Long-term implantation test and tumorigenicity of polyvinyl alcohol hydrogel plates

Two types of flat plates made from a polyvinyl alcohol (PVA) hydrogel with a water content of 80 and 20 (PVA-H80, PVA-H20), 20 x 10 x 1 mm in size, we re subcutaneously implanted into each of 50 young, male Wistar rats. As a c ontrol, a sham operation was done on another set of 50 rats (Sham Op group) . The shape and transparency of the PVA hydrogel were unchanged for up to 2 4 months. Tumors arose in 14 rats from the PVA-H80 group. In the PVA-H20 gr oup, tumors appeared in 15 rats. The average tumor latency was 598 +/- 109 days in the PVA-H80 and 637 +/- 94 days in the PVA-H20. There was no differ ence in tumor incidence between the PVA-H20 and PVA-H80 groups (p < 0.05). In the Sham Op group, no malignant tumors appeared. Histopathologically, th e tumors induced by hydrogel plates were malignant tumors resembling fibros arcoma or malignant fibrous histiocytoma. This indicates that PVA hydrogel implants also induce solid state carcinogenesis at a similarly high rate to medical grade hydrophobic material reported in a previous study. (C) 2001 John Wiley & Sons, Inc. J Biomed Mater Res 56: 289-296, 2001.