Smooth Muscle Progenitor Cells in Human Blood

Abstract

Background-Recent animal data suggest that vascular smooth muscle cells within the neointima of the vessel wall may originate from bone marrow, providing indirect evidence for circulating smooth muscle progenitor cells (SPCs). Evidence for circulating SPCs in human subjects does not exist, and the mechanism whereby such putative SPCs may home to sites of plaque formation is presently not understood but is likely to involve expression of specific surface adhesion molecules, such as integrins. In this study, we aimed to culture smooth muscle outgrowth cells (SOCs) from SPCs in human peripheral blood and characterize surface integrin expression on these cells. Methods and Results-Human mononuclear cells isolated from buffy coat were seeded on collagen type 1 matrix and outgrowth cells selected in endothelial growth medium (EGM-2) or EGM-2 and platelet-derived growth factor BB. Selection in platelet-derived growth factor BB-enriched medium caused rapid outgrowth and expansion of SOC to Ͼ40 population doublings in a 4-month period. These SOCs were positive for smooth muscle cell-specific ␣ actin (␣SMA), myosin heavy chain, and calponin on immunofluorescence and Western blotting and were also positive for CD34, Flt1, and Flk1 receptor but negative for Tie-2 receptor expression, suggesting a potential bone marrow angioblastic origin. In contrast, endothelial outgrowth cells (EOCs) grown in EGM-2 alone and the initial MNC population were negative for these smooth muscle-specific markers. Integrin ␣ 5 ␤ 1 expression by FACS and Western blotting was significantly increased in SOCs compared with EOCs, and this was confirmed by 8-fold greater adhesion of SOC to fibronectin (PϽ0.001), an effect that could be decreased using an ␣ 5 ␤ 1 antibody. Finally, SOC showed a significantly greater in vitro proliferative potential compared with EOCs of similar passage (PϽ0.001). Conclusions-This study demonstrates for the first time outgrowth of smooth muscle cells with a specific growth, adhesion, and integrin profile from putative SPC in human blood. These data have implications for our understanding of adult vascular smooth muscle cell differentiation, proliferation, and homing.

Clonogenic multipotent stem cells in human adipose tissue differentiate into functional smooth muscle cells

“…During development, most smooth muscle progenitors arise mainly from the splanchnic mesoderm and from the neural crest (15). At postnatal life, progenitors for SMC have been found in circulating blood (16) and bone marrow (17). Bone marrow has been the hallmark site in postnatal life known to harbor at least two populations of stem cells: the hematopoietic and the nonhematopoietic mesenchymal stem cell (MSC).…”

Review of Past Research and Current Concepts on the Etiology of Moyamoya Disease

“…55) Since the existence of smooth muscle progenitor cells (SMPCs) was described by Simper et al, attention has focused on the finding that SMPCs have opposite role to EPCs in the development of several vascular diseases. 59) Recently, our laboratory found that the CD34 ＋ VEGFR2 ＋ cells were closely involved in the intimal thickening of the supraclinoid internal carotid artery collected from adult patients with moyamoya disease. 61) This study was interesting in that certain progenitor cells also participated in the progressive occlusive lesion in moyamoya disease.…”

Endothelial Progenitor Cells Are Decreased in Blood of Cardiac Allograft Patients With Vasculopathy and Endothelial Cells of Noncardiac Origin Are Enriched in Transplant Atherosclerosis

“…MNCs were then resuspended in endothelial cell growth medium-2, placed on a 6-well plate coated with collagen type I (Becton Dickinson), and grown in culture as previously described. 8 …”

“…7 These latter cells have many of the characteristics of progenitors undergoing multiple population doublings and exhibit an angioblastic phenotype. 8 In a series of elegant experiments, Lin and colleagues 7 have also shown that CECs originate from the adult vessel wall, whereas EPCs most likely derive from circulating angioblasts.…”