c-kit(+)AT2R(+) Bone Marrow Mononuclear Cell Subset Is a Superior Subset for Cardiac Protection after Myocardial Infarction

The Progress of Stem Cell Therapy in Myocardial-Infarcted Heart Regeneration: Cell Sheet Technology

Various tissues, including the heart, cornea, bone, esophagus, bladder and liver, have been vascularized using the cell sheet technique. It overcomes the limitations of existing techniques by allowing small layers of the cell sheet to generate capillaries on their own, and it can also be used to vascularize tissue-engineered transplants. Cell sheets eliminate the need for traditional tissue engineering procedures such as isolated cell injections and scaffold-based technologies, which have limited applicability. While cell sheet engineering can eliminate many of the drawbacks, there are still a few challenges that need to be addressed. The number of cell sheets that can be layered without triggering core ischemia or hypoxia is limited. Even when scaffold-based technologies are disregarded, strategies to tackle this problem remain a substantial impediment to the efficient regeneration of thick, living three-dimensional cell sheets. In this review, we summarize the cell sheet technology in myocardial infarcted tissue regeneration.

Emerging Role of Angiotensin AT2 Receptor in Anti-Inflammation: An Update

The hyperactive RAS and inflammation are closely associated. The angiotensin-II/AT1R axis of the RAS has been explored extensively for its role in inflammation and a plethora of pathological conditions. Understanding the role of AT2R in inflammation is an emerging area of research. The AT2R is expressed on a variety of immune and non-immune cells, which upon activation triggers the release of a host of cytokines and has multiple effects that coalesce to anti-inflammation and prevents maladaptive repair. The anti-inflammatory outcomes of AT2R activation are linked to its well-established signaling pathways involving formation of nitric oxide and activation of phosphatases. Collectively, these effects promote cell survival and tissue function. The consideration of AT2R as a therapeutic target requires further investigations.

Oestrogen Receptor β Activation Protects Against Myocardial Infarction via Notch1 Signalling

Purpose

Oestrogen receptor β is believed to exert a cardioprotective effect against ischaemic injury. Nonetheless, the mechanism underlying its protective action remains to be fully elucidated. Recently, increased attention has been focused on Notch1 signalling for ameliorating cardiac ischaemic injury. Here, we hypothesised that oestrogen receptor β activation attenuates myocardial infarction (MI)-induced cardiac damage by modulating the Notch1 signalling pathway.

Methods

Male C57BL/6 mice were used to establish an MI model through the ligation of the anterior descending branch of the left coronary artery. Two chemical drugs, 2,3-Bis(4-hydroxyphenyl)-propionitrile (DPN) and N-[N-(3,5-difluorophenacetyl)-l-alanyl]-s-phenylglycine t-butyl ester (DAPT), a specific inhibitor of Notch1 signalling) were administered via intraperitoneal injection to change oestrogen receptor β and Notch1 activities. Immunohistochemistry, western blot analysis, enzyme-linked immunosorbent assay (Elisa) assessment and echocardiography were used in this study to analyse cardiac oxidative stress, apoptosis, infraction volume, fibrosis and cardiac function.

Results

DPN-mediated oestrogen receptor β activation effectively protected cardiomyocytes from MI-induced oxidative damage and apoptosis. Furthermore, oestrogen receptor β activation reduced the infarct size and lowered the levels of myocardial enzymes in the serum, thereby leading to greater overall cardiac function improvement. Ischaemic injury–induced myocardial fibrosis was attenuated by oestrogen receptor β activation. Nevertheless, all of these cardioprotective effects of oestrogen receptor β activation were almost abrogated by DAPT administration, i.e. DAPT attenuated the anti-oxidative and anti-apoptotic effects and the decrease in infarct and fibrotic areas and reversed cardiac functional recovery. The levels of phospho-phosphatidylinositol-3-kinase (PI3K) and phospho-protein kinase B (Akt) were increased after DPN administration, and this change was reversed after DAPT was administered.

Conclusions

All of these new findings indicate that oestrogen receptor β activation is effective in ameliorating MI-induced cardiac dysfunction by enhancing Notch1 signalling and that PI3K/Akt signalling is the downstream mediator.

Electronic supplementary material

The online version of this article (10.1007/s10557-020-06949-3) contains supplementary material, which is available to authorized users.

High-fat diet selectively decreases bone marrow lin- /CD117+ cell population in aging mice through increased ROS production

Bone marrow (BM) stem cells (BMSCs) are an important source for cell therapy. The outcome of cell therapy could be ultimately associated with the number and function of donor BMSCs. The present study was to evaluate the effect of long-term high-fat diet (HFD) on the population of BMSCs and the role of reactive oxygen species (ROS) in aging mice. Forty-week-old male C57BL/6 mice were fed with HFD for 3 months with regular diet as control. Experiments were repeated when ROS production was reduced in mice treated with N-acetylcysteine (NAC) or using mice overexpressing antioxidant enzyme network (AON) of superoxide dismutase (SOD)1, SOD3, and glutathione peroxidase. BM and blood cells were analyzed with flowcytometry for lineage negative (lin^- ) and Sca-1⁺ , or lin^- /CD117⁺ , or lin^- /CD133⁺ cells. Lin^- /CD117⁺ cell population was significantly decreased with increased intracellular ROS and apoptosis and decreased proliferation in BM, not in blood, in HFD-treated mice without change for Sca-1⁺ or CD133⁺ cell populations in BM or blood. NAC treatment or AON overexpression effectively prevented HFD-induced intracellular ROS production and reduction of BM lin^- /CD117⁺ population. These data suggested that long-term HFD selectively decreased BM lin^- /CD117⁺ cell population in aging mice through increased ROS production.

Silk fibroin/poly(L-lactic acid-co-ε-caprolactone) electrospun nanofibrous scaffolds exert a protective effect following myocardial infarction

Electrospinning using biocompatible polymer scaffolds, seeded with or without stem cells, is considered a promising technique for producing fibrous scaffolds with therapeutic possibilities for ischemic heart disease. However, no optimal scaffolds for treating ischemic heart disease have been identified thus far. In the present study, it was evaluated whether electrospun silk fibroin (SF)-blended poly(L-lactic acid-co-ε-caprolactone) [P(LLA-CL)] scaffolds that were seeded with cluster of differentiation 117 (c-kit)⁺ bone marrow (BM) cells may serve a protective role in cardiac remodeling following myocardial infarction (MI). Mechanical characteristics and cytocompatibility were compared between SF/P(LLA-CL) and P(LLA-CL) electrospun nanofibrous scaffolds in vitro. It was observed that MI led to a significant increase of the c-kit⁺ BM cell subpopulation in mice. Magnetic activated cell sorting was performed to harvest the c-kit⁺ cell population from the BM of mice following MI. c-kit⁺ BM cells were seeded on SF/P(LLA-CL) and P(LLA-CL) electrospun nanofibrous scaffolds. Results indicated that SF/P(LLA-CL) electrospun nanofibrous scaffolds were superior to P(LLA-CL) electrospun nanofibrous scaffolds in improving c-kit⁺ BM cell proliferation. Additionally, compared with pure SF/P(LLA-CL) electrospun nanofibrous scaffolds, SF/P(LLA-CL) scaffolds seeded with c-kit⁺ BM cells resulted in lower levels of MI markers and reduced infarct size, leading to greater global heart function improvement in vivo. The findings of the present study indicated that SF/P(LLA-CL) electrospun nanofibrous scaffolds seeded with c-kit⁺ BM cells exert a protective effect against MI and may be a promising approach for cardiac regeneration after ischemic heart disease.

Integrin β1 Increases Stem Cell Survival and Cardiac Function after Myocardial Infarction

Bone mesenchymal stem cells (BMSCs) transplantation is a promising therapeutic approach for myocardial infarction (MI), but its application is limited by poor viability of BMSCs. In this study, we aimed to improve the survival of BMSCs by lentivirus vector mediated overexpression of integrin β1. In vitro study showed that integrin β1 overexpression could facilitate the proliferation of BMSCs under oxygen glucose deprivation condition and regulated the expression of Caspase-3, Bax, Bcl-2, FAK, and ILK in BMSCs. Next, MI was induced in rat model and Igtb1BMSCs, NullBMSCs, or NatBMSCs were transplanted by intramyocardial injection. One week later, the survival of BMSCs was higher in Itgb1 BMSCs group than in other groups. Four weeks after transplantation, heart function was significantly improved in Igtb1BMSCs group compared to other groups. The expression levels of Caspase-3 and Bax were decreased while the expression levels of Bcl-2, FAK, ILK, and VEGF were increased in the cardiomyocytes of Igtb1BMSCs group compared to other groups. In conclusion, integrin β1 overexpression could increase the survival of BMSCs and improve the efficacy of transplanted BMSCs for MI treatment. The beneficial effects may be mediated by inhibiting the apoptosis of both transplanted BMSCs and cardiomyocytes through adhesion-mediated cell survival signaling.