrosis is a fatal disease caused by lack of functional osteoclasts. In most of patients, TCIRG1, encoding a subunit of a proton pump essential for bone resorption, is mutated. Osteopetrosis leads to bone marrow failure and blindness due to optic nerve compression. Oc/oc mice have a deletion in Tcirg1 and die around 3 to 4 weeks, but can be rescued by neonatal stem cell transplantation (SCT) after irradiation conditioning. However, as irradiation of neonatal mice results in retinal degeneration, we wanted to investigate whether conditioning with busulphan prior to SCT can lead to preservation of vision and reversal of osteopetrosis in the oc/oc mouse model. MATERIALS AND METHODS: Pregnant dams were conditioned with busulphan and their litters transplanted with 1 x 10(6) normal lineage-depleted bone marrow cells intravenously or intraperitoneally. Mice were followed in terms of survival and engraftment level, as well as with peripheral blood lineage analysis, bone and eye histopathology and a visual-tracking drum test to assess vision. RESULTS: Busulphan at 15 mg/kg was toxic to oc/oc mice. However, six of seven oc/oc mice conditioned with busulphan 7.5 mg/kg survived past the normal lifespan with 10% engraftment, correction of the skeletal phenotype, and normalization of peripheral blood lineages. Busulphan, in contrast to irradiation, did not have adverse effects on the retina as determined by histopathology, and 8 weeks after transplantation control and oc/oc mice retained their vision. CONCLUSION: Low-dose busulphan conditioning and neonatal SCT leads to prolonged survival of oc/oc mice, reverses osteopetrosis and prevents blindness even at low engraftment levels.
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| 3. |
- Askmyr, Maria, et al.
(författare)
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Prospects for gene therapy of osteopetrosis.
- 2009
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Ingår i: Current gene therapy. - 1566-5232. ; 9:3, s. 150-9
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Forskningsöversikt (refereegranskat)abstract
- Dysfunction in or lack of osteoclasts result in osteopetrosis, a group of rare but often severe, genetic disorders characterized by an increase in bone mass, skeletal malformations and bone marrow failure that may be fatal. Several of the underlying defects have lately been characterized in humans and in animal disease models. In humans, these defects often involve mutations in genes expressing proteins involved in the acidification of the osteoclast sub-cellular compartment, a process necessary for proper bone resorption. So far, the only cure for children with severe osteopetrosis is allogeneic hematopoietic stem cell transplantation (SCT). However, the characterization of the genetic defects opens up the possibility for gene replacement therapy as an alternative to SCT. Recently, gene therapy targeting hematopoietic stem cells (HSC) in a mouse model of infantile malignant osteopetrosis was shown to correct many aspects of the disease. Here we review important aspects of this group of diseases and discuss the prospects for development of gene therapy of osteopetrosis.
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| 4. |
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| 5. |
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| 6. |
- Flores Bjurström, Carmen, et al.
(författare)
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Nonablative neonatal bone marrow transplantation rapidly reverses severe murine osteopetrosis despite low level engraftment and lack of selective expansion of the osteoclastic lineage.
- 2010
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Ingår i: Journal of Bone and Mineral Research. - : Wiley. - 1523-4681 .- 0884-0431. ; 25:9, s. 2069-2077
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Tidskriftsartikel (refereegranskat)abstract
- Infantile malignant osteopetrosis (IMO) is caused by lack of functional osteoclasts leading to skeletal abnormalities, blindness due to compression of the optic nerves, bone marrow (BM) failure and early death. In most patients TCIRG1, a proton pump subunit essential for bone resorption, is mutated. Oc/oc mice represent a model for IMO due to a deletion in Tcirg1 and die around 4 weeks. To determine if hematopoietic stem cell transplantation without prior conditioning can reverse osteopetrosis, neonatal mice were transplanted iv with lineage depleted BM cells. More than 85% of oc/oc mice transplanted with 5 x 10(6) cells survived long term with an engraftment of 3-5% in peripheral blood (PB). At 3 w engraftment in the BM was 1-2% but the cellularity had increased 60-fold compared to non-treated oc/oc and RANKL and M-CSF expression in the BM was normalized. Histopathology and micro-CT revealed almost complete reversal of osteopetrosis after 4 weeks. In vitro studies showed that bone resorption by osteoclasts from transplanted oc/oc mice was 14% of transplanted controls and immunofluorescence microscopy revealed that resorption was mainly associated with osteoclasts of donor origin. Lineage analysis of BM, PB and spleen did not provide any evidence for selective recruitment of cells to the osteoclastic lineage. The vision was also preserved in transplanted oc/oc mice as determined by a visual tracking drum test. In summary, nonablative neonatal transplantation leading to engraftment of only a small fraction of normal cells rapidly reverses severe osteopetrosis in the oc/oc mouse model. (c) 2010 American Society for Bone and Mineral Research.
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| 7. |
- Flores Bjurström, Carmen, et al.
(författare)
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Osteoclasts are not crucial for hematopoietic stem cell maintenance in adult mice
- 2013
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Ingår i: Haematologica. - : Ferrata Storti Foundation (Haematologica). - 1592-8721 .- 0390-6078. ; 98:12, s. 1848-1855
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Tidskriftsartikel (refereegranskat)abstract
- The osteoclast is vital for establishment of normal hematopoiesis in the developing animal. However, its role for maintenance of hematopoiesis in adulthood is more controversial. To shed more light on this process, we transplanted hematopoietic stem cells from two osteopetrotic mouse models, with lack of osteoclasts or defective osteoclast function, to normal adult mice and examined the bone phenotype and hematopoiesis in the recipients. B6SJL mice were lethally irradiated and subsequently transplanted with oc/oc, Receptor Activator of Nuclear Factor Kappa B knockout or control fetal liver cells. Osteoclasts derived from the recipient animals were tested in vitro for osteoclastogenesis and resorptive function. Bone remodeling changes were assessed using biomarkers of bone tumrnover and micro-CT. Hematopoiesis was assessed by flow cytometry and colony formation, and hematopoietic stem cell function by secondary competitive transplantations and cell cycle analysis. After transplantation, a donor chimerism of 97-98% was obtained, and by 15 weeks mild osteopetrosis had developed in recipients of cells from osteopetrotic mice. There were no alterations in the number of bone marrow cells. Colony formation was slightly reduced in Receptor Activator of Nuclear Factor Kappa B knock-out recipients but unchanged in oc/oc recipients. Phenotypically, stem cells were marginally reduced in recipients of cells from osteopetrotic mice, but no significant difference was seen in cell cycle status and in competitive secondary transplantations all three groups performed equally well. Our results indicate that osteoclast function is not crucial for hematopoietic stem cell maintenance in adult mice.
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| 8. |
- Flores Bjurström, Carmen
(författare)
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Targeting the hematopoietic stem cell to correct osteopetrosis
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis focuses on developing stem cell targeted gene therapy for the severe hereditary disorder Infantile Malignant Osteopetrosis (IMO) as well as increasing the understanding of how the genetic defect present in IMO affects the hematopoietic stem cells and hematopoiesis in general. IMO is a rare congenital disorder associated with an increased number of non-functional osteoclasts and the absence of bone resorption results in accumulation of sclerotic bone leading to abnormal bone marrow cavity formation insufficient to support hematopoiesis. The most common mutation is in the TCIRG1 gene seen in over 50% of the patients. The children suffer from bone marrow failure, anemia, thrombocytopenia, hepatosplenomegaly, immune dysfunction and recurrent infections. Furthermore, the impaired remodeling of the developing bone results in compression of cranial nerves which leads to neurological impairment, affecting especially vision and hearing which may progress to blindness and deafness. The only curative treatment available today for IMO is bone marrow transplantation. However, this can only be performed if the patient has a suitable stem cell donor. If untreated, the children die around the age of five. Currently no alternative treatment exists, thus IMO is a candidate disease for development of gene therapy. The first two papers are based on studies conducted with the oc/oc mouse model that has a mutation in the homologous gene and shares the same osteopetrotic phenotype as seen in humans. Paper one focuses on developing a clinically relevant model for cell therapy in the oc/oc mouse by replacing radiation conditioning with low-dose busulfan conditioning prior to neonatal bone marrow transplantation and optimizing the administration procedure. In paper two, neonatal oc/oc mice were treated with bone marrow transplantation without any prior conditioning, which showed a rapid reversal of the severe osteopetrotic phenotype despite low level of engraftment and lack of selective expansion of the osteoclastic lineage. In manuscript three human stem cells from patients with IMO were studied and the paper provides the first proof-of-principle of lentiviral-mediated correction restoring the resorptive function of osteoclasts derived from peripheral blood CD34+ cells of IMO patients. In manuscript four the osteoclast significance in hematopoietic stem cell maintenance was studied by generating two adult osteopetrotic mouse models and subsequently analyzing the hematopoiesis of the mice. The results from this study indicate that osteoclast function is not essential for hematopoietic stem cell maintenance in adult mice. Results obtained from the oc/oc mouse model and from IMO patient cells are encouraging for further development of hematopoietic stem cell targeted gene therapy, and will serve as basis for upcoming development of clinical gene therapy of osteopetrosis.
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| 9. |
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| 10. |
- Henriksen, Kim, et al.
(författare)
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Dissociation of Bone Resorption and Bone Formation in Adult Mice with a Non-Functional V-ATPase in Osteoclasts Leads to Increased Bone Strength
- 2011
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Ingår i: PLoS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 6:11
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Tidskriftsartikel (refereegranskat)abstract
- Osteopetrosis caused by defective acid secretion by the osteoclast, is characterized by defective bone resorption, increased osteoclast numbers, while bone formation is normal or increased. In contrast the bones are of poor quality, despite this uncoupling of formation from resorption. To shed light on the effect of uncoupling in adult mice with respect to bone strength, we transplanted irradiated three-month old normal mice with hematopoietic stem cells from control or oc/oc mice, which have defective acid secretion, and followed them for 12 to 28 weeks. Engraftment levels were assessed by flow cytometry of peripheral blood. Serum samples were collected every six weeks for measurement of bone turnover markers. At termination bones were collected for mu CT and mechanical testing. An engraftment level of 98% was obtained. From week 6 until termination bone resorption was significantly reduced, while the osteoclast number was increased when comparing oc/oc to controls. Bone formation was elevated at week 6, normalized at week 12, and reduced onwards. mu CT and mechanical analyses of femurs and vertebrae showed increased bone volume and bone strength of cortical and trabecular bone. In conclusion, these data show that attenuation of acid secretion in adult mice leads to uncoupling and improves bone strength.
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