ABSTRACT
BACKGROUND: Type I collagen is a polymer material that has good biocompatibility and good cell affinity, and can degrade under certain conditions. It can also develop good mechanical properties after cross-linking, but it is less reported in the reconstruction of the injured median nerve of the forearm. OBJECTIVE: To explore the preparation method of type I collagen nerve conduit and its mechanism in the reconstruction following median nerve injury in the forearm. METHODS: A total of 40 Sprague-Dawley rats were selected from the Medical Animal Experimental Center, the Affiliated Hospital of Guizhou Medical University, 10 of which were randomly selected as sham surgery group. The remaining 30 rats were used to establish a rat model of median nerve injury in the forearm by laser-induced photochemical reaction. After successful modeling, the model rats were randomly divided into positive control group (n=10), type I collagen group (n=10) and autologous nerve group (n=10). The sham surgery group was routinely fed and did not participate in the modeling; the positive control group did not take special treatment after the successful modeling; the type I collagen group was subjected to bridging with type I collagen nerve conduit; and the autologous nerve group was subjected to bridging with autologous nerve. The repair effects were compared among groups. RESULTS AND CONCLUSION: (1) Under the inverted microscope, the type I collagen was loosely arranged before cross-linking, and it had honeycomb-shaped irregular pores with the pore size of 10-100 μm and the porosity of 20-200 μm, and the pore interstitial was relatively thin. After cross-linking, the type I collagen was densely arranged, the collagen fibers could form relatively regular pores with the pore size of 50-100 μm and the porosity of 20-200 μm, the interstitial mass was thickened, and the spatial structure changed significantly. (2) After 4, 8 and 12 weeks of repair, the scores on the Minnesota Manual Dexterity Test in the type I collagen and autologous nerve groups were significantly lower than those in the positive control group (P < 0.05) and higher than those in the sham surgery group (P < 0.05). (3) At 12 weeks after repair, there was no significant difference in amplitude and latency between the type I collagen group and the autologous nerve group (P> 0.05), but the amplitude and latency in both groups were significantly higher than those in the positive control group (P < 0.05). (4) At 12 weeks after repair, the nerve injury site surrounded by necrotic tissues was visible in the positive control group; no injury was found in the autologous nerve group, and the surrounding necrotic area decreased, indicating good recovery; no injury was shown by toluidine blue staining in the type II collagen group, indicating good recovery. Overall, the type I collagen nerve conduit can be successfully prepared by the self-made mold, and it can be used for the reconstruction following median nerve injury in the rat forearm, helping nerve repair.
ABSTRACT
Objective To establish an osteoporosis model in tree shrews by bilateral ovariectomy.Methods One hundred healthy 6-24 month old female tree shrews were used in this study.The diagnosis and treatment of osteoporo-sis in the model tree shrews was assessed according to the Interpretation of the Clinical Practice Guideines for Primary Oste-oporosis 2011 released by the Chinese Medical Association of Osteoporosis and Bone Mineral Salt Disease Branch.① Ac-cording to the human natural life span, sexual maturation time and peak bone mineral density ( PBMD) and the tree shrew natural life span and sexual maturation time, we estimated the PBMD of tree shrew in the age of months.Six 6-, 12-, 18-and 24-month old tree shrews in each group were randomly taken for measurement of BMD, and compared the differences between groups to verify the PBMD age of tree shrews.②We chose 62 6-month old tree shrews from the rest of tree shrews to measure their BMD to determine the mean and standard deviation of BMD.Then we divided them into study group ( n =32) and control group (n =30).Bilateral ovariectomy was performed in the study group, while omentectomy was done in the control group.BMD was measured at 3, 6, 9, 12 months after the surgery, 6 animals from each group.The animals which met the criteria of guideline were taken for pathological examination.Results ①The PBMD of 6-, 12-, 18-, 24-month old tree shrews was 0.138 ±0.012, 0.143 ±0.010, 0.141 ±0.009, and 0.139 ±0.009) g/cm2 , respectively, showing no significant differences among them (P>0.05).②The mean PBMD of the tree shrews was 0.143 ±0.016 g/cm2 .③In the model groups, the number of tree shrews whose BMD met the criteria of guideline was 0, 5, 4, 5, respec-tively.The pathological examination of the proximal tibia from the model group showed sparse and some disrupted trabecu-lae and enlarged inter-trabecular space.In the control group, the tibia tissues showed normal histology of bone structure and no one tree shrew showed a BMD value which met the criteria of diagnosis of osteoporosis.Conclusions An osteopo-rosis model in tree shrews can be established at 6 months after bilateral ovariectomy, showing similar manifestation of osteo-porosis in postmenopausal women.The success rate of this modeling method is high and the model is stable.