SummaryReasons for performing study: To evaluate the long-term clinical outcome after allogeneic chondrocyte and insulin-like growth factor-I (IGF-I) grafting of subchondral cystic lesions (SCLs) of the femoral condyle in horses. Objective: To test the hypothesis that chondrocyte and IGF-I grafts will improve the long-term clinical outcome in arthroscopically debrided SCLs. Methods: Medical records of 49 horses with SCLs of the femoral condyle treated by debridement and implantation of chondrocytes and IGF-I were reviewed. Preoperative radiographs were obtained, and caudocranial radiographic projections were used to establish a ratio between cyst and femoral condyle size. Arthroscopic cyst debridement followed by filling of the bone void with autologous cancellous bone (45 horses) or tricalcium phosphate granules (4 horses) was performed. A paired syringe containing a fibrinogen and chondrocyte mixture in one syringe and calcium-activated bovine thrombin with IGF-I in the other was used to cover the surface. A successful outcome was defined as a horse that performed to its intended use without lameness. Results: A successful outcome was achieved in 36 of 49 horses (74%). Preoperative radiography was performed in all horses, with 33 horses having unilateral SCLs of the medial femoral condyle, 15 horses having bilateral SCLs of the medial femoral condyle, and one horse having bilateral SCLs of the lateral femoral condyle. Median age of the horses was 3.3 years. Fifteen horses had preoperative radiographic and arthroscopic evidence of osteoarthritis (OA). A successful outcome was not influenced by age of horse, presence of pre-existing osteoarthritis or preoperative size of the subchondral cyst. Grafting resulted in success for 80% of horses >3 years old, and in 80% of horses with OA. Conclusions: Implantation of allogeneic chondrocytes supplemented with IGF-I is an effective treatment for horses with SCLs of the femoral condyle, and particularly for older horses and horses with pre-existing osteoarthritis. Potential relevance: Chondrocyte implantation may offer a greater chance of long-term success in older horses and horses with osteoarthritis than has been previously reported with cyst debridement alone.
Cartilage injury often precipitates osteoarthritis which has driven research to bolster repair in cartilage impact damage. Autologous chondrocytes transduced with rAAV5-IGF-I were evaluated in chondral defects in a well-established large animal model. Cartilage was harvested from the talus of 24 horses; chondrocytes were isolated and stored frozen. Twenty million cells were cultured and transduced with 10(5) AAV vg/cell prior to implantation. Chondrocytes from eight horses were transduced with rAAV5-IGF-I, chondrocytes from eight horses with rAAV5-GFP, and chondrocytes from eight horses were not transduced. A 15 mm full-thickness chondral defect was created arthroscopically in the lateral trochlear ridge of the femur in both femoropatellar joints. Treated defects were filled with naive or gene-enhanced chondrocytes, in fibrin vehicle. Control defects in the opposite limb received fibrin alone. rAAV5-IGF-I transduced chondrocytes resulted in significantly better healing at 8 week arthroscopy and 8 month necropsy examination when compared to controls. At 8 months, defects implanted with cells expressing IGF-I had better histological scores compared to control defects and defects repaired with naive chondrocytes. This included increased chondrocyte predominance and collagen type II, both features of hyaline-like repair tissue. The equine model closely approximates human cartilage healing, indicating AAV-mediated genetic modification of chondrocytes may be clinically beneficial to humans.
Racehorses with persistent DDSP can be treated successfully by laryngeal tie-forward or by laryngeal tie-forward followed by laser staphylectomy. Horses with persistent DDSP have a more caudal larynx and more caudal and dorsal basihyoid bone than horses with intermittent DDSP.
Gene therapy promotes the expression of missing or defective genes and can be curative following administration of a single dose. Gene therapy is prohibited in equine athletes by regulatory bodies due to the high potential for abuse and novel analytical methods are needed for detection. The goal of this study was to detect the administration of an experimental gene therapy: a recombinant adeno‐associated viral vector (rAAV) carrying a transgene for the anti‐inflammatory cytokine IL‐10 (rAAV‐IL10). Twelve horses were randomly assigned to receive an intra‐articular injection of rAAV‐IL10 or phosphate buffered saline (vehicle) into a middle carpal joint. Plasma and synovial fluid were collected on days 0, 1, 2, 4, 7, 14, 28, 56, and 84. Primer pairs were designed to detect two unique regions of rAAV. Using quantitative real time PCR, both sets of primers detected rAAV for 14–28 days in joints and up to 4 days in plasma, in all six treated horses. In synovial fluid, rAAV was detected on day 56 in 4/6 horses by both primer sets, and on day 84 in 1/6 horses by one primer set. In plasma, rAAV was detected for 7 days in 5/6 horses, 14 days in 2/6 horses, and 28 days in 1/6 horses by one primer set, and was detected for up to 14 days in 1/6 horses by the other primer set. This study is the first to validate that quantitative real time PCR can be used to systemically detect the local administration of a gene therapy product to horses.
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