FIG. 1.

Characteristics of side population cell-derived thyroid cell line (SPTL) cells. (A) Monolayer culture of SPTL cells (upper: SPTL) and primary thyroid cells (lower: Thy). (B) Representative electron microscopic images. Cells are small, round, elongated, or three- or four-pointed star-shaped (most right panel). LB, lipid body; V, vacuole; Mt, mitochondria; dER, dilated endoplasmic reticulum; G, Golgi apparatus; Pha, Phagosome. The matrix of most mitochondria is not enriched. (C) Fluorescence-activated cell sorting (FACS) analysis for SCA1. Dotted line and straight line show cells treated without and with PE-conjugated SCA1 antibody, respectively. (D) Western blot analysis of SPTL cells for the expression of SCA1, as well as thyroid differentiation markers, NKX2-1 and PAX8, compared with mouse thyroid primary cells (Thy). SPTL cells were those cultured under 10% serum. β-Actin was used as a loading control (15 μg/lane). (E) Quantitative reverse transcription polymerase chain reaction (qRT-PCR) analysis of Sca1 mRNA expression in SPTL, original side population (SP) and main population (MP), and embryonic stem (ES) cells, cultured under 10% serum. Relative expression is shown based on the expression level of ES cells as 1. Mean ± standard deviation (SD) from representative experiment in triplicate are shown. Note that qRT-PCR was carried out at least twice using samples prepared at different times. Similar results to those shown were obtained. ****p < 0.0001 for ES vs. MP, SP, and SPTL by unpaired t-test.