Mg-6Zn alloys promote the healing of intestinal anastomosis via TGF-beta/Smad signaling pathway in regulation of collagen metabolism as compared with titanium alloys

There is a great clinical need for biodegradable materials. This study aimed to investigate the effects of Mg-6Zn and titanium alloy stapler nails on intestinal anastomosis healing mediated via the TGF-beta/Smad signaling pathway, as reflected in collagen metabolism in rabbits. Side-to-side ileo-ileostomy was performed with linear stapler loaded with the two nails. The results showed that no obvious postoperative complications such as abdominal infection and anastomotic leakage were observed. General observation and scanning electron microscope showed that Mg-6Zn alloy nails remained intact in the first week, degraded significantly in the second week, and were little left in the third week, while the titanium alloy nails showed intact substrate throughout the experimental period. Immunohistochemical analysis showed that the expression of TGF-beta 1 in Mg-6Zn alloy group was higher than that in titanium alloy group after I week, but it increased slowly, arrived at a lower level in the third week. Collagen I showed an increased expression in Mg-6Zn alloy group, but decreased with time in titanium alloy group. An enhanced expression of collagen III in Mg-6Zn alloy group in the first week but much lower in the third week as compared to the titanium alloy group. The expression of smad2 in Mg-6Zn alloy group maintained a steady level, while in titanium alloy group it showed a general upward trend. The expression of smad3 in both groups held steady after 2 weeks, then in the third week, it showed a strong uptrend in Mg-6Zn alloy group, while decreased immediately in titanium alloy group. Our findings suggest that Mg-6Zn alloy nails degraded significantly within 3 weeks and could provide stability of intestinal anastomosis in the reconstruction of intestinal tract. TGF-beta/Smad signaling pathway may play a role in regulation of baseline collagen synthesis throughout the process.