De novo myocardial regeneration: advances and pitfalls

Abstract

The capability of adult tissue-derived stem cells for cardiogenesis has been extensively studied in experimental animals and clinical studies for treatment of postischemic cardiomyopathy. The less-than-anticipated improvement in the heart function in most clinical studies with skeletal myoblasts and bone marrow cells has warranted a search for alternative sources of stem cells. Despite their multilineage differentiation potential, ethical issues, teratogenicity, and tissue rejection are main obstacles in developing clinically feasible methods for embryonic stem cell transplantation into patients. A decade-long research on embryonic stem cells has paved the way for discovery of alternative approaches for generating pluripotent stem cells. Genetic manipulation of somatic cells for pluripotency genes reprograms the cells to pluripotent status. Efforts are currently focused to make reprogramming protocols safer for clinical applications of the reprogrammed cells. We summarize the advancements and complicating features of stem cell therapy and discuss the decade-and-a-half-long efforts made by stem cell researchers for moving the field from bench to the bedside as an adjunct therapy or as an alternative to the contemporary therapeutic modalities for routine clinical application. The review also provides a special focus on the advancements made in the field of somatic cell reprogramming.

FIG. 1.

Methods of iPS cell generation. (A) Flow diagram showing general classification of the methods and (B) a simplified overview to generate iPS cells by induction of pluripotency genes. C-Myc, myelocytomatosis; HDAC, histone deacetylase; Klf4, Kruppel like factor-4; iPS, induced pluripotent cells; Sox2, Sry box containing gene 2. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article at www.liebertonline.com/ars).

FIG. 2.

iPS cells derived from bone marrow cells. (A) Phase-contrast and (B) GFP fluorescent photomicrographs of iPS cells derived from mouse bone marrow cells showing an embryonic stem cell-like morphology. Bone marrow was isolated from Oct4-GFP mice and reprogrammed using transduction with viral vectors encoding for Oct4, Sox2, Klf4, and c-Myc. Only the colonies expressing endogenous Oct4 (GFP-positive) were expanded to obtain a pure population of iPS cells. (C–F) Fluorescent immunostaining of bone marrow cell-derived iPS cells for expression of Sox2 (red; C). Endogenous Oct4 expression (GFP green; D) continued during in vitro expansion of iPS cells. The nuclei were observed by DAPI staining (blue; E). Figure 3F represents the merged image of A–C (original magnifications = 200 × ). GFP, green fluorescence protein. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article at www.liebertonline.com/ars).

FIG. 3.

Characterization of bone marrow iPS cells for pluripotency. Fluorescent immunostaining of bone marrow cell-derived iPS cells for expression of pluripotency stage-specific embryonic antigen-1 (SSEA-1; red, A). Endogenous Oct4 expression (GFP green; B) continued during in vitro expansion of iPS cells. (C) The nuclei were observed by 4′,6-diamidino-2-phenylindole staining. (D) shows the merged image (original magnifications =400 × ). (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article at www.liebertonline.com/ars).