CRISPR Insertion of Gene Circuits for On-Demand TIMP Production in Post-Traumatic Osteoarthritis
Abstract
The FY20 PRMRP Topic Areas addressed in this proposal are “Arthritis” and “Musculoskeletal Health.” Osteoarthritis (OA) occurs when the smooth cushions (cartilage) that line the surfaces at the ends of long bones in joints, such as the knee, deteriorate due to aging, obesity, and injury. Loss of cartilage causes bone on bone contact and significant pain. Injury-associated OA, or post-traumatic OA (PTOA), often occurs in younger patients than in age-associated OA. Indeed, PTOA disproportionately affects those working in physically demanding professions where injuries are more likely to occur, such as military personnel. Following a traumatic joint injury in the military, the chance of developing PTOA is exceedingly high, with more than one in two knee, shoulder, foot, ankle, and elbow injuries leading to PTOA. In one study, 100% of those who suffered an anterior cruciate ligament injury went on to develop PTOA. Unfortunately, there are currently no disease-modifying OA drugs (DMOAD), and the available pharmacological interventions merely help with pain until disease progression necessitates an invasive and costly surgery for joint replacement. Although they can offer significant pain relief and restore mobility, joint replacements are restricted to elderly patients due to the limited lifetime of these load-bearing devices; further, such surgical procedures are not without potential for complications. In this proposal, we will address the root cause of OA: cartilage loss. The underlying cause of OA stems from an imbalance of cartilage tissue degrading factors (MMPs and ADAMTS) and tissue protective factors (TIMPs). TIMPs (tissue inhibitors of metalloproteinases) are the natural inhibitors of MMPs (matrix metalloproteinases) and play a key role in tissue homoeostasis. In healthy cartilage, TIMPs are highly expressed to keep the activity of MMPs in check. However, in OA, the levels of TIMPs are downregulated. Conversely, MMPs such as the collagen-degrading MMP-13, are significantly increased in OA. These two factors significantly tip the MMP/TIMP balance to create a cartilage destructive environment. While there are multiple TIMPs that have the ability to inhibit MMPs, TIMP-3 is the most promising as a potential DMOAD candidate. TIMP-3 provides broad MMP inhibiting activity, and it also blocks other OA-driving processes such as angiogenesis, inflammation, and aggrecan loss. Indeed, a previous study found that daily intraarticular injection of TIMP-3 restored the MMP:TIMP balance and prevented cartilage loss. Pharmaceutical companies have tried to develop small-molecule MMP-inhibitors. However, these efforts have failed, principally due to off-target and uncontrolled MMP inhibition resulting in severe side effects; side effects were attributed to excessive and unnatural levels of inhibition of all MMPs in all tissues in the body, which was associated with muscle pain. These efforts indicated that for clinical benefit, MMP inhibition must be highly localized, specific, and balanced so that the relative MMP:inhibitor (TIMP) ratio is not tipped too far in either direction. In this proposal, we aim to develop a TIMP-3 gene therapy that will be injected directly into the affected joint. Cells in the joint will be re-programmed to produce TIMP-3; however, its expression will be tightly limited to the pathological (OA) joint, through the Mmp13 promoter, which is normally only switched-on during OA. Precise gene insertion enabled by CRISPR-Cas9 will facilitate the TIMP-3 gene’s hijacking of the native Mmp13 promoter, turning cells within the joint into “on-demand” TIMP-3 “factories.” Permanence of the gene edits will ensure that this therapy will provide long-acting joint protection, ideal for prophylactic/preventative therapy, while the switch-like “on-demand” behavior will ensure TIMP-3 is only turned on when needed. This feature is designed to reduce the risk of side effects. Non-viral porous silicon nanoparticles will be e
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Dec 05, 2021
- Source ID
- W81XWH2110162
Entities
People
- Richard D Arcy
Organizations
- United States Army
- Vanderbilt University