Fibrin, Bone Marrow Cells And Macrophages Interactively Modulate Cardiomyoblast Fate: An In Vitro Study

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): The study was supported by the Swiss National Science Foundation (SNF 310030_149986) attributed to MNG, the University of Fribourg and the Fonds Scientifique Cardiovasculaire FSC, Fribourg Hospital attributed to SC

The spatiotemporal interaction of macrophages with the cardiac extracellular matrix, cardiomyocytes and non-cardiomyocytes has shown increasing interest in cardiac repair and regeneration. Due to their immunomodulatory capacities, cell-based therapies for myocardial infarction (MI) may influence macrophages fate. In addition, the use of biomaterials combined with cells is nowadays a recommended approach for cell-based therapies to fosters cell retention and survival. Depending on their composition and structure, scaffolds may modulate macrophage phenotypes. We interrogated the influence of fibrin, a biologically active scaffold, on the fate of cells including bone marrow cells (BMC), macrophages and cardiomyoblasts.

Methods

In vivo, two weeks post-MI induction, animals with an ejection fraction between 35-60% were either sham-operated animals or treated with an epicardial implantation of a BMC and fibrin. In vivo, two weeks post-MI induction, animals with an ejection fraction between 35-60% were either sham-operated animals or treated with an epicardial implantation of a BMC and fibrin. In vitro, non-polarized macrophages were differentiated toward either pro-inflammatory or anti-inflammatory phenotypes and stimulated with the conditioned medium of fibrin-primed BMC (F-BMC). Proteomic, cytokine levels quantification, and qPCR were performed. EdU incorporation and real time cell analysis assessed the effect of F-BMC on macrophages and cardiomyoblasts H9C2 proliferation.

Results

In vivo, epicardial implantation of Fibrin and BMC reduced the loss of cardiac function induced by MI and prevented the fibrotic scar expansion. After 4 and 12 weeks, the infarct content of CD68+ and CD206+ macrophages were similar in control and treated animals. To investigate acute effect, we performed in vitro assays. We showed that fibrin profoundly influenced gene expression and the secreted proteome of BMC, simultaneously upregulating both pro- and anti-inflammatory mediators. Furthermore, the conditioned medium from F-BMC significantly increased the proliferation of anti-inflammatory macrophages and modulated their gene expression and cytokines secretion. For example, F-BMC downregulated the expression of pro-inflammatory genes, in particular Nos2, Il6 and Ccl2/Mcp1. Anti-inflammatory genes such as Arg1, Tgfb and IL10 were significantly upregulated. Interestingly, anti-inflammatory macrophages educated by F-BMC stimulated EdU incorporation in H9C2 cardiomyoblasts.

In conclusion, our study provides evidence that F-BMC secretome promoted the growth of anti-inflammatory macrophages, stimulated macrophage plasticity and altered the balance between the pro and anti-inflammatory macrophage subsets. F-BMC secretome favoured the mitogenic properties of anti-inflammatory macrophages promoting cardiac cell growth. In vivo, F-BMC treatment lowered the infarct extent and increased wall thickness and improved cardiac function.

As a biopatch, fibrin and bone marrow-derived cells modulate macrophage polarization and cardiomyobasts proliferation

Introduction

Repair of the cardiac structure and function is the holy grail for curative treatment of myocardial infarction (MI). Clinical trials for cardiac cell-based therapies have revealed numerous challenges and led to a shift in the initial paradigms. The current concept is that cell/matrix-based therapy modifies the local immune response, releases factors involved in tissue repair, mitigates the progression of ventricular remodelling, and rescues the cardiac function. Macrophages are critical players in cardiac remodelling post-MI with a complex role yet not fully elucidated in cell-based therapy.

Purpose

We, first, investigated in an MI animal model, the myocardial macrophage content following an epicardial application of a biopatch composed of bone marrow-derived cells (BMDCs) and fibrin-based matrix. Second, we analyzed in vitro the cell interactions between the biopath, macrophages and cardiomyoblasts.

Methods

Two weeks post-infarct, performed on female rats, a Cell and Matrix BioPatch (CMBP) composed of fibrin and BMDCs was administered. Heart function and infarct were evaluated by high-resolution echocardiography and histology. Macrophages present 4 weeks post-MI were quantified by immunostaining for CD86 and CD206. In vitro, macrophages (undifferentiated (M0), triggered by IL4 (M2) or LPS/IFN-d (M1)), or cardiomyoblasts (H9C2) were cultured with conditioned media from CMBP. Their proliferation and plasticity were assessed by EDU incorporation and real-time cell analyzer and RT-PCR.

Results

Our data showed a significant improvement in ejection fraction after treatment and a reduced infarct expansion index (IEI MI/untreated= 0.08±0.05 vs. IEI MI/CMBP_treated =0.22±0.09, p=0.002). The ratio of CD86+/CD206+ cells was also significantly reduced in treated compared to untreated groups (ratioMI/untreated=0.96±0.82 vs ratioMI/fibrin_treated=0.51±0.12 and ratioMI/CMBP_treated=0.17±0.13, p<0.05) suggesting an alteration of the macrophage polarization. In vitro assays with CMBP-conditioned medium revealed a significant increase in the proliferation of M0 and M2. Also, M0 were polarized towards an M2 profile. A switch of M1 toward M2 was revealed by Gene expression profiles with a reduction of pro-inflammatory markers (CD86, MCP-1, IL-1beta, CD80, RANTES and iNOS) and an increase in the anti-inflammatory ones (Arginase 1, CD163, CD106). The secretion profile of the macrophages was also modified with a lower secretion of IL-6 and TNF-alpha and increased IL-10. Interestingly, when cardiomyoblasts are cultured with the medium conditioned of the macrophages triggered by CMBP, their proliferation was significantly increased by 16%±1 with M0 or M2 and 18%±1 with M1.

Conclusion

Our data point to a new paracrine communication from a biopatch that triggered macrophages and indirectly cardiac cells. Cell cross-talks promoted an anti-inflammatory response that promoted cardiac cells proliferation.

Funding Acknowledgement

Type of funding source: Public Institution(s). Main funding source(s): University of Fribourg

Myocardial infarction does not affect circulating haematopoietic stem and progenitor cell self-renewal ability in a rat model

NEW FINDINGS

What is the central question of this study? Although peripheral blood haematopoietic stem and progenitor cells are potentially important in regeneration after acute myocardial infarction, their self-renewal ability in the post-acute phase has not yet been addressed. What is the main finding and its importance? In rat peripheral blood, we show that myocardial infarction does not negatively affect circulating haematopoietic stem and progenitor cell self-renewal ability 2 weeks after acute infarction, which suggests a constant regenerative potential in the myocardial infarction post-acute phase. Given the importance of peripheral blood haematopoietic stem and progenitor cells (HPCs) in post-acute regeneration after acute myocardial infarction (MI), the aim of the present study was to investigate the number and secondary replating capacity/self-renewal ability of HPCs in peripheral blood before and 2 weeks after MI. In female Lewis inbred rats (n = 9), MI was induced by ligation of the left coronary artery, and another nine underwent sham surgery, without ligation, for control purposes. Myocardial infarction was confirmed by troponin I concentrations 24 h after surgery. Peripheral blood was withdrawn and fractional shortening and ejection fraction of the left ventricle were assessed before (day 0) and 14 days after MI or sham surgery (day 14). After mononuclear cell isolation, primary and secondary functional colony-forming unit granulocyte-macrophage (CFU-GM) assays were performed in order to detect the kinetics of functional HPC colony counts and cell self-renewal ability in vitro. The CFU-GM counts and cell self-renewal ability remained unchanged (P > 0.05) in both groups at day 14, without interaction between groups. In the intervention group, higher day 0 CFU-GM counts showed a relationship to lower fractional shortening on day 14 (ρ = -0.82; P < 0.01). Myocardial infarction did not negatively affect circulating HPC self-renewal ability, which suggests a constant regenerative potential in the post-acute phase. A relationship of cardiac contractile function 14 days after MI with circulating CFU-GM counts on day 0 might imply functional colony count as a predictive factor for outcome after infarction.

Controlled angiogenesis in the heart by cell-based expression of specific vascular endothelial growth factor levels

Vascular endothelial growth factor (VEGF) can induce normal angiogenesis or the growth of angioma-like vascular tumors depending on the amount secreted by each producing cell because it remains localized in the microenvironment. In order to control the distribution of VEGF expression levels in vivo, we recently developed a high-throughput fluorescence-activated cell sorting (FACS)-based technique to rapidly purify transduced progenitors that homogeneously express a specific VEGF dose from a heterogeneous primary population. Here we tested the hypothesis that cell-based delivery of a controlled VEGF level could induce normal angiogenesis in the heart, while preventing the development of angiomas. Freshly isolated human adipose tissue-derived stem cells (ASC) were transduced with retroviral vectors expressing either rat VEGF linked to a FACS-quantifiable cell-surface marker (a truncated form of CD8) or CD8 alone as control (CTR). VEGF-expressing cells were FACS-purified to generate populations producing either a specific VEGF level (SPEC) or uncontrolled heterogeneous levels (ALL). Fifteen nude rats underwent intramyocardial injection of 10(7) cells. Histology was performed after 4 weeks. Both the SPEC and ALL cells produced a similar total amount of VEGF, and both cell types induced a 50%-60% increase in both total and perfused vessel density compared to CTR cells, despite very limited stable engraftment. However, homogeneous VEGF expression by SPEC cells induced only normal and stable angiogenesis. Conversely, heterogeneous expression of a similar total amount by the ALL cells caused the growth of numerous angioma-like structures. These results suggest that controlled VEGF delivery by FACS-purified ASC may be a promising strategy to achieve safe therapeutic angiogenesis in the heart.