Intradiscal Gene Therapy: Therapeutic Implications in Degenerative Disc Disease

Moon, Seong Hwan; Park, Moon Soo; Kang, Yong Ho; Kim, Hyung Jung; Lee, Hwan Mo; Kim, Nam Hyun; Gilbertson, Lars G; Kang, James D

Abstract

STUDY DESIGN: In vitro and in vivo studies to determine the anabolic effects of intervertebral disc (IVD) to adenovirus-mediated therapeutic gene transfer.
OBJECTIVES
To quantify the anabolic effect of human IVD cells in vitro and rabbit IVD in vivo to therapeutic gene transfer. SUMMARY OF LITERATURE REVIEW: An alternative possibility to delivery of growth factors, in continuous manner, is the genetic modification of disc cells through gene transfer. Contemplating to extend this approach to treatment of disc degeneration, it is necessary to demonstrate anabolic effect of human IVD cells and rabbit disc to therapeutic gene transfer.
MATERIALS AND METHODS
In vitro: IVD tissue was obtained from twelve patients. IVD cells were then isolated, cultured, and transduced with Ad/TGF-beta1. Genetically modified disc cells were incorporated into alginate beads and cultured. In vivo: Fifteen skeletally mature New Zealand white rabbit were used. 15ul of saline containing Ad/TGF-beta1 were injected into the nucleus pulposus of the disc in six rabbits. All rabbits were sacrificed 6 weeks after surgery. Nucleus pulposus tissues were harvested, weighted, and cultured. Conditioned medium of alginate bead and rabbit disc tissue cultures were subjected to ELISA to detect TGF-beta1 production. Newly synthesized proteoglycan were analyzed using chromatography on Sephadex G-25 in PD-10 columns after S35-sulfate incorporation.
RESULTS
Concentration of TGF-beta1 increased over time in alginate beads cultures transduced with Ad/TGF- beta1. At 6 weeks nucleus pulposus tissue from the disc injected with Ad/TGF-beta1 exhibited 200% (p<0.05) increase in TGF- beta1 production. There was statistically significant 290% increase in newly synthesized proteoglycan in alginate cultures transduced with Ad/TGF- beta1 (p<0.05) compared to control. At 6 weeks nucleus pulposus tissue from the disc injected with Ad/TGF- beta1 exhibited 85% increase in proteoglycan synthesis (p<0.05) over that of intact control.
CONCLUSION
In this study, we observed the robust upregulation of proteoglycan synthesis in gene transferred disc cells in vitro and in vivo - indicating good prospects for biologic effects of therapeutic gene therapy in the disc using adenovirus-mediated approach.