Orbital fat-derived stem cells secreted stem cell factor and supported Leydig cells. (A) After orbital fat-derived stem cell (OFSC) injection, stem cell factor (SCF) was abundant in damaged testicular tissue. Human (h) immunoglobulin (IgG) and beta-2 microglobulin (β2M), two probes for human cells, were not detectable in (B) the sham operation group (Ctrl) and (C) the torsion–detorsion group (T/D). (D) Most hIgG-expressing and hβ2M-expressing cells could be detectable in the space between the seminiferous tubules. (E) Some of the human cells differentiated into P450-expressing cells and (F) very few human cells differentiated into sex determining region Y-box 9 (Sox-9)-positive cells. DAPI, 4,6-diamidino-2-phenylindole.