Repairing peripheral nerve injury using tissue engineering techniques

Each year approximately 360,000 people in the United States suffer a peripheral nerve injury （PNI）, which is a leading source of lifelong disability （Kelsey et al., 1997; Noble et al., 1998）. The most frequent cause of PNIs is motor vehicle accidents, while gunshot wounds, stabbings, and birth trauma are also common factors. Patients suffering from disabilities as a result of their PNIs are also burdensome to the healthcare system, with aver- age hospital stays of 28 days each year （Kelsey et al., 1997; Noble et al., 1998）.

Interventional effect of hirudin on the expression of microtubule-associated protein 2 in peripheral tissue of hematom of model rats with acute intracerebral hemorrhage

BACKGROUND： It is suspected that dissociation, destruction or synthetic disorder of microtubule-associated protein 2 （MAP-2） may participate in secondary injury of intracerebral hemorrhage （ICH）, and the reason may be related to thrombin in high concentration after ICH; therefore, the mechanism should be studied further. OBJECTIVE： To explore the effect of hirudin on expression of MAP-2 in peripheral tissue of hematom after ICH and changes of water content in brain tissue and analyze pathogenesis of thrombin in secondary injury after ICH. DESIGN ： Completely randomized grouping design and controlled animal study SEn-ING ： Department of Neurology, the First Affiliated Hospital of Jilin University MATERIALS ： The experiment was carried out in the Neurological Laboratory of the First Affiliated Hospital of Jilin University from April 2003 to April 2004. A number of 80 healthy Wistar rats, of both genders, aged 3-4 months, weighing 250-350 g, were randomly divided into 8 groups： normal control group, 6-hour ICH group, 1-day ICH group, 2-day ICH group, 3-day ICH group, 7-day ICH group, 3-day hirudin group and 7-day hirudin group with 10 in each group. Five rats from each group were selected to measure their water content, and the others were undertaken immunohistochemical stain. Hirudin was produced by Sigma Company, USA, and MAP-2 rabbit-rat polyclonal antibody was provided by Fuzhou Maixin Biotechnology Company Limited. METHODS： ① Model establishing and grouping intervention： Rats in simple ICH group were collected their blood from tails and then inserted with 50 μL non-anticoagulant auto-arterial blood into the cauda of the putamen in right brain within 5 minutes. Rats in hirudin groups were inserted with 10 U hirudin （which was diluted with saline to 20 μL） into local hematom regions within 5 minutes, and the needle was pulled out after 10 minutes. Rats in normal control group were untouched. ② Water content in peripheral tissue of hematom： Based on the ratio between dry weight and wet weight, brain tissue at bleeding side and in right frontal lobe was selected to measure dry and wet weights so as to calculate the water content [（wet weight - dry weight） /wet weight] × 100%.③ Positive expression of MAP-2： Based on immunohistochemical stain, positive MAP-2 cells were regarded as neurons and they were buffy morphological. Positive rate of MAP-2 was calculated, i.e., percentage of positive cells in each sight to total cells in all sights. ④ Statistical analysis： Data among groups were compared with one-way analysis of variance, averages were compared with SNK-q test by each other, and relation between water content and MAP-2 was analyzed with linear regression technique. MAIN OUTCOME MEASURES： Changes of water content and MAP-2 expression in peripheral tissue of hematorn at various time points after ICH and intervention of hirudin. RESULTS： All 80 rats were involved in the final analysis. ①Water content： Water content was increased at day 1, reached peak at day 3 and decreased at day 7. It was （72.31±0.32）%, （77.42±0.53）%, （78.44±0.28）%, （74.10±0.13）%, （74.85±0.51）% and （70.07±0.36）%, respectively in 1-day, 2-day, 3-day and 7-day ICH groups and 3-day and 7-day hirudin groups, which was higher than that in normal control group （63.85±0.41, q=-4.684 3 to -7.262 0, P〈 0.05）; that in 2-day and 3-day ICH groups was higher than that in 7-day ICH group （q=-3.053 4, -3.727 0, P 〈 0.05）; and that in 3-day and 7-day ICH groups was higher than that in hirudin groups at the same time points （q=-2.965 6, -2.726 4, P 〈 0.05）. ②Positive expression of MAP-2： Positive expression of MAP-2 was decreased at 6 hours after ICH, reached the lowest value at day 3 and increased at day 7. Positive rate was （78.60±0.42）%, （60.56±0.74）%, （44.60±0.26）%, （25.45±0.85）%, （32.55±0.64）%, （37.69＋0.76）%, （41.75±0.68）%, respectively in 6-hour, 1-day, 2-day, 3-day and 7-day ICH groups and 3-day and 7-day hirudin groups, which was lower than that in normal control group [（96.50±0.33）%, q= -3.074 5 to -8.128 5, P 〈 0.05]. In addition, positive cells of MAP-2 disappeared plentifully at 3-7 days after ICH, stain of positive cells were light, and only stain of plasma was positive. That in 3-day and 7-day hirudin groups was higher than that in ICH groups at the same time points （q= -3.391 8, -2.967 9, P 〈 0.05）. Moreover, positive cells of MAP-2 was formed slightly but deeply stained. ③ Results of linear regression： Water content was negatively related to MAP-2 changes at 7 days after ICH （r= -0.894 9, P〈 0.01）, i.e., water content was increased with decrease of MAP-2 expression. CONCLUSION ： The deterioration of MAP-2 may be involved in the pathogenesis of thrombin within the first week after ICH, and the local administration of hirudin can protect neurons.

Cartilage oligomeric matrix protein enhances the vascularization of acellular nerves

Vascularization of acellular nerves has been shown to contribute to nerve bridging.In this study,we used a 10-mm sciatic nerve defect model in rats to determine whether cartilage oligomeric matrix protein enhances the vascularization of injured acellular nerves.The rat nerve defects were treated with acellular nerve grafting（control group） alone or acellular nerve grafting combined with intraperitoneal injection of cartilage oligomeric matrix protein（experimental group）.As shown through two-dimensional imaging,the vessels began to invade into the acellular nerve graft from both anastomotic ends at day 7 post-operation,and gradually covered the entire graft at day 21.The vascular density,vascular area,and the velocity of revascularization in the experimental group were all higher than those in the control group.These results indicate that cartilage oligomeric matrix protein enhances the vascularization of acellular nerves.

Fabrication and characterization of Antheraea pernyi silk fibroin-blended P（LLA-CL） nanofibrous scaffolds for peripheral nerve tissue engineering

Electrospun nanofibers have gained widespreading interest for tissue engineering application. In the present study, ApF/P（LLA-CL） nanofibrous scaffolds were fabricated via electrospinning. The feasibility of the material as tissue engineering nerve scaffold was investigated in vitro. The average diameter increased with decreasing the blend ratio of ApF to P（LLA-CL）. Characterization of 13C NMR and FTIR clarified that there is no obvious chemical bond reaction between ApF and P（LLA-CL）. The tensile strength and elongation at break increased with the content increase of P（LLA-CL）. The surface hydrophilic property of nanofibrous scaffolds enhanced with the increased content of ApF. Cell viability studies with Schwann cells demonstrated that ApFIP（LLA-CL） blended nanofibrous scaffolds significantly promoted cell growth as compare to P（LLA-CL）, especially when the weight ratio of ApF to P（LLA-CL） was 25：75. The present work provides a basis for further studies of this novel nanofibrous material （ApF/P（LLA-CL）） in peripheral nerve tissue repair or regeneration.