Identification of active and quiescent adipose vascular stromal cells

Recent studies have demonstrated the existence of both active and quiescent stem cells in bone marrow, hair follicle and intestine. We attempted to identify active and quiescent vascular stromal cells (VSC) in adipose tissue.

For identification of active VSC, adult rats were injected intraperitoneally with thymidine analog 5-ethynyl-2-deoxyuridine (EdU) and their subcutaneous tissue harvested 3 days later. For identification of quiescent VSC, newborn rats were injected intraperitoneally with EdU and their subcutaneous tissue harvested 9 weeks later. The harvested adipose tissues were examined for the co-localization of EdU with VSC marker CD34, smooth muscle marker SMA, endothelial marker RECA and pericyte marker CD140b.

In adult rat adipose tissues harvested 3 days after EdU injection, there were 28.80 ± 8.70 (mean ± SD) EdU+ cells/100 × microscopic field, and approximately 6.2% of cell nuclei were labeled with EdU. The percentages of EdU+ cells expressing the following markers were approximately: 84 for CD34, 5.6 for RECA (rat endothelial marker), 3.7 for SMA and 14.8 for CD140b. In the adipose tissues of newborn rats that were harvested 9 weeks after EdU injection, the percentages of EdU+ cells expressing the following markers were approximately: 76 for CD34, 1.8 for RECA, 0 for SMA and 12.9 for CD140b. In both the short-term (active) and long-term (quiescent) EdU-labeled adipose tissues, the EdU label was consistently co-localized with CD34 and in the proximity of CD140b stain or in the adventitia.

Both active and quiescent VSC expressed CD34 and localized to capillaries and the adventitia of larger blood vessels.