Use of Nonautologous Microencapsulated Fibroblasts in Growth Hormone Gene Therapy to Improve Growth of Midget Swine

Abstract

The aim of the present study was to investigate the expression activity, both in vitro and in vivo, of the porcine growth hormone complementary DNA (pGH cDNA) in porcine fetal fibroblast (PFF) cells. The pGH gene had been constructed inside the bicistronic retroviral vector PSN and subsequently transfected into PFF cells further encapsulated with immunoprotective microcapsules. This would provide a way to evaluate the improvement in growth performance of Tao-Yuan swine by the use of nonautologous microencapsulated fibroblasts carrying the pGH cDNA via the technique of somatic gene therapy. Results from Southern blot analysis confirmed that the full length of the pGH cDNA was completely integrated into the genome of the PFF cells after they had been infected one to four times using a PSN retroviral vector. Moreover, Northern blot analysis showed that high transcription activity was present in clones infected twice, and exogenous pGH secretion was found when the pGH-infected PFF had been further cultured for 48 hr in vitro and subjected to immunoblot assay. Encapsulation of the pGH–PFF with an alginate–poly-l-lysine–alginate membrane did not show any deterioration in their proliferation and survival both in vitro and in vivo. The pGH gene in encapsulated recombinant fibroblasts was fully expressed after it had been transplanted into the peritoneal cavity of the Tao-Yuan swine, and reverse transcription-polymerase chain reaction (RT-PCR) analysis was performed on the microcapsules retrieved 1 month later. The feasibility of pGH gene therapy to improve midget Tao-Yuan swine growth enhancement is further supported by the fact that transplantation of the encapsulated recombinant fibroblast cells resulted in a much more significant increase in weight gain than in those swine in either the age-matched untreated control group or in those that had been transplanted with uncapsulated recombinant PFF cells (10.56 ± 1.01 kg versus 6.95 ± 0.94 and 5.27 ± 1.30 kg; p < 0.05). These experimental data suggest that growth hormone gene therapy did provide an alternative approach for growth improvement in midget Tao-Yuan swine.

Overview summary

To improve the growth enhancement of domestic animals, we have developed a novel strategy for nonautologous somatic gene therapy. Primary fibroblasts were modified and directly infected with bicistronic retroviral vector carrying the pGH targeting gene and the neomycin selective gene. After being trapped in immunoprotective microcapsules, the pGH gene in encapsulated recombinant fibroblasts expressed itself when it was transplanted into the peritoneal cavity of swine. The feasibility of pGH gene therapy was demonstrated by enhancing the growth of growth-retarded swine. This model of delivery is clinically benign, potentially economical, highly versatile, and amenable to industrial-scale production and quality control.