Differentiated markers in undifferentiated cells: Expression of smooth muscle contractile proteins in multipotent bone marrow mesenchymal stem cells

Abstract

In studying the differentiation of stem cells along smooth muscle lineage, smooth muscle cell (SMC) contractile proteins serve as markers for the relative state of maturation. Yet, recent evidence suggests that some SMC markers are probably expressed in multipotent mesenchymal stem cells (MSCs). Such a paradox necessitates investigations to re‐examine their role as differentiated markers in MSCs. We tried to detect the expression of four widely used SMC markers including α‐smooth muscle actin (α‐SMA), h1‐calponin, desmin and smooth muscle myosin heavy chain (SM‐MHC), as well as the other isoforms of calponin family in resting MSCs. Then we used three different conditions to initiate MSCs differentiation along SMC lineage, and examined the alternation of SMC markers expression at both the transcript level and protein level. Desmin and h1‐calponin are expressed in MSCs, in the presence or absence of SMC induction conditions. Moreover, MSCs are shown to express all known isoforms of calponin. Double‐staining reveals that h1‐calponin +/α‐SMA – cells constitute the majority of resting MSCs. Under differentiated conditions, expression of SM‐MHC was initiated and expression of α‐SMA was promoted. The expression of SM‐MHC and upregulation of α‐SMA are relatively reliable indications of a mature smooth muscle phenotype in MSCs. Given that the cells are particularly rich in calponins expression, we postulate possible roles of these proteins in regulating cellular function by taking part in actin cytoskeleton and signaling. These findings imply that an extensive study of the cell physiology of MSCs should focus on the functional roles for these proteins, rather than simply regard them as differentiated markers.

Perivascular adipose tissue-derived leptin promotes vascular smooth muscle cell phenotypic switching via p38 mitogen-activated protein kinase in metabolic syndrome rats

“…23 VSMCs in present study were not contaminated with fibroblasts or endothelial cells as evidenced by >98% positive immunofluorescence staining for calponin, The p38 MAPK expression in rat aorta. After fed with HFD for 16 weeks, in MetS rat aorta, the p-p38 MAPK expression was significantly increased.…”

Regenerative potential of human adipose-derived stromal cells of various origins

“…Its presence represents a negative control for endothelial cells. a-SMA is transitorily expressed by a variety of mesodermally derived cells during their proliferation and development or in processes of tissue repair (Liu et al, 2013). The presence of a-SMA as hADSC marker has already been described in the literature (Cheng et al, 2011).…”

Human mesenchymal stem cells cultured on silk hydrogels with variable stiffness and growth factor differentiate into mature smooth muscle cell phenotype

“…However, these studies only investigated early (αSMA, calponin) myogenic markers, but often achieving directed stem cell differentiation towards a mature status is desired [52]. Stem cell differentiation into SMC-like populations is repeatedly evaluated by identifying the expression of several candidates involved in the contractile apparatus such as αSMA, h1-calponin, MYH11 and desmin [53]. However, recent evidence suggests that some SMC markers are potentially expressed at measurable levels in multipotent MSCs.…”