Abstract: Objective To observe the effects of early applying of microporous polysaccharide on foreign body reaction induced by subcutaneously imbedding expanded polytetrafluoroethylene (e-PTFE) in mice. Methods Ten wide type adult C57BL/6J mice were collected and made a full-thickness skin incision on both sides of their back. The two incisions on the back of each mouse were divided into two groups according the random number table, with 10 incisions in each group. A tube-shaped e-PTFE was imbedded into each incision in microporous polysaccharide group, and then 0.03 g microporous polysaccharide was evenly sprayed in the cavity. Whereas, a tube-shaped e-PTFE was imbedded into each incision in control group without other treatment. The incisions in two groups were performed with conventional full-thickness suture. On post operation day (POD) 14, the e-PTFE surrounded with fibrous capsule in each incision of two groups was taken out, and then fibrous capsule tissue was harvested. The thickness of fibrous capsule was observed and measured with HE staining. Collagen fiber distribution in fibrous capsule tissue was observed with Masson staining to calculate the collagen fiber index. Neovascularization and macrophage infiltration in fibrous capsule tissue were observed respectively with immunohistochemical staining, and the numbers of new vessels and macrophages were counted. Data were processed with t test. Results On POD 14, the thickness of fibrous capsule surrounding e-PTFE imbedded into the incision of microporous polysaccharide group was (127±19) μm, which was significantly thinner than that of control group [(250±35) μm, t=4.13, P<0.05]. On POD 14, the collagen fiber index of fibrous capsule tissue surrounding e-PTFE imbedded into the incision of microporous polysaccharide group was 0.500±0.003, which was significantly higher than that of control group (0.488±0.004, t=5.00, P<0.05). On POD 14, the number of new vessels in fibrous capsule tissue surrounding e-PTFE imbedded into the incision of microporous polysaccharide group was 19±3 per 400 fold visual field, which was significantly more than that of control group (11±3 per 400 fold visual field, t=2.05, P<0.05). On POD 14, the number of macrophages in fibrous capsule tissue surrounding e-PTFE imbedded into the incision of microporous polysaccharide group was 64±5 per 400 fold visual field, which was close to that of control group (66±7 per 400 fold visual field, t=0.78, P>0.05). Conclusions Topically applying microporous polysaccharide can reduce the formation of fibrous capsule after subcutaneous imbedding of e-PTFE in mice, and it can improve the collagen deposition and angiogenesis but not impact on macrophage infiltration.