[Hypotensive effect of encapsulated genetically engineered fibroblasts expressing mutant atrial natriuretic peptide in hypertensive rats].

OBJECTIVE

To study the inhibitive effect of subcutaneous implantation of capsule filled with fibroblasts engineered to secrete the mutant human atrial natriuretic peptide (mhANP) on blood pressure in young spontaneously hypertensive rats (SHR) and to explore the feasibility of gene therapy for the treatment of hypertension.

METHODS

A recombinant retroviral vector pLHY24 bearing mhANP cDNA was constructed. Primary fibroblasts derived from the skin of new born SHR were cultured and transfected with the vector pLHY24 to establish a genetically modified fibroblast line or transfected with the blank vector pLNCX. Then the two kinds of cell culture were put into specially made capsules with microholes. The capsules filled with the genetically modified allogenic fibroblasts and those with blank vector were implanted into the dorsal subcutaneous tissues of two groups of 10 young SHR respectively. The plasma ANP, blood pressure, urine volume, potassium and sodium concentrations in urine, and body weight were determined every week for 7 weeks.

RESULTS

After delivery of retroviral vector bearing mhANP gene into the packaging cell PA317 and the primary fibroblasts, immunoreactive mhANP were detected in the cell culture medium at the concentration of (5.84 +/- 0.07) and (13.37 +/- 2.36) ng.10(-6) cells.24 h(-1) respectively. One week after implantation of the genetically modified allogenic fibroblasts the plasma level of mhANP was 131 pg/ml +/- 8 pg/ml, significantly higher than that in control group (104 pg/ml +/- 7 pg/ml, t = 8.62, P < 0.001). Although the blood pressure increased along with aging after the gene transfer, an obvious delay of blood pressure increase was seen significantly lower in test group [from (129 +/- 9) to (169 +/- 9) mm Hg] than that in the control group [from (145 +/- 10) to (181 +/- 9) mm Hg, P < 0.05 or 0.01]. A maximal blood pressure reduction of 28 mm Hg in young SHR was observed 7 days after transplantation as compared with controls. In addition, there was an obvious increase in urine volume of test group 2 weeks after transplantation and the effect lasted for more than 2 weeks. However, there were no statistical differences in body weight and the concentrations of K(+) and Na(+) in urine.

CONCLUSION

Subcutaneous implantation of the encapsulated genetically modified fibroblasts engineered to secrete mutant ANP causes a lowering effect of blood pressure in young SHR.