Stromal vascular progenitors in adult human adipose tissue

Abstract

Background The in vivo progenitor of culture-expanded mesenchymal-like adipose-derived stem cells (ADSC) remains elusive, owing in part to the complex organization of stromal cells surrounding the small vessels, and the rapidity with which adipose stromal vascular cells adopt a mesenchymal phenotype in vitro. Methods Immunohistostaining of intact adipose tissue was used to identify 3 markers (CD31, CD34, CD146) which together unambiguously discriminate histologically distinct inner and outer rings of vessel-associated stromal cells, as well as capillary and small vessel endothelial cells. These markers were used in multiparameter flow cytometry in conjunction with stem/progenitor markers (CD90, CD117) to further characterize stromal vascular fraction (SVF) subpopulations. Two mesenchymal and two endothelial populations were isolated by high speed flow cytometric sorting, expanded in short term culture and tested for adipogenesis. Results The inner layer of stromal cells in contact with small vessel endothelium (pericytes) was CD146+/α-SMA+/CD90±/CD34−/CD31−; the outer adventitial stromal ring (designated supra adventitial-adipose stromal cells, SA-ASC) was CD146−/α-SMA−/CD90+/CD34+/CD31−. Capillary endothelial cells were CD31+/CD34+/CD90+ (endothelial progenitor), while small vessel endothelium was CD31+/CD34−/CD90− (endothelial mature). Flow cytometry confirmed these expression patterns and revealed a CD146+/CD90+/CD34+/CD31− pericyte subset that may be transitional between pericytes and SA-ASC. Pericytes had the most potent adipogenic potential, followed by the more numerous SA-ASC. Endothelial populations had significantly reduced adipogenic potential compared to unsorted expanded SVF cells. Conclusions In adipose tissue perivascular stromal cells are organized in two discrete layers, the innermost consisting of CD146+/CD34− pericytes, and the outermost of CD146−/CD34+ SA-ASC, both of which have adipogenic potential in culture. A CD146+/CD34+ subset detected by flow cytometry at low frequency suggests a population transitional between pericytes and SA-ASC.

Concise Review: Adipose-Derived Stromal Vascular Fraction Cells and Stem Cells: Let's Not Get Lost in Translation

“…While some have attempted to apply these criteria to ASC, there is a reason to doubt their applicability because early passage ASCs are routinely CD34 þ [22,23]. Investigators continue to search for ASC specific surface markers.…”

“…Some have used the protein Pref1, first identified on murine 3T3-L1 preadipocytes, as a putative ASC marker [24]. Others have reported the use of pericytic markers such as plateletderived growth factor receptor b and 3G5 [23,[25][26][27][28]. Finally, combinatorial phage display approaches have associated the presence of a 5 b 1 integrin with ASCs [29].…”

Phenotypic Characterization and In Vivo Localization of Human Adipose-Derived Mesenchymal Stem Cells

“…Many types of primitive cells in the vascular wall may share morphological properties or immunophenotypic markers (Klein et al, 2010;Majesky et al, 2011a;2011b;Pacilli et al, 2009;Traktuev et al, 2008;Zimmerlin et al, 2010). These different types of resident progenitor cells include he-mangiblasts, bone marrow-derived endothelial progenitors, vascular wall resident endothelial progenitors, vascular wall resident smooth muscle progenitors, and vascular wall resident mesenchymal stromal cells.…”

Phenotypes of stem cells from diverse origin

“…Therefore, we asked all authors to revisit the table and upgrade their part either by own data or based on additional literature, as necessary. This resulted in the upgraded Table 1 showing phenotypes of very small embryonic-like stem cells (vSELs) (5,6), neural stem cells (NSCs) (7)(8)(9)(10)(11)(12)(13)(14)(15)(16), hematopoietic stem cells (HSCs) from two organs (4,17), MSCs (4,18), EpSC (4), limbal epithelial stem cells (LSCs) (19), endothelial progenitor cells (EPCs) from different organs (3,4,(20)(21)(22)(23)(24)(25), supra-adventitial adipose stromal cells (SA-ASCs) (3,(22)(23)(24)(25), adipose pericytes (pericyte) (3,(22)(23)(24)(25), and finally cancer stem cells (CSCs) (26).…”

“…VI (4) VII (19) VIII (20,21) IX (3,(22)(23)(24)(25) X (4) XI (3,(22)(23)(24)(25) XII (3,(22)(23)(24)(25) XIII ( (17) IV (4) V (4,18) VI (4) VII (19) VIII (20,21) IX (3,(22)(23)(24)(25) X (4) XI (3,(22)(23)(24)(25) XII (3,(22)(23)(24)(25) XIII (26) RHAMM/HMMR marker expression in the same stem cell lineage obtained from various tissues may indicate differences in their pluripotency. It is also possible that stem cell marker expression pattern and levels depend on respective cell cycle phases.…”