Transdifferentiation is the conversion of cells from one differentiated cell type into another. How functionally differentiated cells already committed to a specific cell lineage can transdifferentiate into other cell types is a key question in cell biology and regenerative medicine. In the present study we show that porcine ovarian follicular GCs (granulosa cells) can transdifferentiate into osteoblasts in vitro and in vivo. Pure GCs isolated and cultured in Dulbecco's modified Eagle's medium supplemented with 20% FBS (fetal bovine serum) proliferated and dedifferentiated into fibroblast-like cells. We referred to these cells as DFOG (dedifferentiated follicular granulosa) cells. Microarray analysis showed that DFOG cells lost expression of GC-specific marker genes, but gained the expression of osteogenic marker genes during dedifferentiation. After osteogenic induction, DFOG cells underwent terminal osteoblast differentiation and matrix mineralization in vitro. Furthermore, when DFOG cells were transplanted subcutaneously into SCID mice, these cells formed ectopic osteoid tissue. These results indicate that DFOG cells derived from GCs can differentiate into osteoblasts in vitro and in vivo. We suggest that GCs provide a useful model for studying the mechanisms of transdifferentiation into other cell lineages in functionally differentiated cells.
dedifferentiated fat cell (DFAT cell); dedifferentiated follicular granulosa (DFOG); differentiation; osteoblast; ovary; transdifferentiation; ACAN, aggrecan; ALP, alkaline phosphatase; ALPL, ALP liver/bone/kidney; BMP, bone morphogenetic protein; BMSC, bone marrow stromal cell; BSP, bone sialoprotein; Cy3, indocarbocyanine; CYP11A1, cytochrome P450 family 11 subfamily A1; CYP19A3, cytochrome P450 family 19 subfamily A3; DAPI, 4′6-diamidino-2-phenylindole; DEX, dexamethasone; DFAT, dedifferentiated fat; DFOG, dedifferentiated follicular granulosa; DLX5, distal-less homeobox 5; DMEM, Dulbecco's modified Eagle's medium; FBS, fetal bovine serum; FSH, follicle-stimulating hormone; GAPDH, glyceraldehyde-3-phosphate dehydrogenase; GC, granulosa cell; GEO, Gene Expression Omnibus; IBSP, integrin-binding sialoprotein; INHBB, inhibin β B; LHCGR, luteinizing hormone/choriogonadotropin receptor; LIF, leukaemia-inhibiting factor; NR, nuclear receptor; OM, osteogenic medium; OSX, osterix; POU5F1, POU class 5 homeobox 1; RT, reverse transcription; RUNX2, Runt-related transcription factor 2; Sox9, SRY (sex determining region Y)-box 9; SPP1, secreted phosphoprotein 1; TC, theca cell