Purpose

The purpose of the present study was to explore and compare inflammatory responses in the allogeneic immune reactions of adult and juvenile chondrocytes.

Methods and Materials

Cell Culture: Human adult articular chondrocytes (AChs) were isolated from 12 OA joints aged 64-72 when total knee replacements were performed. Juvenile chondrocytes (JChs) aged 4-12 years old were isolated from knee osteochondritis dissecans and polydactyly.

Mixed lymphocyte reaction (MLR): Peripheral blood mononuclear cells (PBMCs) were collected from healthy donors. AChs or JChs were co-cultured with PBMCs as responder cells for 5 days.

Activated Lymphocyte Proliferation Assay: PBMCs were activated by simultaneously cross-linking the T cell receptor complex using anti-CD3 and -CD28 mAbs for 2 hours.

Cytokine enzyme-linked Immunosorbent assay: To quantify the concentrations of proteins were quantified by ELISA.

Results

AChs and JChs were unable to stimulate the proliferation of allogeneic PBMCs in MLR assay. AChs and JChs inhibited the proliferation of activated PBMCs when chondrocytes/lymphocytes were 5/1 - 125/1. The inhibition rate of JChs was higher than AChs.

In MLR assay, IL-2 secretion by JChs was lower than AChs, but on introduction of co-cultured PBMCs both increased by the same amount. The increase in IL-6 by JChs was lower than AChs. MMP-3 increased by the same amount through introduction of AChs and JChs co-culture with allogeneic PBMCs. The concentration of IL-10, TGF-β, TIMP-1 and TIMP-2 were the same with both chondrocytes statistically.

Conclusion

We demonstrated that human AChs and JChs failed to stimulate allogeneic reactions in MLR and they inhibited proliferation of activated PBMCs, but AChs to a slightly lesser degree than JChs. Inflammatory cytokine of IL-2 and IL-6 were different between AChs and JChs during allogeneic reaction, but the catabolic cytokine MMP-3 had increased by the same amount. Immunosuppressive and protective cytokine secretions including IL-10, TGF-β, TIMP1 and TIMP2 levels were the same at allogeneic reaction.