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Integrative Physiology |
From the Cardiovascular Research Institute (J.K., M.R., B.W., S.C., T.H., C.B., D.N., E.Z., M.B., B.N.-G., D.T., A.N., F.Q., K.U., A.L., P.A.), Department of Medicine, New York Medical College, Valhalla; and Department of Physiology and Functional Genomics (H.K.), University of Florida Gainesville.
Correspondence to Jan Kajstura, PhD, or Piero Anversa, MD, Cardiovascular Research Institute, Department of Medicine, Vosburgh Pavilion, Rm 302, New York Medical College, Valhalla, NY 10595. E-mail jan_kajstura{at}nymc.edu or piero_anversa@nymc.edu
| Abstract |
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Key Words: transdifferentiation myocardial regeneration cell fusion
| Introduction |
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In spite of the therapeutic efficacy of BMCs in heart failure4,612 and models mimicking the human disease,3,10,1719 two studies13,14 and two commentaries15,16 have presented and discussed negative results, criticizing the early experimental data and clinical trials. They question the ability of BMCs to regenerate dead myocardium and claim that the original findings were a collection of artifacts and all clinical trials were premature and "may have in fact place a group of sick patients at risk."14 Because of the impact that these positive and negative findings have in the future treatment of the postinfarcted heart in humans, we have implemented a simple protocol that can easily be reproduced in laboratories with experience in models of myocardial infarction in small animals. Additionally, we have applied and emphasized the type of analysis that has to be performed to obtain reliable information. By this approach, we have demonstrated that BMCs differentiate into myocytes and coronary vessels replacing the infarcted myocardium independently of cell fusion.
| Materials and Methods |
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| Results |
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Myocardial Infarction and BMCs
BMCs were combined with rhodamine-labeled microspheres for the identification of the injection sites. Because EGFP was present in a small fraction of cells, male EGFP-positive BMCs were injected in female infarcted mice so that EGFP and the Y-chromosome were detected in the progeny of the BMCs in vivo. Two injections of 5x104 BMCs each mixed with rhodamine particles were made in proximity of the border zone (Figure 2A through 2F). We knew that the procedure was difficult with an inherent variability in infarct size and a 50% probability3 of correct injection. The mouse heart beats
600 times per minute and has a left ventricular (LV) wall that is less than 1 mm thick. These factors make the injection of cells within the LV wall highly problematic. Thus, the unsuccessfully injected mice (no rhodamine particles) were considered the most appropriate control animals for the successfully treated mice. 5-Bromodeoxyuridine (BrdUrd) was given daily for the recognition of newly formed cells with time.
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Thirty-seven infarcted mice were obtained, and 18 of these mice were studied at 5 days and 19 at 10 days after surgery. Rhodamine particles were found in 9 and 11 mice at 5 and 10 days, respectively. Thus, a 54% rate of proper injection was accomplished. Infarct size varied from 15% to 60% in both groups of mice (see online data supplement). Therefore, without an appropriate protocol it is impossible to predict the successful or unsuccessful treatment of animals and the actual size of the infarct in each mouse.
Myocardial Regeneration and BMCs
Myocardial regeneration was found in each of the 20 infarcted-treated mice showing rhodamine particles (Figure 2G through 2J). Conversely, myocardial regeneration was not found in the 17 infarcted mice with unsuccessful administration of BMCs as documented by the absence of rhodamine particles. In these cases, the lost myocardium was replaced by collagen (Figure 2K) and there were no EGFP or Y-chromosome labeled cells. This was in sharp contrast to treated infarcts in which the quantity of collagen was minimal and the cells contained in the regenerated myocardium expressed in
20% to 25% of the cases EGFP and in
60% to 80% of the cases carried the Y-chromosome (Figure 2L through 2O). EGFP-Y chromosomepositive cells within the infarct were all CD45 negative, indicating that there was no commitment to the hematopoietic lineages (see online data supplement). However, in nontreated infarcts, numerous CD45-positive cells were detected at 5 and significantly less at 10 days (see online data supplement). CD45-positive cells were EGFP and Y-chromosome negative. Thus, consistent with previous results,3,20 tissue regeneration with BMCs attenuates inflammation and myocardial scarring.
In all cases, the regenerated myocardium contained new myocytes that expressed GATA-4, Nkx2.5, MEF2C,
-sarcomeric actin, cardiac myosin heavy chain, troponin I, and desmin. Connexin 43 and N-cadherin were detected at 5 days but were more apparent at 10 days (Figure 3A through 3J). Fibroblasts were identified between developing myocytes (see online data supplement). Because BrdUrd was injected daily, most of the new myocytes were labeled by BrdUrd confirming their formation after the injection of BMCs (Figure 4A). Two markers of cell proliferation, Ki673,19,21 and MCM5,22 were used at euthanasia to evaluate cell growth at 5 and 10 days after BMC implantation. A significant fraction of cycling cells was found at both intervals with both markers (Figure 4B and 4C). The presence of EGFP and/or the Y-chromosome offered the unequivocal documentation of the origin of these myocytes from the BMCs. The new myocytes were predominantly mononucleated with a small fraction binucleated (Figure 4D). Conversely, differentiated mouse myocytes are
94% binucleated and
5% mononucleated.23 Thus, these results exclude the contribution of preexisting myocytes to the generation of new myocytes. The volume of new myocytes was
350 and
600 µm3 at 5 and 10 days, respectively. Together,
2.5 and
4 million myocytes were formed within the infarct at 5 and 10 days, respectively (Figure 4E). New myocytes were
1/40 of spared myocytes: 23 000 to 25 000 µm3. In fact, surviving myocytes showed a 16% and 25% hypertrophy at 5 and 10 days after infarction, respectively (Figure 4F). As a result of myocyte formation, infarct size was reduced by 6% at 5 and by 17% at 10 days (Figure 4G and 4H).
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The repair of the infarct involved the formation of arterioles and capillaries (Figure 4I through 4N). At 10 days, there were 13±9 mm of arterioles and 98±31 mm of capillaries per mm3 of new myocardium. For comparison, there are
10 arterioles and
3500 capillaries per mm2 of tissue in the adult heart. Thus, the size of myocytes and the characteristics of the coronary vasculature were consistent with a rather immature phenotype of the regenerated myocardium. In the spared myocardium of treated hearts, only two EGFP-positive vascular cells were found. At most, only a few vessels were formed by BMCs in the noninfarcted myocardium. Therefore, BMCs appear to acquire the cardiac cell phenotype repairing the infarcted heart.
Cell Fusion and Myocardial Regeneration
Myocardial regeneration could be the result of fusion of the injected BMCs with existing cells and formation of hybrid cells, the consequence of BMC differentiation and cardiac lineage commitment, or both. Because male BMCs were injected in female infarcted mice, the X- and Y-chromosomes were measured to evaluate whether cell fusion was implicated in de novo myocardial growth. Additionally, DNA content/nucleus was determined.21 Newly formed myocytes and vascular cells had only one set of X- and Y-chromosomes, whereas two X-chromosomes were detected exclusively in the surviving myocytes (Figure 5A through 5L). There were no cells in the area of cardiac repair that showed Y-chromosome labeling in combination with more than one X-chromosome signal. Also newly formed binucleated myocytes carried only one Y- and one X-chromosome in each nucleus (Figure 5G and 5H). Thus, the regenerated myocytes were of male origin, whereas the spared myocytes retained their female phenotype. Finally, a 2C DNA content was found in each nucleus of noncycling myocytes (see online data supplement) further minimizing the role of cell fusion in myocardial repair.
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Myocyte and Vessel Growth in the Surviving Myocardium
To determine whether the injection of BMCs had a paracrine effect on the spared myocardium, BrdUrd-labeled myocytes were measured in the border and distant region of treated and untreated infarcted hearts. Additionally, the fraction of Ki67-positive myocytes was determined to evaluate the degree of cell replication at death. In both regions, the percentage of BrdUrd- and Ki67-positive myocytes was comparable between treated and nontreated infarcted mice (Figure 6A and 6B). Also, capillary length density was similar in treated and untreated mice (Figure 6C). These data are not consistent with a paracrine effect of BMCs on myocytes and vessels of the noninfarcted portion of the heart.
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Ventricular Function
Myocardial regeneration did not ameliorate LV end-diastolic pressure, developed pressure and + and dP/dt at 5 days. However, at 10 days, these hemodynamic parameters were improved in treated-infarcted mice (Figure 6D). These positive effects on LV performance were not observed in untreated-infarcted mice. The improvement in cardiac function with BMCs can only be accounted for by the regeneration of myocardial mass and reduction of infarct size. Whether few or numerous vessels are formed within the infarct, the contractile behavior of this region does not change. Vessels do not contract or generate force; force is developed by myocytes. It is erroneous15 to assume that regeneration of vessels only can restore contractile activity in the infarcted myocardium.
Immunocytochemistry and Autofluorescence
The ability of BMCs to commit to the myocyte lineage has been challenged by negative results13,14 and observations suggesting that the identification of GFP in skeletal myofibers is the consequence of autofluorescence.24 The study performed in Goodells laboratory24 erroneously implies that native GFP fluorescence present in frozen sections of skeletal myofibers can be confused with autofluorescence. This has nothing to do with the detection of the overexpression of EGFP in cardiomyocytes by immunolabeling with specific anti-GFP antibody performed in this study and previously.3,21 It is difficult to understand why this unusual protocol was used24 because immunostaining is the standard procedure today. The advantage of the use of the antibody is apparent in the amplification of the signal associated with the expression of the transgene (Figure 7A through 7D). By this approach, the signal-to-background ratio increases dramatically,
300-fold. To confirm the presence of EGFP in the regenerated myocardium, thick sections of the paraffin-embedded tissue that corresponded to the areas of newly formed myocytes and coronary vessels were used for the detection of the EGFP transgene by PCR. A distinct band reflecting the amplified EGFP-DNA sequence was identified (Figure 7E).
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It is common practice to stain samples in the presence of a well-established positive and negative control. Moreover, the level of autofluorescence of the formalin-fixed, paraffin-embedded and cut tissue section is always determined and compared with the intensity of the fluorescence signal of the labeled epitope. Also, the background fluorescence generated by staining sections with the secondary antibody only is determined. Our working policy is that the fluorescence signal generated by immunostaining of a structure has to be at least 30-fold higher than that accounted for by background autofluorescence together with secondary antibody unspecific staining (Figure 7F through 7I). Therefore, autofluorescence is not a relevant factor when an adequate protocol of tissue labeling and detection is used.
| Discussion |
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There are several other factors that support BMC transdifferentiation rather than cell fusion in myocardial regeneration after infarction. After permanent coronary occlusion, all cells in the supplied myocardium die in less than 5 hours. Essentially, there are no partner cells left for fusion. Adult myocytes have a volume of
20 000 µm3 and if cell fusion occurred in our conditions, new myocytes should have a volume of at least 20 000 µm3 or larger. In contrast, these myocytes have a maximum size of
2000 µm3 and a minimum size of
100 µm3. Donor-derived cells divide rapidly and extensively, whereas tetraploid cells divide slowly and might not divide at all if one of the partners is a terminally differentiated myocyte.19 Fusion of a BMC to a myocyte that has reached irreversible growth arrest cannot stimulate its reentry into the cell cycle.26 Cell fusion should generate binucleated myocytes, with one tetraploid and one diploid nucleus, or myocytes with three diploid nuclei. This was not the case.
The cre-lox genetic system is frequently used to detect cell fusion. However, this system is not perfect. It is surprising that the possibility of metabolic cooperation27 was not considered because this phenomenon may account for some of these observations. By metabolic cooperation, a cell acquires the cre-recombinase from a neighboring cell and undergoes excision of the flox-flanked DNA segment in the absence of cell fusion. The exchange of the enzyme between the donor cell and the recipient cell occurs through intercellular junctions. Metabolic cooperation is important in a tissue that is functionally a syncytium. Theoretically, Y-chromosome-EGFPpositive myocytes could have resulted from hybrid cells that underwent reductive cell division converting the hyperploid cell to a diploid karyotype, which concealed their fusion history.2 Reductive cell division of hybrid cells in vivo has only been documented in hepatocytes generated under a stringent selection pressure that conferred them survival and growth advantage.28 These "pseudodiploid" cells accumulate slowly and are found together with a large number of fused cells.25 Conversely, we found the
2.5 to 4 million donor-derived myocytes to be diploid with an XY-chromosome complement as early as 5 and 10 days after cell implantation. The short interval between the injection of BMCs and the generation of diploid male cells makes reductive mitosis an unlikely possibility.
Controversy on BMC Transdifferentiation
The current results are consistent with previous observations made in our laboratory3,19,20 in which an enriched population of c-kitpositive BMCs regenerated the infarcted myocardium. Similarly, BMCs and endothelial progenitor cells improve cardiac function in humans.4,612 So far, only one negative study has been reported.5 Moreover, a variety of bone marrowderived cells capable of differentiating into the cardiac myogenic lineage have been described.3,10,17,18,20,29,30 It is therefore, difficult to reconcile our findings and the clinical and experimental studies with the claim made recently.13,14 The most likely possibility is a technical difference in the experimental protocol, identity of the therapeutic cell(s), tissue preparation, and immunocytochemical analysis of the myocardium.
The utilization of frozen tissue samples13,14 has severe limitations in terms of the quality of the sections, immunolabeling, and microscopic resolution. The infarct is rarely preserved in frozen sections. Similarly, the 100% degree of success in the injection of cells in the mouse heart14 has no precedent and will never be matched. Moreover, the lack of changes in LVEDP and an 8% mortality with infarcts of 60% is astonishing.14 This unusual result has been attributed to a better postoperative care of the animals. Infarct size is a critical determinant of survival in animals and humans. In spite of the perfect care that patients have in the most sophisticated medical centers, a 46% infarct results in intractable heart failure. Rodents are not different although they can survive slightly larger infarcts.31 The hearts analyzed immunocytochemically for the presence of cardiac regeneration were not the same studied functionally or with routine histology.13,14 Thus, whether coronary ligation was unsuccessful or a small or large infarct was obtained was not determined. This is critical because of the complexity of the model and the difficulty of producing an infarct and a correct injection of cells. Most importantly, as shown here, the size of new myocytes averages 500 µm3 and cells of this volume would not be recognized by the approach and methodology used in these studies.13,14 This is apparent in the micrographs that illustrate clusters of EGFP-positive cells; the EGFP signal is diffuse to the cell cytoplasm and can easily obfuscate a thin rim of myocyte specific proteins. Double labeling for the EGFP-transgene and myocyte cytoplasmic proteins was never performed on the same section13 and negative claims were based on only two animals14 that were supposedly properly infarcted and injected with cells comparable to those used in our early study.3 The improvement in ventricular function claimed in chronically treated animals in the absence of myocardial regeneration is based on unusual echocardiographic data that are not supported by hemodynamic measurements.14
The same limitations can be found in another study in which engraftment of BMCs was observed within the infarct but myocyte formation was considered modest and restricted to the surviving myocardium.32 In fact, myocyte regeneration in the infarcted region seems to be present in some of the illustrations although the colocalization of ß-Gal and GFP indicative of cell fusion was never determined in the same sections. Histochemistry was used to detect ß-Gal, and immunolabeling was used for the identification of GFP. Moreover, the utilization of frozen sections precludes the subsequent recognition of small cells of the size of newly formed myocytes. Also, the diffuse localization of CD45 to the cell cytoplasm further questions some of the technical aspects of this report.
Intrinsic genetic markers have been proposed as the today gold standard for these types of studies.1316 We believe that the detection of the Y chromosome in newly generated myocytes implemented in the early report3 and used in this study falls well within this category. Most importantly, any genetic marker requires its subsequent identification by histochemical13 or immunocytochemical14 procedures. If limitations exist in these protocols, the powerful genetic markers lead to false collection of data and erroneous interpretations and conclusions. The assumption made by Balsam et al14 and Murry at al13 that the technical approach that they have used in the identification and measurement of myocardial structures is superior to that used in our laboratory does not reflect any scientific reality but the emotional disbelief that BMCs can adopt myocardial cell lineages and repair the injured heart. It is unfortunate that two editorials15,16 accompanying the publication of these studies further promoted this negative view.
The esoteric nonphysiological models of parabiosis with complete blood chimerism14 or with reconstituted EGFP-positive bone marrow13 were introduced to question the ability of BMCs to acquire a cardiomyocyte lineage. Surprisingly, the negative results were considered of great relevance for the understanding of BMC transdifferentiation. The limitation of the therapeutic potential of circulating BMCs is not new. Therefore, the paradigm offered in these studies1316 defeats any clinical reality and the dramatic problem of ischemic heart failure. If circulating BMCs would have the ability to spontaneously repair damaged organs, infarcts of the heart, brain, skin, kidney, and intestine would be easily reconstituted and the majority of current human diseases would not exist. These models are of little value to resolve the controversy at hand and can only add confusion to the confusion. The issue in need of resolution is whether BMCs injected directly in the infarct or in the border zone differentiate into the cardiac cell lineages and contribute to myocardial regeneration.
Over the past 2 years, most of the results claiming hematopoietic stem cell (HSC) plasticity have been questioned2 because of imprecise identification of the administered cells, incomplete characterization of their differentiated progeny, and/or the formation of hybrid cells by fusion of the donor to the differentiated recipient cells. At the same time, there have been an increasing number of detailed reports documenting the existence of multipotent cells in the bone marrow and, among them, cells able to differentiate into the cardiac myocyte lineage.20 Why myocardial regeneration from BMCs has been caught in the HSC controversy remains unexplained.
| Acknowledgments |
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| Footnotes |
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X. Hu, S. P. Yu, J. L. Fraser, Z. Lu, M. E. Ogle, J.-A. Wang, and L. Wei Transplantation of hypoxia-preconditioned mesenchymal stem cells improves infarcted heart function via enhanced survival of implanted cells and angiogenesis. J. Thorac. Cardiovasc. Surg., April 1, 2008; 135(4): 799 - 808. [Abstract] [Full Text] [PDF] |
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J. L. Spees, M. J. Whitney, D. E. Sullivan, J. A. Lasky, M. Laboy, J. Ylostalo, and D. J. Prockop Bone marrow progenitor cells contribute to repair and remodeling of the lung and heart in a rat model of progressive pulmonary hypertension FASEB J, April 1, 2008; 22(4): 1226 - 1236. [Abstract] [Full Text] [PDF] |
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A. Orlandi, F. Pagani, D. Avitabile, G. Bonanno, G. Scambia, E. Vigna, F. Grassi, F. Eusebi, S. Fucile, M. Pesce, et al. Functional properties of cells obtained from human cord blood CD34+ stem cells and mouse cardiac myocytes in coculture Am J Physiol Heart Circ Physiol, April 1, 2008; 294(4): H1541 - H1549. [Abstract] [Full Text] [PDF] |
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M. Koyanagi, P. Bushoven, M. Iwasaki, C. Urbich, A. M. Zeiher, and S. Dimmeler Notch Signaling Contributes to the Expression of Cardiac Markers in Human Circulating Progenitor Cells Circ. Res., November 26, 2007; 101(11): 1139 - 1145. [Abstract] [Full Text] [PDF] |
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C. Valina, K. Pinkernell, Y.-H. Song, X. Bai, S. Sadat, R. J. Campeau, T. H. Le Jemtel, and E. Alt Intracoronary administration of autologous adipose tissue-derived stem cells improves left ventricular function, perfusion, and remodelling after acute myocardial infarction Eur. Heart J., November 1, 2007; 28(21): 2667 - 2677. [Abstract] [Full Text] [PDF] |
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J. Endo, M. Sano, J. Fujita, K. Hayashida, S. Yuasa, N. Aoyama, Y. Takehara, O. Kato, S. Makino, S. Ogawa, et al. Bone Marrow-Derived Cells Are Involved in the Pathogenesis of Cardiac Hypertrophy in Response to Pressure Overload Circulation, September 4, 2007; 116(10): 1176 - 1184. [Abstract] [Full Text] [PDF] |
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P. Batten, N. A Rosenthal, and M. H Yacoub Immune response to stem cells and strategies to induce tolerance Phil Trans R Soc B, August 29, 2007; 362(1484): 1343 - 1356. [Abstract] [Full Text] [PDF] |
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V. Zaca, S. Rastogi, M. Imai, M. Wang, V. G. Sharov, A. Jiang, S. Goldstein, and H. N. Sabbah Chronic Monotherapy With Rosuvastatin Prevents Progressive Left Ventricular Dysfunction and Remodeling in Dogs With Heart Failure J. Am. Coll. Cardiol., August 7, 2007; 50(6): 551 - 557. [Abstract] [Full Text] [PDF] |
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D. K. Singla, G. E. Lyons, and T. J. Kamp Transplanted embryonic stem cells following mouse myocardial infarction inhibit apoptosis and cardiac remodeling Am J Physiol Heart Circ Physiol, August 1, 2007; 293(2): H1308 - H1314. [Abstract] [Full Text] [PDF] |
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C. Ventura, S. Cantoni, F. Bianchi, V. Lionetti, C. Cavallini, I. Scarlata, L. Foroni, M. Maioli, L. Bonsi, F. Alviano, et al. Hyaluronan Mixed Esters of Butyric and Retinoic Acid Drive Cardiac and Endothelial Fate in Term Placenta Human Mesenchymal Stem Cells and Enhance Cardiac Repair in Infarcted Rat Hearts J. Biol. Chem., May 11, 2007; 282(19): 14243 - 14252. [Abstract] [Full Text] [PDF] |
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V. L.T. Ballard and J. M. Edelberg Stem Cells and the Regeneration of the Aging Cardiovascular System Circ. Res., April 27, 2007; 100(8): 1116 - 1127. [Abstract] [Full Text] [PDF] |
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B. J. Muller-Borer, W. E. Cascio, G. L. Esch, H.-S. Kim, W. B. Coleman, J. W. Grisham, P. A. W. Anderson, and N. N. Malouf Mechanisms controlling the acquisition of a cardiac phenotype by liver stem cells PNAS, March 6, 2007; 104(10): 3877 - 3882. [Abstract] [Full Text] [PDF] |
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N. Tran, P. R. Franken, F. Maskali, J. Nloga, P. Maureira, S. Poussier, F. Groubatch, C. Vanhove, J.-P. Villemot, and P.-Y. Marie Intramyocardial Implantation of Bone Marrow-Derived Stem Cells Enhances Perfusion in Chronic Myocardial Infarction: Dependency on Initial Perfusion Depth and Follow-up Assessed by Gated Pinhole SPECT J. Nucl. Med., March 1, 2007; 48(3): 405 - 412. [Abstract] [Full Text] [PDF] |
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M. Serafini, S. J. Dylla, M. Oki, Y. Heremans, J. Tolar, Y. Jiang, S. M. Buckley, B. Pelacho, T. C. Burns, S. Frommer, et al. Hematopoietic reconstitution by multipotent adult progenitor cells: precursors to long-term hematopoietic stem cells J. Exp. Med., January 22, 2007; 204(1): 129 - 139. [Abstract] [Full Text] [PDF] |
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A. D. Moelker, T. Baks, E.J. van den Bos, R.J. van Geuns, P.J. de Feyter, D. J. Duncker, and W.J. van der Giessen Reduction in infarct size, but no functional improvement after bone marrow cell administration in a porcine model of reperfused myocardial infarction Eur. Heart J., December 2, 2006; 27(24): 3057 - 3064. [Abstract] [Full Text] [PDF] |
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M. Xiang, J. Wang, E. Kaplan, P. Oettgen, L. Lipsitz, J. P. Morgan, and J.-Y. Min Antiapoptotic Effect of Implanted Embryonic Stem Cell-Derived Early-Differentiated Cells in Aging Rats After Myocardial Infarction J. Gerontol. A Biol. Sci. Med. Sci., December 1, 2006; 61(12): 1219 - 1227. [Abstract] [Full Text] [PDF] |
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L. C. Amado, K. H. Schuleri, A. P. Saliaris, A. J. Boyle, R. Helm, B. Oskouei, M. Centola, V. Eneboe, R. Young, J. A.C. Lima, et al. Multimodality Noninvasive Imaging Demonstrates In Vivo Cardiac Regeneration After Mesenchymal Stem Cell Therapy J. Am. Coll. Cardiol., November 21, 2006; 48(10): 2116 - 2124. [Abstract] [Full Text] [PDF] |
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K. H. Wu, Y. L. Liu, B. Zhou, and Z. C. Han Cellular therapy and myocardial tissue engineering: the role of adult stem and progenitor cells Eur. J. Cardiothorac. Surg., November 1, 2006; 30(5): 770 - 781. [Abstract] [Full Text] [PDF] |
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C. Kubal, K. Sheth, B. Nadal-Ginard, and M. Galinanes Bone marrow cells have a potent anti-ischemic effect against myocardial cell death in humans. J. Thorac. Cardiovasc. Surg., November 1, 2006; 132(5): 1112 - 1118. [Abstract] [Full Text] [PDF] |
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C.-H. Wang, N. Anderson, S.-H. Li, P. E. Szmitko, W.-J. Cherng, P. W.M. Fedak, S. Fazel, R.-K. Li, T. M. Yau, R. D. Weisel, et al. Stem Cell Factor Deficiency Is Vasculoprotective: Unraveling a New Therapeutic Potential of Imatinib Mesylate Circ. Res., September 15, 2006; 99(6): 617 - 625. [Abstract] [Full Text] [PDF] |
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H. Mollmann, H. M. Nef, S. Kostin, C. von Kalle, I. Pilz, M. Weber, J. Schaper, C. W. Hamm, and A. Elsasser Bone marrow-derived cells contribute to infarct remodelling Cardiovasc Res, September 1, 2006; 71(4): 661 - 671. [Abstract] [Full Text] [PDF] |
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M. Hendrikx, K. Hensen, C. Clijsters, H. Jongen, R. Koninckx, E. Bijnens, M. Ingels, A. Jacobs, R. Geukens, P. Dendale, et al. Recovery of Regional but Not Global Contractile Function by the Direct Intramyocardial Autologous Bone Marrow Transplantation: Results From a Randomized Controlled Clinical Trial Circulation, July 4, 2006; 114(1_suppl): I-101 - I-107. [Abstract] [Full Text] [PDF] |
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P. Anversa, A. Leri, and J. Kajstura Cardiac Regeneration J. Am. Coll. Cardiol., May 2, 2006; 47(9): 1769 - 1776. [Abstract] [Full Text] [PDF] |
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F. Ishikawa, H. Shimazu, L. D. Shultz, M. Fukata, R. Nakamura, B. Lyons, K. Shimoda, S. Shimoda, T. Kanemaru, K.-i. Nakamura, et al. Purified human hematopoietic stem cells contribute to the generation of cardiomyocytes through cell fusion FASEB J, May 1, 2006; 20(7): 950 - 952. [Abstract] [Full Text] [PDF] |
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P. Anversa, J. Kajstura, A. Leri, and R. Bolli Life and Death of Cardiac Stem Cells: A Paradigm Shift in Cardiac Biology Circulation, March 21, 2006; 113(11): 1451 - 1463. [Full Text] [PDF] |
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F. G.P. Welt and D. W. Losordo Cell Therapy for Acute Myocardial Infarction: Curb Your Enthusiasm? Circulation, March 14, 2006; 113(10): 1272 - 1274. [Full Text] [PDF] |
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P. Menasche You Can't Judge a Book by Its Cover Circulation, March 14, 2006; 113(10): 1275 - 1277. [Full Text] [PDF] |
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D. Zohlnhofer, I. Ott, J. Mehilli, K. Schomig, F. Michalk, T. Ibrahim, G. Meisetschlager, J. von Wedel, H. Bollwein, M. Seyfarth, et al. Stem Cell Mobilization by Granulocyte Colony-Stimulating Factor in Patients With Acute Myocardial Infarction: A Randomized Controlled Trial JAMA, March 1, 2006; 295(9): 1003 - 1010. [Abstract] [Full Text] [PDF] |
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S. P. Raikwar, T. Mueller, and N. Zavazava Strategies for Developing Therapeutic Application of Human Embryonic Stem Cells Physiology, February 1, 2006; 21(1): 19 - 28. [Abstract] [Full Text] [PDF] |
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Y. Misao, G. Takemura, M. Arai, S. Sato, K. Suzuki, S. Miyata, K.-i. Kosai, S. Minatoguchi, T. Fujiwara, and H. Fujiwara Bone marrow-derived myocyte-like cells and regulation of repair-related cytokines after bone marrow cell transplantation Cardiovasc Res, February 1, 2006; 69(2): 476 - 490. [Abstract] [Full Text] [PDF] |
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J. J. Minguell and A. Erices Mesenchymal Stem Cells and the Treatment of Cardiac Disease Experimental Biology and Medicine, January 1, 2006; 231(1): 39 - 49. [Abstract] [Full Text] [PDF] |
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S. Ausoni, T. Zaglia, A. Dedja, R. Di Lisi, M. Seveso, E. Ancona, G. Thiene, E. Cozzi, and S. Schiaffino Host-derived circulating cells do not significantly contribute to cardiac regeneration in heterotopic rat heart transplants Cardiovasc Res, December 1, 2005; 68(3): 394 - 404. [Abstract] [Full Text] [PDF] |
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F. Mouquet, O. Pfister, M. Jain, A. Oikonomopoulos, S. Ngoy, R. Summer, A. Fine, and R. Liao Restoration of Cardiac Progenitor Cells After Myocardial Infarction by Self-Proliferation and Selective Homing of Bone Marrow-Derived Stem Cells Circ. Res., November 25, 2005; 97(11): 1090 - 1092. [Abstract] [Full Text] [PDF] |
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H. Ince, M. Petzsch, H. D. Kleine, H. Schmidt, T. Rehders, T. Korber, C. Schumichen, M. Freund, and C. A. Nienaber Preservation From Left Ventricular Remodeling by Front-Integrated Revascularization and Stem Cell Liberation in Evolving Acute Myocardial Infarction by Use of Granulocyte-Colony-Stimulating Factor (FIRSTLINE-AMI) Circulation, November 15, 2005; 112(20): 3097 - 3106. [Abstract] [Full Text] [PDF] |
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B. E. Strauer, M. Brehm, T. Zeus, T. Bartsch, C. Schannwell, C. Antke, R. V. Sorg, G. Kogler, P. Wernet, H.-W. Muller, et al. Regeneration of Human Infarcted Heart Muscle by Intracoronary Autologous Bone Marrow Cell Transplantation in Chronic Coronary Artery Disease: The IACT Study J. Am. Coll. Cardiol., November 1, 2005; 46(9): 1651 - 1658. [Abstract] [Full Text] [PDF] |
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V. J. Dzau, M. Gnecchi, and A. S. Pachori Enhancing Stem Cell Therapy Through Genetic Modification J. Am. Coll. Cardiol., October 4, 2005; 46(7): 1351 - 1353. [Full Text] [PDF] |
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A. Leri, J. Kajstura, and P. Anversa Cardiac Stem Cells and Mechanisms of Myocardial Regeneration Physiol Rev, October 1, 2005; 85(4): 1373 - 1416. [Abstract] [Full Text] [PDF] |
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M. L. Springer, R. E. Sievers, M. N. Viswanathan, M. S. Yee, E. Foster, W. Grossman, and Y. Yeghiazarians Closed-chest cell injections into mouse myocardium guided by high-resolution echocardiography Am J Physiol Heart Circ Physiol, September 1, 2005; 289(3): H1307 - H1314. [Abstract] [Full Text] [PDF] |
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A. Linke, P. Muller, D. Nurzynska, C. Casarsa, D. Torella, A. Nascimbene, C. Castaldo, S. Cascapera, M. Bohm, F. Quaini, et al. Stem cells in the dog heart are self-renewing, clonogenic, and multipotent and regenerate infarcted myocardium, improving cardiac function PNAS, June 21, 2005; 102(25): 8966 - 8971. [Abstract] [Full Text] [PDF] |
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A. Leri, J. Kajstura, and P. Anversa Identity Deception: Not a Crime for a Stem Cell Physiology, June 1, 2005; 20(3): 162 - 168. [Abstract] [Full Text] [PDF] |
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S. Fazel, G. H.L. Tang, D. Angoulvant, M. Cimini, R. D. Weisel, R.-K. Li, and T. M. Yau Current Status of Cellular Therapy for Ischemic Heart Disease Ann. Thorac. Surg., June 1, 2005; 79(6): S2238 - S2247. [Abstract] [Full Text] [PDF] |
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F. P. Limbourg and H. Drexler Bone Marrow Stem Cells for Myocardial Infarction: Effector or Mediator? Circ. Res., January 7, 2005; 96(1): 6 - 8. [Full Text] [PDF] |
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