Myoblast cell sheet transplantation enhances the endogenous regenerative abilities of infant hearts in rats with myocardial infarction

Cell sheet formation enhances the therapeutic effects of human umbilical cord mesenchymal stem cells on myocardial infarction as a bioactive material

Stem cell-based therapy has been used to treat ischaemic heart diseases for two decades. However, optimal cell types and transplantation methods remain unclear. This study evaluated the therapeutic effects of human umbilical cord mesenchymal stem cell (hUCMSC) sheet on myocardial infarction (MI).

Methods

hUCMSCs expressing luciferase were generated by lentiviral transduction for in vivo bio-luminescent imaging tracking of cells. We applied a temperature-responsive cell culture surface-based method to form the hUCMSC sheet. Cell retention was evaluated using an in vivo bio-luminescent imaging tracking system. Unbiased transcriptional profiling of infarcted hearts and further immunohistochemical assessment of monocyte and macrophage subtypes were used to determine the mechanisms underlying the therapeutic effects of the hUCMSC sheet. Echocardiography and pathological analyses of heart sections were performed to evaluate cardiac function, angiogenesis and left ventricular remodelling.

Results

When transplanted to the infarcted mouse hearts, hUCMSC sheet significantly improved the retention and survival compared with cell suspension. At the early stage of MI, hUCMSC sheet modulated inflammation by decreasing Mcp1-positive monocytes and CD68-positive macrophages and increasing Cx3cr1-positive non-classical macrophages, preserving the cardiomyocytes from acute injury. Moreover, the extracellular matrix produced by hUCMSC sheet then served as bioactive scaffold for the host cells to graft and generate new epicardial tissue, providing mechanical support and routes for revascularsation. These effects of hUCMSC sheet treatment significantly improved the cardiac function at days 7 and 28 post-MI.

Conclusions

hUCMSC sheet formation dramatically improved the biological functions of hUCMSCs, mitigating adverse post-MI remodelling by modulating the inflammatory response and providing bioactive scaffold upon transplantation into the heart.

Translational perspective

Due to its excellent availability as well as superior local cellular retention and survival, allogenic transplantation of hUCMSC sheets can more effectively acquire the biological functions of hUCMSCs, such as modulating inflammation and enhancing angiogenesis. Moreover, the hUCMSC sheet method allows the transfer of an intact extracellular matrix without introducing exogenous or synthetic biomaterial, further improving its clinical applicability.

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Cell sheet formation of hUCMSCs dramatically improves post transplantation cell survival in the infarcted heart.

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hUCMSC sheet protects cardiomyocytes from infarction by alleviating acute inflammation.

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The ECM of cell sheet serves as bioactive scaffold to allow the host cells to integrate and form new epicardial tissue.

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The new epicardial tissue can provide mechanical support and new routes for revascularization.

Heart-derived fibroblasts express LYPD-1 and negatively regulate angiogenesis in rat

Angiogenesis is regulated by a balance between promoting and inhibitory mechanisms. Although angiogenesis-promoting mechanisms have been well studied in ischemic heart diseases, angiogenesis-inhibitory mechanisms have not. Recently, we identified LYPD-1 as a novel anti-angiogenic factor derived from human heart-derived fibroblasts, which suppresses endothelial cell network formation in co-culture. However, it remains unclear whether the low angiogenicity of heart-derived fibroblasts with high expression of LYPD-1 is also observed in other mammalian species, and the properties of LYPD-1 under normal and pathological conditions remain elusive. Fibroblasts isolated from neonatal and adult rat heart also express LYPD-1 and inhibit endothelial network formation in co-culture. Moreover, immunohistochemical analysis revealed that LYPD-1 was predominantly observed in the interstitial tissues of rat heart and LYPD1 expression levels were identical from late developmental period to adult. Conversely, LYPD-1 mRNA expression was significantly downregulated temporally in myocardial infarction model rats, suggesting that angiogenesis-inhibitory mechanisms might not be sufficiently suppressed to promote angiogenesis in ischemic heart diseases. These findings suggest that heart has relatively low angiogenicity compared with other organs via the high expression of LYPD-1 by fibroblasts. Moreover, understanding the regulatory mechanisms of LYPD-1-mediated inhibition of angiogenesis might lead a novel angiogenic therapy for ischemic heart diseases and contribute to development of bioengineered cardiac tissue.

Analyzing Impetus of Regenerative Cellular Therapeutics in Myocardial Infarction

Both vasculature and myocardium in the heart are excessively damaged following myocardial infarction (MI), hence therapeutic strategies for treating MI hearts should concurrently aim for true cardiac repair by introducing new cardiomyocytes to replace lost or injured ones. Of them, mesenchymal stem cells (MSCs) have long been considered a promising candidate for cell-based therapy due to their unspecialized, proliferative differentiation potential to specific cell lineage and, most importantly, their capacity of secreting beneficial paracrine factors which further promote neovascularization, angiogenesis, and cell survival. As a consequence, the differentiated MSCs could multiply and replace the damaged tissues to and turn into tissue- or organ-specific cells with specialized functions. These cells are also known to release potent anti-fibrotic factors including matrix metalloproteinases, which inhibit the proliferation of cardiac fibroblasts, thereby attenuating fibrosis. To achieve the highest possible therapeutic efficacy of stem cells, the other interventions, including hydrogels, electrical stimulations, or platelet-derived biomaterials, have been supplemented, which have resulted in a narrow to broad range of outcomes. Therefore, this article comprehensively analyzed the progress made in stem cells and combinatorial therapies to rescue infarcted myocardium.

Stem cell-derived cell sheet transplantation for heart tissue repair in myocardial infarction

Stem cell-derived sheet engineering has been developed as the next-generation treatment for myocardial infarction (MI) and offers attractive advantages in comparison with direct stem cell transplantation and scaffold tissue engineering. Furthermore, induced pluripotent stem cell-derived cell sheets have been indicated to possess higher potential for MI therapy than other stem cell-derived sheets because of their capacity to form vascularized networks for fabricating thickened human cardiac tissue and their long-term therapeutic effects after transplantation in MI. To date, stem cell sheet transplantation has exhibited a dramatic role in attenuating cardiac dysfunction and improving clinical manifestations of heart failure in MI. In this review, we retrospectively summarized the current applications and strategy of stem cell-derived cell sheet technology for heart tissue repair in MI.

Mesenchymal Stem Cell Sheets Exert Antistenotic Effects in a Rat Arterial Injury Model

Restenosis after catheter or surgical intervention substantially affects the prognosis of arterial occlusive disease. Mesenchymal stem cells (MSCs) may have antistenotic effects on injured arteries. MSC transplantation from the adventitial side of an artery is safer than endovascular transplantation but has not been extensively examined. In this study, a rat model of femoral artery injury was used to compare the antistenotic effects of transplanted cell sheets and transplanted cell suspensions. Rat adipose-derived stem cells (ASCs) were used as the source of MSCs. For both cell sheets and suspensions, 6 × 10⁶ MSCs were transplanted on the day of arterial injury. MSC sheets attenuated neointimal hyperplasia more than MSC suspensions (intima-to-media ratio in hematoxylin/eosin-stained sections: 0.55 ± 0.13 vs. 1.14 ± 0.12; p < 0.05). Cell engraftment (assessed by immunohistochemistry or bioluminescence imaging of luciferase-expressing cells), arterial re-endothelialization (evaluated by immunohistochemical staining for rat endothelial cell antigen-1), and restriction of vascular smooth muscle cell proliferation in the neointima (double-staining of alpha-smooth muscle actin and phospho-histone H3) were greater when MSC sheets were applied than when MSC suspensions were used. In conclusion, MSC sheets exhibited better antistenotic and cell engraftment properties than MSC suspensions. MSC sheet transplantation from the adventitial side is a promising therapy for prevention of arterial restenosis.

Myocardial Tissue Engineering for Regenerative Applications

PURPOSE OF REVIEW

This review provides an overview of the current state of tissue-engineered heart repair with a special focus on the anticipated modes of action of tissue-engineered therapy candidates and particular implications as to transplant immunology.

RECENT FINDINGS

Myocardial tissue engineering technologies have made tremendous advances in recent years. Numerous different strategies are under investigation and have reached different stages on their way to clinical translation. Studies in animal models demonstrated that heart repair requires either remuscularization by delivery of bona fide cardiomyocytes or paracrine support for the activation of endogenous repair mechanisms. Tissue engineering approaches result in enhanced cardiomyocyte retention and sustained remuscularization, but may also be explored for targeted paracrine or mechanical support. Some of the more advanced tissue engineering approaches are already tested clinically; others are at late stages of pre-clinical development. Process optimization towards cGMP compatibility and clinical scalability of contractile engineered human myocardium is an essential step towards clinical translation. Long-term allograft retention can be achieved under immune suppression. HLA matching may be an option to enhance graft retention and reduce the need for comprehensive immune suppression. Tissue-engineered heart repair is entering the clinical stage of the translational pipeline. Like in any effective therapy, side effects must be anticipated and carefully controlled. Allograft implantation under immune suppression is the most likely clinical scenario. Strategies to overcome transplant rejection are evolving and may further boost the clinical acceptance of tissue-engineered heart repair.