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INTRODUCTION: IFATS COLLECTION: THE STEM CELL NICHE

IFATS Collection: Stem Cell Antigen-1-Positive Ear Mesenchymal Stem Cells Display Enhanced Adipogenic Potential

^aRegenerative Biology Laboratory and
^cStem Cell Biology Laboratory, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, Louisiana, USA;
^bDepartment of Animal Physiology, Warmia and Mazury University in Olsztyn, Olsztyn, Poland

Key Words. Stem cell antigen 1 • Mesenchymal stem cells • Adipogenesis • Differentiation

Correspondence: Correspondence: Barbara Gawronska-Kozak, Ph.D., Pennington Biomedical Research Center, Louisiana State University System, 6400 Perkins Road, Baton Rouge, Louisiana 70808, USA. Telephone: 225-763-0254; Fax: 225-763-0273; e-mail: KozakB{at}pbrc.edu

Received on March 19, 2008; accepted for publication on June 20, 2008.

First published online in STEM CELLS EXPRESS  July 3, 2008.

Hyperplasia is a major contributor to the increase in adipose tissue mass that is characteristic of obesity. However, the identity and characteristics of cells that can be committed into adipocyte lineage remain unclear. Stem cell antigen 1 (Sca-1) has been used recently as a candidate marker in the search for tissue-resident stem cells. In our quest for biomarkers of cells that can become adipocytes, we analyzed ear mesenchymal stem cells (EMSC), which can differentiate into adipocytes, osteocytes, chondrocytes, and myocytes. Our previous studies have demonstrated that EMSC abundantly expressed Sca-1. In the present study, we have analyzed the expression of adipogenic transcription factors and adipocyte-specific genes in Sca-1-enriched and Sca-1-depleted EMSC fractions. Sca-1-enriched EMSC accumulated more lipid droplets during adipogenic differentiation than Sca-1-depleted. Similarly, EMSC isolated from Sca-1^–/– mice displayed reduced lipid accumulation relative to EMSC from wild-type controls (p < .01). Comparative analysis of the adipogenic differentiation process between Sca-1-enriched and Sca-1-depleted populations of EMSC revealed substantial differences in the gene expression. Preadipocyte factor 1, CCAAT enhancer-binding protein (C/EBP) β, C/EBP, peroxisome proliferator-activated receptor 2, lipoprotein lipase, and adipocyte fatty acid binding protein were expressed at significantly higher levels in the Sca-1-enriched EMSC fraction. However, the most striking observation was that leptin was detected only in the conditioned medium of Sca-1-enriched EMSC. In addition, we performed loss-of-function (Sca-1 morpholino oligonucleotide) experiments. The data presented here suggest that Sca-1 is a biomarker for EMSC with the potential to become functionally active adipocytes.

Disclosure of potential conflicts of interest is found at the end of this article.