Derivation of Transgene-Free Human Induced Pluripotent Stem Cells from Human Peripheral T Cells in Defined Culture Conditions

<div><p>Recently, induced pluripotent stem cells (iPSCs) were established as promising cell sources for revolutionary regenerative therapies. The initial culture system used for iPSC generation needed fetal calf serum in the culture medium and mouse embryonic fibroblast as a feeder layer, both of which could possibly transfer unknown exogenous antigens and pathogens into the iPSC population. Therefore, the development of culture systems designed to minimize such potential risks has become increasingly vital for future applications of iPSCs for clinical use. On another front, although donor cell types for generating iPSCs are wide-ranging, T cells have attracted attention as unique cell sources for iPSCs generation because T cell-derived iPSCs (TiPSCs) have a unique monoclonal T cell receptor genomic rearrangement that enables their differentiation into antigen-specific T cells, which can be applied to novel immunotherapies. In the present study, we generated transgene-free human TiPSCs using a combination of activated human T cells and Sendai virus under defined culture conditions. These TiPSCs expressed pluripotent markers by quantitative PCR and immunostaining, had a normal karyotype, and were capable of differentiating into cells from all three germ layers. This method of TiPSCs generation is more suitable for the therapeutic application of iPSC technology because it lowers the risks associated with the presence of undefined, animal-derived feeder cells and serum. Therefore this work will lead to establishment of safer iPSCs and extended clinical application.</p></div

Analysis of TiPSCs genome modification and karyotype.

<p>(A): Bisulfite sequencing analysis of the <i>NANOG</i> and <i>OCT3/4</i> promoter regions in peripheral T cells, ESCs, and M-TiPSCs. Each row of circles for a given amplicon represents the methylation status of the CpG dinucleotides in one bacterial clone for that region. Open circles represent unmethylated CpGs and closed circles represent methylated CpGs. (B): G-band analysis for karyotypes of M-TiPSCs generated under a defined culture condition. M-TiPSCs1 and M-TiPSCs2 at passages 6 and 15, respectively, were used for G-band analysis. (C): Analysis of TCR rearrangements. V, D, and J segment usages in the <i>TCRB</i> gene locus were sequenced and identified by comparison to the international ImMunoGeneTics information system database. M-TiPSCs showed rearrangements of Vβ/Dβ1,2 and Dβ1,2/Jβ2.</p

Characterization of M-TiPSCs generated under a defined culture condition.

<p>(A): ALP staining in M-TiPSCs. (B): QT-PCR analyses of M-TiPSCs for the ESC marker genes <i>OCT3/4</i>, <i>NANOG</i>, <i>SOX2</i>, <i>KLF4</i>, <i>c-MYC</i>, and <i>TERT1</i>. (C): QT-PCR analyses of M-TiPSCs for the transgenes, <i>OCT3/4</i>, <i>SOX2</i>, <i>KLF4</i>, and <i>c-MYC</i>. (D): Immunofluorescence staining for pluripotency and surface markers (NANOG, OCT3/4, SSEA3, SSEA4, TRA-1–60, and TRA-1–81) in M-TiPSCs1. (E): Heat map analyses of M-TiPSCs, ESCs, and the parental human T cells. (F): Scatter plots comparing the global gene expression profiles of M-TiPSCs with those of T cells and ESCs.</p

Generation of human TiPSCs under defined conditions.

<p>(A): Strategy used in the present study for reprogramming T cells. (B): Typical ESC-like TiPSC colony on day 25 after blood sampling under the defined culture condition. (C): Comparison of reprogramming efficiencies between the culture system using a feeder cell layer and that using defined culture conditions. Data show the mean ± s.d. (D): Comparison of representative 10-cm dishes stained for ALP (red spots) between feeder layer condition and defined culture condition (Matrigel) on day 25. (E): Comparison of reprogramming efficiencies between a culture system using a feeder cell layer and one using Matrigel and mTeSR1 medium for samples from five donors. Data show the mean ± s.d.</p

In vitro and in-TiPSCs.

<p>(A): Immunofluorescence staining for Sox17 (endodermal marker), αSMA (mesodermal marker), and Nestin (ectodermal marker) in each TiPSCs1-derived differentiated cell in vitro. (B): Gross morphology of representative teratomas derived from TiPSCs1 in vivo (hematoxylin and eosin staining).</p

Thrombogenicity and cell adhesion of gelatin hydrogel (GH).

<p>(A) Thrombogenicity of gelatin hydrogel (GH) was compared with that of collagen. In a 1500-s^-1 blood stream, non-specific aggregation took place in 1 to 2 minutes, but no aggregation was induced after 3 minutes. In a 750-s^-1 blood stream, GH induced no aggregation at all. Bars are 10 μm. (B) Cardiomyocytes (CM) were premixed with GH before transplantation. CM were stained with cardiac troponin-T and 4',6-diamidino-2-phenylindole dihydrochloride (DAPI). Most of the CM were entwined with GH, and they were distributed evenly. Bar is 100 μm.</p

Transplantation of CM with GH improved cardiac function.

<p>(A) The representative figures of fractional area change (FAC) in the GH and CM+GH groups are shown. Only the CM+GH group showed better anterior wall motion. (B-C) Left ventricular systolic function was assessed by ejection fraction (EF), fractional shortening (FS), and FAC. All of them were significantly improved in the CM+GH group. (* P<0.05) Left ventricular internal diameter in diastole (LVDd) was elongated in all groups except sham group. Left ventricular internal diameter in systole (LVDs) was shorter in the CM+GH group. HR; heart rate.</p

Transplantation of CM with GH increased the release of angiogenic cytokines.

<p>RNA was extracted from infarcted hearts, and angiogenic factors were evaluated. Basic fibroblast growth factor (FGF), vascular endothelial growth factor (VEGF), and hepatocyte growth factor (HGF) increased in the CM+GH group. (* P<0.05)</p

GH enhanced engraftment of CM.

<p>(A-B) Cardiac sections were stained with azan to evaluate the infarcted area. The CM+GH group tended to have a smaller infarcted area. Bars are 1 mm. (C) CM were prestained with MitoTracker-Red and sections were co-stained with cardiac troponin T and DAPI. In the GH group, there were no red signals in infarcted hearts. In the CM+PBS group, few CM were engrafted in the infarcted area. In the CM+GH group, more CM remained in the infarcted area. Bars are 100 μm. (D) The number of engrafted CM was increased significantly when transplanted with GH compared with CM transplanted with PBS. (** P<0.01)</p