CD8+ T cells are involved in early inflammation before macrophages in a rat adipose tissue engineering chamber model

Adipose tissues regenerated using tissue engineering chambers (TECs) show the potential for applications in reconstruction of soft tissue defects. Previous studies have shown that early inflammation plays a key role in angiogenesis and adipogenesis required for adipose tissue generation. However, the sequence of events of the early inflammatory cascade is unclear. In this study, we investigated the role of early inflammatory cells in adipose tissue engineering using a rat TEC model. Rats in the TEC model were divided into five groups: the control group, the zymosan A-treated group, the 5-AIQ-treated group, the imatinib-treated group, and the CD8+ T cell injection group. Fat pad volume, angiogenesis, adipogenesis, inflammatory factor levels, and inflammatory cell infiltration in chambers after implantation were evaluated at different time points. The volume of fat pads of was higher in the zymosan A-treated and CD8+ T cell injection groups than other groups, and these two groups also showed higher levels of proinflammatory factors, greater numbers of CD31+ cells and perillipin+/Ki67+ cells, and higher macrophage infiltration. The infiltration of CD8+ T cell peaked at 3 days after implantation, which was earlier than that of macrophages. However, inhibition of CD8+ T cells reduced the recruitment of macrophages and lowered inflammation in the TECs. CD8+ T cells played a key role in promoting inflammation at earlier stages than macrophages in adipose TECs. Increased levels of interleukin-2 secretion by CD8+ T cells resulted in recruitment of more infiltrating macrophages to enhance inflammation, as required for adipose tissue regeneration.