An experimental study on Host Versus Graft Reaction at different stages of autologous or allogeneic transplantation of large-area full-thickness cartilage defects in rats
Authors: Yang Fan , Li Zhenhao , Liu Baoyi , Liu Jiahe , Li Chenzhi , Wu Mingjian , Li Yancheng , Cui Yan , Xiong Wanqi , Wang Zewen , Zhao Dewei , Yang Ke 
Published: March 2023

Abstract
Objective : To observe the regularity of host-anti-graft reaction in animal model full-thickness cartilage defect after autologous or allogeneic full-thickness cartilage transplantation.
Methods :The model of cartilage combined with subchondral bone defect was selected from 36 healthy adult male SD rats and randomly divided into three groups: blank control group (group A), autograft group (group B), and allograft group (group C). The gait of the rats was observed after transplantation, The rats were killed at 3, 5 and 7 days after operation. After operation, the cells in blood and spleen were separated for flow cytometry and ELISA detection, and the local bone tissue sections were subjected to hematoxylin-eosin(HE) staining. All the results of inflammatory reaction were studied by statistical analysis method.
Results :After allogeneic full-thickness cartilage transplantation, the expression of inflammatory cells increased significantly in the blood samples of the three groups on the 3rd-5th day after operation. Compared with groups A and B, the expressions of inflammatory cells (monocytes, NK cells, T cells) and inflammatory factors (IL-1β, IL-6, TNF-α) in group C increased significantly, and decreased slightly after7 days. The expression of monocytes in this group on the 5th and 7th day was higher than that on the 3rd day. The expression of Tregs in group B was higher than that in the other two groups from the first time after operation, and the difference became more and more obvious in the first week after surgery. In spleen cells, the expression of monocytes in group C was markedly higher than that in the other two groups on the 5th and 7th after operation, and the expression of NK was also higher than that in the A and B groups on the 3rd and 5th after operation. The change of Tregs in group B showed the same trend as that of blood sample one week after operation. In all groups, the expression levels of monocytes and T cells on the 5th and 7th day were higher than those on the 3rd day. The results of histological staining showed that the local inflammation was obvious on the 3rd day after operation. The section on the 5th day after the operation showed that the inflammatory manifestations at the interface between the recipient and the graft continued to expand,and some grafts were involved, and the immune response reached the peak. On the 7th day after operation, the whole implant was destroyed, and the response intensity decreased gradually, which echoed the results of flow cytometry and ELISA.
Conclusions :The acute immune response after allogeneic cartilage transplantation is a complex process, which is intervented and jointed acted by CD4+T, CD8+T, NK cells, IL-1β, IL-6, TNF-α and other cells and extracellular factors.Our study shows that the intensity of host versus graft reaction after allogeneic full-thickness cartilage transplantation reached the highest in the 5th day after operation, and then decreased gradually.This conclusion provides a theoretical basis for the implantation of bioengineered orthopaedic materials and the timing of immunosuppressive interventions in the implantation allogeneic or xenogeneic osteochondral transplantation in the future.