502. Biomaterial-Mediated Lentiviral Delivery of Anti-Inflammatory Genes in Cartilage-Derived Matrix Hemispheres

Objectives: Cartilage tissue engineering seeks to provide a functional replacement for damaged or degenerated articular surfaces that develop in osteoarthritis (OA). Human bone marrow-derived mesenchymal stem cells (MSCs) seeded within cartilage-derived matrix (CDM) hemispherical scaffolds exhibit robust chondrogenic differentiation and extracellular matrix (ECM) deposition without evidence of a hypertrophic phenotype. However, inflammation within an OA joint may inhibit chondrogenesis of MSCs and induce degradation of both native and engineered cartilage, particularly through the action of interleukin-1 (IL-1). The goal of this study was to develop an anatomically-shaped, tissue-engineered cartilage capable of tunable and inducible expression of IL-1 receptor antagonist (IL-1Ra) in MSCs via biomaterial-mediated lentiviral gene delivery. Methods: IL-1Ra or eGFP coding sequences were cloned into doxycycline(dox)-inducible lentiviral vectors. Hemispherical scaffolds were fabricated from resuspended cartilage powder in hemispherical molds (outer radius 4.76 mm, inner radius 3.175 mm). Scaffolds were crosslinked and sterilized via dehydrothermal treatment. Dox-inducible eGFP or IL-1Ra lentivirus was immobilized to PLL-coated CDM scaffolds to transduce MSCs upon seeding. Non-transduced (NT), eGFP-expressing, or IL-1Ra-expressing constructs were treated with 0 or 0.1 ng/mL IL-1 during 28 days of chondrogenesis (+10 ng/mL TGF-s3) with 1 µg/mL dox. Results: Transduction of MSCs occurred throughout the CDM hemispheres (Fig 1AFig 1A) and the transduction efficiency of MSCs isolated from the construct was 57±5% eGFP+ by flow cytometry. Hemispherical constructs maintained their anatomical shape throughout chondrogenic culture (Fig 1BFig 1B). IL-1Ra-expressing constructs produced over 200 ng/mL of IL-1Ra, a concentration expected to inhibit pathologic IL-1 concentrations, and IL-1 treatment did not affect IL-1Ra production (Fig 1CFig 1C). IL-1 treatment reduced ECM deposition by NT and eGFP-expressing MSCs but not IL-1Ra-expressing MSCs, as evidenced by safranin-O/fast green staining for glycosaminoglycans and total collagen, respectively (Fig 1DFig 1D). After 28 days of chondrogenesis, IL-1 treatment significantly increased matrix metalloproteinase (MMP) activity in the conditioned media of NT and eGFP-expressing constructs but not in IL-1Ra-expressing constructs (p