Biomedical subjects

Xing Zhao

Publications and source records attributed to Xing Zhao.

23 records · Page 2Linked to original sources

PubMed2002

Adult corneal limbal epithelium: a model for studying neural potential of non-neural stem cells/progenitors.

Recent studies suggest that tissue-specific stem cells possess much wider potential for differentiation than previously thought and can, in some instances, even cross germ layer boundaries. However, information is lacking regarding the efficiency and the fidelity of their differentiation along heterologous lineages. To address these issues of transdifferentiation, we have analyzed the heterologous potential of stem cells within the same germ layer. We report the neural potential of cells isolated from the limbal epithelium of the adult cornea. Limbal epithelium, which, like the neuroepithelium, is ectodermally derived, participates in the regeneration of cornea throughout life. We have observed that limbal epithelial cells, when removed from their niche and cultured in the presence of mitogens, begin to express neural progenitor markers. Based on the self-renewal property, it is likely that the nestin-positive progenitors are derived from limbal stem cells rather than transit-amplifying (TA) cells that have limited proliferating potential. In differentiation conditions, a subset of these cells acquire neural morphology and express transcripts and proteins specific to neurons and glia, suggesting their differentiation along neural lineage. The acquisition of neural properties is regulated by BMP signaling. Neural differentiation of these cells is also observed upon heterotopic transplantation. Investigation of functional differentiation of cells by electrophysiological analysis reveals properties consistent with the presence of glia that are influenced by extracellular cues. However, similar analyses coupled with Ca(2+) imaging suggest an incomplete differentiation of limbal epithelial-derived neural progenitors into neurons in the condition studied. Our study, therefore, draws attention toward the necessity for rigorous characterization of transdifferentiation and offers a model for characterizing neural potential of heterologous stem cells/progenitors.

Animals↗

PubMed2002

Differentiation of embryonic stem cells into retinal neurons.

Mouse embryonic stem (ES) cells are continuous cell lines derived from the inner mass of blastocysts. Neural progenitors derived from these cells serve as an excellent model for controlled neural differentiation and as such have tremendous potential to understand and treat neurodegenerative diseases. Here, we demonstrate that ES cell-derived neural progenitors express regulatory factors needed for retinal differentiation and that in response to epigenetic cues a subset of them differentiate along photoreceptor lineage. During the differentiation, they activate photoreceptor regulatory genes, suggesting that ES cell-derived neural progenitors recruit mechanisms normally used for photoreceptor differentiation in vivo. These observations suggest that ES cells can serve as an excellent model for understanding mechanisms that regulate specification of retinal neurons and as an unlimited source of neural progenitors for treating degenerative diseases of the retina by cell replacement.

Animals↗

PubMed2002

An open-label trial of theophylline for functional chest pain.

Visceral hypersensitivity may play a role in the pathogenesis of functional chest pain, although the underlying mechanism(s) is unknown. We investigated the effects of theophylline, an adenosine receptor antagonist, on sensory perception and biomechanical properties of esophagus in patients with functional chest pain. Esophageal balloon distention was performed using impedance planimetry in 21 consecutive patients with functional chest pain. Patients found to have a hypersensitive esophagus received intravenous theophylline and balloon distension was repeated. If the hypersensitivity improved, oral theophylline was prescribed for three months as an open label trial. Balloon distension reproduced typical chest pain in 16 (76%) patients at thresholds suggestive of hypersensitivity. After theophylline infusion, pain thresholds increased in 12 (75%) patients. Median threshold pressures for discomfort and pain improved (P < 0.01). Cross-sectional area increased (P < 0.05) and the tension/strain association shifted to the right (P < 0.01). Seven of eight patients reported sustained improvement in pain after oral theophylline. Theophylline may ameliorate chest pain in patients with hypersensitive esophagus, possibly by altering adenosine-mediated nociception.

Biomechanical Phenomena↗

PubMed2002

[Laggera pterodonta--a Yunnan Herbal Medicine]

OBJECTIVE: A systematic study of Laggera pterodonta was performed in order to identify its bioactive compounds. METHODS: Solvent partition and column chromatography used to isolate and purify Laggera pterodonta compounds. The isolated compounds were further elucidated by high field NMR spectroscopy. RESULTS: Fifty-two compounds were separated and the structures of 39 compounds were elucidated. Twenty-four compounds have not been previously reported. For example, the structure of compound 19, a previously undetected compound was elucidated as 4gamma, 9alpha,11-triol-enantio-eudesmane using both 1D and 2D NMR spectroscopy. Major secondary metabolites of the Laggera pterodonta included eudesmane-type sesquiterpenes and flavone derivatives. CONCLUSION: A systematic study of a yunnan herbal medicine Laggera pterodonta resvealed several novel compounds that may have clinical significance. Further in vivo animal studies should be performed to assess their bioactive role.

Journal Article↗

PubMedDate not supplied

Stem cell therapy for retinal degeneration: retinal neurons from heterologous sources.

Over the past few years a great deal of interest has been generated in using stem cells/progenitors to treat degenerative diseases that afflict different tissues, including retina. This interest is due to the defining properties of stem cells/progenitors, the ability of these cells to self-renew and generate all the basic cell types of the particular tissue to which they belong. In addition, the recent reports of plasticity of the adult tissue-specific stem cells/progenitors and directed differentiation of the embryonic cells (ES) has fueled the hope for cell and gene therapy using stem cells from heterologous sources. Will this approach work for treating retinal degeneration? Here, we review the current state of knowledge about obtaining retinal cells from heterologous sources, including ES cells.

Animals↗