Fig 2: Deletion of FSP1+ cells significantly delayed thymus recovery.(A) Cyclophosphamide (Cy)-induced thymus regeneration model was established in TK- and TK+ mice. These mice were treated with GCV for 14 days during thymus recovery. TECs subsets were analyzed at indicated time points. (B) The recovery curve of thymus weight of untreated (triangle), TK- (open cycle) and TK+ (closed cycle) mice at various time-points after Cy injection. (C) Thymic sections from untreated and Cy/GCV-treated TK- and TK+ mice after 14 days recovery were stained for the expression of FSP1 (the upper panel) and CK5/CK8 (the lower panel). (D) Recovery of cell number of TECs, TEChigh, TEClow and mTECs from Cy/GCV-treated TK- and TK+ mice at different time points. (E) The recovery of mTECs of MHCIIhigh, Aire+, CD80+ and MHCIIlow in Cy/GCV-treated TK- and TK+ mice at indicated time points were present. Data presented are the mean ± SD (N = 6), representing one representative of three independent experiments with identical results. *P < 0.05, **P < 0.01 and ***P < 0.001 compared with TK- controls.

Fig 3: Deletion of FSP1+ cells dramatically altered thymus structure and cell composition.(A) Representative photographs of thymus organs in TK- and TK+ transgenic mice with and without GCV treatment for 18 days were shown. (B) Thymus weight and total cell numbers of thymocytes in TK- and TK+ mice with GCV treatment were summarized. (C) Thymic sections from GCV treated TK- and TK+ mice were stained with FSP1 to determine the ablating efficiency (upper). The H&E and CK5/CK8 staining of thymic sections showed decreased area of thymic medullary region in TK+ mice than in TK- mice after GCV treatment (middle and lower). (D) Representative FACS analysis of CD45-EpCAM+ TECs, MHCIIhigh and MHCIIlow TECs in the isolated thymic cells was shown. The cell number of TECs in TK+ mice was less than in TK- mice after GCV treatment. (E) The percentage and the total cell number of MHCIIhigh and MHCIIlow TECs in GCV-treated TK- and TK+ mice were summarized. Representative FACS profiles (F), and the percentage and total cell number (G) of mTECs and cTECs in CD45-EpCAM+ cells in GCV-treated TK- and TK+ mice were shown. Phenotypic characterization (H) and the percentages (I) of MHCII+, CD80+ and Aire+ mTECs in the gated thymic CD45- or CD45-EpCAM+ cells of TK- and TK+ mice with GCV treatment. (J) The total cell numbers of CD45-EpCAM+UEA-1+MHCIIhigh, CD45-EpCAM+UEA-1+CD80high, CD45-EpCAM+UEA-1+CD80low and CD45-EpCAM+UEA-1+Aire+ cells in GCV-treated TK- and TK+ mice. Representative results are shown from one of three independent experiments performed. Data were shown as mean ± SD (N = 5). *P < 0.05, **P < 0.01, ***P < 0.001 compared with TK- mice.