Effects of phenytoin and Echinacea purpurea extract on proliferation and apoptosis of mouse embryonic palatal mesenchymal cells

Involvement of microRNA-4680-3p against phenytoin-induced cell proliferation inhibition in human palate cells

Cleft palate (CP) is one of the most common birth defects and is caused by a combination of genetic and/or environmental factors. Environmental factors such as pharmaceutical exposure in pregnant women are known to induce CP. Recently, microRNA (miRNA) was found to be affected by environmental factors. The aim of the present study was to investigate the involvement of miRNA against phenytoin (PHE)-induced inhibition of proliferation in human embryonic palatal mesenchymal (HEPM) cells. We demonstrated that PHE inhibited HEPM cell proliferation in a dose-dependent manner. We found that treatment with PHE downregulated cyclin-D1 and cyclin-E expressions in HEPM cells. Furthermore, PHE increased miR-4680-3p expression and decreased two downstream genes (ERBB2 and JADE1). Importantly, an miR-4680-3p-specific inhibitor restored HEPM cell proliferation and altered expression of ERBB2 and JADE1 in cells treated with PHE. These results suggest that PHE suppresses cell proliferation via modulation of miR-4680-3p expression.

Associations between the proliferation of palatal mesenchymal cells, Tgfβ2 promoter methylation, Meg3 expression, and Smad signaling in atRA-induced cleft palate

All-trans retinoic acid (atRA) is a teratogen that can induce cleft palate formation. During palatal development, murine embryonic palate mesenchymal (MEPM) cell proliferation is required for the appropriate development of the palatal frame, with Meg3 serving as a key regulator of the proliferative activity of these cells and the associated epithelial-mesenchymal transition process. DNA methylation and signaling via the TGFβ/Smad pathway are key in regulating embryonic development. Here, the impact of atRA on MEPM cell proliferation and associations between Tgfβ2 promoter methylation, Meg3, and signaling via the Smad pathway were explored using C57BL/6 N mice treated with atRA (100 mg/kg) to induce fetal cleft palate formation. Immunohistochemistry and BrdU assays were used to detect MEPM proliferation and DNA methylation assays were performed to detect Tgfβ2 promoter expression. These analyses revealed that atRA suppressed MEPM cell proliferation, promoted the upregulation of Meg3, and reduced the levels of Smad2 and Tgfβ2 expression phosphorylation, whereas Tgfβ2 promoter methylation was unaffected. RNA immunoprecipitation experiments indicated that the TgfβI receptor is directly targeted by Meg3, suggesting that the ability of atRA to induce cleft palate may be mediated through the Tgfβ/Smad signaling pathway.

Susceptibility to DNA damage caused by abrogation of Rad54 homolog B: A putative mechanism for chemically induced cleft palate

Exposure to environmental toxicants such as all-trans retinoic acid (atRA) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) may cause cleft palate (CP), which process is related to DNA damage. Rad54B, an important DNA damage repaired protein, has been proved to be associated with non-syndromic cleft lip with palate (NSCLP). In the present study, we sought to clarify the role of Rad54B in palatal development and environment-induced CP. atRA (100 mg/kg) and TCDD (40 μg/kg) were used to induce CP in mice (C57BL/6 J mice). In this study, mouse embryonic heads were collected on embryonic day (E) 13.5∼16.5. The expression level of DNA repair protein Rad54 homolog B (Rad54B) was significantly decreased while those of the DNA double-strand breaks (DSBs) marker γ-H2A.X, apoptosis marker caspase-3 and p53 were significantly increased in the palatal shelves upon exposure to atRA and TCDD relative to the control. Primary mouse embryonic palatal mesenchymal cells (MEPMs) were cultured and transfected with siRNA or adenovirus in vitro to knock down or increase the level of Rad54B. Rad54B knockdown resulted in increased cellular S-phase arrest and apoptosis as well as decreased cell proliferation. Rad54B overexpression also increased apoptosis and reduced cell proliferation. Western blotting was used to detect the level of γ-H2A.X in transfected cells stimulated with etoposide (ETO, a DSBs inducer), and after 5 μM ETO stimulation of transfected MEPMs, the expression of γ-H2A.X was increased in Rad54B-knockdown cells. The expression of Mdm2, Mdmx and p53 with changes in Rad54B was also detected and coimmunoprecipitation was performed to analyze the combination of Mdm2 and p53 when Rad54B was changed in MEPMs. Knockdown of Rad54B inhibited the expression of Mdm2 and Mdmx, while the level of p53 increased. The coimmunoprecipitation results showed a decreased combination of Mdm2 and p53 when Rad54B was knocked down. Therefore, Rad54B can regulate the cell cycle, proliferation, and apoptosis of MEPMs. The loss of Rad54B increased the sensitivity of MEPMs to DSBs inducers, promoted apoptosis, and suppressed the proliferation of MEPMs by inhibiting the degradation of p53. Taken together, these findings suggest that Rad54B may play a key regulatory role in environment-induced CP.

Phenytoin Inhibits Cell Proliferation through microRNA-196a-5p in Mouse Lip Mesenchymal Cells

Cleft lip (CL) is one of the most common birth defects. It is caused by either genetic mutations or environmental factors. Recent studies suggest that environmental factors influence the expression of noncoding RNAs [e.g., microRNA (miRNA)], which can regulate the expression of genes crucial for cellular functions. In this study, we examined which miRNAs are associated with CL. Among 10 candidate miRNAs (miR-98-3p, miR-101a-3p, miR-101b-3p, miR-141-3p, miR-144-3p, miR-181a-5p, miR-196a-5p, miR-196b-5p, miR-200a-3p, and miR-710) identified through our bioinformatic analysis of CL-associated genes, overexpression of miR-181a-5p, miR-196a-5p, miR-196b-5p, and miR-710 inhibited cell proliferation through suppression of genes associated with CL in cultured mouse embryonic lip mesenchymal cells (MELM cells) and O9-1 cells, a mouse cranial neural crest cell line. In addition, we found that phenytoin, an inducer of CL, decreased cell proliferation through miR-196a-5p induction. Notably, treatment with a specific inhibitor for miR-196a-5p restored cell proliferation through normalization of expression of CL-associated genes in the cells treated with phenytoin. Taken together, our results suggest that phenytoin induces CL through miR-196a-5p induction, which suppresses the expression of CL-associated genes.

Mouse embryonic palatal mesenchymal cells maintain stemness through the PTEN-Akt-mTOR autophagic pathway

BACKGROUND

Both genetic and environmental factors are implicated in the pathogenesis of cleft palate. However, the molecular and cellular mechanisms that regulate the development of palatal shelves, which are composed of mesenchymal cells, have not yet been fully elucidated. This study aimed to determine the stemness and multilineage differentiation potential of mouse embryonic palatal mesenchyme (MEPM) cells in palatal shelves and to explore the underlying regulatory mechanism associated with cleft palate formation.

METHODS

Palatal shelves excised from mice models were cultured in vitro to ascertain whether MEPM are stem cells through immunofluorescence and flow cytometry. The osteogenic, adipogenic, and chondrogenic differentiation potential of MEPM cells were also determined to characterize MEPM stemness. In addition, the role of the PTEN-Akt-mTOR autophagic pathway was investigated using quantitative RT-PCR, Western blotting, and transmission electron microscopy.

RESULTS

MEPM cells in culture exhibited cell surface marker expression profiles similar to that of mouse bone marrow stem cells and exhibited positive staining for vimentin (mesodermal marker), nestin (ectodermal marker), PDGFRα, Efnb1, Osr2, and Meox2 (MEPM cells markers). In addition, exposure to PDGFA stimulated chemotaxis of MEPM cells. MEPM cells exhibited stronger potential for osteogenic differentiation as compared to that for adipogenic and chondrogenic differentiation. Undifferentiated MEPM cells displayed a high concentration of autophagosomes, which disappeared after differentiation (at passage four), indicating the involvement of PTEN-Akt-mTOR signaling.

CONCLUSIONS

Our findings suggest that MEPM cells are ectomesenchymal stem cells with a strong osteogenic differentiation potential and that maintenance of their stemness via PTEN/AKT/mTOR autophagic signaling prevents cleft palate development.

Retinoic acid alters the proliferation and survival of the epithelium and mesenchyme and suppresses Wnt/β-catenin signaling in developing cleft palate

Retinoic acid (RA) contributes to cleft palate; however, the cellular and molecular mechanisms responsible for the deleterious effects on the developing palate are unclear. Wnt signaling is a candidate pathway in the cleft palate and is associated with RA in organ development; thus, we aim to investigate whether RA-induced cleft palate also results from altered Wnt signaling. Administration of RA to mice altered cell proliferation and apoptosis in craniofacial tissues by regulating molecules controlling cell cycle and p38 MAPK signaling, respectively. This altered cell fate by RA is a crucial mechanism contributing to 100% incidence of cleft palate. Moreover, Wnt/β-catenin signaling was completely inhibited by RA in the early developing palate via its binding and activation with RA receptor (RAR) and is responsible for RA-induced cleft palate. Furthermore, PI3K/Akt signaling was also involved in actions of RA. Our findings help in elucidating the mechanisms of RA-induced cleft palate.

Down-regulation of Wnt10a by RNA interference inhibits proliferation and promotes apoptosis in mouse embryonic palatal mesenchymal cells through Wnt/β-catenin signaling pathway

Cleft palate is one of the most common birth defects. Both environmental and genetic factors are involved in this disorder. Here, we investigated the function of Wnt10a in proliferation and apoptosis of mouse embryonic palatal mesenchymal (MEPM) cells. Expression of Wnt10a was down-regulated at both the mRNA and protein levels in transfected MEPM cells containing Wnt10a-specific small hairpin RNA (shRNA) plasmid. Down-regulation of Wnt10a inhibited cell proliferation and induced cell cycle arrest in the S phase in MEPM cells. Moreover, apoptosis was significantly increased in MEPM cells of Wnt10a gene silencing. Finally, the expression of β-catenin was markedly reduced in MEPM cells transfected with shRNA plasmid, indicating that the canonical Wnt/β-catenin signaling pathway was involved in the alterations of cell proliferation and apoptosis induced by Wnt10a knockdown. Thus, our findings reveal that Wnt10a regulates proliferation and apoptosis of MEPM cells at least partially through the canonical Wnt/β-catenin signaling pathway.

Korean mistletoe lectin regulates self-renewal of placenta-derived mesenchymal stem cells via autophagic mechanisms

OBJECTIVES

The balance between survival and death is a key point for regulation of physiology of stem cells. Recently, applications of natural products to enhance efficiencies in culturing and differentiation of stem cells are increasing. Korean mistletoe lectin (Viscum album L. var. coloratum agglutinin, VCA) has been known to be toxic to some cancer cells, but it is still unclear whether VCA has a cytotoxic or indeed a proliferative effect on mesenchymal stem cells (MSCs). Here, we have compared effects of VCA in naïve placenta-derived stem cells (PDSCs), immortalized PDSCs and cancer cells (HepG2), and analysed their mechanisms.

MATERIALS AND METHODS

MTT assay was performed to analyse effects of VCA on naïve PDSCs, immortalized PDSCs and HepG2. FACS, ROS, caspase-3 assay, western blotting and immunofluorescence were performed to detect signalling events involved in self-renewal of the above cell types.

RESULTS

VCA had cancer cell-specific toxicity to HepG2 cells even with low concentrations of VCA (1-5 pg/ml), toxicity was observed to immortalized PDSCs and HepG2s, while proliferation of naïve PDSCs was significantly increased (P < 0.05). ROS production by VCA treatment in naïve PDSCs was significantly lower compared to controls (P < 0.05). Furthermore, autophagy was activated in naïve PDSCs treated with VCA through increase in type II LC3 and decrease in phosphorylated mTOR.

CONCLUSIONS

VCA can promote MSC proliferation through an activated autophagic mechanism.

Dermatoglyphic Features in Nonsyndromic Cleft Lip and/or Palate Patients and Their Parents in China

OBJECTIVE

To test the hypothesis that indicators and fluctuating asymmetry (FA) on fingers and palms in nonsyndromic cleft lip and/or palate (NSCL/P) and their parents were affected by developmental instability and to investigate a potential way for prenatal diagnosis of NSCL/P.

DESIGN

Case-control study.

SETTING

West China College of Stomatology and Chengdu Children's Hospital, Chengdu, China.

PARTICIPANTS

Three hundred sixty NSCL/P patients and their 720 unaffected parents were collected. Two hundred ninety normal children and their 580 parents were selected as the control.

MAIN OUTCOME MEASURES

Total ridge counts, atd angle, fingerprints pattern types, a-b ridge count, and true pattern (TP) on palm were determined. For each indicator, asymmetry between hands was defined. Pattern types and asymmetries were statistically compared among groups.

RESULT

Compared with the control, NSCL/P patients had significantly greater a-b ridge count for both hands (P < .001), decreased TP in the left thenar area (TA) as well as in the hypothenar area (HA) and interdigital third area (I3) (all P < .05), and increased FA in HA and I3 (both P < .05), while their parents had greater a-b ridge counts (P < .001). NSCL/P patients possessed more slowly developing patterns and higher levels of FA on their palms, followed by their parents and then the controls.

CONCLUSION

A-b ridge count could be a potential prenatal indicator in people without family history that are at increased risk of having a child with NSCL/P. The increased tendency for slower development of patterns and higher levels of FA indirectly support the possibility that the developmental sequence of ridges in NSCL/P is retarded. However, further work is still needed.