Efficacy of argyrrophilic nucleolar organizer region count test for in vivo biomaterial evaluation

Abstract

The efficacy of argyrophilic Nucleolar organizer Region (AgNOR) count test in the evaluation of biomaterial was assessed in this study utilizing a reactive (medium chromic catgut) and a non-reactive (Polypropylene) material. The materials were implanted into rat gluteus muscle for a duration of seven and 14 days and sham surgery done on a separate group of animals served as the control. The tissue response such as inflammation, muscle degeneration and peri-implant scar thickness around the reactive and non-reactive implant and the controls at seven and 14 days were studied using H&E and special stains for collagen. Besides this the estimation of collagen of the reactive and non-reactive material implanted tissue was studied. The observations made in this were compared with the fibroblast proliferation response at the respective durations as assessed by the AgNOR count estimation. On histopathological evaluation, the reactive material showed an initial acute inflammatory response with mild fibrosis and collagen deposition which subsequently settled into a chronic form with severe fibrosis and more collagen deposition at the end of 14 days. Non-reactive material elicited an acute inflammation initially (seven days post implantation) which settled into a mild chronic response at 14 days post implementation. Mild fibrosis and less collagen deposition were noticed in the peri-implant area at both the duration. Observations on fibroblast proliferation as assessed by AgNOR count test well correlated to the above findings. The AgNOR counts observed with reactive material at seven days and 14 days were 1.97 + 0.03 and 2.23 + 0.02 respectively. The counts for non-reactive material were 1.81 + 0.01 and 1.67 + 0.02 at seven and 14 days post implantation respectively. The collagen content of the reactive and non-reactive implanted tissue did not reveal any statistically significant difference as compared with the respective control. From this investigation it was proved that AgNOR count test could be reliably applied for biomaterial evaluation even at seven days duration and it formed a valuable adjunct to the routine method employed in the in vivo evaluation of biomaterials.