Regulated ex vivo regional gene therapy for bone repair using an inducible caspase-9 suicide gene system

Gene Ther. 2019 Jun;26(6):230-239. doi: 10.1038/s41434-019-0069-4. Epub 2019 Apr 8.

Abstract

In order to adapt ex vivo regional gene therapy for clinical applications in orthopaedic surgery, safety issues must be considered. In this study we developed a suicide approach using a dual gene expression two step transcriptional amplification lentiviral vector (LV-TSTA) encoding BMP-2 and an inducible caspase 9 (iC9) system that selectively induces apoptosis upon activation with a chemical inducer of dimerization (CID). Transduction of rat bone marrow stromal cells (RBMSCs) with LV-TSTA-iC9/BMP-2 led to abundant BMP-2 production (90.3 ± 7.9 ng/24 h/106 cells) in vitro and stimulated bone formation in a mouse muscle pouch in the absence of CID. Moreover it was shown that CID could be used to selectively induce apoptosis in iC9-transduced cells both in vitro and in vivo. Double exposure to serial dilutions of CID decreased in vitro production of BMP-2 by 85-87% and Luc activity by 97-99% in iC9/BMP-2 or iC9/Luc-transduced cells respectively. Early administration of CID (Days 0-1 post-op) in mice implanted with iC9/BMP-2-transduced RBMSCs was effective in blocking bone formation, indicating that CID was toxic to the transduced cells. In iC9/Luc-implanted mice, late administration of two doses of CID (Days 27-28 post-op) significantly reduced the luciferase signal. The current study provides proof of concept for the potential clinical application of regulated gene therapy to promote bone repair.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Animals
  • Apoptosis*
  • Bone Morphogenetic Protein 2 / genetics
  • Bone Morphogenetic Protein 2 / metabolism
  • Bone Regeneration*
  • Caspase 6 / genetics*
  • Caspase 6 / metabolism
  • Cells, Cultured
  • Female
  • Genetic Therapy / methods*
  • Genetic Vectors / genetics
  • Lentivirus / genetics
  • Mice
  • Mice, Inbred NOD
  • Protein Multimerization
  • Rats

Substances

  • Bone Morphogenetic Protein 2
  • Caspase 6