Background

Mesenchymal stromal cells (MSC) repair infarcted hearts mainly through paracrine mechanisms. Low cell engraftment limits the release of soluble paracrine factors (SF) over time and, consequently, MSC efficacy. We tested whether a synthetic extracellular matrix mimic, a hydrogel containing heparin (H-HG), could ameliorate MSC engraftment and binding/release of SF, thus improving MSC therapy efficacy.

Methods and Results

In vitro, rat bone-marrow MSC (rBM-MSC) were seeded and grown into H-HG. Under normoxia, the hydrogel did not affect cell survival (rBM-MSC survival >90% at each time point tested); vice versa, under hypoxia the biomaterial resulted to be protective for the cells (p<0.001 vs rBM-MSC alone).

cells were protected from hypoxia. H-HG or control PEG hydrogels (HG) were incubated with VEGF or bFGF for binding/release quantification. Data showed significantly higher amount of VEGF and bFGF bound by H-HG compared with HG (p<0.05) and a constant release over time.

In vivo

myocardial infarction (MI) was induced in female Sprague Dawley rats by permanent coronary ligation. One week later, saline, rBM-MSC, H-HG or rBM-MSC/H-HG were injected in the infarct zone. The co-injection of rBM-MSC/H-HG into infarcted hearts significantly increased cardiac function. Importantly, we observed a significant gain in MSC engraftment, reduction of ventricular remodeling and stimulation of neo-vasculogenesis. We also documented higher amounts of several pro-angiogenic factors in hearts treated with rBM-MSC/H-HG.

Conclusions

Our data show that H-HG increases MSC engraftment, efficiently fine tunes the paracrine MSC actions and improves cardiac function in infarcted rat hearts. Given its efficacy and safety, documented by the absence of immunoreaction, our strategy appears readily translatable to pre-clinical and clinical settings.

Statement of significance

Transplantation of mesenchymal stromal cells (MSC) is a promising treatment for ischemic heart disease, but low cell engraftment limits the release of soluble paracrine factors (SF) and, consequently, MSC efficacy. Thus, in this study we developed an enzymatically degradable polyethylene glycol hydrogel containing heparin (H-HG) able to increase MSC retention and to bind and release paracrine soluble factors secreted by the cells. The result was a significant amelioration in cardiac function, neo-vasculogenesis, endogenous cardiac regeneration and a reduction in ventricular remodeling and scarring. The beneficial effects observed in our study are comparable to those obtained using a much greater number of cells, strengthening the efficacy of the biomaterial used in increasing the therapeutic effects of MSC.

中文翻译：

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合成的细胞外基质模拟水凝胶可提高间充质基质细胞治疗缺血性心肌病的疗效

背景

间充质基质细胞（MSC）主要通过旁分泌机制修复梗塞的心脏。低细胞植入限制了可溶性旁分泌因子（SF）随时间的释放，因此限制了MSC的功效。我们测试了合成的细胞外基质模拟物（一种含有肝素（H-HG）的水凝胶）是否可以改善MSC的植入和SF的结合/释放，从而提高MSC的治疗功效。

方法与结果

在体外，将大鼠骨髓MSC（rBM-MSC）接种并生长为H-HG。在常氧下，水凝胶不影响细胞存活（在每个测试时间点，rBM-MSC存活> 90％）；反之亦然，在缺氧条件下，生物材料对细胞具有保护作用（相对于单独的rBM-MSC，p <0.001）。

保护细胞免于缺氧。将H-HG或对照PEG水凝胶（HG）与VEGF或bFGF孵育以进行结合/释放定量。数据显示，与HG相比，H-HG结合的VEGF和bFGF的量明显更高（p <0.05），并且随着时间的推移不断释放。

体内

通过永久性冠状动脉结扎术在雌性Sprague Dawley大鼠中诱发心肌梗塞（MI）。一周后，在梗死区注射生理盐水，rBM-MSC，H-HG或rBM-MSC / H-HG。将rBM-MSC / H-HG共注射到梗塞的心脏中可显着增强心脏功能。重要的是，我们观察到了MSC植入，心室重构减少和新血管生成刺激的显着增加。我们还记录了用rBM-MSC / H-HG治疗的心脏中较高数量的几种促血管生成因子。

结论

我们的数据表明，H-HG增加了MSC的植入，有效地微调了旁分泌MSC的作用并改善了梗塞大鼠心脏的心脏功能。鉴于其有效性和安全性（无免疫反应可证明），我们的策略似乎很容易转化为临床前和临床环境。

重要声明

间充质基质细胞（MSC）的移植是缺血性心脏病的一种有希望的治疗方法，但低细胞植入会限制可溶性旁分泌因子（SF）的释放，从而限制MSC的疗效。因此，在这项研究中，我们开发了一种含有肝素（H-HG）的可酶降解的聚乙二醇水凝胶，能够增加MSC的保留并结合和释放细胞分泌的旁分泌可溶性因子。结果显着改善了心脏功能，新血管生成，内源性心脏再生以及心室重构和瘢痕形成的减少。在我们的研究中观察到的有益效果与使用大量细胞获得的有益效果相当，从而增强了用于增强MSC治疗效果的生物材料的功效。