Biocompatibility of n-butyl-2-cyanoacrylate (Histoacryl) in cervical structures of rats: prospective in vivo study

Purpose: We investigated the biocompatibility of n-butyl-2-cyanoacrylate (NBCA) in the cervical deep tissues of rats to assess its biocompatibility. Methods: A total of 30 Sprague-Dawley rats were injected with NBCA. After 30, 90, 180, and 360 days, cubes of tissue (1 cm x 1 cm x 1 cm) surrounding the NBCA and normal tissue from the other side of the neck were excised from each rat. The adhesion of NBCA to adjacent structures was examined histologically. Cells were counted per high-power field (HPF), and fibrosis was graded with the measurement of fibrotic thickening. Results: All animals displayed normal behavior without any symptoms of distress throughout the study. There was no recognizable inflammatory reaction, foreign body reaction, or fibrosis in the 30 control samples. The analyses of experimental samples showed significantly decreased inflammatory cell counts over time (lymphoplasma cell count decreased from 100 (range, 70-100) to 30 (range, 30-50) per HPF, P = 0.010; neutrophil count decreased from 2 (range, 2-30) to 0 (range, 0-2) per HPF, P = 0.017). However, there was no significant difference in the number of multinuclear giant cells throughout the study period (a decrease from 22 [range, 16-34] to 16 [range, 12-22] per HPF, P = 0.287). The level of fibrosis was Common Toxicity Criteria ver. 4.0 Grade 1 without further thickening (P = 0.600). However, maturation of fibrosis progressed gradually. Conclusion: NBCA was biologically tolerable in the cervical deep tissues of rats. However, precautions are needed with respect to preventing a sustained foreign body reaction and fibrosis.