Giuseppe Malpasso

Paracrine Mechanisms of Mesenchymal Stem Cells in Tissue Repair

Tissue regeneration from transplanted mesenchymal stromal cells (MSC) either through transdifferentiation or cell fusion was originally proposed as the principal mechanism underlying their therapeutic action. However, several studies have now shown that both these mechanisms are very inefficient. The low MSC engraftment rate documented in injured areas also refutes the hypothesis that MSC repair tissue damage by replacing cell loss with newly differentiated cells. Indeed, despite evidence of preferential homing of MSC to the site of myocardial ischemia, exogenously administered MSC show poor survival and do not persist in the infarcted area. Therefore, it has been proposed that the functional benefits observed after MSC transplantation in experimental models of tissue injury might be related to the secretion of soluble factors acting in a paracrine fashion. This hypothesis is supported by pre-clinical studies demonstrating equal or even improved organ function upon infusion of MSC-derived conditioned medium (MSC-CM) compared with MSC transplantation. Identifying key MSC-secreted factors and their functional role seems a reasonable approach for a rational design of nextgeneration MSC-based therapeutics. Here, we summarize the major findings regarding both different MSC-mediated paracrine actions and the identification of paracrine mediators.

Conditioned Medium From Human Amniotic Mesenchymal Stromal Cells Limits Infarct Size and Enhances Angiogenesis

The paracrine properties of human amniotic membrane‐derived mesenchymal stromal cells (hAMCs) have not been fully elucidated. The goal of the present study was to elucidate whether hAMCs can exert beneficial paracrine effects on infarcted rat hearts, in particular through cardioprotection and angiogenesis. Moreover, we aimed to identify the putative active paracrine mediators. hAMCs were isolated, expanded, and characterized. In vitro, conditioned medium from hAMC (hAMC‐CM) exhibited cytoprotective and proangiogenic properties. In vivo, injection of hAMC‐CM into infarcted rat hearts limited the infarct size, reduced cardiomyocyte apoptosis and ventricular remodeling, and strongly promoted capillary formation at the infarct border zone. Gene array analysis led to the identification of 32 genes encoding for the secreted factors overexpressed by hAMCs. Among these, midkine and secreted protein acidic and rich in cysteine were also upregulated at the protein level. Furthermore, high amounts of several proangiogenic factors were detected in hAMC‐CM by cytokine array. Our results strongly support the concept that the administration of hAMC‐CM favors the repair process after acute myocardial infarction.

Combination of miRNA499 and miRNA133 exerts a synergic effect on cardiac differentiation

Several studies have demonstrated that miRNA are involved in cardiac development, stem cell maintenance, and differentiation. In particular, it has been shown that miRNA133, miRNA1, and miRNA499 are involved in progenitor cell differentiation into cardiomyocytes. However, it is unknown whether different miRNA may act synergistically to improve cardiac differentiation. We used mouse P19 cells as a cardiogenic differentiation model. miRNA499, miRNA1, or miRNA133 were transiently over‐expressed in P19 cells individually or in different combinations. The over‐expression of miRNA499 alone increased the number of beating cells and the association of miRNA499 with miRNA133 exerted a synergistic effect, further increasing the number of beating cells. Real‐time polymerase chain reaction showed that the combination of miRNA499 + 133 enhanced the expression of cardiac genes compared with controls. Western blot and immunocytochemistry for connexin43 and cardiac troponin T confirmed these findings. Importantly, caffeine responsiveness, a clear functional parameter of cardiac differentiation, was increased by miRNA499 in association with miRNA133 and was directly correlated with the activation of the cardiac troponin I isoform promoter. Cyclic contractions were reversibly abolished by extracellular calcium depletion, nifedipine, ryanodine, and IP3R blockade. Finally, we demonstrated that the use of miRNA499 + 133 induced cardiac differentiation even in the absence of dimethyl sulfoxide. Our results show that the areas spontaneously contracting possess electrophysiological and pharmacological characteristics compatible with true cardiac excitation‐contraction coupling. The translational relevance of our findings was reinforced by the demonstration that the over‐expression of miRNA499 and miRNA133 was also able to induce the differentiation of human mesenchymal stromal cells toward the cardiac lineage. Stem Cells 2015;33:1187–1199

Protocols for in vitro Differentiation of Human Mesenchymal Stem Cells into Osteogenic, Chondrogenic and Adipogenic Lineages.

Mesenchymal stem cells (MSC) possess high plasticity and the potential to differentiate into several different cell types; this characteristic has implications for cell therapy and reparative biotechnologies. MSC have been originally isolated from the bone marrow (BM-MSC), but they have been found also in other tissues such as adipose tissue, cord blood, synovium, skeletal muscle, and lung. MSC are able to differentiate in vitro and in vivo into several cell types such as bone, osteocytes, chondrocytes, adipocytes, and skeletal myocytes, just to name a few.During the last two decades, an increasing number of studies have proven the therapeutic potential of MSC for the treatment of neurodegenerative diseases, spinal cord and brain injuries, cardiovascular diseases, diabetes mellitus, and diseases of the skeleton. Their immuno-privileged profile allows both autologous and allogeneic use. For all these reasons, the scientific appeal of MSC is constantly on the rise.The identity of MSC is currently based on three main criteria: plastic-adherence capacity, defined epitope profile, and capacity to differentiate in vitro into osteocytes, chondrocytes, and adipocytes. Here, we describe standard protocols for the differentiation of BM-MSC into the osteogenic, chondrogenic, and adipogenic lineages.

Synthetic extracellular matrix mimic hydrogel improves efficacy of mesenchymal stromal cell therapy for ischemic cardiomyopathy

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 < .001 vs rBM-MSC alone). 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 < .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. STATEMENT OF SIGNIFICANCE Transplantation of MSC is a promising treatment for ischemic heart disease, but low cell engraftment has so far limited its efficacy. The enzymatically degradable H-HG that we developed is able to increase MSC retention/engraftment and, at the same time, to fine-tune the paracrine effects mediated by the cells. Most importantly, the co-transplantation of MSC and H-HG in a rat model of ischemic cardiomyopathy improved heart function through a significant reduction in ventricular remodeling/scarring and amelioration in neo-vasculogenesis/endogenous cardiac regeneration. These beneficial effects are comparable to those obtained by others using a much greater number of cells, strengthening the efficacy of the biomaterial used in increasing the therapeutic effects of MSC. Given its efficacy and safety, documented by the absence of immunoreaction, our strategy appears readily translatable to clinical scenarios.

Testing the Paracrine Properties of Human Mesenchymal Stem Cells Using Conditioned Medium.

Mesenchymal stem cells (MSC) produce and secrete a great variety of cytokines and chemokines that play beneficial paracrine actions when MSC are used for tissue repair. The conditioned medium (CM) derived from MSC can be used both in vitro and in vivo to test specific paracrine effects or to screen putative paracrine/autocrine mediators by proteomics.In this chapter, we describe a straightforward method to prepare MSC-derived CM. Furthermore, we summarize some in vitro assays useful for testing the cytoprotective, angiogenic, and regenerative activity of CM. These assays are very helpful when studying the role of MSC in cardiac repair and regeneration.

Proteotoxicity in cardiac amyloidosis: amyloidogenic light chains affect the levels of intracellular proteins in human heart cells

AL amyloidosis is characterized by widespread deposition of immunoglobulin light chains (LCs) as amyloid fibrils. Cardiac involvement is frequent and leads to life-threatening cardiomyopathy. Besides the tissue alteration caused by fibrils, clinical and experimental evidence indicates that cardiac damage is also caused by proteotoxicity of prefibrillar amyloidogenic species. As in other amyloidoses, the damage mechanisms at cellular level are complex and largely undefined. We have characterized the molecular changes in primary human cardiac fibroblasts (hCFs) exposed in vitro to soluble amyloidogenic cardiotoxic LCs from AL cardiomyopathy patients. To evaluate proteome alterations caused by a representative cardiotropic LC, we combined gel-based with label-free shotgun analysis and performed bioinformatics and data validation studies. To assess the generalizability of our results we explored the effects of multiple LCs on hCF viability and on levels of a subset of cellular proteins. Our results indicate that exposure of hCFs to cardiotropic LCs translates into proteome remodeling, associated with apoptosis activation and oxidative stress. The proteome alterations affect proteins involved in cytoskeletal organization, protein synthesis and quality control, mitochondrial activity and metabolism, signal transduction and molecular trafficking. These results support and expand the concept that soluble amyloidogenic cardiotropic LCs exert toxic effects on cardiac cells.