Abstract
BackgroundMesenchymal stem cells (MSCs) migrate via the bloodstream to sites of injury and are possibly attracted by inflammatory factors. As a proinflammatory mediator, angiotensin II (Ang II) reportedly enhances the migration of various cell types by signaling via the Ang II receptor in vitro. However, few studies have focused on the effects of Ang II on MSC migration and the underlying mechanisms.MethodsHuman bone marrow MSCs migration was measured using wound healing and Boyden chamber migration assays after treatments with different concentrations of Ang II, an AT1R antagonist (Losartan), and/or an AT2R antagonist (PD-123319). To exclude the effect of proliferation on MSC migration, we measured MSC proliferation after stimulation with the same concentration of Ang II. Additionally, we employed the focal adhesion kinase (FAK) inhibitor PF-573228, RhoA inhibitor C3 transferase, Rac1 inhibitor NSC23766, or Cdc42 inhibitor ML141 to investigate the role of cell adhesion proteins and the Rho-GTPase protein family (RhoA, Rac1, and Cdc42) in Ang II-mediated MSC migration. Cell adhesion proteins (FAK, Talin, and Vinculin) were detected by western blot analysis. The Rho-GTPase family protein activities were assessed by G-LISA and F-actin levels, which reflect actin cytoskeletal organization, were detected by using immunofluorescence.ResultsHuman bone marrow MSCs constitutively expressed AT1R and AT2R. Additionally, Ang II increased MSC migration in an AT2R-dependent manner. Notably, Ang II-enhanced migration was not mediated by Ang II-mediated cell proliferation. Interestingly, Ang II-enhanced migration was mediated by FAK activation, which was critical for the formation of focal contacts, as evidenced by increased Talin and Vinculin expression. Moreover, RhoA and Cdc42 were activated by FAK to increase cytoskeletal organization, thus promoting cell contraction. Furthermore, FAK, Talin, and Vinculin activation and F-actin reorganization in response to Ang II were prevented by PD-123319 but not Losartan, indicating that FAK activation and F-actin reorganization were downstream of AT2R.ConclusionsThese data indicate that Ang II-AT2R regulates human bone marrow MSC migration by signaling through the FAK and RhoA/Cdc42 pathways. This study provides insights into the mechanisms by which MSCs home to injury sites and will enable the rational design of targeted therapies to improve MSC engraftment.
Highlights
Mesenchymal stem cells (MSCs) migrate via the bloodstream to sites of injury and are possibly attracted by inflammatory factors
The results demonstrated that cultured human bone marrow MSCs in vitro expressed both angiotensin II type 1 receptor (AT1R) and angiotensin II type 2 receptor (AT2R) mRNA
Ang Angiotensin II (II) promotes the migration of human bone marrow MSCs via AT2R To determine the dose-dependent effects of angiotensin II (Ang II) on cell migration, MSCs were treated with concentrations of 10–8, 10–7, 10–6, 10–5, and 3 × 10–5 M Ang II in scratch assays and Transwell assays
Summary
Mesenchymal stem cells (MSCs) migrate via the bloodstream to sites of injury and are possibly attracted by inflammatory factors. A prerequisite for these cells to participate in tissue repair is migration of injected MSCs to the damaged tissues [2]. Injured tissues and organs release various factors including chemoattractants, growth factors, and inflammatory factors, which can recruit MSCs to the injured site [8]. In addition to being a physiological mediator that restores circulatory integrity, angiotensin II (Ang II) has been reported to be involved in key events of the inflammatory process and tissue damage [9]. Together with being a proinflammatory mediator, Ang II participates in numerous life processes, including cell proliferation, apoptosis, and migration. It is assumed that Ang II might be a key inflammatory factor that mediates MSC migration to sites of injury
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