Edited by: Elena G. Pasyukova, Institute of Molecular Genetics (RAS), Russia
Reviewed by: Federico Quaini, Università degli Studi di Parma, Italy; Georgina May Ellison-Hughes, King's College London, United Kingdom
*Correspondence: Shibashish Giri
Augustinus Bader
This article was submitted to Genetics of Aging, a section of the journal Frontiers in Genetics
†These authors have contributed equally to this work.
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We aimed to identify and quantify CD117+ and CD90+ endogenous cardiac progenitor cells (CPC) in human healthy and diseased hearts. We hypothesize that these cells perform a locally acting, contributing function in overcoming medical conditions of the heart by endogenous means. Human myocardium biopsies were obtained from 23 patients with the following diagnoses: Dilatative cardiomyopathy (DCM), ischemic cardiomyopathy (ICM), myocarditis, and controls from healthy cardiac patients. High-resolution scanning microscopy of the whole slide enabled a computer-based immunohistochemical quantification of CD117 and CD90. Those signals were evaluated by Definiens Tissue Phenomics® Technology. Co-localization of CD117 and CD90 was determined by analyzing comparable serial sections. CD117+/CD90+ cardiac cells were detected in all biopsies. The highest expression of CD90 was revealed in the myocarditis group. CD117 was significantly higher in all patient groups, compared to healthy specimens (*
The World Health Organization reports cardiovascular diseases as the main cause of 29% of global death each year (Lozano et al.,
Due to the profound importance of cardiovascular diseases, the natural endogenous regenerative capacity of the human heart has been a topic of debate for decades. Accumulating evidence over the last decade has suggested that the human heart has the potential to undergo natural regeneration. Locally resident cardiac progenitor or stem cells might play a vital role toward the natural regeneration capacity of the heart. Myocyte proliferation happens to a low extent in the human heart, while enhanced proliferation was observed following injuries of the heart such as myocardial infarction (Beltrami et al.,
Of particular interest are cells with the c-Kit receptor (CD117 or SCFR-stem cell factor receptor) on the surface. Beltrami and colleagues reported the existence of CD117+ cells with characteristics of CPCs (Beltrami et al.,
Nurzynska and colleagues conducted a comparative study of human CPCs in normal and pathological conditions (ischemic heart disease) and confirmed that the differentiation potential of CD117+ CPCs of the adult human pathological heart is weak in comparison to healthy cardiac tissue (Nurzynska et al.,
Previous identifications of CD117 and CD90 in human along with patient age, diagnosis, and additional major details.
CD117 | Outflow tract | Aortic stenosis ( |
73 ± 10 71 ± 8 | Formalin-fixed tissue | – | IHC | Increased number of stem-like cells in aortic stenosis | Urbanek et al., |
CD117 | Right ventricle | DCM ( |
73 ± 2 61 ± 4 76 ± 4 | Tissue sections from biopsies with a size of nearly 3 mm3 | – | IHC; Confocal microscopy | Cellular senescence and death of CD117+ cells leads to HF and premature cardiac aging | Chimenti et al., |
CD117 | Left ventricular wall | Acute infarcts ( |
62 ± 13 56 ± 7 60 ± 20 | Formalin-fixed tissue | – | IHC | Increased number of CPCs in acute and chronic infarcts | Urbanek et al., |
CD117 | Right ventricle; Right atrial appendage | Heart transplant recipients ( |
45.8 ± 11 65.3 ± 8.1 | Formalin-fixed, paraffin-embedded tissue; Culture of right atrial appendage specimens | IHC; Immuno-fluorescence; Confocal laser microscopy; Flow cytometry | Higher number of CD117+ cells in right ventricle than in atrial appendage; small number of CD117+ cells in cultured right atrial appendages | Pouly et al., |
|
CD117 | Right + left ventricle; Left atrium; Left atrio-ventricular junction; Apex | End-stage HF with ICM ( |
55 ± 5.5 41 ± 12 | Formalin-fixed, paraffin-embedded tissue; Isolation and culture from fragments of left ventricular myocardium | Immuno-fluorescence | Increased number of CD117+ cells in ICM; Higher number of CD117+ cells in the atrial subepicardium than in the myocardium | Castaldo et al., |
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CD117 CD90 | Ventricle | Endomyocardial biopsy ( |
Recipients: 52 ± 14 Donors: 32 ± 12 CM: 49 ± 15 | Direct culture and expansion of CPCs from myocardial tissue | IHC; Confocal microscopy; Flow cytometry | Expansion and proliferation of CPCs is simple | Davis et al., |
|
CD117 | Right atrium | Coronary artery disease ( |
38–72 | Culture of biopsy tissue, non-enzymatic isolation of CSCs | Flow cytometry | Number of CSCs is not influenced by disease severity or risk factors for coronary artery disease | Aghila Rani et al., |
|
CD117 | Left ventricular walls | Hearts from patients who died from non-cardiovascular diseases ( |
<1–75 | Formalin-fixed, paraffin-embedded tissue | – | IHC | A subpopulation of CD117+ cardiac cells may be authentic stem/progenitor cells | Zhou et al., |
CD117 | Atrium | Coronary artery disease, Valvular disease, Atrial fibrillation ( |
47–84 | Directly isolated cells, monolayer and explant cultured cells | Flow cytometry; RT-PCR | Number of CD117+ cells in directly isolated cells is lower than in monolayer culture | Sandstedt et al., |
|
CD117 | Atrial appendage; Left ventricle | ICM ( |
55 ± 5.5 41 ± 12 | Formalin-fixed, paraffin-embedded tissue; Epicardial cell culture from fragments of the appendages | IHC; Immuno-fluorescence | Number of CD117+ cells increased in ICM, higher number in epicardium than in myocardium; EDCs partially express CD117 | Di Meglio et al., |
|
CD117 | Left ventricle | Hearts from patients who died from non-cardiovascular diseases (n = 74) | 19–104 | Formalin-fixed, paraffin-embedded tissue | – | ICC; Spectral Analysis | The female myocardium possesses more CSCs and younger myocytes than the male myocardium. | Kajstura et al., |
CD117 CD90 | Atrium | ICM, Idiopathic CM, HCM, Valvular disease, Acromegaly ( |
39–65 45.8 ± 15.7 | Formalin-fixed, paraffin-embedded tissue; Isolation and expansion of CSCs | Flow cytometry; Immunolabeling; RT-PCR; Spectral analysis | Number of CD117+ cells was higher in explanted hearts than in donor hearts | Cesselli et al., |
|
CD117 | Right atrial appendage | Patients with postinfarction LV dysfunction, treated ( |
56 ± 8.8 57.3 ± 8.9 | Isolation, expansion and intracoronary re-infusion of autologous CSCs | Immunolabeling; Confocal microscopy; Flow cytometry | No adverse effects after infusion of CSCs; Improvement in left ventricular systolic function; Increased functional capacity; Reduced left ventricular scar size | Bolli et al., |
|
CD117 | Right atrial appendage | During routine procedure ( |
– | Fixed tissue sections, freshly isolated or cultured CSCs | IHC; ICC; Flow cytometry; RT-PCR | Tissue sections and freshly isolated cells contain CD117 | He et al., |
|
CD117 CD90 | Atrial appendages | Patients undergoing aorto-coronary bypass grafting | – | Atrial appendage tissue specimens and cultured cells | Immuno-fluorescence; Confocal analysis; Flow cytometry; qRT-PCR | CD117+ cardiac progenitors are primitive stem cells with multilineage differentiation potential; Possible relationship between CD117+cells and a heart-specific MSC population | Gambini et al., |
|
CD117 CD90 | Right portion of the septum; Apex of the left ventricle | Patients undergoing cardiac transplantation LVAD implantation ( |
23–67 | Collection and expansion of CSCs | Flow cytometry | Successful isolation and expansion to a clinically relevant number for autologous delivery | D'Amario et al., |
|
CD117 | Left ventricle; Atrial appendages | Patients undergoing cardiac surgery | 67 ± 2 | Isolation of mononuclear cells; Analysis of formalin-fixed, paraffin-embedded tissue | – | Flow cytometry; IHC | Number of CSCs is higher in atria than in left ventricle | Arsalan et al., |
CD117 | Endo-myocardium | Pressure overloaded single right ventricles ( |
<1–19 | Formalin-fixed, paraffin-embedded tissue; | – | IHC; Confocal microscopy | Number of CD117+ cells is increased in human hearts exposed to pressure overload | Rupp et al., |
CD117 | Right and left atrium | Patients undergoing cardiac surgery ( |
32–79 | Isolation and differentiation of side population cells | Flow cytometry; RT-PCR | Identification of side population cells in left atrial biopsies | Sandstedt et al., |
|
CD117 CD90 | Right atrium; Left ventricular epicardium | Chronic IHD ( |
67 ± 2 | Isolation and culture of explant- and CDCs | Flow cytometry; Immuno-fluorescence | No routine culture of CDCs from ventricular epicardial biopsies; atrial and ventricular epicardial CDCs comprise few CD117+ cells & a various number of CD90+ cells | Chan et al., |
|
CD117 | Atrial appendages | Oncologic patients with CHF ( |
53 ± 6 63, 61 50 ± 9 | Isolation and culture of CPCs and treatment with doxorubicin | Immuno-fluorescence | Doxorubicin exposure adversely affects the population of CPCs and their function | Piegari et al., |
|
CD117 | Atrial appendage | Patients with end-stage HF due to ICM undergoing heart transplants ( |
55.8 ± 3.1 50.4 ± 4.1 | Isolation and proliferation of CD117+ cells | Immuno-fluorescence | CD117+ cells do not reach terminal differentiation and functional competence in pathological conditions | Nurzynska et al., |
|
CD117 | Atrium | Patients undergoing CABG surgery ( |
52–65 | Isolation and expansion of CSCs | ICC; Flow cytometry | Characterization of ion-channels in CD117+ cells from all patients | Zhang et al., |
|
CD117 CD90 | Ventricle | DCM; ICM; CHD ( |
<1–59 | Enzymatic processing of heart tissue, Culture and differentiation of cardiospheres | Immuno-fluorescence; Confocal microscopy; Flow Cytometry; RT-PCR | CD117+ cells also expressed CD34, CD90, CD31, or CD144; CD90+ cells expressed mesenchymal cell markers and showed incomplete differentiation into cardiomyocyte—like cells | Gago-Lopez et al., |
|
CD117 CD90 | Right and left ventricle; Intra-ventricular septum, Atrium, Apex | Explanted hearts removed during heart transplant surgery, including IHD, DCM, HCM, congenital heart defect ( |
3–65 | Formalin-fixed, paraffin-embedded tissue; Isolation and primary cardiac cell culture from tissue fragments | IHC; Flow cytometry | Identification of CD117+ cells directly in myocardial tissue and CD117+ and CD90+ cells in cell culture | Matuszczak et al., |
|
CD117 | Appendages | Patients undergoing cardiac surgery ( |
1–78 (55.6 ± 17.0) | Isolation and culture of CSCs | Flow cytometry | The percentage of CD117+ CSCs decreases with age, DM and CHD | Hu et al., |
|
CD117 | Right atrium; Left ventricle | Patients undergoing left ventriculoplasty due to ICM ( |
65.1 ± 9.1 | CSC isolation and culture | ICC; Fluorescent microscopy | Successful preparation of CD117+ CSCs | Hayashi, |
|
CD90 | Atrium | Hypoplastic left heart syndrome ( |
1.8 ± 1.5 | Isolation and expansion of autologous CDCs followed by intracoronary infusion | Flow cytometry | Intracoronary infusion of autologous CDCs is safe and practicable | Ishigami et al., |
|
CD117 | Left ventricle | ICM and end-stage HF submitted to LVAD implantation ( |
– | Formalin-fixed, paraffin-embedded tissue | – | IHC | CSCs are present in left ventricular apical segment of patients with LVAD implantation | Cameli et al., |
CD90 | Right atrium | Patients who underwent heart surgery ( |
2–83 | Isolation and culture of CDCs | Flow cytometry | Age has a limited influence on the quantity and quality of CDCs | Nakamura et al., |
|
CD117 CD90 | Atrial appendage | Patients who underwent CABG surgery | – | Isolation, culture as CDCs, simulation of HR injury | Flow cytometry | CDCs showed expression of CD117 and CD90, CDCs have greater resistance to HR injury compared to MSCs | RajendranNair et al., |
|
CD117 | Right atrium; Left atrium; Left ventricle | Valvular heart diseases ( |
66.1 ± 10.0 | Isolation and culture of CSCs from fresh and frozen tissue | ICC | Cryopreservation has no influence on proliferative potential of CSCs | Hosoda et al., |
|
(Ishigami et al., |
Atrium | Single ventricle physiology ( |
≤20 | Isolation, expansion and intracoronary infusion of autologous CDCs | Flow cytometry | Intracoronary infusion of CDCs improved cardiac function | Ishigami et al., |
|
CD117 CD90 | Right ventricle; Left ventricle; Septum | DCM ( |
DCM: 44 ICM: 58 Myocarditis: 24 Control hearts: 35 (mean values) | Formalin-fixed, paraffin-embedded tissue | – | IHC; Digital image analysis | Identification of CD117+ and CD90+ cells directly in myocardial tissue, CD117 is increased in ICM, DCM and myocarditis in comparison to control hearts | Present study |
Schematic representation of the human heart showing biopsy locations used for previous identifications of CD117 and CD90.
In the current study, we obtained myocardium biopsies from 23 patients with the following diagnoses: dilatative cardiomyopathy (DCM), ICM, myocarditis, and controls from cardiac healthy. The collected material was characterized by immunohistochemistry. Currently, paraffin-based histopathological tissue analysis represents the main conventional method for confirmation of presence or absence of histological markers, grading, or the quantification of stem cells markers in ready tissue sections. Additional quantification of these histopathological slides using an automated image analysis perspective, though providing with more sensitive and qualitative information on the presence of local CPCs in myocardium biopsies, represents a new set of challenges. In our previous studies, we compared immunohistochemical data with an automated image analysis method of digitized slides by Definiens Tissue Studio software (Abraham et al.,
In the present study, we combined a fully automated digital image analysis with conventional histological slides to more sensitively confirm the presence of potential local endogenous CPCs and to perform a quantitative analysis of the cardiac cell signals in human myocardium biopsies from patients with various cardiac diseases.
Ready sections (
Two serial sections of each patient were utilized, one for CD90 staining and the other for CD117 staining, and a partial third one for CD105. The skin specimens were then embedded. The paraffin sections, 8–10 μm in thickness were cut with a rotary microtome (model RM2165; Leica Microsystems). The slides were deparaffinized and rehydrated. Afterwards, cells were blocked with 0.6% H2O2 in phosphate-buffered saline (PBS; pH 7.4) and washed in PBS/0.3% Triton-x. For antigen retrieval, the heat-induced epitope retrieval method was used. The slides were incubated in retrieval solution (10 mM citrate buffer) in a water bath set to 60°C overnight. On day 2, the slides were washed in PBS and blocked for 30 min at room temperature with 5% normal goat serum in PBS. Primary antibodies, in specific, CD90 [anti-CD90/Thy-1 antibody, rabbit monoclonal IgG, clone EPR3133, ab 133350 (dilution 1:100) Abcam Cambridge, UK] and CD117 [anti-c-kit/CD117 antibody, rabbit monoclonal IgG, clone YR145, ab 32363 (dilution 1:50) Abcam Cambridge, UK] were added and incubated overnight at 4°C. All primary antibodies are particularly suitable for immunohistochemistry of paraffin sections (IHC-P). For supplementary investigations, a further primary antibody was applied on an additional serial section [anti-CD105 antibody, rabbit monoclonal IgG, clone EPR10145, ab 169545 (dilution 1:200) Abcam Cambridge, UK]. Negative control staining was performed whereby the primary antibody was omitted. As isotype control served rabbit monoclonal IgG [clone EPR25A, ab172730 (dilution 1:100) Abcam Cambridge, UK]. The images of the positive and negative controls can be found in the
On day 3, the slides were washed in PBS and incubated with the secondary antibody [secondary horseradish peroxidase conjugated goat anti-rabbit IgG (H + L), 111-035-003 (dilution 1:100 in PBS + 1% goat serum + 1% human serum), Dianova Jackson Immuno-research Hamburg, Germany], for 45 min at room temperature, followed by incubation with 3-amino-9-ethyl-carbazole (AEC) in sodium acetate buffer (0.1 mol/L, pH 5.2) containing hydrogen peroxide. After rinsing, the sections were counterstained with hematoxylin Lillie's modification (ready-to-use formulation; DakoCytomation, Copenhagen, Denmark) and mounted in glycergel (Kaiser's glycerol gelatine; Merck KGaA, Darmstadt, Germany).
Scanning of the complete slide was performed by Virtual Microscope Olympus VS 120 (Ruhr-University Bochum Faculty of Medicine, Anatomy and Molecular Embryology). Individual image processing and optimization were performed via cellSens Software (OLYMPUS Germany). Fully automatic image analysis using the Definiens Tissue Phenomics® Technology (DEFINIENS AG, Munich, Germany) and the image analysis platform Developer XD enabled a quantitative image analysis of the whole slide. The analysis was made with the original image files (*vsi), which were created by the Olympus Virtual Slide Microscope using the 20x objective and have a very high resolution until the cellular level. A tailored image analysis solution (rule set) was developed using Definiens AG Software. The rule set separated first foreground (tissue regions) from the background (image regions without tissue) and excluded tissue along the edge to avoid artifacts. In the next step, the solution segmented and classified signals according to their individual morphology and their relative staining intensity. Afterwards, the solution reclassified the signals into two groups: in single signals and concatenated signals. The relative number of CD90+ signals (total number of signals divided by the total area of tissue section), the relative area of CD90+ signals and relative area of CD117+ signals (total area of signals divided by the total area of tissue section) were calculated.
To classify the cells as local progenitor cells, the detection of several stem cell markers was necessary. As we utilized only one antibody per slide, the identification of cells with co-expression of several markers was done through visual comparison of two or rather three serial sections each. A representative field (4 mm2) with high histological quality was chosen to account for the variable size of the tissue samples. The total number of cells, which expressed both stem cell markers, CD90 and CD117, was counted and normalized per square millimeter. This procedure was performed in three examples of each group; the ones that had the best histological quality were chosen.
The data obtained from digital image analysis are best analyzed on the logit scale [logit (
Scanning of the whole slide enabled a detailed view of the tissue sections in entirety and provided the basis for creating new images for the digital image analysis (Figures
Histological and digital images of all tissue sections (
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The digital image analysis facilitated a specialized quantitative analysis of the whole slide to CD90+ and CD117+ signals. The relative
Detailed patient information including biopsy location, diagnosis, and results of the digital image analysis (
Patient 1 | Right ventricle | Healthy | 1,766 | 0.00006964 | 0.00657148 | 0.15489015 |
Patient 2 | Ventricle | Healthy | 986 | 0.00034775 | 0.02691154 | 0.00128155 |
Patient 3 | Ventricle | Healthy | 357 | 0.00003978 | 0.00351804 | 0.02040115 |
Average | 1,036 | 0.00015239 | 0.012333687 | 0.058857617 | ||
Patient 4 | Septum | Myocarditis | 14,493 | 0.00073061 | 0.08861789 | 0.28542232 |
Patient 5 | Septum | Myocarditis | 870 | 0.00004446 | 0.00457649 | 0.60600118 |
Patient 6 | Septum | Myocarditis | 13,860 | 0.00035446 | 0.04414038 | 0.64796254 |
Average | 9,741 | 0.00037651 | 0.045778253 | 0.51312868 | ||
Patient 7 | Septum | ICM | 3,003 | 0.00009935 | 0.00788957 | 0.07027659 |
Patient 8 | Left ventricle | ICM | 7,000 | 0.00021093 | 0.01858989 | 0.01535276 |
Patient 9 | Left ventricle | ICM | 1,562 | 0.00008959 | 0.00703351 | 0.41275665 |
Patient 10 | Septum | ICM | 3,566 | 0.00013633 | 0.01256228 | 0.40487681 |
Patietn 11 | Septum | ICM | 1,230 | 0.00006138 | 0.00538673 | 0.48448345 |
Patient 12 | Septum | ICM | 12,254 | 0.00055332 | 0.04938569 | 0.13488475 |
Patient 13 | Left ventricle | ICM | 1,977 | 0.00008794 | 0.00760771 | 0.48799854 |
Patient 14 | Left ventricle | ICM | 1,190 | 0.0001929 | 0.01611067 | 0.57780017 |
Patient 15 | Left ventricle | ICM | 781 | 0.00003774 | 0.00313921 | 0.41058415 |
Patient 16 | Left ventricle | ICM | 793 | 0.00004349 | 0.00341586 | 0.32906417 |
Average | 3,336 | 0.000151297 | 0.013112112 | 0.332807804 | ||
Patient 17 | Left ventricle | DCM | 1,634 | 0.00005087 | 0.00423627 | 0.15127794 |
Patient 18 | Septum | DCM | 626 | 0.00004535 | 0.00356114 | 0.21075096 |
Patient 19 | Septum | DCM | 4,203 | 0.00022521 | 0.01916202 | 0.45260291 |
Patient 20 | Left ventricle | DCM | 1,388 | 0.00006808 | 0.00492588 | 0.3632407 |
Patient 21 | Septum | DCM | 96 | 0.00000503 | 0.00120728 | 0.36082968 |
Patient 22 | Left ventricle | DCM | 3,251 | 0.00008052 | 0.00644762 | 0.1610318 |
Patient 23 | Septum | DCM | 3,808 | 0.00011138 | 0.00938711 | 0.30622664 |
Average | 2,144 | 8.37771E-05 | 0.006989617 | 0.286565804 |
As CD117 staining included not only individual signals but also larger stained areas, the focus was set on the relative area of CD117+ signals (total area of signals divided by the total area of the tissue section) and not on the number of CD117+ signals (Table
Relative
The co-localized signals were evaluated and counted manually, based on the comparison of the histological images. CD90+ cells, which were co-localized with CD117, were identified in all patient groups (Figure
Coexpression of CD90 and CD117. Two serial sections of the same patient (Patient 4) are stained with different antibodies (
A number of cells with co-expression of CD90 and CD117 per square millimeter (
Co-expression of CD90, CD117, and CD105. Three serial sections of the same patient (Patient 4) are stained with different antibodies: CD90, CD117, and CD105. The circles mark cells, which are positive for all three antibodies.
Numerous stem cell markers were analyzed especially referring to CPCs. In the present study, the focus was mainly set on the co-expression of CD90 and CD117 in the human heart, which was already demonstrated (Gambini et al.,
Moreover, various researchers identified CD117+ cells in human myometrium (Ciontea et al.,
CD117+ local CPCs had already been used for the treatment of heart diseases in both human cases and animal models (Bolli et al.,
In comparison with conventional stem cell therapy, the activation of local endogenous progenitor cells is a holistic approach to both preventing and regulating the heart. We are aware that the characterization of progenitor cells requires the identification of various stem cell markers and it is of high importance to exclude unspecific signals. Here, we analyzed the co-expression of CD117, CD90, and partially CD105, also. Previous studies underline our analyses: Gambini and colleagues demonstrated a co-expression of CD117 and CD90 or rather CD105 in human heart auricle primary cultured cells (Gambini et al.,
Vicinanza et al. also showed that cardiac CD117+/CD45− cells are clonogenic and multipotent, but they determined that >90% of cardiac CD117+ cells contain endothelial cells and their precursors (Vicinanza et al.,
Nevertheless, future experiments with additional stem cell markers are necessary to prove the progenitor cell identity of CD117+ cardiac cells and to exclude unspecific labeling. We identified many CD117+ stained cardiomyocytes, which do not belong to the local progenitor cells. Other researchers studied CD117+ hematopoietic bone marrow cells and their ability to act as cardiac progenitors and to transdifferentiate into cardiomyocytes (Orlic et al.,
In the present study, it was not our purpose to perform a series analysis of cardiac stem cell markers. Rather than that, the present study mainly focuses on investigating the combination of a traditional histological method with a novel digital image analysis technology. This technology enables a quantitative evaluation of two CPC markers in comparison of paraffin–embedded tissue sections of healthy and diseases heart samples. It would be of high interest to complement these experiments with other techniques such as immunofluorescence and high magnification confocal microscopy in the future.
In the present experiment, we identified CD90+ and CD117+ cells in all patient groups: Myocarditis, ICM, DCM, and healthy cardiac patients. With the novel digital image analysis technology, a comparison of differently sized paraffin-embedded tissue sections is available. Taking into consideration that the sample size in the present experiment was limited, we proved an increase of CD90+/CD117+ cells in acute myocarditis. This finding supports our theory that endogenous cardiac stem or progenitor cell activation is part of the repairing mechanism after acute myocardial damage, as in cases of acute myocarditis. A similar inflammation process is described for acute myocardial infarction. Nevertheless, in most cases, acute myocardial infarction leads to the development of a scar. Further studies may show, how an amplification of the local myocardial stem or progenitor cell activation may contribute to the myocardial regeneration and healing process.
This study aimed at the identification and the quantitative analysis of CD90+ and CD117+ cardiac cells from human myocardium biopsies of 23 patients. Besides the conventional histological image analysis, the digital image analysis enabled a computer-based immunohistochemical quantification of some stem cell markers, using whole-slide images created by the virtual slide scanning microscopy. In our experiments, the number of CD90 and CD117 signals in patients with myocarditis was higher than in all other groups. Taking into consideration the regenerative healing potential prospects of myocarditis, it is likely that there is a relation between CD90 and CD117 expression and clinical outcome. Future studies with larger sample size are necessary to confirm that theory. The proof on the existence of endogenous resident progenitor cells not only in the healthy but also in the diseased human heart opens up the promising concept of regeneration instead of repair, which has an impressive scope in treating or preventing cardiovascular diseases.
MG, JS, SE, SG, and AB: conceived and designed the experiments; NS, WM, and JS: organized the human tissue samples; MG and SE: performed the experiments; MG, SE, BB-S, and MA: analyzed the data; MG, JS, SE, SG, AB, and MA: wrote the paper; SG and AB: provided guidance on the whole study.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Maria Athelogou was employed by company Definiens AG, Munich, Germany. All other authors declare no competing interests.
Special thanks are extended to Prof. Dr. med. K. Klingel (Department of Molecular Pathology, University of Tuebingen, Germany) for providing the human endomyocardial biopsies and Prof. Dr. med. Christian Wittekind (Institute of Pathology, University of Leipzig, Germany) for providing human kidney tissue.
The Supplementary Material for this article can be found online at: