Phenotypic loss of fibrocartilaginous markers during monolayer expansion. Inner and outer MFCs were expanded from Passage 1 (P1, grey bars) to Passage 3 (P3, white bars) under normal (21%) or low (3%) oxygen tension. mRNA transcript levels of collagen type I (Col1), collagen type II (Col 2), aggrecan and COMP were compared within groups at P1 and P3. Marked dedifferentiation is seen between P1 and P3 for all genes of interest except collagen type I. Expression was normalized to levels of the housekeeping gene β-actin using 2-ΔCT method. * = p < 0.05 ** = p < 0.01 represents significant difference between P1 and P3 values within a single group using Student’s two-tailed t-test.