Animals ; Cells, Cultured ; DNA ; analysis ; Flow Cytometry ; methods ; Fluorescence ; G1 Phase ; Resting Phase, Cell Cycle

The stem/progenitor cell has long been regarded as a central cell type in development, homeostasis, and regeneration, largely owing to its robust self-renewal and multilineage differentiation abilities. The balance between self-renewal and stem/progenitor cell differentiation requires the coordinated regulation of cell cycle progression and cell fate determination. Extensive studies have demonstrated that cell cycle states determine cell fates, because cells in different cell cycle states are characterized by distinct molecular features and functional outputs. Recent advances in high-resolution epigenome profiling, single-cell transcriptomics, and cell cycle reporter systems have provided novel insights into the cell cycle regulation of cell fate determination. Here, we review recent advances in cell cycle-dependent cell fate determination and functional heterogeneity, and the application of cell cycle manipulation for cell fate conversion. These findings will provide insight into our understanding of cell cycle regulation of cell fate determination in this field, and may facilitate its potential application in translational medicine.
Animals ; Cell Cycle ; Cell Physiological Phenomena ; Epigenomics ; G1 Phase ; G2 Phase ; Humans ; Translational Medical Research

BACKGROUND: Type I collagen is a major component of extracellular cellular matrix in tissue. It is synthesized by human skin fibroblasts. However, synthesis of type I collagen is markedly-decreased in senescent fibroblasts. In the cell cycle, the hallmark of senescent fibroblasts is a permanent G1 phase arrest. However it is largely unknown whether the expression of type I collagen protein is decreased by the G1 phase arrest in human skin fibroblasts after UVB irradiation, serum starvation, or mimosine, an inducer of the G1 phase arrest treatment. OBJECTIVE: The purpose of this study was to investigate the expression of type I collagen protein in G1 phase- arrested human skin fibroblasts after UVB irradiation, serum starvation, and mimosine treatment. METHODS: To induce G1 phase arrest in the cell cycle, human skin fibroblasts were irradiated by UVB (100, 200, 300 mJ/cm(2)), subjected to serum starvation for 5 days, or mimosine treatment (50, 100, 200 uM). The expressions of type I collagen protein were analyzed by Western blot analysis. RESULTS: The G1 phase of cell populations were increased by a dose or time-dependent manner with UVB irradiation, serum starvation, and mimosine-treated human skin fibroblasts. The expression of type I collagen protein was markedly-decreased by UVB, serum starvation, and mimosine treatment. CONCLUSION: The expression of type I collagen protein in human skin fibroblasts is decreased by UVB irradiation, serum starvation, and mimosine treatment through induction of G1 phase cell cycle arrest.
Blotting, Western ; Cell Cycle ; Cell Cycle Checkpoints ; Collagen Type I* ; Down-Regulation* ; Fibroblasts* ; G1 Phase ; G1 Phase Cell Cycle Checkpoints* ; Gene Expression* ; Humans* ; Mimosine ; Skin* ; Starvation

BACKGROUND: The function of the p53 protein is known to regulate cell proliferation by inhibiting cells entering S phase, so DNA damaged cell proliferation is inhibited by apoptosis. p21 is a cyclin dependent kinase inhibitor induced by wild type p53, not mutant p53. Thus p21 is thought to mediate the signal of p53 induced by DNA damaged agents to arrest the cell cycle in G1 phase. p53 and p21 are expressed in many malignant tumors, and its role in oncogenesis, tumor progression and prognosis are important. OBJECTIVE: The purpose of this study was to analyze immunohistochemical expression of mutant p53 and p21 protein in melanocytic lesions. METHOD: 11 cases of intradermal nevus, 7 cases of junctional nevus and 6 cases of malignant melanoma were immunohistochemically stained with p53 and p21 monoclonal antibodies. RESULTS: 1. In intradermal nevus, the p53 was negative in 100% and the p21 was negative in 98%. These findings suggest that the composing cells of intradermal nevus is completely mature cell. 2. The positive rates of p53 and p21 in junctional nevus were 43% and 43%, respectively. The positive rates of p53 and p21 in malignant melanoma were 82% and 67%, respectively. CONCLUSION: If the expression of p21 is induced by p53 independent pathway, the cell cycle can be arrested in G1 phase, so the tumor cell proliferation is inhibited. But if the expressed p21 is mutated as p53, it means that the natural function of p21 disappears. More research is necessary about the nature of p21 which is expressed with mutant p53.
Antibodies, Monoclonal ; Apoptosis ; Carcinogenesis ; Cell Cycle ; Cell Proliferation ; Cyclins ; DNA ; G1 Phase ; Melanoma* ; Nevus* ; Nevus, Intradermal* ; Phosphotransferases ; Prognosis ; S Phase

OBJECTIVE: We investigated the effects on the cell cycle and p53 expression by the treatment of various concentrations of staurosporine to elucidate the molecular mechanism of staurosporine induced cell cycle arrest in MCF-7 cell line. METHODS: Various concentrations of staurosporine were treated in MCF-7 cells cultured with RPMI 1640 media. The harvested cells were fixed and permeabilized with 1% paraformaldehyde and absolute methanol. Then the cells were stained indirectly with anti-p53 primary antibody and FITC conjugated goat anti-mouse(GAM)-IgG secondary antibody. Sequentially DNA were stained with 0.1% RNase and PI solution. These stained cells were analyzed by the standard FACScan flow cytometer. The obtained results were analyzed further with WinList 3.0, and ModiFit LT software program. RESULTS: MCF-7 cells were arrested mostly in G1 phase of cell cycle at 5-10 nM of staurosporine, however, the cells were arrested in G2 phase at 20-100 nM of staurosporine. The expressions of p53 protein were higher in the MCF-7 cells treated with both concentrations of 10 nM and 100 nM of staurosporine compaired with the control cells. This suggests that the p53 may be involved in the mechanism of G1 and G2M arrest of cell cycle in MCF-7 cell. CONCLUSIONS: The points of arrest in cell cycle differred depending on the concentrations of staurosporine and these cell cycle arrests at G0G1 and G2M pahse were related with p53 protein expression. It suggested that these results could be extended to study for staurosporine to be usefull as a potential anti-tumor agent.
Cell Cycle Checkpoints ; Cell Cycle* ; DNA ; Fluorescein-5-isothiocyanate ; G1 Phase ; G2 Phase ; Goats ; MCF-7 Cells* ; Methanol ; Ribonucleases ; Staurosporine*

OBJECTIVE: We compared the cell responsiveness of activated lymphocytes to rapamycin, which blocks the G1/S transition, between patients with Alzheimer's disease (AD) and normal controls to assess the early phase control defect in cell cycle. METHODS: Blood samples of 26 patients with AD and 28 normal controls were collected to separate peripheral lymphocytes. We measured the proportion of each cell cycle phase in activated lymphocytes using flow cytometry and evaluated the responsiveness of these lymphocytes to rapamycin. RESULTS: The patients with AD were older than the normal controls (AD 74.03+/-7.90 yr vs. control 68.28+/-6.21 yr, p=0.004). The proportion of G1 phase cells in the AD group was significantly lower than that in the control group (70.29+/-6.32% vs. 76.03+/-9.05%, p=0.01), and the proportion of S phase cells in the AD group was higher than that in control group (12.45+/-6.09% vs. 6.03+/-5.11%, p=0.001). Activated lymphocytes in patients with AD were not arrested in the G1 phase and they progressed to the late phase of the cell cycle despite rapamycin treatment, in contrast to those of normal subjects. CONCLUSION: The patients with AD probably have a control defect of early phase cell cycle in peripheral lymphocytes that may be associated with the underlying pathology of neuronal death.
Alzheimer Disease ; Cell Cycle ; Cell Cycle Checkpoints ; Flow Cytometry ; G1 Phase ; Humans ; Lymphocytes ; Neurons ; S Phase ; Sirolimus

The cell cycle is the set of events that is responsible for the duplication of the cells. Recent studies indicate that cell cycle regulatory proteins, mainly the cyclins and cyclin-related genes, can be critical targets during oncogenesis. The genes and gene products normally control specific events in the cell cycles, particularly during the late G1 and early S phase and G2/M phase. A large body of date implicates cyclins in oncogenesis. The first evidence came from human cyclin A in oncogenesis. Cyclin A is expressed from the late G1 phase through the M-phase of the cell cycle. Cyclin A is known as positive regulator of cell cycle and participates in the tumorigenesis. Overexpression of cyclin A has been reported in several cancers. Ki-67 is a nuclear protein expressed during the cell cycle except in Go. The labeling index of Ki-67 in the tumor cell nuclei has been used as a good prognostic factor. In this study, we compared labeling index of cyclin A and Ki-67 to assess the feasibility between them with 30 cases of cervical intraepithelial neoplasia(CIN) and 20 cases of invasive squamous cell carcinoma(SCC)by immunohistochemistry. The results were as follow; 1. Cyclin A expressed in normal parabasal cells and their labeling index was 0.8+/-0.4%, while in CIN and invasive SCC 65.5+/-9.4% and 86.5+/-12.3% respectively. Ki-67 expressed in normal parabasal cells as 1.3+/-0.7% while in CIN and invasive SCC as 77.8+/-12.9% and 92.2+/-17.6% respectively. 2. In CIN, the expression of cyclin A increased according to the grades of the CIN as 32.5+/-5.7%, 75.8+/-9.0%, and 83.2+/-13.4% in CIN I, II and III respectively. The expression of the Ki-67 also increased according to the grades of the CIN as 51.8+/-9.8%, 87.9+/-11.3%, and 93.6+/-17.5% respectively in CIN I, II and III. 3. There was no differences of cyclin A and Ki-67 expressions according to the histologic types of invasive SCC. Above results suggests that the cyclin A labeling index could be used as a marker of tumor progression in the uterine cervical carcinoma as Ki-67.
Carcinogenesis ; Cell Cycle ; Cell Cycle Proteins ; Cell Nucleus ; Cyclin A* ; Cyclins* ; G1 Phase ; Humans ; Immunohistochemistry ; Nuclear Proteins ; S Phase

OBJECTIVETo explore the changes of liver regeneration after partial hepatectomy on rats with nonalcoholic fatty liver disease (NAFLD) caused by a high fat diet.

METHODSOne hundred Wistar rats were randomly divided into a control group (group C, n = 45), fed with normal diet, and a NAFLD group, fed with fat-rich diet (group F, n = 55). All rats had a 70% partial hepatectomy at the end of the 12th week. They were sacrificed at postoperative 0, 1, 12, 24, or 36 hours and the percentages of their regenerated liver masses were calculated. The mitosis index was measured microscopically and the changes of cell ultrastructure were observed under an electron microscope. The expression of proliferating cell nuclear antigen (PCNA) was detected using immunohistochemistry. The expression of mRNA of cyclin D1 was measured by RT-PCR.

RESULTSThe light and electron microscopy showed that the hepatic sinusoids expanded at an early period after the partial hepatectomy. The mitochondria and rough endoplasmic reticulum (RER) expanded and their number increased. The mitosis index was increased. The sinusoids of the livers in group F were narrow and irregular. The nuclei were smaller and the necrotic cells increased. As compared with the control group, the mitosis index was significantly decreased (P < 0.01), and the regenerative liver weight ratio in group F was lower at postoperative 12 h, 24 h, 36 h (P < 0.01). PCNA labeling index in group F also was lower than that in group C. The peak of the PCNA in group F was later than that of the control group (P < 0.01). In group C, the mRNA of cyclin D1 peaked at the 24th hour after the partial hepatectomy, and then decreased afterwards. In group F, it was lower than that of group C at the same time (P < 0.01).

CONCLUSIONAfter NAFLD rats had partial hepatectomies, the capacity of their liver regeneration decreased and the peak of DNA synthesis was delayed, and at the same time the morbidity of the rats increased.

Animals ; Fatty Liver ; pathology ; physiopathology ; G1 Phase ; Hepatectomy ; Liver Regeneration ; Male ; Postoperative Period ; Rats ; Rats, Wistar ; S Phase

OBJECTIVE: To show that Stat3 played a key role in the G1 to S phase transition in laryngocarcinoma cells. METHOD: Human laryngocarcinoma cell lines Hep-2 were transfected with Stat3 antisense oligonucleotide mediated by liposome, MTT assay was used to measure the proliferation, flow cytometry was applied to analyze the cell cycle, and the expressions of Stat3, phosphorylation specific Stat3 (tyrosine705), CyclinD1, Cyclin E, CDK2, CDK4, CDK6, p21 and p27 were detected by western blot. RESULT: Hep-2 laryngocarcinoma cell lines expressed constitutively activated Stat3. Antisense oligonucleotide which directed blocked up the translation site resulted in growth inhibition, downregulation of Stat3, p-Stat3, Cyclins and CDKs, and upregulation of p21 and p27. CONCLUSION Our findings suggested that Stat3 played an important role in the G1 to S phase transition in laryngocarcinoma cells, Stat3 orchestrated cell cycle by regulating the balance between CDK/Cyclin complex and CKI.
Cell Line, Tumor ; G1 Phase ; Humans ; Laryngeal Neoplasms ; metabolism ; pathology ; S Phase ; STAT3 Transcription Factor ; genetics ; metabolism ; Signal Transduction ; Transfection

PURPOSE: Because NELL2 expression is strictly restricted only in neurons in developing and post- differentiated neural tissues, it is thought to be involved in the neuronal differentiation during development and in the maintenance of neuronal physiology in the post-differentiated neurons. In this study, we examined whether NELL2 is involved in the regulation of cell cycle and apoptosis in the hippocampal neuroprogenitor HiB5 cells. METHODS: Effects of NELL2 on the cultured HiB5 cell numbers, DNA fragmentation, and proteins involved in the regulation of the cell cycle were measured. RESULTS: NELL2 induced a decrease in cell numbers and an increase in G1 phase arrest. Moreover, transfection of NELL2 resulted in an increase of DNA fragmentation that shows an evidence of apoptosis. Contents of proteins involved in the regulation of cell cycle were also changed by transfection of NELL2 expression vectors. CONCLUSION: This study suggests that NELL2 plays an important role in the regulation of cell cycle and apoptosis of neurons.
Apoptosis ; Cell Count ; Cell Cycle* ; DNA Fragmentation ; G1 Phase ; Neurons* ; Physiology ; Transfection