Erythropoietin preserves the endothelial differentiation capacity of cardiac progenitor cells and reduces heart failure during anticancer therapies.

Anticancer therapies, such as targeting of STAT3 or the use of anthracyclins (doxorubicin), can induce cardiomyopathy. In mice prone to developing heart failure as a result of reduced cardiac STAT3 expression (cardiomyocyte-restricted deficiency of STAT3) or treatment with doxorubicin, we observed impaired endothelial differentiation capacity of Sca-1(+) cardiac progenitor cells (CPCs) in conjunction with attenuated CCL2/CCR2 activation. Mice in both models also displayed reduced erythropoietin (EPO) levels in the cardiac microenvironment. EPO binds to CPCs and seems to be responsible for maintaining an active CCL2/CCR2 system. Supplementation with the EPO derivative CERA in a hematocrit-inactive low dose was sufficient to upregulate CCL2, restore endothelial differentiation of CPCs, and preserve the cardiac microvasculature and cardiac function in both mouse models. Thus, low-dose EPO treatment could potentially be exploited as a therapeutic strategy to reduce the risk of heart failure in certain treatment regimens.

Prominin-1 (CD133) is not restricted to stem cells located in the basal compartment of murine and human prostate.

BACKGROUND: Rodent and human prominin-1 are expressed in numerous adult epithelia and somatic stem cells. A report has shown that human PROMININ-1 carrying the AC133 epitope can be used to identify rare prostate basal stem cells (Richardson et al., J Cell Sci 2004; 117:3539­3545). Here we re-investigated its general expression in male reproductive tract including mouse and human prostate and in prostate cancer samples using various anti-prominin-1 antibodies. METHODS: The expression was monitored by immunohistochemistry and blotting. Murine tissues were stained with 13A4 monoclonal antibody (mAb) whereas human samples were examined either with the AC133 mAb recognizing the AC133 glycosylation-dependent epitope or 80B258 mAb directed against the PROMININ-1 polypeptide. RESULTS: Mouse prominin-1 was detected at the apical domain of epithelial cells of ductus deferens, seminal vesicles, ampullary glands, and all prostatic lobes. In human prostate, immunoreactivity for 80B258, but not AC133 was revealed at the apical side of some epithelial (luminal) cells, in addition to the minute population of AC133/80B258-positive cells found in basal compartment. Examination of prostate adenocarcinoma revealed the absence of 80B258 immunoreactivity in the tumor regions. However, it was found to be up-regulated in luminal cells in the vicinity of the cancer areas. CONCLUSIONS: Mouse prominin-1 is widely expressed in prostate whereas in human only some luminal cells express it, demonstrating nevertheless that its expression is not solely associated with basal stem cells. In pathological samples, our pilot evaluation shows that PROMININ-1 is down-regulated in the cancer tissues and up-regulated in inflammatory regions.

Signal transducer and activator of transcription 3-mediated regulation of miR-199a-5p links cardiomyocyte and endothelial cell function in the heart: a key role for ubiquitin-conjugating enzymes.

AIMS: Mice with a cardiomyocyte (CM)-restricted knockout of signal transducer and activator of transcription 3 (STAT3-KO) develop spontaneous heart failure. We investigated the impact of STAT3-mediated regulation of microRNAs for pathophysiological alterations in the heart. METHODS AND RESULTS: MicroRNAchip and qRT-PCR analysis revealed elevated cardiac expression of miR-199a in STAT3-KO mice. Lentiviral shRNA-mediated STAT3-knock-down in neonatal rat CMs markedly increased miR-199a promoter activity and miR-199a levels indicative of a suppressive effect of STAT3 on miR-199a transcription. Up-regulated miR-199a in CM by pre-miR-199a transfection (pre-miR-199a-CM) reduced expression of components of the ubiquitin-proteasome system (UPS), i.e. the ubiquitin-conjugating enzymes Ube2g1 (mRNA and protein) and Ube2i (protein). Pre-miR-199a-CM or CM with siRNA-mediated down-regulation of Ube2i and Ube2g1 (siRNA-Ube2i/2g1-CM) displayed massive down-regulation of α- and ß-myosin heavy chain expression associated with disrupted sarcomere structures. In addition, protein arginine methyltransferase I (PRMT-I) expression and asymmetric dimethylarginine (ADMA) synthesis were increased in pre-miR-199a-CM or in siRNA-Ube2i/2g1-CM. Increased ADMA in cell culture supernatant (SN) from pre-miR-199a-CM or siRNA-Ube2i/2g1-CM lowered nitric oxide (NO) bioavailability of rat cardiac endothelial cells while lowering ADMA concentration in CM SNs by the PRMT inhibitor arginine methyltransferase inhibitor 1 (AMI-1) (100 µM) improved NO bioavailability. In STAT3-KO hearts Ube2i and Ube2g1 expression were markedly reduced. Human terminal failing hearts harbouring low STAT3 protein levels displayed increased miR-199a levels and decreased Ube2g1 expression. CONCLUSION: This study identifies a novel pathophysiological circuit in the heart between reduced STAT3 protein levels, increased miR-199a expression, and subsequent impairment of the UPS that disrupts CM sarcomere structure and impairs via the release of ADMA endothelial cell function.

Loss of the cholesterol-binding protein prominin-1/CD133 causes disk dysmorphogenesis and photoreceptor degeneration.

Prominin-1/CD133 (Prom-1) is a commonly used marker of neuronal, vascular, hematopoietic and other stem cells, yet little is known about its biological role and importance in vivo. Here, we show that loss of Prom-1 results in progressive degeneration of mature photoreceptors with complete loss of vision. Despite the expression of Prom-1 on endothelial progenitors, photoreceptor degeneration was not attributable to retinal vessel defects, but caused by intrinsic photoreceptor defects in disk formation, outer segment morphogenesis, and associated with visual pigment sorting and phototransduction abnormalities. These findings shed novel insight on how Prom-1 regulates neural retinal development and phototransduction in vertebrates.

The stem cell marker CD133 (Prominin-1) is expressed in various human glandular epithelia.

Human prominin-1 (CD133) is expressed by various stem and progenitor cells originating from diverse sources. In addition to stem cells, its mouse ortholog is expressed in a broad range of adult epithelial cells, where it is selectively concentrated in their apical domain. The lack of detection of prominin-1 in adult human epithelia might be explained, at least in part, by the specificity of the widely used AC133 antibody, which recognizes an epitope that seems dependent on glycosylation. Here we decided to re-examine its expression in adult human tissues, particularly in glandular epithelia, using a novel monoclonal antibody (80B258) generated against the human prominin-1 polypeptide. In examined tissues, we observed 80B258 immunoreactivity at the apical or apicolateral membranes of polarized cells. For instance, we found expression in secretory serous and mucous cells as well as intercalated ducts of the large salivary and lacrimal glands. In sweat glands including the gland of Moll, 80B258 immunoreactivity was found in the secretory (eccrine and apocrine glands) and duct (eccrine glands) portion. In the liver, 80B258 immunoreactivity was identified in the canals of Hering, bile ductules, and small interlobular bile ducts. In the uterus, we detected 80B258 immunoreactivity in endometrial and cervical glands. Together these data show that the overall expression of human prominin-1 is beyond the rare primitive cells, and it seems to be a general marker of apical or apicolateral membrane of glandular epithelia. This manuscript contains online supplemental material at http://www.jhc.org. Please visit this article online to view these materials.

Combination of IL-12 gene therapy and CTX chemotherapy inhibits growth of primary B16(F10) melanoma tumors in mice.

We investigated suppression of murine B16(F10) melanoma tumor growth following a therapy which involved concomitant administration of cyclophosphamide and plasmid DNA bearing interleukin-12 gene. Since both therapeutic factors display antiangiogenic capabilities, we assumed that their use in blocking the formation of new blood vessels would result in augmented inhibition of tumor growth. This combined therapy regimen indeed resulted in a considerable suppression of tumor growth. We observed a statistically significant extension of treated animals' lifespan. Interestingly, the therapeutic effect was also obtained using a plasmid without an interleukin gene insert. This observation suggests that plasmid DNA, which has been widely applied for treating neoplastic tumors, contains element(s) that elicit immune response in mice.

Tumour therapy with genes encoding apoptin and E4orf4.

The aim of our study was to investigate whether apoptin and e4orf4 pro-apoptotic genes, transferred by means of electroporation, were suitable for gene therapy of tumours. The two genes were chosen for our study because the proteins they encode induce apoptosis in transformed cells only. The apoptin gene was synthesised based on a published nucleotide sequence. MTT and TUNEL tests confirmed that both the synthesised apoptin gene and the e4orf4 gene indeed induced apoptosis in COS-7, Renca and B16(F10) cell lines. Therapeutic DNA was then administered via electroporation directly into murine B16(F10) tumours. Distinct tumour growth inhibition was seen only during the treatment. The cessation of therapy caused tumour re-growth. Obviously, the efficiency of gene transfer using electroporation is low and did not induce a permanent therapeutic effect.

Identification of novel Prominin-1/CD133 splice variants with alternative C-termini and their expression in epididymis and testis.

Prominin-1/CD133 is a five-membrane-span glycoprotein that is thought to act as an organizer of plasma-membrane protrusions. Here, we report the molecular and cell-biological characterization of four novel prominin-1 splice variants isolated from a mouse testis cDNA library and referred to as prominin-1.s3 to prominin-1.s6. Compared with kidney-derived prominin-1.s1, the s3, s4 and s5 variants contain a distinct cytoplasmic C-terminal domain. The s4 and s5 variants bear, in addition, two and one inframe deletion(s), respectively, in the extracellular domains. The s6 variant displays a truncated C-terminal domain caused by a premature termination resulting from intron retention. Upon their ectopic expression in Chinese hamster ovary cells, the s3 and s6 variants were found to be concentrated in plasma-membrane protrusions, whereas the s4 and s5 variants did not reach the cell surface. Biochemical analyses suggest that most of the prominin-1 in the adult male reproductive system is expressed as the s6 variant. Immunohistological and electron microscopic analyses show that prominin-1 is: (1) confined to the apical surface of the epithelium all along the epididymal duct, with the exception of the initial segment; (2) concentrated in stereocilia of the epididymal duct epithelium; and (3) found on the tail of developing spermatozoa in seminiferous tubules. Our data suggest that prominin-1 is involved in the formation and/or stabilization of epididymal stereocilia and the tail of spermatozoa, and hence might play a dual role in the biogenesis of spermatozoa.

Electrotransfer of gene encoding endostatin into normal and neoplastic mouse tissues: inhibition of primary tumor growth and metastatic spread.

Electroporation-mediated gene transfer relies upon direct delivery of plasmids into cells permeabilized by electric fields, a method more efficient than transfer using nonviral vectors, although neither approaches the transfer efficiency of viral vectors. Here we studied electrotransfer of a gene encoding an angiogenesis inhibitor (endostatin) into primary tumors and muscle tissues, which would serve as a site of synthesis and secretion into the bloodstream of a therapeutic antimetastatic protein with systemic effects. Optimum electroporation conditions (voltage, number and duration of impulses, separation of caliper electrodes) were first established to maximize expression of a reporter gene transferred into murine Renca kidney carcinoma, B16(F10) melanoma, or skeletal muscle tissues. In neoplastic tissues, electrotransfer of plasmid DNA was far more efficient than electroporation with lipoplexes, but no differences between naked DNA and lipoplexes were found in case of electroporated muscles. We then studied the electrotransfer of plasmid DNA carrying the endostatin gene into pre-established experimental Renca tumors. A significant inhibition of tumor growth was observed in animals electroporated with this construct. Electrotransfer of the endostatin gene into muscle tissues resulted in reduced numbers of experimental B16(F10) metastases in the lungs. This study clearly shows that electroporation may be used to efficiently transfer antiangiogenic genes into both normal and neoplastic tissues.

Various cationic carriers for in vitro transfection of tumor and endothelial cell lines.

We compared the efficiency of in vitro DNA transfer into selected tumor and endothelial cell lines using complexes of plasmid DNA and cationic carriers: DDAB/DOPE, DC-Chol/DOPE, Arg-Chol/DOPE, Gly-Chol/DOPE, Arg-Gly-Chol/DOPE, BGTC/DOPE, and PEI. The best carriers for transfecting the majority of tested cells lines at optimized carrier-to-DNA weight ratios were PEI and BGTC/DOPE.