Osteochondral allograft and xenograft immunogenicity decrease following ex vivo tissue culture

Introduction/Objective

Osteochondral allografting can be an effective option for the treatment of focal cartilage injuries. However, wide scale applicability of this technique is limited by availability of donor tissue. To overcome this limitation, osteochondral xenografting has been proposed as a potential alternative, but immune-mediated rejection precludes its clinical application at this time. We hypothesized that removing much of the marrow cell content through tissue culture would result in a decrease in xenograft immunogenicity. We believed this could be tested in a preclinical animal model.

Methods

Fresh porcine femoral condyles were harvested and cultured for 0, 14, or 28 days before coculture with either allogeneic enriched porcine T-cells or xenogeneic enriched equine T-cells for 5 days. After 5 days, these cocultures were pulsed with 5-ethynyl-2′deoxyuridine then analyzed by flow cytometry to assess the level of cell proliferation. Coculture supernatant samples were also collected to evaluate the levels of prostaglandin-E2 and monocyte chemotactic protein-1 (MCP-1) as markers of inflammation.

Results

The osteochondral tissue induced significantly less T-cell proliferation, prostaglandin-E2, and MCP-1 production when the tissue had been cultured for either 14 or 28 days prior to the coculture assay (P < .0001).

Conclusions

We conclude that T-cell responses to either allogeneic or xenogeneic osteochondral tissues were significantly reduced by 14 days of preculture prior to exposure to T-cells.