The degradation and local tissue effects of collagen hydrogel and sponge implants in muscle

Collagen products will degrade and evoke certain local tissue reaction after being implanted. ISO 10993.6 is the international standard to evaluate local tissue reaction for biomaterials. However, even in the present version, it does not define the specific view fields for scoring local tissue reaction in the sections, which may influence the fair evaluation for the degradable polymer, such as collagen. In this study, 4 kinds of collagens and 2 kinds of bio-inert products were implanted into the rabbit muscle for 26 weeks, and two different scoring methods (uniform distribution scoring method and area locating scoring method) were applied to evaluate the local tissue reaction for each implant. The results showed that the tissue reaction on the interface was active, but the various scores in the implant and surrounding areas could help us to understand the differences of the degradation process. An area locating scoring method which selected the fields in the implant, interface and surroundings respectively showed a higher total score and offered more detailed information compared to the uniform distribution scoring method. Since the degradation and tissue reaction degree in the different areas are ever changing for the degradable implants, this area locating scoring method is sensitive, effective and applicable for the semi-quantitative evaluating system of ISO 10993.6.