Bone Marrow-Derived Regenerated Smooth Muscle Cells Have Ion Channels and Properties Characteristic of Vascular Smooth Muscle Cells

Rationale: Numerous reports, including our own, have recently suggested the presence of putative smooth muscle progenitor cells in the bone marrow (BM) and those smooth muscle-like cells may be differentiated from BM stromal cells (BMSCs). However, few studies have addressed whether the differentiated cells also possess the functional properties of smooth muscle cells (SMCs). Contractility is the primary function of native vascular SMCs. Objective: The aim of this electrophysiological study was to characterize BM-derived SMCs using the patch- clamp technique and Ca2+ imaging with fura-2. Methods and results: To investigate whether BM-derived SMCs exhibit functional vascular SMC properties, we measured Ca 2+ and K + currents in BM-derived SMCs using the whole-cell patch-clamp method. The cells showed L-type and T-type Ca 2+ channel currents, Ca 2+ -activated K + channel (KCa) currents, and delayed rectifier K + channel (KV) currents. We also measured agonist-evoked (Ca2+) i transients in BM-derived SMCs using fura-2 imaging. Such (Ca2+) i transients were observed in response to the vascular SMC-specific agonists, bradykinin (10 -6 M) and angiotensin II (10-7 M). Conclusions: BM-derived SMCs displayed contractile activity and expressed several ion channels critical for contractile behavior in a manner compatible with native vascular SMCs. BMSC-derived cells thus have the potential to differentiate into functional vascular SMCs, suggesting bone marrow stromal tissue as a useful source of cells for the treatment of injured arteries and to construct tissue-engineered grafts for adult arterial revascularization.