mRNA transcript levels of key transcription factors at P3 versus D21. Expression levels of mRNA transcript were analyzed for transcription factors hypoxia-inducible factor 1α (HIF-1α), hypoxia-inducible factor 2α (HIF-2α) and Sry-related HMG box-9 (Sox9) at the end of P3 monolayer expansion (P3, white bars) compared to 21 days scaffold culture (D21, hatched bars). Scaffold culture increased Sox9 expression in all culture conditions. Gene expression was normalized to levels of the housekeeping gene β-actin using 2-ΔCT method. * = p < 0.05 represents significant difference between P3 and D21 values within groups using Student’s two-tailed t-test. There was no significant difference in expression levels of these mRNA transcripts between D21 scaffold constructs from inner or outer MFCs cultured under 21% or 3% oxygen tension. # = p <0.05 by one-way ANOVA with Games-Howell multiple comparisons post-test.