Biomechanical Research Of Tissue Engineered Canine Trachea

Objective:Tracheal defects caused by wounds,tumors or battlefield hurt are tough problems for clinic doctors.While the end-to-end suture can not be used in repairing the large defect,tracheal substitute became the only effective way to reconstruct the form and function of airway.Tissue-engineered trachea has become more and more hot due to its advantages in the area of immunologic rejection and material resource.The problem that trachea grafts will sink after transplantation is still exist.Whether the process of making tracheal acellular matrix will decrease biomechanical property besides the immunological rejection and the revascularization of the tracheal allografts is still unknown.The aim of this experiment is to detect the opening angle and residual strain of acellular matrix of canine trachea under unload and zero stress situation,in order to find the basic mechanical property change of tissue engineered trachea,and provide the basic mechanical reference for tracheal tissue engineering.Method:The 5^th-10^thtrachea rings below thyroid cartilage of canine were chosen,and were divided into three groups.Group A:cryopreserved tracheal acellular matrix(n=14),Group B:fresh trachea(n=14),Group C:acellular matrix treated with modified Courtman to remove epithelium of tracheal mucosa(n=12).Group A:The acellular matrix were stored in liquid nitrogen(-196 degrees C)for six weeks and then rewarmed,Group B:fresh trachea stored in 4℃D-Hanks solution without any disposal.Group C:The acellular matrix were treated with non-ionic surfactants(NIS) (Triton X-100 and enzyme preparation)to remove epithelium of mucosa. The index and method of detection:The trachea segments of similar diameter and shape were marked at the middle point of muscle and the junction between cartilage and muscle,then sniped the ligaments between cartilage tings to achieve unload single tracheal rings.These rings were put into culture capsule which contain normal saline and detected by scanner.After stored the digital messages into computer,cut off the muscle at the middle point of the tracheal rings to achieve the tracheal sector. Then they were placed for 20 minutes for stabilization,and detected by scanner.The pictures were analyzed by special software to achieve the opening angle and inner and outer arc length under unload and zero stress situation.Results:The mean opening angle of Group B(fresh trachea)was 101.379±12.290 degree,of group A(cryopreserved tracheal acellular matrix)was 42.879±12.295 degree,of group C(acellular matrix treated with modified Courtman) was 72.211±10.487 degree.The opening angles between each group had statistical difference:A and B q=18.5742,P＜0.0010,B and C q=8.8979,P＜0.0010;A and C t=8.9476,P＜0.0010。This result showed that both two process of making tracheal acellular matrix will decrease the opening angle,the modified Courtman method might had a lighter influence than hypothermal method.The variance analysis of outer residual strain showed that they had different means(P=0.0018,α=0.0500).The "q" test of independent sample between each group showed that residual strain of group B was bigger than A(q=5.3402,p＜0.01)(had statistical difference);residual strain of group B was bigger than group C(q=3.6547, p＜0.05)(had statistical difference),while group A and group C had no statistical difference(q=1.4761,P＞0.05).This result showed that fresh trachea had bigger residual strain than that of the other two acellular matrix groups,and there was no statistical difference between cryopreserved tracheal acellular matrix and acellular matrix treated with modified Courtman.Conclusion:Fresh trachea has distinct larger opening angle than that of acellular matrix.This means in the process of removing cells from the tracheas,various physical and chemical factors can deduce the anti- compressibility of acellular trachea matrix,and the tissue engineered acellular matrix treated with modified Courtman has a better anti- compressibility than cryopreserved tracheal acellular matrix.