Myocardial Regeneration

Direct reprogramming of fibroblasts into cardiomyocytes

Cardiovascular diseases are the leading causes of death in the world. The limited regenerative capacity of adult cardiomyocytes is the major barrier for heart regeneration. After myocardial infarction, myofibroblasts are the dominant cell type in the infarct zone. Therefore, it is a good idea to reprogram terminally differentiated myofibroblasts into cardiomyocyte-like cells directly, providing a good strategy to simultaneously reduce scar tissue and increase functional cardiomyocytes. Transcription factors were first identified to reprogram myofibroblasts into cardiomyocytes. Thereafter, microRNAs and/or small molecules showed great potential to optimize the reprogramming process. Here, we systemically summarize and compare the major progress in directed cardiac reprogramming including transcription factors and miRNAs, especially the small molecules. Furthermore, we discuss the challenges needed to be overcome to apply this strategy clinically.

Therapeutic efficacy of bone marrow-derived mononuclear cells in diabetic polyneuropathy is impaired with aging or diabetes

Aims/Introduction

Recent studies have shown that cell transplantation therapies, such as endothelial precursor cells, bone marrow-derived mononuclear cells (BM-MNCs) and mesenchymal stem cells, are effective on diabetic polyneuropathy through ameliorating impaired nerve blood flow in diabetic rats. Here, we investigated the effects of BM-MNCs transplantation in diabetic polyneuropathy using BM-MNCs derived from adult (16-week-old) diabetic (AD), adult non-diabetic (AN) or young (8-week-old) non-diabetic (YN) rats.

Materials and Methods

BM-MNCs of AD and AN were isolated after an 8-week diabetes duration. The BM-MNCs were characterized using flow cytometry analysis of cell surface markers and reverse transcription polymerase chain reaction of several cytokines. BM-MNCs or saline were injected into hind limb muscles. Four weeks later, the thermal plantar test, nerve conduction velocity, blood flow of the sciatic nerve and capillary-to-muscle fiber ratio were evaluated.

Results

The number of CD29⁺/CD90⁺ cells that host mesenchymal stem cells in BM-MNCs decreased in AD compared with AN or YN, and transcript expressions of basic fibroblast growth factor and nerve growth factor in BM-MNCs decreased in AD compared with AN or YN. Impaired thermal sensation, decreased blood flow of the sciatic nerve and delayed nerve conduction velocity in 8-week-diabetic rats were significantly ameliorated by BM-MNCs derived from YN, whereas BM-MNCs from AD or AN rats did not show any beneficial effect in these functional tests.

Conclusions

These results show that cytokine production abilities and the mesenchymal stem cell population of BM-MNCs would be modified by aging and metabolic changes in diabetes, and that these differences could explain the disparity of the therapeutic efficacy of BM-MNCs between young and adult or diabetic and non-diabetic patients in diabetic polyneuropathy.

Comparison of transendocardial and intracoronary CD34+ cell transplantation in patients with nonischemic dilated cardiomyopathy

BACKGROUND

In an open-label blinded study, we compared intracoronary and transendocardial CD34(+) cell transplantation in patients with nonischemic dilated cardiomyopathy.

METHODS AND RESULTS

Of the 40 patients with dilated cardiomyopathy, 20 were randomized to receive intracoronary injection and 20 received transendocardial CD34(+) cell delivery. In both groups, CD34(+) cells were mobilized by filgrastim, collected via apheresis, and labeled with technetium-99m radioisotope for single-photon emission computed tomographic imaging. In the intracoronary group, cells were injected intracoronarily in the artery supplying segments of greater perfusion defect on myocardial perfusion scintigraphy. In the transendocardial group, electroanatomic mapping was used to identify viable but dysfunctional myocardium, and transendocardial cell injections were performed. Nuclear single-photon emission computed tomographic imaging for quantification of myocardial retention was performed 18 hours thereafter. At baseline, groups did not differ in age, sex, left ventricular ejection fraction, or N-terminal pro-brain natriuretic peptide levels. The number of CD34(+) cells was also comparable (105 ± 31 × 10(6) in the transendocardial group versus 103 ± 27 × 10(6) in the intracoronary group, P=0.62). At 18 hours after procedure, myocardial retention was higher in the transendocardial group (19.2 ± 4.8%) than in the intracoronary group (4.4 ± 1.2%, P<0.01). At 6 months, left ventricular ejection fraction improved more in the transendocardial group (+8.1 ± 4.3%) than in the intracoronary group (+4.2 ± 2.3%, P=0.03). The same pattern was observed for the 6-minute walk test distance (+125 ± 33 m in the transendocardial group versus +86 ± 13 m in the intracoronary group, P=0.03) and N-terminal pro-brain natriuretic peptide (-628 ± 211 versus -315 ± 133 pg/mL, P=0.04).

CONCLUSIONS

In patients with dilated cardiomyopathy, transendocardial CD34(+) cell transplantation is associated with higher myocardial retention rates and greater improvement in ventricular function, N-terminal pro-brain natriuretic peptide, and exercise capacity compared with intracoronary route.

CLINICAL TRIAL REGISTRATION URL

http://www.clinicaltrials.gov. Unique identifier: NCT01350310.