Adult stem cell-derived secretome based strategies to promote myocardial regeneration

Abstract

Restoring the functionality of the heart after the occurrence of an acute myocardial infarction requires the design of specific therapies aimed to induce an intricate cascade of biological events necessary to promote myocardium regeneration. To achieve such a challenging task, it is necessary to consider the milieu of proangiogenic, anti-inflammatory and anti-apoptotic paracrine molecules involved in the process of myocardial remodeling that occurs after an acute myocardial infarction. A potential approach is the use of stem cell-derived secretome-based strategies. The secretome is an array of multiple factors including growth factors, cytokines, microRNA (miRNA), and extracellular vesicles (EVs) that are secreted by stem cells to regulate tissue homeostasis. Several pre-clinical studies have shown that the secretome can be delivered to the peri-infarct area of the heart to improve cardiac function and prevent heart failure. Unfortunately, the clinical translation of secretome-based therapies has been hampered by its heterogeneous nature and by the limited identification of key therapeutic factors responsible for its regenerative potential. Additionally, the lack of retention of the therapeutic factors at the damage site upon delivery imposes another obstacle. Therefore, it is necessary to identify new strategies to standardize the production of secretome and to develop new carriers that will allow the efficient delivery and retention of these therapeutic factors at the therapeutic site. To address these challenges, the work presented in this thesis aimed to accomplish the following goals: (1) identify the optimal culture strategies for the production of a reproducible stem cell-derived secretome that exhibits cardioprotective and angiogenic properties in vitro and in vivo as well as, (2) to deliver them efficiently using hydrogels. Several methods have been investigated to reach this goal (1). The first strategy represented the use of stem cell spheroids to produce a concentrated secretome enriched with angiogenic growth factors that could display a superior angiogenic and cardioprotective efficacy. Additionally, the work of this thesis has been focused on another approach in which stem cells were genetically modified to upregulate the production of a miRNA-146a (miR-146a) in the secretome to further enhance its therapeutic properties (proangiogenic and anti-inflammatory). Finally, to address goal (2), this thesis has also been focused on designing a suitable strategy for the delivery of secretome in a non-invasive manner to the peri-infarct area of the heart. Therefore, a novel nanocomposite injectable hydrogel has been designed as a delivery platform for the secretome and tested both in vitro and in vivo in an acute myocardial infarction rat model. Overall, the strategies and findings of this thesis are beneficial to further advance the therapeutic efficacy of secretome-based therapies to promote myocardial regeneration by inhibiting of cardiomyocyte apoptosis, promoting angiogenesis, and modulating of inflammation.