ABSTRACT
Side population (SP) cells are an enriched population of stem, and the existence of SP cells has been reported in human cancer cell lines. In this study, we performed an SP analysis using 11 human cancer cell lines and confirmed the presence of SP cells in an embryonic carcinoma cell line, NEC8. NEC8 SP cells showed characteristics of cancer stem cells, such as high growth rate, chemoresistance and high invasiveness. To further characterize the NEC8 SP cells, we used DNA microarrays. Among 38,500 genes, we identified 12 genes that were over-expressed in SP cells and 1 gene that was over-expressed in non-SP cells. Among these 13 genes, we focused on GADD45b. GADD45b was over-expressed in non-SP cells, but the inhibition of GADD45b had no effect on non-SP cells. Paradoxically, the inhibition of GADD45b significantly reduced the viability of NEC8 SP cells. The inhibition of ABCG2, which determines the SP phenotype, had no effect on the invasiveness of NEC8 SP cells, but the inhibition of GADD45b significantly reduced invasiveness. These results suggest that GADD45b, but not ABCG2, might determine the cancer stem cell-like phenotype, such as chemoresistance and the high invasiveness of NEC8 SP cells, and might be a good therapeutic target.
ABSTRACT
The existence of adult stem-like cells such as side population (SP) cells is reported in various kinds of animal tissues, and we recently reported that mice kidney SP cells differentiate into multilineage. However, there has thus far been no report about human kidney SP cells. In the present study, we examined the existence of SP cells in human kidney tissue by using Hoechst 33342 staining and fluorescence-activated cell sorting analysis. We used porcine kidney tissue to optimize the analysis conditions for human tissue, and found that the SP population in human kidney was 1.3%. The existence of SP cells in human kidney suggests that the cells could be good targets for clinical renal regenerative medicine.
Subject(s)
Cell Separation , Flow Cytometry , Kidney/cytology , Stem Cells , Adult , Aged , Animals , Female , Humans , Male , Middle Aged , SwineABSTRACT
Bone morphogenic protein (BMP)-7 is expressed in the adult kidney and reverses chronic renal injury when given exogenously. Here, we report that a histone deacetylase inhibitor, trichostatin A (TSA), attenuates chronic renal injury, in part, by augmenting the expression of BMP-7 in kidney side population (SP) cells. We induced accelerated nephrotoxic serum nephritis (NTN) in C57BL/6 mice and treated them with TSA for 3 weeks. Compared with vehicle-treated NTN mice, treatment with TSA prevented the progression of proteinuria, glomerulosclerosis, interstitial fibrosis, and loss of kidney SP cells. Basal gene expression of renoprotective factors such as BMP-7, vascular endothelial growth factor, and hepatocyte growth factor was significantly higher in kidney SP cells as compared with non-SP cells. Treatment with TSA significantly upregulated the expression of BMP-7 in SP cells but not in non-SP cells. Moreover, initiation of treatment with TSA after 3 weeks of NTN (for 3 weeks, until 6 weeks) partially but significantly reversed renal dysfunction. Our results indicate an important role of SP cells in the kidney as one of the possible generator cells of BMP-7 and TSA as a stimulator of the cells in reversing chronic renal disease. Disclosure of potential conflicts of interest is found at the end of this article.
Subject(s)
Glomerulonephritis/drug therapy , Glomerulosclerosis, Focal Segmental/drug therapy , Hematopoietic Stem Cells/drug effects , Histone Deacetylase Inhibitors , Hydroxamic Acids/pharmacology , Kidney/cytology , Multipotent Stem Cells/drug effects , Acetylation/drug effects , Animals , Basic Helix-Loop-Helix Transcription Factors , Disease Progression , Gene Expression Regulation/drug effects , Glomerulonephritis/etiology , Glomerulonephritis/metabolism , Glomerulosclerosis, Focal Segmental/etiology , Glomerulosclerosis, Focal Segmental/metabolism , Hematopoietic Stem Cells/metabolism , Histones/metabolism , Hydroxamic Acids/therapeutic use , Mice , Mice, Inbred C57BL , Multipotent Stem Cells/metabolism , Nephritis, Interstitial/drug therapy , Nephritis, Interstitial/etiology , Nephritis, Interstitial/metabolism , Nephritis, Interstitial/prevention & control , Protein Processing, Post-Translational/drug effects , Sheep/blood , Specific Pathogen-Free Organisms , Transcription Factors/biosynthesis , Transcription Factors/geneticsABSTRACT
Musculin/MyoR is a new member of basic helix-loop-helix transcription factors, and its expression is limited to skeletal muscle precursors. Here, we report that musculin/MyoR is expressed in adult kidney side population (SP) cells and can regulate their function. SP phenotype can be used to purify stem cell-rich fractions. Microarray analysis clarified that musculin/MyoR was exclusively expressed in kidney SP cells, and the cells resided in the renal interstitial space. Musculin/MyoR-positive cells were decreased in acute renal failure, but infusion of kidney SP cells increased musculin/MyoR-positive cells and improved renal function. Kidney SP cells in reversible acute renal failure expressed a high level of renoprotective factors and leukemia inhibitory factor (LIF), but not in irreversible chronic renal failure. In cultured kidney SP cells, LIF stimulated gene expression of renoprotective factors, and down-regulation of musculin/MyoR augmented LIF-induced gene expression. Our results suggest that musculin/MyoR may play important roles not only in developmental processes but also in regenerative processes in adult tissue.
