[雙語翻譯]--醫(yī)學(xué)外文翻譯--心臟衰竭末期的心肌細(xì)胞再生（英文）

1、Proc. Natl. Acad. Sci. USA Vol. 95, pp. 8801–8805, July 1998 Medical SciencesMyocyte proliferation in end-stage cardiac failure in humans(mitotic index?cytokinesis)JAN KAJSTURA*?, ANNAROSA LERI*, NICOLETTA FINATO?, CARLA

2、 DI LORETO?, CARLO A. BELTRAMI?,AND PIERO ANVERSA**Department of Medicine, New York Medical College, Valhalla, NY 10595; and ?Department of Pathology, University of Udine 33100, Udine, ItalyCommunicated by Eugene Braunwa

3、ld, Partners HealthCare System, Inc., Boston, MA, May 18, 1998 (received for review January 14, 1998)ABSTRACT Introduced several decades ago, the dogma persists that cardiac myocytes are terminally differentiated cells a

4、nd that division of muscle cells is impossible in the adult heart. More recently, nuclear mitotic divisions in myocytes occasionally were seen, but those observations were challenged on the as- sumption that the rate of

5、cell proliferation was inconsequential for actual tissue regeneration. Moreover, mitoses were never detected in normal myocardium. However, the analysis of routine histologic preparations constituted the basis for the be

6、lief that myocytes were unable to reenter the cell cycle and divide, ignoring the limitations of these techniques. We report here by confocal microscopy that 14 myocytes per million were in mitosis in control human heart

7、s. A nearly 10-fold increase in this parameter was measured in end-stage ischemic heart disease (152 myocytes per million) and in idiopathic dilated cardiomy- opathy (131 myocytes per million). Because the left ventricle

8、 contains 5.8 ? 109 myocytes, these mitotic indices imply that 81.2 ? 103, 882 ? 103, and 760 ? 103 myocytes were in mitosis in the entire ventricular myocardium of control hearts and hearts affected by ischemic and idio

9、pathic dilated cardiomyop- athy, respectively. Additionally, mitosis lasts less than 1 hr, suggesting that large numbers of myocytes can be formed in the nonpathologic and pathologic heart with time. Evidence of cytokine

10、sis in myocytes was obtained, providing unequivocal proof of myocyte proliferation.It is a general contention that cardiac myocytes are unable to divide in the adult heart (1, 2). However, quantitative results suggest th

11、at an increase in myocyte number occurs with severe myocardial hypertrophy (3, 4), but because mitoses in myocytes were not identified, this deficiency led to disbelief of these morphometric results. The occasional detec

12、tion of nuclear mitotic divisions in the pathologic heart (5, 6), was considered of no value in terms of actual regeneration of myocardial mass. Additionally, mitoses were never observed in control myocar- dium. Similarl

13、y, documentation of cytokinesis in myocytes was lacking. Ischemic and idiopathic dilated cardiomyopathies in humans are characterized structurally by severe myocardial scarring consisting of multiple sites of replacement

14、 fibrosis and diffuse interstitial fibrosis (7–10). Moreover, areas of segmen- tal fibrosis are present in all cases of ischemic myopathies (7, 9). Segmental, replacement, and interstitial fibrosis are the consequence of

15、 myocyte necrosis. However, a discrepancy exists between the extensive collagen accumulation and the modest reduction in the number of ventricular myocytes in the postinfarcted human heart (9). The deposition of 1 mm3 of

16、 collagen reflects the loss of 50 ? 103 muscle cells (11), and the magnitude of fibrosis in end-stage ischemic cardiomyopathy would imply a nearly 90% decrease in the total number of left ventricular myocytes (9). Conver

17、sely, decreases of less than30% have been reported (9). This discrepancy is even more apparent in idiopathic dilated cardiomyopathy in which myo- cardial fibrosis is associated with preservation of the number of myocytes

18、 in the ventricles (10). Understanding of the cellular basis of wall restructuring in the diseased heart is complicated further by the documentation that programmed myocyte cell death occurs with ventricular decom- pensa

19、tion (12, 13). Apoptosis does not result in tissue fibrosis; dying myocytes are removed from neighboring cells in the ab- sence of an inflammatory reaction (14). These phenomena, indicating severe ongoing necrotic and ap

20、optotic myocyte death, point to the possibility that myocytes are not terminally differ- entiated and cell proliferation may be stimulated in the pathologic heart. Immunocytochemistry and confocal microscopy were used he

21、re to measure a mitotic index in myocytes of hearts obtained from patients undergoing cardiac transplantation as a result of chronic ischemic heart disease and dilated cardiomyopathy. Hearts collected at autopsy were use

22、d as controls.MATERIALS AND METHODSCardiac Characteristics. Twenty-seven patients undergoing cardiac transplantation, 12 for ischemic and 15 for idiopathic dilated cardiomyopathy, were studied. The first group included 1

23、1 males and one female, with an average age of 52 ? 9 years, and the second 11 males and four females, with an average age of 55 ? 11 years. Nine control hearts, seven males and two females, with an average age of 48 ? 1

24、5 years, were collected at autopsy within 15 hr after death; death occurred from causes other than cardiovascular disease. Mitotic Index. In the 27 explanted and nine control hearts, specimens comprising the entire thick

25、ness of the anterior and posterior aspects of the left ventricular wall were obtained halfway between the apex and the base of the heart. Samples were fixed in formalin and embedded in paraffin. Sections were stained wit

26、h propidium iodide (20 ?g?ml) and ?-sarco- meric actin antibody (clone 5C5, Sigma) to visualize DNA and myofibrillar structures. These sections were examined by con- focal microscopy (MRC-1000, Bio-Rad) with an optical s

27、ec- tion thickness of 0.57 ?m. The percentage of myocyte nuclei undergoing mitosis was obtained by sampling a number of myocyte nuclei, varying from 12,000 to 67,000. Values in control hearts were 75,000 and 230,000. The

28、 evaluation of a mitotic index in interstitial cells included seven cases with ischemic cardiomyopathy, five with dilated cardiomyopathy, and four control hearts. In each pathologic and normal heart 30,000 and 100,000 nu

29、clei were sampled, respectively. Data Collection and Analysis. Results are presented as mean ? SD. Significance between two measurements was determined by the Student’s t test, and in multiple comparisons was evaluated b

30、y the Bonferroni method (15). P ? 0.05 was considered significant. The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked ‘‘a(chǎn)dvertisement’’ in acc

31、ordance with 18 U.S.C. §1734 solely to indicate this fact.© 1998 by The National Academy of Sciences 0027-8424?98?958801-5$2.00?0 PNAS is available online at http:??www.pnas.org.?To whom reprint requests should

32、 be addressed at: Department of Medicine, Vosburgh Pavilion, Room 302, New York Medical College, Valhalla, NY 10595.8801RESULTSPatients. All patients had New York Heart Association functional class III or IV. Left and ri

33、ght ventricular weights were 189 ? 26 and 62 ? 18 g, respectively, in controls, 281 ? 51 and 110 ? 33 g, respectively, in ischemic cardiomyopathy, and 362 ? 129 and 96 ? 36 g, respectively, in dilated cardiomyopathy. The

34、 49% (P ? 0.05) and 92% (P ? 0.001) increase in left ventricular weight, and 77% (P ? 0.01) and 55% (P ? 0.05) increase in right ventricular weight with ischemic and dilated cardiomyopathy, respectively, were sig- nifica

35、nt. Tissue sampling of the left ventricle was restricted to regions in which areas of scarring were not macroscopically visible. However, small foci of replacement fibrosis and diffuse interstitial fibrosis were present

36、in the tissue sections from pathologic hearts. Areas of reparative and interstitial fibrosis occasionally were seen in the left ventricle of control hearts. Confocal Microscopy. Sections of myocardium were labeled with p

37、ropidium iodide and ?-sarcomeric actin antibody; this antibody is specific for I bands of cardiac and skeletal muscle cells and does not react with other actin isoforms (16). Confocal microscopy allowed an accurate ident

38、ification of mitosis in myocytes. Chromosomes were depicted by the green color assigned to propidium iodide fluorescence, and myofi- brillar structures were recognized by the red color assigned to the fluorescence of ?-s

39、arcomeric actin antibody labeling. Fig. 1 A–C illustrates a nucleus in mitosis and two daughter cells at the completion of cytokinesis in a patient affected by dilated cardiomyopathy. In this latter example, the aggregat

40、es of chromosomes mirror each other in the two newly generated myocytes. Fig. 1E shows a late prophase that is characterized by the preservation of nuclear shape in the absence of nuclear membrane. Two more myocyte nucle

41、i exhibiting metaphase chromosomes are depicted in Fig. 1 D and F. The initial separation of chromosomes in Fig. 1D may correspond to late metaphase or onset of anaphase. These three mitotic figures were found in a case

42、of ischemic cardiomyopathy, dilated cardiomyopathy, and a control heart, respectively. A mitotic image in an interstitial cell and three additional mitoses in myocytes are depicted in Fig. 1 G–L. Undifferentiated cyto- p

43、lasm surrounding the nucleus undergoing division (Fig. 1I) was observed in 52% of the cases (74 of 142). Organelles break up into small fragments to allow more uniform distribution of these components in the two daughter

44、 cells. The distinction between myocyte and nonmyocyte nuclei was extremely sim- ple, because interstitial cells were not stained by ?-sarcomeric actin antibody and only the nucleus could be identified by propidium iodid

45、e staining (Fig. 1 G, H, and J–L). This was apparent in nondividing and dividing interstitial cells (Fig. 1G). There was no apparent difference in the localization of mitoses in the anterior and posterior aspects of the

46、left ventricle in control and pathologic hearts. The average area of myocardium examined by confocal microscopy in each patient was 609 ? 240 mm2 in controls, 327 ? 193 mm2 in ischemic cardiomyopathy, and 341 ? 194 mm2 i

47、n dilated cardiomyopathy. Corresponding numbers ofmyocyte nuclei counted were 141,136 ? 56,699, 38,854 ? 16,766, and 36,013 ? 17,134. Values for myocyte mitotic figures were 1.8 ? 0.6, 5.1 ? 3.5, and 4.3 ? 2.0, respectiv

48、ely. These data allowed the computation of a myocyte mitotic index in each group (Fig. 2). In normal left ventricles, an average of 14 myocytes per million cells were undergoing mitosis, but a much higher mitotic index w

49、as measured in pathologic hearts. In ischemic cardiomyopathy, 152 myocytes per million were dividing, and in dilated cardiomyopathy, 131 myocytes per million were in mitosis. The small difference between the two groups o

50、f patients with cardiac failure was not significant, yielding an average value of 140 proliferating myocytes per million cells. In comparison with healthy myo- cardium, cardiac failure was characterized by a 10-fold incr

51、ease in the number of dividing myocytes (P ? 0.0001). No gender difference in this parameter could be detected. The mitotic index in interstitial cells was 18 ? 13 per million cells in controls (n ? 4) and 106 ? 42 per m

52、illion cells in failing hearts (n ? 12; seven ischemic and five idiopathic myopathies). With respect to myocytes (140 ? 50; n ? 27), the 24% lower value in interstitial cells was not significant.DISCUSSIONCardiac Hypertr

53、ophy. In the early 1920s, anatomical studies emphasized the difficulties of detecting mitotic figures in myocytes and, on this basis, introduced the concept that muscle cell proliferation is absent in the adult, fully di

54、fferentiated, mammalian myocardium (1). Moreover, experimental results of acute cardiac hypertrophy in rodents demonstrated the inability of myocytes to reenter the cell cycle, synthesize DNA, and undergo mitotic divisio

55、n (17–19). These observations were responsible for the creation of the dogma that, shortly after birth, ventricular myocytes withdraw permanently from the cell cycle and are destined to die without further replication. S

56、uch a contention was challenged by the morphometric find- ings of Linzbach in the mid-1950s, suggesting that myocyteFIG. 2. Mitotic index in myocytes from control hearts (Controls), and hearts affected by ischemic cardio

57、myopathy (IC) and idiopathic dilated cardiomyopathy (IDC). Results are presented as means ? SD. ?, P ? 0.00l. Controls: n ? 9; IC, n ? 12; IDC, n ? l5.FIG. 1. (On the opposite page) Left ventricular myocardial section of

58、 a patient affected by end-stage dilated cardiomyopathy. Large field area illustrated by propidium iodide labeling only (green; A) and by a combination of propidium iodide and ?-sarcomeric actin staining of the myocyte c

59、ytoplasm (red; B). Arrowhead indicates a myocyte nucleus in metaphase, and arrows indicate a myocyte at completion of cytokinesis. Myocyte cytokinesis is shown at higher magnification in C by a combination of propidium i

60、odide and ?-sarcomeric actin antibody staining (green and red, respectively). (D–F) Three mitotic figures in the center of myocytes corresponding to a patient with ischemic cardiomyopathy (D), dilated cardiomyopathy (E),

61、 and control left ventricle (F). Staining in D–F consists of a combination of propidium iodide and ?-sarcomeric actin antibody. The punctate red staining in D corresponds to lipofuscin. (G) Two interstitial cell nuclei (

62、arrow and arrowhead) (green), one of which is in mitosis (arrowhead). The cytoplasm of these nonmyocytes is not visible because it is not stained by ?-sarcomeric actin antibody. (H) A mitotic figure in a myocyte from a p

63、atient with dilated myopathy is apparent (arrowhead); two interstitial cell nuclei (green) also are noted (arrows). These interstitial cells are not ?-sarcomeric actin positive. (I) A mitotic figure in a center of a myoc

64、yte in which a large area of undifferentiated cytoplasm (negative to ?-sarcomeric actin staining) surrounds the dividing nucleus is illustrated (patient with ischemic cardiomyopathy). (J–L) Patient with dilated cardiomyo

65、pathy. Two nuclei by propidium iodide (J, green), myocyte cytoplasm labeled by ?-sarcomeric actin (K, red), and a combination of these two images (L). Note the myocyte nucleus in late telophase (arrows) and the nondividi

66、ng interstitial cell nucleus (arrowheads). Magnifications: (A and B) ?700; (C) ?1,300; (D) ?2,700; (E, F, H, and I) ?1,500; (G) ?1,200; (J–L) ?1,600.Medical Sciences: Kajstura et al. Proc. Natl. Acad. Sci. USA 95 (1998)