Spatial and temporal control of transgene expression in vivo using a heat-sensitive promoter and MRI-guided focused ultrasound.

BACKGROUND: Among the techniques used to induce and control gene expression, a non-invasive, physical approach based on local heat in combination with a heat-sensitive promoter represents a promising alternative but requires accurate temperature control in vivo. MRI-guided focused ultrasound (MRI-FUS) with real-time feedback control allows automatic execution of a predefined temperature-time trajectory. The purpose of this study was to demonstrate temporal and spatial control of transgene expression based on a well-defined local hyperthermia generated by MRI-FUS. METHODS: Expression of the green fluorescent protein (GFP) marker gene was used. Two cell lines were derived from C6 glioma cells. The GFP expression of the first one is under the control of the CMV promoter, whereas it is under the control of the HSP70 promoter in the second one and thus inducible by heat. Subcutaneous tumours were generated by injection in immuno-deficient mice and rats. Tumours were subjected to temperatures varying from 42 to 50 degrees C for 3 to 25 min controlled by MRI-FUS and analyzed 24 h after the heat-shock. Endogenous HSP70 expression and C6 cell distribution were also analyzed. RESULTS: The results demonstrate strong expression at 50 degrees C applied during a short time period (3 min) without affecting cell viability. Induced expression was also clearly shown for temperature in the range 44-48 degrees C but not at 42 degrees C. CONCLUSIONS: Heating with MRI-FUS allows a tight and non-invasive control of transgene expression in a tumour.

Successful therapeutic effect in a mouse model of erythropoietic protoporphyria by partial genetic correction and fluorescence-based selection of hematopoietic cells.

Erythropoietic protoporphyria is characterized clinically by skin photosensitivity and biochemically by a ferrochelatase deficiency resulting in an excessive accumulation of photoreactive protoporphyrin in erythrocytes, plasma and other organs. The availability of the Fech(m1Pas)/Fech(m1Pas) murine model allowed us to test a gene therapy protocol to correct the porphyric phenotype. Gene therapy was performed by ex vivo transfer of human ferrochelatase cDNA with a retroviral vector to deficient hematopoietic cells, followed by re-injection of the transduced cells with or without selection in the porphyric mouse. Genetically corrected cells were separated by FACS from deficient ones by the absence of fluorescence when illuminated under ultraviolet light. Five months after transplantation, the number of fluorescent erythrocytes decreased from 61% (EPP mice) to 19% for EPP mice engrafted with low fluorescent selected BM cells. Absence of skin photosensitivity was observed in mice with less than 20% of fluorescent RBC. A partial phenotypic correction was found for animals with 20 to 40% of fluorescent RBC. In conclusion, a partial correction of bone marrow cells is sufficient to reverse the porphyric phenotype and restore normal hematopoiesis. This selection system represents a rapid and efficient procedure and an excellent alternative to the use of potentially harmful gene markers in retroviral vectors.

[Congenital erythropoietic porphyria. Apropos of a fatal case in the neonatal period due to acute hemolysis with hepatic failure]. / Porphyrie érythropoïétique congénitale. A propos d'un cas fatal en période néonatale dû à une hémolyse aiguë avec insuffisance hépatique.

BACKGROUND: Congenital erythropoietic porphyria, an autosomal recessive disease, is characterized by deficiency of uroporphyrinogen III synthase. Clinical variability of the disease is related to the different mutations found in the patients. CASE REPORT: A newborn suffered one hour after birth from jaundice and polypnea with acute hemolysis. Severe cutaneous photosensitivity occurred after phototherapy. Congenital erythropoietic porphyria was suspected because of reddish-colored urine and confirmed by porphyrin analyses. The baby died one month later due to severe hemolytic anemia with hepatic failure. Uroporphyrinogen III synthase activity was decreased by 99% in bone marrow cells and established lymphoblastoid cells from the patient. Molecular biology studies demonstrated the presence of the Cys 73-->Arg substitution at the homozygous state in the patient. CONCLUSION: This mutation, the most frequently found in this disease, is responsible for a severe phenotype. Molecular characterization provides genotype/phenotype correlations in this porphyria and allows to clarify unusual cases of porphyrias.

Biochemical diagnosis of a fatal case of Günther's disease in a newborn with hydrops foetalis.

The birth of a male baby was induced at 32 weeks. In utero, the child presented, inter alia, signs of hydrops, hepatosplenomegaly and anaemia. Two in utero transfusions for correction of the anaemia were performed at 28 and 29 weeks, respectively. The baby rapidly presented respiratory distress with mixed acidosis. Three hours after birth, pink urine was excreted. Signs of icterus necessitated phototherapy, after which photosensitivity occurred. Erythrocytes were fluorescent under long-wavelength UV light. The baby died 24 hours after birth, displaying severe acidosis, a diffuse haemorrhagic syndrome, and repeated brady-cardia which did not respond to isoprenaline. The analysis of porphyrins in urine, blood and faeces of the baby gave the following results: 1) uroporphyrin (I and III isomeric series) was increased in urine and faeces, with traces in erythrocytes and plasma; 2) heptacarboxyporphyrin I was found mainly in urine and much less in erythrocytes, plasma and faeces; 3) coproporphyrin I was increased in urine, erythrocytes, plasma and faeces, and 4) 5-aminolaevulinic acid and porphobilinogen in urine and plasma were within the reference ranges. Determination of the enzymes of haem biosynthesis in erythrocytes and lymphocytes showed that both parents possessed only 50% of the normal activity of cosynthase. A previously described point mutation in codon 73 was observed in one parent. Fatal cases of neonatal Günther's disease are extremely rare and such an observation, according to our knowledge, is probably one of the first described.