Synthetic hydrogel capacity to induce formation of foreign-body giant multinucleate cells differs in vivo and in vitro.

The granulomatous reaction accompanied with MGC formation represents the most striking feature of the non-favourable biological tolerance of implanted devices. We compared MGC formation in the course of the granulomatous reaction in vitro and in vivo employing three types of hydrogels whose biocompatibility had been well studied earlier. The efficiency of the in vitro assay for the granulomatous reaction, including MGC formation, was verified employing the nematode Nippostrongylus brasiliensis, a well-known inductor of MGC formation in vitro. The in vitro results demonstrated a very low level of MGC formation in reaction against all three types of hydrogels without polymer-specific differences in comparison with the nematode experiment characterized by a high extent of MGC formation. On the other hand, the extent of MGC formation was implant type-specific in vivo: pHEMA-co-DMAEMA > pHEMA > pHEMA-co-NaMA. These results indicate that in the in vitro assay it was not possible to discriminate among the types of polymers used in the experiment in comparison with the animal experiment. They also indicate potential differences between granuloma formation induced by parasites and by foreign bodies.