Abstract
As a non-crosslinked osteochondral xenograft would be mechanically inferior to native cartilage and vulnerable to premature degradation, we seek a safe and effective method of xenograft stabilization. The purpose of this study was to evaluate the capacity for epigallocatechin gallate (EGCG) to stabilize a decellularized porcine osteochondral xenograft through collagen crosslinking. Our objectives were to assess the effects of EGCG on the degree of crosslinking, mechanical properties, collagenase resistance, cytotoxicity, and in vitro biocompatibility. EGCG is a green tea polyphenol that acts as a collagen crosslinker. Porcine osteochondral plugs were decellularized and then crosslinked by soaking in EGCG. The degree of crosslinking, cartilage compressive stiffness, cartilage-bone interface strength, coefficient of friction, and residual mass after collagenase exposure all increased with an increasing EGCG concentration. With the exception of the coefficient of friction, EGCG treatment could restore mechanical properties to levels equal to, or exceeding those, of native cartilage. EGCG treatment profoundly increased the enzymatic resistance, and 1% EGCG provided protection equivalent to 1% glutaraldehyde. EGCG up to 0.5 mM was essentially not cytotoxic to chondrocytes embedded in alginate, and autologous chondrocytes attached to decellularized, EGCG-fixed cartilage were all viable five days after seeding. Results demonstrate that EGCG has many beneficial effects on a decellularized osteochondral xenograft, and may be suitable for use in stabilizing such a graft prior to implantation for the repair of a defect.
Highlights
Focal cartilage defects in the knee are often debilitating [1], and only a few treatments immediately restore functional hyaline cartilage to the joint surface
In light of the limited availability of fresh osteochondral allografts [2] and the questionable performance of decellularized osteochondral allografts [3], it is prudent to investigate alternative approaches whereby a cartilage defect is filled with functional hyaline cartilage
It is advisable to stabilize the xenograft through collagen crosslinking in the same manner as porcine bioprosthetic heart valves that are stabilized by using glutaraldehyde
Summary
Focal cartilage defects in the knee are often debilitating [1], and only a few treatments immediately restore functional hyaline cartilage to the joint surface. In light of the limited availability of fresh osteochondral allografts [2] and the questionable performance of decellularized osteochondral allografts [3], it is prudent to investigate alternative approaches whereby a cartilage defect is filled with functional hyaline cartilage. The focus of the current study is a decellularized porcine osteochondral xenograft, an attractive alternative due to its widespread availability [4], potentially long storage time, and amenability to effective sterilization methods that reduce the risk of disease transmission [5]. All xenografts, including osteochondral scaffolds, must be efficiently decellularized in order to avoid adverse immune reactions [6]. It is advisable to stabilize the xenograft through collagen crosslinking in the same manner as porcine bioprosthetic heart valves that are stabilized by using glutaraldehyde
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