Shaoheng Zhang(a,b,d), Shun Lu(c), Junbo Ge(d), Jingxuan Guo(a), Ping Chen(c), Tao Li(c), Ping Zhang(a,b), Zhuqing Jiaa(c), Kangtao Ma(c), Yonggang Liu(a), Chunyan Zhou(b,c), Linsong Li(b)

a: Department of Cardiology, The Third Hospital of Peking University, Beijing, China
b: Stem Cell Research Center, Peking University, Beijing, China
c: Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Peking University, Beijing 100083, China
d: Shanghai Institute of Cardiovascular Disease, Zhongshan Hospital, Fudan University, Shanghai, China

19 August 2004

Source: http://www.sciencedirect.com

Abstract

Heme oxygenase-1 (HO-1) plays an important role in oxidative stress and recent studies indicate that it is a graft survival protein in cardiac and liver transplant models. In this study, we investigated the relation between the expressions of HO-1 and the effects of human bone marrow mesenchymal cells (MSCs) transplantation to xenogenic rat hearts with experimental myocardial infarction (MI). A total of 5 _ 106 cells in 100 Al PBS or equal volume PBS alone were injected into the ischemic zones immediately post-MI. At 1, 3, and 7 days post-MI, cardiac function was evaluated by echocardiography, the expression of HO-1 was assessed by real-time PCR and Western blot, the localization of HO-1 protein was determined under immunofluorescence microscopy. The infarct size was examined by histology. The numbers of Hoechst-33342 positive MSCs were evaluated under immunofluorescence microscopy and also by flow cytometry after isolation from the host hearts. The results indicated that the HO-1 expressions were markedly increased at both mRNA and protein levels in comparison with injection of PBS at each time point post MSCs transplantation (P b 0.01). HO-1 was revealed both in transplanted MSCs and recipient cardiomyocytes by immunofluorescence. Up-regulated HO-1 expression was accompanied by increase of the numbers of Hoechst-33342 positive MSCs, the reduction of infarct size, and the improvement of cardiac function. Transplantation of human MSCs could up-regulate HO-1 expression in infarct rat hearts, which might play an important role in protecting transplanted MSCs, cardiomyocytes survival, and cardiac function improvement during the early stage after MI.

Introduction

Myocardial infarction causes cessation of oxidation and reduction of energy metabolism, thus damages the function and structure of cardiomyocytes. The extent of damage after myocardial infarction (MI) reflects the balance between deleterious events and protective factors. Heat shock proteins, which can be induced by brief episodes of several stresses including ischemia, heat shock, or injury, could mediate protective effects (Benjamin and McMillan, 1998). Heme oxygenase-1 (HO-1), a stress response and cytoprotective heat shock protein (HSP), also known as HSP32, has shown to protect cells from death due to athophysiological stress (Dennery et al., 1997; Yet et al., 1999). By degrading the pro-oxidant heme and generating the antioxidant bilirubin, HO-1 may protect cells from oxidative injury (Stocker et al., 1987). It has been shown that HO-1 was upregulated in the heart and blood vessels in response to myocardial ischemia (Lakkisto et al., 2002; Yet et al., 2001), suggesting an important role of HO-1 in cardiovascular homeostasis. Suzuki et al. showed that heat shock treatment could enhance the graft skeletal myoblasts survival after transplantation to heart (Suzuki et al., 2000). Pileggi and colleagues found that HO-1 protected islet cells from apoptosis and improved their function after transplantation (Pileggi et al., 2001).

It is suggested that bone marrow cell transplantation might be effective in the treatment of MI (Orlic et al., 2001). Previous studies showed that mesenchymal stem cells (MSCs) transplantation reduced infarct area and improved cardiac function via differentiation and angiogenesis in rat MI model in the late phase post-transplantation (N7 days) (Davani et al., 2003; Kawada et al., 2004). However, the mechanism via which MSCs transplantation improves cardiac function in the early phase post-transplantation (V7 days), generally before cell differentiation and angiogenesis, remains largely a matter of speculation. HSPs are correlated with enhanced recovery of myocardial contractility after acute myocardial infarction (Currie et al., 1988; Hutter et al., 1994). Whether transplantation of human MSCs improves cardiac function in the early phase post-MI by further up-regulating HO-1 expression remains unknown.

In the present study, we attempted to study the relationship between HO-1 expression and cardiac function improvement post xenogenic transplantation of human bone marrow mesenchymal cells with cyclosporin A (CsA; Novartis Pharma, Basel, Switzerland) in a rat MI model. To observe whether CsA alone had an effect on HO-1 expression in infarcted hearts, we added two groups with PBS injection with or without CsA treatment.

Summary

In summary, HO-1 expression was increased and cardiac function was improved after xenogenic human MSCs transplantation. Over-expression of cytoprotective proteins, especially HO-1, might be one of the mechanisms via which human MSCs transplantation improves cardiac function at the early days after myocardial infarction.