Implantation of rAAV5-IGF-I Transduced Autologous Chondrocytes Improves Cartilage Repair in Full-thickness Defects in the Equine Model

Abstract

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.

Mechanical properties and structure–function relationships in articular cartilage repaired using IGF‐I gene‐enhanced chondrocytes

“…Cells were transduced for 2 h with a viral dose of 10 5 viral genomes/cell. Following transduction, chondrocytes were suspended in cryoprecipitated autogenous fibrinogen that was prepared from previously collected plasma …”

“…At 8 months post‐implantation, horses were euthanized and a 3 mm × 20 mm osteochondral block was harvested from the defect, immersed in protease inhibitors, snap‐frozen in liquid nitrogen, and stored at −80 °C for mechanical testing. Separate osteochondral blocks and cartilage segments were collected for toluidine blue staining, type II collagen immunohistochemistry, and biochemical analyses including GAG quantification using the DMMB assay22 and type II collagen quantification using ELISA (Chondrex, Redmond, WA) …”

Updated Animal Models in Orthopaedic Research

“…Control defects in the opposite limb received fi brin alone. The rAAV5-IGF-I transduced chondrocytes demonstrated signifi cantly better healing at week 8 compared with controls [ 40 ].…”

Gene therapy approaches to regenerating the musculoskeletal system

“…24,25 Confirmation of efficacy in larger animals has been provided by Nixon and colleagues, who used horse models. 26–29 Implantation of allograft chondrocytes following adenoviral transduction with BMP-7 accelerated the early repair process, but by 8 months there was little difference compared with controls. 26 Transduction with IGF-1, by contrast, provided a sustained improvement in repair.…”

“…27–28 In their most recent work, this group used AAV to transfer IGF-1 to autologous chondrocytes, noting improved repair of full-thickness chondral defects. 29 …”