Lianhong Jin

ES Cell Extract‐Induced Expression of Pluripotent Factors in Somatic Cells

Reprogramming of somatic cells was induced by ES cell‐free extract. The system relied on the transient uptake of regulatory components from a nuclear and cytoplasmic extract derived from ES cells by the nucleus of a reversibly permeabilized NIH3T3 cell. NIH3T3 cells were permeabilized by streptolysin O (SLO). Reprogramming cell‐free extracts were prepared by repeatedly freezing and thawing ES cells in liquid nitrogen. After incubation in the extract for 1 hr, permeabilized NIH3T3 cells were resealed by CaCl2 and continually cultured for weeks to assess expression of ES cell specific markers. As we observed using FACS and fluorescence microscope, the optimal SLO concentration for permeabilizing NIH3T3 cells was 25 U. After 2 weeks of culture, the treated NIH3T3 cells began to express Nanog, c‐Myc, Klf4, and 6 weeks later Oct4 was detectable. However, Sox2 was detected only after 8 weeks of culture. Differentiated somatic cells could be reprogrammed in ES extract in vitro, which provides a new approach to decreasing differentiation levels in somatic cells without disturbing the DNA sequences. Anat Rec, 292:1229–1234, 2009.

MSCs guide neurite directional extension and promote oligodendrogenesis in NSCs.

Previous studies have shown that mesenchymal stem cells (MSCs) enhance repair following injury or degenerative diseases in the central nervous system, but the underlying mechanisms remain unclear. The present study investigated the functional relationship between MSCs and neural stem cells (NSCs) using co-culture systems. Results demonstrated that MSCs promoted outgrowth and guided directional extension of NSC-derived neurites. The majority of neurites were oriented parallel along the MSC axis. Stripe assay results indicated that cell adhesion molecule and extracellular matrix, such as N-cadherin, fibronectin, and laminin, contributed to this effect. Furthermore, Western blot analysis revealed that phosphorylation of cAMP response element-binding protein (CREB) increased during this process. In addition, MSCs promoted differentiation of NSCs into oligodendrocytes via secreted soluble factors. The oligodendrocytes were distributed along the MSC surface in a regular pattern. This study demonstrated that MSC transplantation could be a potential strategy for treating central nervous system injuries.

Icariin induces mouse embryonic stem cell differentiation into beating functional cardiomyocytes

Icariin, the primary active component of Epimedium extracts, has recently been shown to induce cardiomyocyte differentiation of murine embryonic stem (mES) cells in vitro. However, as these cardiomyocytes were not functionally characterized, the potential application of icariin-induced cardiomyocytes in clinical practice remains unclear. Therefore, in this study, we characterized the structure and function of icariin-induced cardiomyocytes to evaluate their potential application in transplantation for cardiac failure treatment. mES cells were cultured as embryoid bodies (EBs) via the direct suspension method in the presence of icariin. The protein expression profiles and ultrastructural characteristics of mES cell-derived cardiomyocytes were then characterized by immunofluorescence and transmission electron microscopy, respectively. In addition, the expression of cardiac-specific and calcium handling genes was detected by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR). Cardiomyocytes induced by icariin treatment expressed the cardiac-specific proteins myosin light chain-1v (MLC1v), atrial natriuretic polypeptide (ANP), and cardiac troponin I (cTnI). Furthermore, these cells appeared to possess myofibrils organized into mature sarcomeres that had formed A and I bands. In addition, icariin treatment upregulated the mRNA levels of MLC1v, ANP, cTnI, calsequestrin (CSQ), and sodium–calcium exchanger (NCX) in these cells. Icariin induces the differentiation of mES cells into beating cardiomyocytes with normal structure and function. Therefore, these cells may have promising applications in cardiac cell therapy or tissue engineering.

RA induces the neural-like cells generated from epigenetic modified NIH/3T3 cells

Recently, differentiated somatic cells had been reprogrammed to pluripotential state in vitro, and various tissue cells had been elicited from those cells. Epigenetic modifications allow differentiated cells to perpetuate the molecular memory needed for the cells to retain their identity. DNA methylation and histone deacetylation are important patterns involved in epigenetic modification, which take critical roles in regulating DNA expression. In this study, we dedifferentiated NIH/3T3 fibroblasts by 5-aza-2-deoxycytidine (5-aza-dC) and Trichstatin A (TSA) combination, and detected gene expression pattern, DNA methylation level, and differentiation potential of reprogrammed cells. As the results, embryonic marker Sox2, klf4, c-Myc and Oct4 were expressed in reprogrammed NIH/3T3 fibroblasts. Total DNA methylation level was significant decreased after the treatment. Moreover, exposure of the reprogrammed cells to all trans-retinoic acid (RA) medium elicited the generation of neuronal class IIIβ-tubulin-positive, neuron-specific enolase (NSE)-positive, nestin-positive, and neurofilament light chain (NF-L)-positive neural-like cells.

pCREB is Involved in Neural Induction of Mouse Embryonic Stem Cells by RA

Mouse embryonic stem (ES) cells can be induced by various chemicals to differentiate into a variety of cell types in vitro. In our study, retinoic acid (RA), one of the most important inducers, used at a concentration of 5 μM, was found to induce the differentiation of ES cells into neural progenitor cells (NPCs). During embryoid body (EB) differentiation, the level of active cyclic AMP response element‐binding protein (CREB) was relatively high when 5 μM RA treatment was performed. Inhibition of CREB activity committed EBs to becoming other germ layers, whereas increased expression of CREB enhanced NPC differentiation. Moreover, RA increased the expression of active CREB by enhancing the activity of JNK. Our research suggests that CREB plays a role in RA‐induced NPC differentiation by increasing the expression of active JNK. Anat Rec, 291:519–526, 2008.

Generation of dorsal spinal cord GABAergic neurons from mouse embryonic stem cells.

Developmental signaling molecules involved in dorsal patterning of the spinal cord have been identified in vivo; however, studies have not produced specific functional dorsal spinal cord neurons in vitro. We present here differentiation of R1 embryonic stem (ES) cells into GABAergic dorsal spinal cord neurons by sequential treatment with developmental signaling molecules. We found that retinoic acid, Bmp4 altered the specification of neural progenitors and instructed neural fate when applied at distinct stages of development. High concentration of retinoic acid initiated caudal patterning during early differentiation; Bmp4 induced dorsal development. The combination of retinoic acid and different concentration Bmp4 controlled the differing regional progenitors of spinal cord. Low-concentration Bmp4 and high concentration of retinoic acid-treated embryoid bodies resulted in the differentiation of GABAergic neurons. In summary, we demonstrate this simple treatment paradigm produced simple dorsal spinal cord neurons, which could be utilized for developmental and preclinical studies.

ApoER2 and VLDLR in the developing human telencephalon

The Reelin-Dab1 signaling pathway plays a crucial role in regulating the migration and position of cortical neurons during the development of the cerebral cortex. Mutation in Reelin may result in severe developmental disorders such as autosomal recessive lissencephaly. Apolipoprotein E receptor type-2 (ApoER2) and very low-density lipoprotein receptor (VLDLR) are canonical receptors of Reelin, through which extracellular Reelin activates the intracellular adapter, Disabled1(Dab1), and subsequently interacts with other molecules. Although it is widely accepted that ApoER2 and VLDLR are indispensable components of the Reelin signaling pathway, little is known of their expression pattern in the laminated developing human brain. Here, we collected 18 cases of human fetal brains of 6-18 gestational weeks (GW) old and examined the expression of ApoER2 and VLDLR in the their telencephalon using immunocytochemical staining. We found that both receptors were absent in the preplate (PP) and the earliest stage of the cortical plate (CP). In later stages of CP development, ApoER2 was expressed earlier than VLDLR in the migrating neurons. Thus, the Reelin-Dab1 signaling pathway may not be involved in the formation of the preplate and deep layers of the CP. Instead, the pathway may act on neurons that are destined to form the more superficial layers of the CP. In addition, the pathway required ApoER2 only rather than both ApoER2 and VLDLR at the initiation of activity.

Selection and expression profiles of reference genes in mouse preimplantation embryos of different ploidies at various developmental stages.

Real-time reverse transcription quantitative polymerase chain reaction (qPCR) has become the most frequently used system for studies of gene expression. Manystudies have provided reliable evidence that the transcription levels of reference genes are not constant at different developmental stages and in different experimental conditions. However, suitable reference genes which are stably expressed in polyploid preimplantation embryos of different developmental stages have not yet been identified. Therefore, it is critical to verify candidate reference genes to analyze gene expression accurately in both diploid and polyploid embryos. We examined the expression levels of 12 candidate reference genes in preimplantation embryos of four different ploidies at six developmental stages. Stability analysis of the reference genes was performed by four independent software programs, and the stability of three genes was evaluated by comparison with the Oct4 expression level during preimplantation development in diploid embryos. The expression levels of most genes in the polyploid embryos were higher than that in the diploid embryos, but the increasing degree were disproportionate with the ploidies. There were no significant difference in reference gene expressions among embryos of different ploidies when they reached the morula stage, and the expression level remained flat until the blastocyst stage. Ubc, Ppia, and Pgk1 were the three most stable reference genes in diploid and polyploid embryos.

Comparison of Reprogramming Genes in Induced Pluripotent Stem Cells and Nuclear Transfer Cloned Embryos

The most effective reprogramming methods, somatic cell nuclear transfer (SCNT) and induced pluripotent stem cells (iPSCs), are widely used in biological research and regenerative medicine, yet the mechanism that reprograms somatic cells to totipotency remains unclear and thus reprogramming efficiency is still low. Microarray technology has been employed in analyzing the transcriptomes changes during iPS reprogramming. Unfortunately, it is difficult to obtain enough DNA from SCNT reconstructed embryos to take advantage of this technology. In this study, we aimed to identify critical genes from the transcriptional profile for iPS reprogramming and compared expression levels of these genes in SCNT reprogramming. By integrating gene expression information from microarray databases and published studies comparing somatic cells with either miPSCs or mouse embryonic stem cells (ESCs), we obtained two lists of co-upregulated genes. The gene ontology (GO) enriched analysis of these two lists demonstrated that the reprogramming process is associated with numerous biological processes. Specifically, we selected 32 genes related to heterochromatin, embryonic development, and cell cycle from our co-upregulated gene datasets and examined the gene expression level in iPSCs and SCNT embryos by qPCR. The results revealed that some reprogramming related genes in iPSCs were also expressed in SCNT reprogramming. We established the network of gene interactions that occur with genes differentially expressed in iPS and SCNT reprogramming and then performed GO analysis on the genes in the network. The network genes function in chromatin organization, heterochromatin, transcriptional regulation, and cell cycle. Further researches to improve reprogramming efficiency, especially in SCNT, will focus on functional studies of these selected genes.