Reprogramming for cardiac regeneration

Auto/paracrine factors and early Wnt inhibition promote cardiomyocyte differentiation from human induced pluripotent stem cells at initial low cell density

Cardiomyocytes derived from human induced pluripotent stem cells (hiPSCs) have received increasing attention for their clinical use. Many protocols induce cardiomyocytes at an initial high cell density (confluence) to utilize cell density effects as hidden factors for cardiomyocyte differentiation. Previously, we established a protocol to induce hiPSC differentiation into cardiomyocytes using a defined culture medium and an initial low cell density (1% confluence) to minimize the hidden factors. Here, we investigated the key factors promoting cardiomyocyte differentiation at an initial low cell density to clarify the effects of cell density. Co-culture of hiPSCs at an initial low cell density with those at an initial high cell density showed that signals secreted from cells (auto/paracrine factors) and not cell–cell contact signals, played an important role in cardiomyocyte differentiation. Moreover, although cultures with initial low cell density showed higher expression of anti-cardiac mesoderm genes, earlier treatment with a Wnt production inhibitor efficiently suppressed the anti-cardiac mesoderm gene expression and promoted cardiomyocyte differentiation by up to 80% at an initial low cell density. These results suggest that the main effect of cell density on cardiomyocyte differentiation is inhibition of Wnt signaling at the early stage of induction, through auto/paracrine factors.

Long-term metabolic risk for the metabolically healthy overweight/obese phenotype

BACKGROUND/OBJECTIVES

The clinical relevance of the metabolically healthy overweight/obese (MHO) phenotype is controversial and the relationships between weight change and the development of cardiometabolic risk factors is unknown. Therefore, we aim to: (1) Assess the long-term risk of developing one or more components of the metabolic syndrome in MHO adults compared with metabolically healthy normal weight (MHNW); (2) Evaluate risk of a composite of death, cardiovascular disease (CVD), and risk of developing type 2 diabetes between adults defined according to baseline body mass index and metabolic health.

SUBJECTS/METHODS

Retrospective cohort study of adults 18-65 years of age seen at our institution between 1998 and 2000 who lived in Olmsted County. Metabolically healthy was defined as the absence of all components of the metabolic syndrome (except for waist circumference). Main outcome was the development of metabolic risk factors. The secondary outcome was a composite of mortality, CVD and heart failure.

RESULTS

Of the 18 070 individuals with complete data at baseline, 1805 (10%) were MHO (mean age 38±11 years) and 3047 were MHNW (mean age 35±11 years). After a median follow-up of 15 years, interquartile range 10-17, 80% of MHO vs 68% of MHNW developed at least one cardiometabolic risk factor (P<0.001). In multivariate analysis, MHO individuals who gained ⩾10% of their body weight were more likely to have developed metabolic complications compared to MHO individuals that did not gain weight (P=0.001 for 10-15%, P<0.001 for >15% weight gain). The risk for the secondary composite end point was similar between MHO and MHNW, number of events 218/1805 vs 217/3048 for MHO and MHNW, respectively, (hazard ratio: 1.16, 95% confidence interval: 0.96-1.40).

CONCLUSIONS

MHO are more likely to develop metabolic complications than MHNW, especially if they gain weight.