CD4 and renal fibrosis: H&E staining (Figure 5I), PAS staining (Figures 5J,K), immunohistochemistry (Figures 5L,M), and Masson trichrome staining (Figures 5N,O) indicated that CD4+ Treg depletion negated the therapeutic effects of hUCMSCs-Exo@Ex-4 in glomerular injury, reduced podocytes, and renal fibrosis in DN mice, but had little impact on the effects of hUCMSCs-Exo.