Ultrasound enhanced gene delivery of secreted Interleukin 1 receptor antagonist in a murine vascular injury model

Ultrasound (US) mediated gene delivery (UMGD) is a non-viral technique for gene transfer that has been a developing technology over the past 18 years. Non-viral UMGD as an approach is safe, relatively cheap and can be tolerated even over multiple exposures. US exposure has previously been demonstrated to increase DNA transfer and expression in endothelial cells (EC) and vascular smooth muscle cells (VSMC) in vitro and ex vivo in a saphenous vein graft model. Interleukin-1 (IL-1) is a pro-inflammatory cytokine that plays a key role in cardiovascular diseases and vascular injury. Treatment with the endogenous inhibitor interleukin-1 receptor antagonist (IL-1Ra) is an effective treatment in animal models of vascular disease and some inflammatory clinical conditions. However, Anakinra (the clinically approved formulation of IL-1Ra) must be given as daily subcutaneous (SC) injections (due to a short t ½), which is inconvenient (high burden for compliance) and very expensive. In this project I have tested US parameters for ‘best’ gene expression in the mouse hind limb, demonstrated long-term expression utilising a repeat dosing regime and finally investigated the therapeutic efficacy of intramuscular (IM) UMGD of pCMV6-SIL1Ra in a rodent arterial injury model compared with continuous delivery of Anakinra via osmotic mini-pump.
Following experiments to determine the US dose, duration of expression and therefore treatment schedule, I have demonstrated that this new UMGD technique of pCMV6-SIL1Ra, every 4 days over a period of 28 days significantly decreased neointima/media (N/M) ratio in a murine vascular injury model. Furthermore, there was no significant difference between mice treated with pCMV6-SIL1Ra-UMGD and those receiving continuous Anakinra infusion by osmotic mini-pump (25 mg/kg/), suggesting that UMGD was at least as efficacious as drug treatment in reducing neointima formation.
The role of IL-1 in neointima formation following vascular injury is not new but these novel data demonstrate the potential for UMGD to achieve therapeutic levels of gene/protein expression in an animal model and highlight the potential for further development. This technique of UMGD utilising a secreted protein and easily accessible muscle tissue from which to express it warrants further investigation as a possible treatment for other cardiovascular and systemic/peripheral diseases where a secreted protein is an attractive drug treatment.