Fig. 2. AHNPs avoid immortalizing mutations, and exhibit mitogen- and telomerase-dependent growth. (A) Cultured AHNPs express major growth regulatory proteins longitudinally throughout culture. (B) Karyotyped AHNPs display normal ploidy and have no gross cytogenetic malformations. (C) Following growth arrest by an exogenous TERT inhibitor (EGCG) or growth factor withdrawal cultured cells express SA-ß-Gal. However, only mitogen-withdrawn (-bFGF) cells lose TERT expression when evaluated 7 days later. (D) Physiological (x-irradiation) or chemical inhibitors (apidicolin, EGCG) consistently increase the fraction of cells expressing SA-ß-Gal. (E) Application of reversible growth inhibitors yields a significant reduction in growth rate. AHNPs revert to previous proliferative levels following arrestor washout. (F) Age-matched AHNPs placed in either basic media (N2) or media containing EGF or bFGF only (N2E, N2F) enter irreversible growth arrest compared to defined proliferative conditions (N2EF) and subsequently become unviable. Data shown for temporal cortex derived cells. ^*P<0.05, Student's t-test. Scale bar: 75 µm in C.