Cardiac regeneration therapy: connections to cardiac physiology

Novel insights into cardiac regeneration based on differential fetal and adult ovine heart transcriptomic analysis

The adult mammalian cardiomyocyte has a very limited capacity to reenter the cell cycle and advance into mitosis. Therefore, diseases characterized by lost contractile tissue usually evolve into myocardial remodeling and heart failure. Analyzing the cardiac transcriptome at different developmental stages in a large mammal closer to the human than laboratory rodents may serve to disclose positive and negative cardiomyocyte cell cycle regulators potentially targetable to induce cardiac regeneration in the clinical setting. Thus we aimed at characterizing the transcriptomic profiles of the early fetal, late fetal, and adult sheep heart by employing RNA-seq technique and bioinformatic analysis to detect protein-encoding genes that in some of the stages were turned off, turned on, or differentially expressed. Genes earlier proposed as positive cell cycle regulators such as cyclin A, cdk2, meis2, meis3, and PCNA showed higher expression in fetal hearts and lower in AH, as expected. In contrast, genes previously proposed as cell cycle inhibitors, such as meis1, p16, and sav1, tended to be higher in fetal than in adult hearts, suggesting that these genes are involved in cell processes other than cell cycle regulation. Additionally, we described Gene Ontology (GO) enrichment of different sets of genes. GO analysis revealed that differentially expressed gene sets were mainly associated with metabolic and cellular processes. The cell cycle-related genes fam64a, cdc20, and cdk1, and the metabolism-related genes pitx and adipoq showed strong differential expression between fetal and adult hearts, thus being potent candidates to be targeted in human cardiac regeneration strategies.NEW & NOTEWORTHY We characterized the transcriptomic profiles of the fetal and adult sheep hearts employing RNAseq technique and bioinformatic analyses to provide sets of transcripts whose variation in expression level may link them to a specific role in cell cycle regulation. It is important to remark that this study was performed in a large mammal closer to humans than laboratory rodents. In consequence, the results can be used for further translational studies in cardiac regeneration.

Unknown biological effects of L-glucose, ALA, and PUFA

Key substrates including glucose, amino acids, and fatty acids play core roles in nutrient metabolism. In this review, we describe phenomena observed when key substrates are applied to cells. We focused on three promising substrates: L-glucose derivatives, 5-aminolevulinic acid, and polyunsaturated fatty acid. Since they are assumed to give a specific reaction when they are transported into cells or metabolized in cells, they are expected to be applied in a clinical setting. We provide the latest knowledge regarding their behaviors and effects on cells.

Novel xeno-free human heart matrix-derived three-dimensional scaffolds

Rationale

Myocardial infarction (MI) results in damaged heart tissue which can progress to severely reduce cardiac function, leading to death. Recent studies have injected dissociated, suspended cardiac cells into coronary arteries to restore function with limited results attributed to poor cell retention and cell death. Extracellular matrix (ECM) injected into damaged cardiac tissue sites show some promising effects. However, combined use of human cardiac ECM and cardiac cells may produce superior benefits to restore cardiac function.

Objective

This study was designed to assess use of new three-dimensional human heart ECM-derived scaffolds to serve as vehicles to deliver cardiac-derived cells directly to damaged heart tissue and improve cell retention at these sites while also providing biomechanical support and attracting host cell recruitment.

Methods and Results

ECM-derived porous protein scaffolds were fabricated from human heart tissues. These scaffolds were designed to carry, actively promote and preserve cardiac cell phenotype, viability and functional retention in tissue sites. ECM scaffolds were optimized and were seeded with human cardiomyocytes, cultured and subsequently implanted ex vivo onto infarcted murine epicardium. Seeded human cardiomyocytes readily adhered to human cardiac-derived ECM scaffolds and maintained representative phenotypes including expression of cardiomyocyte-specific markers, and remained electrically synchronous within the scaffold in vitro. Ex vivo, cardiomyocyte-seeded ECM scaffolds spontaneously adhered and incorporated into murine ventricle.

Conclusions

Decellularized human cardiac tissue-derived 3D ECM scaffolds are effective delivery vehicles for human cardiac cells to directly target ischemic heart tissue and warrant further studies to assess their therapeutic potential in restoring essential cardiac functions.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-015-0559-0) contains supplementary material, which is available to authorized users.

Fatty acid composition in fetal, neonatal, and cultured cardiomyocytes in rats

Reconstructed myocardial tissue still does not have enough pulsatile contraction. It is well known that fetal and mature neonatal cardiomyocytes utilize glucose and lipid, respectively, as their energy substrates, and that cultured ones mainly use glucose in spite of their age comparable to neonate ones, probably due to insufficient supply of lipids from culture medium. In the present study, we compared 7 saturated, 6 monounsaturated, and 11 polyunsaturated fatty acid contents in cultured cardiomyocytes (Cul group) with those in fetal (Fet group, approximately 17 d after impregnation) and neonatal (Neo group, 9 d old) rats, where the age of the Cul cells were set nearly equal to the Neo ones. Saturated fatty acid contents in the Cul group were generally lower than those in the Fet group and were close to those in the Neo group, except for C12:0 of which content was highest in the Neo group. Monounsaturated fatty acid contents in the Cul group were generally lower than those in the Fet group but similar to or higher than those in the Neo group, except for C24:1n-9 of which content was again highest in the Neo group. In contrast, most of polyunsaturated fatty acid (PUFA) contents in the Cul group appeared lower than those in both the Fet and Neo groups, and differences in 5 of 10 detected PUFAs were significant between the Cul and Neo groups. The results suggest that PUFA contents in cultured cardiomyocytes might be insufficient to exert enough contractile ability. In conclusion, it could be necessary for cultured cardiomyocytes to uptake more lipid; PUFAs in particular.

Stromal Cell-Derived Factor 1α Induces Accumulation of Intraveneously Administered Marrow-Derived Stromal Cells in the Partially Obstructed Rat Bladder

OBJECTIVES

We investigated the time course of the stromal cell-derived factor 1α (SDF1α) expression and behavior of intravenously administered bone marrow-derived stromal (BMS) cells in the urinary bladder of partial bladder outlet obstruction (PBOO) rats.

METHODS

Study 1: Recombinant SDF1α or saline was directly injected into the bladder wall of female rats followed by intravenous administration of BMS cells isolated from green fluorescent protein (GFP) transgenic rats. The bladder was examined with immunohistochemistry to determine whether SDF1α would enhance migration of BMS cells to the bladder. Study 2: Following surgery of PBOO or sham in female rats, bladders were removed on days 1-14, and expression of hypoxia inducible factor 1α (HIF1α) and SDF1α were examined with real-time polymerase chain reaction (PCR) to determine if PBOO preferentially increased their expression. Study 3: Female rats underwent PBOO or sham surgery followed by intravenous administration of GFP-positive BMS cells. Bladders were examined with immunohistochemistry on days 1-14 to determine whether BMS cells preferentially accumulated in the bladder.

RESULTS

BMS cells were accumulated in the injection site of SDF1α but not saline in the bladder. SDF1α and HIF1α increased at day 1 after PBOO compared to sham. More BMS cells accumulated in the bladder of PBOO on day 1, and some BMS cells expressed smooth muscle phenotypes by day 14.

CONCLUSION

SDF1α induced with ischemia/hypoxia due to PBOO is implicated in the accumulation of BMS cells in the bladder and regeneration of the bladder for PBOO.