An attempt to generate neurons from an astrocyte progenitor cell line FBD-104

Effects of apolipoprotein E gene polymorphism on the intracellular Ca2+ concentration of astrocytes in the early stages post injury

The present study aimed to investigate the correlation between apolipoprotein E (APOE) polymorphisms and the intracellular concentration of Ca²⁺ in astrocytes in the early stages after an injury. The chondroitin sulfate region of three APOE alleles (ε2, ε3 and ε4) was obtained by reverse transcription-polymerase chain reaction (RT-PCR). A recombinant plasmid, pEGFP-N1-APOE, was constructed and identified by sequencing, while astrocytes were isolated from APOE gene-knockout mice and examined using immunocytochemistry. The recombinant plasmid was transfected into the astrocytes using the liposome-mediated method and cell injury models were constructed by a scratch assay. Laser confocal scanning microscopy (LCSM) was used to detect dynamic alterations in intracellular Ca²⁺ concentration at 12, 24, 48 and 72 h after injury. Compared with the control group, cells transfected with any of the three alleles demonstrated significant increases in the fluorescence intensity of Ca²⁺ (P<0.05). The fluorescence intensity of Ca²⁺ was weak at 12 h after injury, with no statistically significant difference detected between any two groups at this time point (P>0.05). However, the fluorescence intensity increased in a time-dependent manner and at 24, 48 and 72 h post injury, the fluorescence intensity of the ε4 allele-containing cells was significantly higher when compared with that of cells harboring the other two alleles (P<0.05). These results indicate that intracellular Ca²⁺ overloading may contribute to the deterioration of brain cells and poor outcome subsequent to traumatic brain injury in APOE ε4 carriers.

Successful reconstruction of tooth germ with cell lines requires coordinated gene expressions from the initiation stage

Tooth morphogenesis is carried out by a series of reciprocal interactions between the epithelium and mesenchyme in embryonic germs. Previously clonal dental epithelial cell (epithelium of molar tooth germ (emtg)) lines were established from an embryonic germ. They were odontogenic when combined with a dental mesenchymal tissue, although the odontogenesis was quantitatively imperfect. To improve the microenvironment in the germs, freshly isolated dental epithelial cells were mixed with cells of lines, and germs were reconstructed in various combinations. The results demonstrated that successful tooth construction depends on the mixing ratio, the age of dental epithelial cells and the combination with cell lines. Analyses of gene expression in these germs suggest that some signal(s) from dental epithelial cells makes emtg cells competent to communicate with mesenchymal cells and the epithelial and mesenchymal compartments are able to progress odontogenesis from the initiation stage.

Establishment of adipose-derived mesenchymal stem cell lines from a p53-knockout mouse

Mesenchymal stem cells (MSCs) can differentiate into a variety of cell types. MSCs exist in several tissues such as the bone marrow, adipose, muscle, cartilage, and tendon. This differentiation potential makes MSCs candidates for cell-based therapeutic strategies for mesenchymal tissue injuries. MSCs can be prepared from bone marrow (BM-MSCs) and adipose (AD-MSCs); however, these MSCs exhibit senescence-associated growth arrest and display inevitable heterogeneity. We established several AD-MSC cell lines from a p53-knockout (KO) mouse. These cell lines were immortalized, but no cell lines grew anchorage-independently, suggesting that they are not cancerous. They differentiated into adipocytes, osteoblasts, and chondrocytes by treatment with certain stimuli. Moreover, following injection into the tail vein, the cells migrated into the wounded region of the liver and differentiated into hepatocytes. We succeeded in establishing several AD-MSC clonal cell lines that maintain the tissue-specific markers and characteristics of the developmental phase. These clonal cell lines will serve as important tools to study the mechanism of differentiation of MSCs.

Attempt to develop taste bud models in three-dimensional culture

Taste buds are the end organs of taste located in the gustatory papillae, which occur on the surface of the oral cavity. The goal of the present study was to establish a culture model mimicking the lingual taste bud of the mouse. To this end, three cell lines were employed: taste bud-derived cell lines (TBD cell lines), a lingual epithelial cell-derived cell line (20A cell line), and a mesenchymal cell-derived cell line (TMD cell line). TBD cells embedded in collagen gel formed three-dimensional clusters, which had an internal cavity equipped with a tight junction-like structure, a microvilluslike structure, and a laminin-positive layer surrounding the cluster. The cells with this epitheliumlike morphology expressed marker proteins of taste cells: gustducin and NCAM. TBD cells formed a monolayer on collagen gel when they were co-cultured with TMD cells. TBD, 20A, and TMD cell lines were maintained in a triple cell co-culture, in which TBD cells were pre-seeded as aggregates or in suspension on the collagen gel containing TMD cells, and 20A cells were laid over the TBD cells. TBD cells in the triple cell co-culture expressed NCAM. This result suggests that co-cultured TBD cells exhibited a characteristic of Type III taste cells. The culture model would be useful to study morphogenesis and functions of the gustatory organ.

Roles of p53 and p27(Kip1) in the regulation of neurogenesis in the murine adult subventricular zone

The tumor suppressor protein p53 (Trp53) and the cell cycle inhibitor p27(Kip1) (Cdknb1) have both been implicated in regulating proliferation of adult subventricular zone (aSVZ) cells. We previously reported that genetic ablation of Trp53 (Trp53-/-) or Cdknb1 (p27(Kip1-/-) ) increased proliferation of cells in the aSVZ, but differentially affected the number of adult born neuroblasts. We therefore hypothesized that these molecules might play non-redundant roles. To test this hypothesis we generated mice lacking both genes (Trp53-/- ;p27(Kip1-/-) ) and analysed the consequences on aSVZ cells and adult neuroblasts. Proliferation and self-renewal of cultured aSVZ cells were increased in the double mutants compared with control, but the mice did not develop spontaneous brain tumors. In contrast, the number of adult-born neuroblasts in the double mutants was similar to wild-type animals and suggested a complementation of the p27(Kip1-/-) phenotype due to loss of Trp53. Cellular differences detected in the aSVZ correlated with cellular changes in the olfactory bulb and behavioral data on novel odor recognition. The exploration time for new odors was reduced in p27(Kip1-/-) mice, increased in Trp53-/- mice and normalized in the double Trp53-/- ;p27(Kip1-/-) mutants. At the molecular level, Trp53-/- aSVZ cells were characterized by higher levels of NeuroD and Math3 and by the ability to generate neurons more readily. In contrast, p27(Kip1-/-) cells generated fewer neurons, due to enhanced proteasomal degradation of pro-neural transcription factors. Together, these results suggest that p27(Kip1) and p53 function non-redundantly to modulate proliferation and self-renewal of aSVZ cells and antagonistically in regulating adult neurogenesis.

Study on the correlation between synaptic reconstruction and astrocyte after ischemia and the influence of electroacupuncture on rats

OBJECTIVE

To observe the effects of electroacupuncture (EA) on the structure parameters of synapse and reactive changes of astrocyte in the marginal zone of focal cerebral ischemia in rats at different time zones so as to further explore its underlying mechanisms in the treatment of cerebral ischemia.

METHODS

Ninety male Wistar rats were randomly assigned to sham-operation, model, and EA groups, with 30 animals in each group. Each group was subdivided into 1 h, as well as 1, 3, 7, and 21 days post-operation groups, with 6 animals assigned to each time point subgroup. Heat coagulation-induced occlusion of the middle cerebral artery was performed to establish a model of focal cerebral ischemia. EA was applied immediately following surgery to the EA group [4/20 Hz, 2.0-3.0 V, 1-3 mA, to Baihui (GV20) and Dazhui (GV14)] for 30 min. Treatment was performed once a day, and experimental animals were sacrificed at 1 h, as well as 1, 3, 7 and 21 days postoperation. The ultrastructure changes in synapse and astrocytes were observed by using transmission electron microscopy. Glial fibrillary acidic protein (GFAP) expression and Ca(2+) of astrocytes were measured by using laser confocal scanning microscope. Excitatory amino acid transporters-2 (EAAT2) and connexin 43 (CX43) expressions were assayed with immunohistochemical method. Canonical correlation analysis was conducted between structure parameters of synapse and parameters of astrocyte in the same time and group.

RESULTS

Broken synapses were observed following cerebral ischemia, and the numbers of synapses were significantly decreased. Compared with the model group, synaptic ultrastructure was significantly improved in the EA group. Compared with the sham-operation group, synaptic number density was significantly decreased, as were postsynaptic density thickness, synaptic cleft width and synaptic interface curvature in the EA and model groups. However, compared with the model group, postsynaptic density thickness was significantly increased in the EA group at the same time points post-operation (P <0.05, P<0.01). In addition, synaptic cleft width, synaptic number density and synaptic interface curvature were significantly increased with the passage of time (P <0.05, P<0.01). The expression of GFAP in the EA group were significantly lower than those in the model group at all the time points (P <0.05, P<0.01). OD values of EAAT2 in the EA group were significantly higher than those in the model group at the same time (P <0.05, P<0.01). Compared with that in the model group, the expressions of CX43 in the EA group increased significantly at 3 days and 7 days (P <0.05, P<0.01). Ca(2+) average fluorescence intensity of astrocytes in the EA group was significantly lower than those in the model group at 1 h, 1 day, 3 days and 7 days (P <0.05, P<0.01). The changes in structure parameters of synapse were closely related to the changes of CX43, EAAT2, GFAP, Ca(2+) of astrocytes by EA treatment at all the time points.

CONCLUSIONS

EA is helpful for synaptic reorganization, which may be related to its effect on intervening the activation state of astrocytes and promoting the beneficial interaction between astrocytes and synapses. Acupuncture could start the adjustment of neuron-glial network so as to promote the synaptic reorganization, which may be the key mechanism of treating cerebral ischemia.

Establishment of clonal cell lines of taste buds from a p53(-/-) mouse tongue

A taste bud is a sensory organ and consists of 50-100 spindle-shaped cells. The cells function as taste acceptors. They have characteristics of both epithelial and neuronal cells. A taste bud contains four types of cells, type I, type II, type III cells, and basal cells. Taste buds were isolated from a tongue of a p53-deficient mouse at day 12, and 11 clonal taste bud (TBD) cell lines were established. In immunochemical analysis, all cell lines expressed cytokeratin 18, gustducin, T1R3, and neural cellular adhesion molecule, but not GLAST. In RT-PCR analysis, shh was not expressed in any of the cell lines. Further analysis with RT-PCR was conducted on four cell lines. They expressed G protein-coupled taste receptors; T1R3, T2R8 for sweet, bitter, umami. And they also expressed α-ENaC for salty taste. While, a candidate for sour receptor HCN4 was expressed in TBD-a1 and TBD-a7 lines. And another candidate for sour receptor PKD1L3 was slightly expressed in TBD-a1 and TBD-c1.

Follistatin-like-1, a diffusible mesenchymal factor determines the fate of epithelium

Mesenchyme is generally believed to play critical roles in "secondary induction" during organogenesis. Because of the complexity of tissue interactions in secondary inductions, however, little is known about the precise mechanisms at the cellular and molecular levels. We have demonstrated that, in mouse oviductal development, the mesenchyme determines the fate of undetermined epithelial cells to become secretory or cilial cells. We have established a model for studying secondary induction by establishing clonal epithelial and mesenchymal cell lines from perinatal p53(-/-) mouse oviducts. The signal sequence trap method collected candidate molecules secreted from mesenchymal cell lines. Naive epithelial cells exposed to Follistatin-like-1 (Fstl1), one of the candidates, became irreversibly committed to expressing a cilial epithelial marker and differentiated into ciliated cells. We concluded that Fstl1 is one of the mesenchymal factors determining oviductal epithelial cell fate. This is a unique demonstration that the determination of epithelial cell fate is induced by a single diffusible factor.

Newly established cell lines from mouse oral epithelium regenerate teeth when combined with dental mesenchyme

The present study attempted to examine whether clonal cell lines of the oral epithelium can differentiate into ameloblasts and regenerate tooth when combined with dental germ mesenchyme. Clonal cell lines with a distinct morphology were established from the oral epithelium of p53-deficient fetal mice at embryonic day 18 (E18). The strain of mouse is shown to be a useful source for establishing clonal and immortalized cell lines from various tissues and at various stages of development. Tooth morphogenesis is almost completed and the oral epithelium is segregated from the dental epithelium at E18. In RT-PCR analysis of cell lines, mucosal epithelial markers (cytokeratin 14) were detected, but ameloblast markers such as amelogenin and ameloblastin were not detected when cells were cultured on plastic dish. They formed stratified epithelia and expressed a specific differentiation marker (CK13) in the upper layer when cultured on feeder layer or on collagen gel for 1–3 wk, demonstrating that they are of oral mucosa origin. Next, bioengineered tooth germs were prepared with cell lines and fetal molar mesenchymal tissues and implanted under kidney capsule for 2–3 wk. Five among six cell lines regenerated calcified structures as seen in natural tooth. Our results indicate that some oral epithelial cells at E18 possess the capability to differentiate into ameloblasts. Furthermore, cell lines established in the present study are useful models to study processes in tooth organogenesis and tooth regeneration.

Pathologic changes in chronic intraorbital optic nerve damage in rabbits

OBJECTIVES

To construct a chronic intraorbital optic nerve compression damage model in rabbits and investigate pathologic changes of the retina and optic nerve.

METHODS

A balloon was implanted into the orbit of rabbits, in which contrast medium was filled at designated time points to simulate chronic tumor compression on the intraorbital optic nerve. Funduscopy, visual electrophysiology, histopathology, immunohistochemistry, apoptosis and gene assays were used to examine the changes of retinal ganglion cells (RGCs) and neuroglial cells, as well as the expression of ciliary neurotrophic factor (CNTF) and growth associated protein 43 (GAP-43) in each phase of the chronic intraorbital optic nerve damage (2, 4 and 8 weeks after modeling).

RESULTS

Funduscopic examination showed that there was no significant change in the optic disk in non-compression group; the optic disk was congested and edematous in 2 w-compression group, but with no significant change in color; in 4 w-compression group, edema was lessened but color became lighter; in 8 w-compression group, no edema was found but the color was pale. Flash visual evoked potential (FVEP) suggested that the change of FVEP wave forms was more obvious as the compression extended, especially the low, flat, wide and irregular wave forms; the latent period of P(1), N(1) and P(2) was prolonged and the amplitude became lower. Compared with the wave form in non-compression group, there was no significant difference in 2 w-compression group (P>0.05), but the differences were prominent in 4 w- and 8 w-compression groups (P<0.01). Histopathology checks indicated no changes in the retina and optic nerve in non-compression group; in 2 w-compression group, there were also no significant changes, but the cell number of optic nerve decreased, the fibers were deranged, and the bundle membrane was damaged; in 4 w-compression group, nuclei in the RGC layer became sparse, the cell number of optic nerve increased significantly, the optic nerve bundles were deranged; in 8 w-compression group, nuclei in the RGC layer remained sparse and disordered, in the optic nerve there were a large number of disordered and deranged cells, the structure of fiber bundles was not clear, the bundle membrane was incomplete. Immunohistochemistry results showed there was no obvious change in the content of glial fibrillary acidic protein (GFAP) in the optic nerve in non-compression group; its expression began increasing in 2 w-compression group and remained high level in 8 w-compression group. With the compression extending, the number of apoptotic cells in RGCs layer increased gradually, and it was positive correlation with the compression time. CNTF and GAP-43 expressions were low in blank control and non-compression groups, and were up-regulated in 2 w-compression group (P<0.01); with the compression extending, the expressions of two genes increased gradually (P<0.01).

CONCLUSION

A chronic intraorbital optic nerve compression damage model was constructed successfully, and in that way we found that with the compression extending, more RGCs were lost; the structure of optic nerve fibers was damaged; the number of neuroglial cells tended to decreased at the beginning and then increased; and the CNTF and GAP-43 expressions increased gradually 2 weeks after damage.

Tooth regeneration from newly established cell lines from a molar tooth germ epithelium

In order to investigate tooth development, several cell lines of the dental epithelium and ectomesenchyme have been established. However, no attempt has been reported to regenerate teeth with cell lines. Here, we have established several clonal cell lines of the dental epithelium from a p53-deficient fetal mouse. They expressed specific markers of the dental epithelium such as ameloblastin and amelogenin. A new method has been developed to bioengineer tooth germs with dental epithelial and mesenchymal cells. Reconstructed tooth germs with cell lines and fetal mesenchymal cells were implanted under kidney capsule. The germs regenerated teeth with well-calcified structures as seen in natural tooth. Germs without the cell lines developed bone. This is the first success to regenerate teeth with dental epithelial cell lines. They are useful models in vitro for investigation of mechanisms in morphogenesis and of cell lineage in differentiation, and for clinical application for tooth regeneration.

Plexin-A4 is expressed in oligodendrocyte precursor cells and acts as a mediator of semaphorin signals

Class 3 semaphorin acts as a guidance clue for both cell migration and nerve fiber projection. The signal of class 3 semaphorin travels via a receptor complex consisting of neuropilins and Plexin-A subfamily. Although it has been reported that class 3 semaphorin acts as a repellent for oligodendrocyte precursor cells (OPCs), which migrate actively during brain development, the expression of Plexin-A subfamily has not been reported in OPCs yet. Therefore, it is currently unclear how semaphorin signals can travel in OPCs. In the present study, the expression of Plexin-A4 (PlexA4) was first demonstrated in a newly established OPC line and OPCs in developing brain. In the OPC line, repulsion for process extension was caused by both Sema3A and Sema6A, and the effect of the semaphorins was diminished in cells expressing PlexA4 lacking the cytoplasmic domain. These results strongly suggest that PlexA4 expressed in OPCs acts as a mediator of semaphorin signals.

An oligodendroglial progenitor cell line FBD-102b possibly secretes a radial glia-inducing factor

Interactions between oligodendroglial and astroglial lineages during development are still unclear. In this study, FBD-102b, derived from p53-/- fetal brains, was characterized as an oligodendroglial progenitor cell (OPC) line. In co-culture with 102b cells, cells of an astrocyte progenitor cell line, FBD-104, elongated monopolar processes, like radial glia, and actively proliferated. Conditioned medium of 102b cells also induced the process elongation that was associated with down-regulation of GFAP and up-regulation of vimentin and nestin. These results suggested that OPCs secrete a radial glia-inducing factor that might maintain the radial glial processes to use as scaffolds of migration.