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- Sandstedt, Joakim, et al.
(author)
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Left atrium of the human adult heart contains a population of side population cells.
- 2012
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In: Basic research in cardiology. - : Springer Science and Business Media LLC. - 1435-1803 .- 0300-8428. ; 107:2
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Journal article (peer-reviewed)abstract
- Cardiac "side population" (SP) cells have previously been found to differentiate into both endothelial cells and cardiomyocytes in mice and rats, but there are no data on SP cells in the human adult heart. Therefore, human cardiac atrial biopsies were dissociated, stained for SP cells and analyzed with FACS. Identified cell populations were analyzed for gene expression by quantitative real-time PCR and subjected to in vitro differentiation. Only biopsies from the left atrium contained a clearly distinguishable population of SP cells (0.22±0.08%). The SP population was reduced by co-incubation with MDR1 inhibitor Verapamil, while the ABCG2 inhibitor FTC failed to decrease the number of SP cells. When the gene expression was analyzed, SP cells were found to express significantly more MDR1 than non-SP cells. For ABCG2, there was no detectable difference. SP cells also expressed more of the stem cell-associated markers C-KIT and OCT-4 than non-SP cells. On the other hand, no significant difference in the expression of endothelial and cardiac genes could be detected. SP cells were further subdivided based on CD45 expression. The CD45-SP population showed evidence of endothelial commitment at gene expression level. In conclusion, the results show that a SP population of cells is present also in the human adult heart.
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| 2. |
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| 3. |
- Sandstedt, Joakim, et al.
(author)
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C-kit+ CD45- cells found in the adult human heart represent a population of endothelial progenitor cells.
- 2010
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In: Basic research in cardiology. - : Springer Science and Business Media LLC. - 1435-1803 .- 0300-8428. ; 105:4, s. 545-56
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Journal article (peer-reviewed)abstract
- Although numerous reports support the existence of stem cells in the adult heart, few studies have been conducted using human cardiac tissue. Therefore, cells from human cardiac atrial biopsies were analyzed regarding progenitor properties. Expression of stem cell markers was analyzed using fluorescence-activated cell sorting. This identified a small population of C-kit+ cells, which could be further subdivided based on expression of CD45. The C-kit+ CD45+ population was determined to be of mast cell identity, while the C-kit+ CD45- population expressed mRNA of the endothelial lineage. Since the number of cells obtainable from biopsies was limited, a comparison between directly isolated and monolayer and explant cultured cells, respectively, was carried out. While both cultures retained a small population of mast cells, only monolayer culture produced a stable and relatively high percentage of C-kit+ CD45- cells. This population was found to co-express endothelial progenitor cell markers such as CD31, CD34, CXCR4, and FLK-1. The mRNA expression profile was similar to the one from directly isolated cells. When sorted cells were cultured in endothelial differentiation medium, the C-kit+ CD45- population retained its expression of endothelial markers to a large extent, but downregulated progenitor markers, indicating further differentiation into endothelial cells. We have confirmed that the human cardiac atrium contains a small C-kit+ CD45- population expressing markers commonly found on endothelial progenitor cells. The existence of an endothelial progenitor population within the heart might have future implications for developing methods of inducing neovascularization after myocardial infarction.
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| 5. |
- Sandstedt, Joakim, et al.
(author)
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Human C-kit+CD45- cardiac stem cells are heterogeneous and display both cardiac and endothelial commitment by single-cell qPCR analysis.
- 2014
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In: Biochemical and biophysical research communications. - : Elsevier BV. - 1090-2104 .- 0006-291X. ; 443:1, s. 234-238
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Journal article (peer-reviewed)abstract
- C-kit expressing cardiac stem cells have been described as multipotent. We have previously identified human cardiac C-kit+CD45- cells, but only found evidence of endothelial commitment. A small cardiac committed subpopulation within the C-kit+CD45- population might however be present. To investigate this at single-cell level, right and left atrial biopsies were dissociated and analyzed by FACS. Only right atrial biopsies contained a clearly distinguishable C-kit+CD45- population, which was single-cell sorted for qPCR. A minor portion of the sorted cells (1.1%) expressed early cardiac gene NKX2.5 while most of the cells (81%) expressed late endothelial gene VWF. VWF- cells were analyzed for a wider panel of genes. One group of these cells expressed endothelial genes (FLK-1, CD31) while another group expressed late cardiac genes (TNNT2, ACTC1). In conclusion, human C-kit+CD45- cells were predominantly localized to the right atrium. While most of these cells expressed endothelial genes, a minor portion expressed cardiac genes.
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| 6. |
- Sandstedt, Joakim
(author)
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Identification and characterization of progenitor populations in the human adult heart
- 2014
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Doctoral thesis (other academic/artistic)abstract
- Traditionally, the heart has been regarded as a non-regenerative organ. During the last 10 years, this notion has been challenged. By 14C measurements, it was calculated that at the age of 50, about 45% of all cardiomyocytes had formed after birth. An endogenous population of progenitor cells in the heart has been suggested as the source of this regeneration. Until now, most studies have however been conducted in animal models which may not fully reflect the human situation. The overall aim of this thesis was to add to our knowledge of the identity, distribution and function of endogenous progenitor cells in the human adult heart. In paper I, a small population of C-kit+ cells was identified, that could be sub-divided based on expression of the hematopoietic marker CD45. The C-kit+CD45+ population was determined to be of mast cell phenotype whereas the C-kit+CD45- population expressed endothelial associated markers. Differentiation assays showed further endothelial maturation but no evidence of cardiac differentiation. In paper II, heterogeneity within the C-kit+CD45- population was further investigated by single cell qPCR. The results indicated that while most of the C-kit+CD45- cells were committed to the endothelial lineage, a minor portion of them could represent cardiac progenitors. In paper III, Side Population (SP) cells were identified in the left atrium. The SP phenotype was linked to the MDR1 protein. On gene expression level, the SP cells expressed high levels of MDR1 as well as stem cell associated genes C-KIT and OCT-4. Furthermore, the SP could be subdivided based on expression of the hematopoietic marker CD45. The CD45- SP cells had an endothelial profile while the CD45+ SP cells were neither committed to the endothelial, nor the cardiomyogenic lineage. In paper IV, expression of SSEA-1, 3 and 4 was investigated. All SSEAs were expressed at variable levels. The SSEA-1+ population was determined to be of hematopoietic origin. Of the SSEA-4+ cells, some co-expressed CD34. In right atrium, the SSEA-4+CD34- population displayed a high expression of cardiomyocyte genes. By immunohistochemistry, SSEA-4+ cells were identified both within and outside the myocardium. In conclusions, in the present thesis, three different cell populations with characteristics were isolated from human cardiac biopsy material. One C-kit+CD45- population that consisted of both endothelial and cardiac committed progenitors. SP cells where the CD45- fraction showed evidence of endothelial commitment and SSEA-4+CD34- cells that showed signs of cardiac commitment.
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| 7. |
- Sandstedt, Joakim, et al.
(author)
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SSEA-4+ CD34- Cells in the Adult Human Heart Show the Molecular Characteristics of a Novel Cardiomyocyte Progenitor Population.
- 2014
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In: Cells, tissues, organs. - : S. Karger AG. - 1422-6421 .- 1422-6405. ; 199:2-3, s. 103-116
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Journal article (peer-reviewed)abstract
- Stage-specific embryonic antigen (SSEA) expression is used to describe the differentiation state of an embryonic stem cell (ESC). In human ESCs, SSEA-3 and SSEA-4 are highly expressed in undifferentiated cells and downregulated upon differentiation. SSEA-4 has also been described as a marker for adult stem cells in various tissues, including human neonatal cardiac tissue. However, there is currently little data on the expression of SSEAs in human adult cardiac tissue. We obtained right and left atrial biopsies from patients undergoing cardiac surgery. These were dissociated, stained for SSEAs and other cardiac stem cell markers and analyzed by flow cytometry. Directly isolated cells expressed variable levels of SSEA-1, SSEA-3 and SSEA-4. The SSEA-1+ population was established as contaminating hematopoietic cells. The SSEA-4+ population, on the other hand, could be subdivided based on the endothelial progenitor marker CD34. The SSEA-4+ CD34- population in the right atrium had a high gene expression of both early (TBX5, NKX2.5) and late (TNNT2) cardiomyocyte markers. The SSEA-4+ CD34+ population, on the other hand, overlapped with previously described C-kit+ CD45- cardiac stem cells. Primary monolayer-cultured cells retained expression of SSEAs while the cardiomyogenic specification in the SSEA-4+ CD34- population was lost. In tissue sections, SSEA-4+ cells could be identified both within and outside the myocardium. Within the myocardium, some SSEA-4+ cells coexpressed cardiomyogenic markers. In conclusion, the results show that the adult human heart expresses SSEAs and that there is a subpopulation of SSEA-4+ CD34- cells that show features of a cardiomyocyte progenitor population. © 2014 S. Karger AG, Basel.
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