Survival, integration, and differentiation of unrestricted somatic stem cells in the heart

Cardiac injection of USSC boosts remuscularization of the infarcted heart by shaping the T-cell response

Regenerating the injured heart remains one of the most vexing challenges in cardiovascular medicine. Cell therapy has shown potential for treatment of myocardial infarction, but low cell retention so far has limited its success. Here we show that intramyocardial injection of highly apoptosis-resistant unrestricted somatic stem cells (USSC) into infarcted rat hearts resulted in an unprecedented thickening of the left ventricular wall with cTnT⁺/BrdU⁺ cardiomyocytes that was paralleled by progressively restored ejection fraction. USSC induced significant T-cell enrichment in ischemic tissue with enhanced expression of T-cell related cytokines. Inhibition of T-cell activation by anti-CD28 monoclonal antibody, fully abolished the regenerative response which was restored by adoptive T-cell transfer. Secretome analysis of USSC and lineage tracing studies suggest that USSC secrete paracrine factors over an extended period of time which boosts a T-cell driven endogenous regenerative response mainly from adult cardiomyocytes.

Umbilical cord mesenchymal stem/stromal cells potential to treat organ disorders; an emerging strategy

Currently, mesenchymal stem/stromal cells (MSCs) have attracted growing attention in the context of cell-based therapy in regenerative medicine. Following the first successful procurement of human MSCs from bone marrow (BM), these cells isolation has been conducted from various origins, in particular, the umbilical cord (UC). Umbilical cord-derived mesenchymal stem/stromal cells (UC-MSCs) can be acquired by a non-invasive plan and simply cultured, and thereby signifies their superiority over MSCs derived from other sources for medical purposes. Due to their unique attributes, including self-renewal, multipotency, and accessibility concomitant with their immunosuppressive competence and lower ethical concerns, UC-MSCs therapy is described as encouraging therapeutic options in cell-based therapies. Regardless of their unique aptitude to adjust inflammatory response during tissue recovery and delivering solid milieu for tissue restoration, UC-MSCs can be differentiated into a diverse spectrum of adult cells (e.g., osteoblast, chondrocyte, type II alveolar, hepatocyte, and cardiomyocyte). Interestingly, they demonstrate a prolonged survival and longer telomeres compared with MSCs derived from other sources, suggesting that UC-MSCs are desired source to use in regenerative medicine. In the present review, we deliver a brief review of UC-MSCs isolation, expansion concomitantly with immunosuppressive activities, and try to collect and discuss recent pre-clinical and clinical researches based on the use of UC-MSCs in regenerative medicine, focusing on with special focus on in vivo researches.

CD73 Expression on Mesenchymal Stem Cells Dictates the Reparative Properties via Its Anti-Inflammatory Activity

Mesenchymal stem cells (MSC) are not universal and may be subject to dynamic changes upon local milieus in vivo and after isolation and cultivation in vitro. Here, we demonstrate that MSC derived from murine pericardial adipose tissue (pMSC) constitute two cohorts of population distinguished by the level of CD73 expression (termed as CD73high and CD73low pMSC). Transplantation of two types of cells into mouse hearts after myocardial infarction (MI) revealed that the CD73high pMSC preferentially brought about structural and functional repair in comparison to the PBS control and CD73low pMSC. Furthermore, the CD73high pMSC displayed a pronounced anti-inflammatory activity by attenuating CCR2+ macrophage infiltration and upregulating several anti-inflammatory genes 5 days after in vivo transplantation and ex vivo cocultivation with peritoneal macrophages. The immunomodulatory effect was not seen in cocultivation experiments with pMSC derived from CD73 knockout mice (CD73-/-) but was partially blocked by pretreatment of the A2b receptor antagonist, PSB603. The results highlight a heterogeneity of the CD73 expression that may be related to its catalytic products on the modulation of the local immune response and thus provide a possible explanation to the inconsistency of the regenerative results when different sources of donor cells were used in stem cell-based therapy.

Persistence and proliferation of human mesenchymal stromal cells in the right ventricular myocardium after intracoronary injection in a large animal model of pulmonary hypertension

BACKGROUND AIMS

In this study, we demonstrate long-term persistence of human mesenchymal stromal cells (hMSCs) after intracoronary injection in a large animal model of pulmonary hypertension (PH).

METHODS

Commercially available placenta-derived hMSCs were used. Experiments were conducted on 14 female Yorkshire swine. Four animals served as controls, and 10 underwent pulmonary vein (PV) banding. After 12 ± 2 weeks, PH and PV dysfunction were confirmed by right heart catheterization and cardiac magnetic resonance imaging. hMSCs were injected in the marginal branch of the right coronary artery. Tissues were harvested 6, 9 or 24 days after infusion.

RESULTS

After 12 ± 2 weeks after PV banding, all subjects had increased mean pulmonary artery pressure (13.6 ± 3.6 versus 30.8 ± 4.5 mm Hg, P < 0.007) and a decrease in right ventricular ejection fraction from 51.7 ± 5.7% versus 30.5 ± 11.3% (P = 0.003). Intracoronary injection of hMSCs was well tolerated. Up to 24 days after hMSC injection, immunohistochemistry revealed extravascular viable human CD105⁺ mononuclear cells in the right ventricle (RV) that were Ki67⁺. This was confirmed by fluorescence in situ hybridization. CD45⁺ porcine inflammatory cells were identified, commonly seen adjacent to areas of healing microscopic infarction that likely dated to the time of the original hMSC injection. Anti-CD31 staining produced strong signals in areas of injected hMSCs. Immunohistochemistry staining for vascular cell adhesion molecule-1 showed upregulation in the clusters, where mononuclear cells were located.

CONCLUSIONS

hMSCs injected via intracoronary infusion survived up to 24 days and demonstrated proliferative capacity. hMSCs can persist long term in the RV and are potential cell source for tissue repair in RV dysfunction.

Pharmacological Therapy in the Heart as an Alternative to Cellular Therapy: A Place for the Brain Natriuretic Peptide?

The discovery that stem cells isolated from different organs have the ability to differentiate into mature beating cardiomyocytes has fostered considerable interest in developing cellular regenerative therapies to treat cardiac diseases associated with the loss of viable myocardium. Clinical studies evaluating the potential of stem cells (from heart, blood, bone marrow, skeletal muscle, and fat) to regenerate the myocardium and improve its functional status indicated that although the method appeared generally safe, its overall efficacy has remained modest. Several issues raised by these studies were notably related to the nature and number of injected cells, as well as the route and timing of their administration, to cite only a few. Besides the direct administration of cardiac precursor cells, a distinct approach to cardiac regeneration could be based upon the stimulation of the heart's natural ability to regenerate, using pharmacological approaches. Indeed, differentiation and/or proliferation of cardiac precursor cells is controlled by various endogenous mediators, such as growth factors and cytokines, which could thus be used as pharmacological agents to promote regeneration. To illustrate such approach, we present recent results showing that the exogenous administration of the natriuretic peptide BNP triggers “endogenous” cardiac regeneration, following experimental myocardial infarction.

Myogenic differentiation and reparative activity of stromal cells derived from pericardial adipose in comparison to subcutaneous origin

Introduction

Adipose tissue-derived stromal cells (ADSCs) are abundant and easy to obtain, but the diversity of differentiation potential from different locations may vary with the developmental origin of their mesenchymal compartment. We therefore aim to compare the myogenic differentiation and reparative activity of ADSCs derived from the pericardial tissue to ADSCs of subcutaneous origin.

Methods

Pericardial and inguinal adipose tissues from Wistar rats were surgically obtained, and the stromal fraction was isolated after enzymatic digestion. The phenotypic epitopes of the resultant two types of ADSCs were analyzed with flow cytometry, and the expression of transcriptional factors was analyzed with immunostaining. Furthermore, their potential toward adipogenic, osteogenic, and myogenic differentiation also was compared. Finally, the reparative activity and the resultant functional benefits were examined by allograft transplantation into an infarcted model in rats.

Results

ADSCs from two adipose sources showed identical morphology and growth curve at the initial stage, but inguinal ADSCs (ingADSCs) sustained significantly vigorous growth after 25 days of cultivation. Although both ADSCs shared similar immunophenotypes, the pericardial ADSCs (periADSC) intrinsically exhibited partial expression of transcription factors for cardiogenesis (such as GATA-4, Isl-1, Nkx 2.5, and MEF-2c) and more-efficient myogenic differentiation, but less competent for adipogenic and osteogenic differentiation. After in vivo transplantation, periADSCs exhibited significantly vigorous reparative activity evidenced by thickening of ventricular wall and pronounced vasculogenesis and myogenesis, although the majority of prelabeled cells disappeared 28 days after transplantation. The structural repair also translated into functional benefits of hearts after infarction.

Conclusions

Although two sources of ADSCs are phenotypically identical, pericADSCs constituted intrinsic properties toward myogenesis and vasculogenesis, and thus provided more potent reparative effects after transplantation; therefore, they represent an attractive candidate cell donor for cardiac therapy.

Potential application of cord blood-derived stromal cells in cellular therapy and regenerative medicine

Neonatal stromal cells from umbilical cord blood (CB) are promising alternatives to bone marrow- (BM-) derived multipotent stromal cells (MSCs). In comparison to BM-MSC, the less mature CB-derived stromal cells have been described as a cell population with higher differentiation and proliferation potential that might be of potential interest for clinical application in regenerative medicine. Recently, it has become clear that cord blood contains different stromal cell populations, and as of today, a clear distinction between unrestricted somatic stromal cells (USSCs) and CB-MSC has been established. This classification is based on the expression of DLK-1, HOX, and CD146, as well as functional examination of the adipogenic differentiation potential and the capacity to support haematopoiesis in vitro and in vivo. However, a marker enabling a prospective isolation of the rare cell populations directly out of cord blood is yet to be found. Further analysis may help to reveal even more subpopulations with different properties, which could be useful for the directed application of these cells in preclinical models.