IMG-A1: A Novel Immortalized Granulosa Cell Line for Investigating FSH-Dependent Folliculogenesis and Ovarian...

The study of ovarian biology is hampered by the lack of in vitro models that faithfully recapitulate the physiology of granulosa cells (GCs). Primary GCs have a limited lifespan, while most immortalized lines are tumor-derived and exhibit non-physiological hormonal responses. The purpose of this study was to develop and characterize a novel immortalized GC line with a stable, physiologically relevant phenotype. We immortalized primary murine GCs from early antral follicles using lentiviral vector to introduce human telomerase reverse transcriptase (hTERT) gene to create the IMG-A1 cell line. The line was extensively characterized using molecular (qRT-PCR, Western blot), cytogenetic (karyotyping), and functional (hormone stimulation, ELISA, proliferation assays) methods to assess its phenotype and responsiveness to gonadotropins and metabolic stressors. Exhibiting a non-transformed phenotype, IMG-A1 cells retain a stable karyotype and express the follicle-stimulating hormone receptor (FSHR) but not the luteinizing hormone/chorionic gonadotropin receptor (LHCGR). Accordingly, they respond to FSH by upregulating steroidogenic genes like aromatase (Cyp19a1) but are unresponsive to LH/hCG. Furthermore, the line exhibits physiologically relevant responses to hormonal stimulation, including a strong induction of aromatase by FSH and its synergistic upregulation in a hyperandrogenic and hyperinsulinemic milieu. The IMG-A1 cell line is a unique and robust model of early antral granulosa cells, offering a valuable new tool for studying FSH-dependent folliculogenesis, cellular aspects of ovarian pathophysiology, and drug discovery.