The quantity and accessibility of subcutaneous adipose tissue in humans make it an attractive alternative to bone marrow as a source of adult stem cells for therapeutic purposes. However, before such a cell source substitution can be proposed, the properties of stem cells derived from adipose tissue (ADSC) and bone marrow (BMSC), and their differentiated progeny must be compared in an animal model, such as swine, that adequately simulates the structure and physiology of humans. The objective of this work was to induce adult porcine stem cells isolated from subcutaneous adipose tissue and bone marrow to differentiate in vitro along the adipogenic lineage and to compare their transcript profile properties. ADSC and BMSC were isolated from subcutaneous adipose tissue and femurs of adult pigs, respectively, and differentiated along the adipogenic lineage using specific inducing medium. Cells were incubated up to 4 weeks with medium replaced every 3 days. Histological staining with Oil Red O was performed at 0, 2, 4, 7, 14, 21, 28 days of differentiation (dd) to confirm the adipogenic differentiation. RNA was also extracted at these time points. qPCR was performed on PPARG, DBI, ACSL1, CD36, CEBPA, DGAT2, ADFP, ADIPOQ, SCD. The geometrical mean of GTF2H3, NUBP, and PPP2CB was used as an internal control. Gene expression was analyzed using a mixed model of SAS with repeated time. The adipogenic differentiation of both ADSC and BMSC was confirmed by the Oil Red O positive staining. The relative mRNA abundance of all the genes at dd0 was similar between the ADSC and BMSC. The relative mRNA abundance of most of the genes was also similar between ADSC and BMSC throughout the adipogenic differentiation. ACSL1 and ADIPOQ had analogous expression patterns among the cell types. ACSL1 had relatively large mRNA abundance before differentiation, but ADIPOQ was barely detectable. As a consequence of differentiation, ACSL1 increased in relative mRNA abundance about 10-fold, whereas ADIPOQ mRNA increased about 1000-fold. Temporal expression patterns of SCD, DGAT2, and ADFP were similar. The increase in gene expression was >800% for SCD, >500% for ADFP, and >50 000% for DGAT2 after 7dd. ADSC had significantly higher expression of those genes compared to BMSC at 14 and 28dd. Both ADIPOQ and DGAT2 were almost undetectable prior to differentiation. mRNA expression of CD36 and DBI was similar with a significantly larger increase in expression of ADSC compared with BMSC. Relative mRNA abundance of CEBPA and PPARG was also larger in ADSC compared with BMSC; however, BMSC had a remarkable increase in temporal expression of those genes throughout adipogenic differentiation. These results suggest both cell types can differentiate towards the adipogenic lineage but with quantitatively different gene expression patterns. More investigation is needed before the ADSC can be considered a practical alternative source for stem cells in future human clinical applications.
This research was supported by the Illinois Regenerative Medicine Institute.
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