Lu Tao, Huang Yiwei, Liu Yu, Shen Yaxing, Qiao Yulei, Zhang Yongxing
Department of Thoracic Surgery, Zhongshan Hospital, Fudan University, Shanghai 200032, China.
J Thorac Dis. 2017 Jul;9(7):2038-2047. doi: 10.21037/jtd.2017.06.67.
Prolonged cryopreservation (~8-10 months) has been shown to reduce the antigenicity of tracheal allografts due to subsequent denuding of epithelium. In the present study, tracheal epithelium was assessed after variable periods of cryopreservation. Immunosuppressant-free allotransplantation was then undertaken to evaluate the impact of cryopreservation on tracheal antigenicity in dogs.
Tracheal rings [7-8] were removed from mongrel adult dogs for cryopreservation (1-10 months, -85 °C) and grafting. Before transplantation, one ring was sectioned from each end for histologic examination. The residual five-ring segments of mediastinal trachea were then transplanted into recipient dogs after 1-7 months (group 1, n=9) or 8-10 months (group 2, n=6) of cryopreservation. Anastomotic sites and allografts were covered by omental pedicles. No immunosuppressants whatsoever were administered.
In microscopic views, the ciliated tracheal epithelium of most grafts showed variable loss but was generally intact after cryopreservation, still demonstrating major histocompatibility complex (MHC)-II positivity. By postoperative bronchoscopy, allografts in both groups had largely developed lethal strictures. In group 1, eight dogs were sacrificed or died within 50 days post-transplantation, whereas survival times in group 2 were somewhat longer, with three dogs surviving for >60 days. Upon sacrifice, histologic preparations of grafted tissue in both groups were typically denuded of epithelium, with marked lymphocytic/monocytic submucosal infiltrates. Tracheal cartilage had been absorbed or destroyed.
After cryopreservation, some degree of tracheal epithelium loss maybe expected, but complete denudation is not obligatory. Retained epithelial antigenicity is thus capable of triggering rejection, resulting in transplant failures. Although prolonging transplant survival to an extent, fatal rejection of tracheal allografts was not preventable by prior cryopreservation.
长期冷冻保存（约8 - 10个月）已被证明可降低气管同种异体移植物的抗原性，这是由于随后上皮的剥脱。在本研究中，评估了不同冷冻保存时间后的气管上皮。然后进行无免疫抑制剂的同种异体移植，以评估冷冻保存对犬气管抗原性的影响。
从成年杂种犬身上取出气管环[7 - 8个]进行冷冻保存（1 - 10个月，-85°C）和移植。移植前，从每个末端切下一个环进行组织学检查。然后将纵隔气管的剩余五环段在冷冻保存1 - 7个月（第1组，n = 9）或8 - 10个月（第2组，n = 6）后移植到受体犬体内。吻合部位和同种异体移植物用网膜蒂覆盖。未给予任何免疫抑制剂。
在显微镜下观察，大多数移植物的纤毛气管上皮显示出不同程度的丧失，但在冷冻保存后通常仍保持完整，仍显示主要组织相容性复合体（MHC）-II阳性。通过术后支气管镜检查，两组的同种异体移植物大多形成了致命性狭窄。在第1组中，8只犬在移植后50天内被处死或死亡，而第2组的存活时间稍长，有3只犬存活超过60天。处死时，两组移植组织的组织学标本通常上皮剥脱，黏膜下有明显的淋巴细胞/单核细胞浸润。气管软骨已被吸收或破坏。
冷冻保存后，可以预期会有一定程度的气管上皮丧失，但不一定会完全剥脱。保留的上皮抗原性因此能够引发排斥反应，导致移植失败。尽管冷冻保存可在一定程度上延长移植存活时间，但无法通过预先冷冻保存预防气管同种异体移植物的致命性排斥反应。
