Wei-Jin Zang

Differentiating characterization of human umbilical cord blood‐derived mesenchymal stem cells in vitro

It has been demonstrated that the number and differentiating potential of bone marrow mesenchymal stem cells (MSCs) decrease with age. Therefore, the search for alternative sources of MSCs is of significant value. In the present study, MSCs were isolated from umbilical cord blood (UCB) by combining gradient density centrifugation with plastic adherence. Cultured cells were treated with ascorbate acid‐2‐phosphate, dexamethasone, β‐glycerophosphate dexamethasone, insulin, 1‐methyl‐3‐isobutylxamthine, indomethacin, β‐mercaptoethanol, butylated hydroxyanisole, FGF‐4 and HGF. Differentiating characterization of UCB‐derived MSCs were detected by cytochemistry, immunocytochemistry, radioimmunoassay, RT‐PCR and urea assay. The results showed UCB‐derived MSCs could differentiate into osteoblasts, adipocytes and neuron‐like cells. When MSCs were cultured with FGF‐4 and HGF, approximately 63.6% of cells became small, round and epithelioid on day 28 by morphology. Compared with the control, levels of AFP in the supernatant liquid increased significantly from day 12 and were higher on day 28 (P < 0.01). Albumin increased significantly from day 16 (P < 0.01). Urea was first detected on day 20 (P < 0.01), and continued to increase on day 28 (P < 0.01). Cells first expressed CK‐18 on day 16 through immunocytochemistry analysis. RT‐PCR analysis showed that differentiated cells could express a number of hepatocyte‐specific genes in a time‐dependent manner. Glycogen storage was first seen on day 24. Our results suggest that UCB‐derived MSCs can differentiate not only into osteoblasts, adipocytes and neuron‐like cells, but also into hepatocytes. Human UCB‐derived MSCs are a new source of cell types for cell transplantation and therapy.

Association study between polymorphisms in selenoprotein genes and susceptibility to Kashin-Beck disease

OBJECTIVES Kashin-Beck disease (KBD) is a disabling osteoarthropathy involving growth cartilage endemic to selenium (Se)-deficient regions in China. Associations between genetic variation in selenoprotein genes and susceptibility to many diseases have recently been investigated but few studies have been performed on KBD. We found four genetic polymorphisms in selenoprotein genes and assessed their association with increased susceptibility to KBD. METHODS Four polymorphisms including GPX1 (rs1050450), TrxR2 (rs5748469), SEPP1 (rs7579) and DIO2 (rs225014) were analyzed for 161 KBD patients and 312 controls using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) or tetra-primer amplification refractory mutation system PCR (Tetra-primer ARMS PCR). Glutathione peroxidase (GPX) activity in whole blood was measured using a GPX assay kit. The mRNA expression of GPX1, nuclear factor-kappaB (NF-kappaB) p65 and p53 in both whole blood and articular cartilage tissue were detected using Real-Time PCR. RESULTS The genotypic and allelic frequency of GPX1 Pro198Leu was significantly different between KBD patients and controls (P=0.013, P=0.037). A significant increased KBD risk was observed in individuals with Pro/Leu or Leu/Leu (odds ratio=1.781; 95% confidence interval: 1.127-2.814) compared with Pro/Pro. No association was observed between the other three single nucleotide polymorphisms (SNPs) and KBD risk. In addition, GPX enzyme activity in whole blood was lower in the KBD group (P<0.01), and the GPX activity in whole blood decreased significantly in a subgroup of individuals representing Pro/Leu and Leu/Leu compared to Pro/Pro (P<0.01). In whole blood and articular cartilage tissue samples of KBD patients, GPX1 and NF-kappaB p65 mRNA levels were lower (P<0.01) while p53 levels were higher (P<0.001). CONCLUSION GPX1 Pro198Leu is a potential genetic risk factor in the development of KBD and the GPX1 Leu allele is significantly associated with higher KBD risk among the Chinese Han population and with lower GPX enzyme activity. The expression of apoptosis related molecules in KBD patients significantly differs from controls.

Phenotype Variability in Patients Carrying KCNJ2 Mutations

Background— Mutations of KCNJ2, the gene encoding the human inward rectifier potassium channel Kir2.1, cause Andersen-Tawil syndrome (ATS), a disease exhibiting ventricular arrhythmia, periodic paralysis, and dysmorphic features. However, some KCNJ2 mutation carriers lack the ATS triad and sometimes share the phenotype of catecholaminergic polymorphic ventricular tachycardia (CPVT). We investigated clinical and biophysical characteristics of KCNJ2 mutation carriers with “atypical ATS.” Methods and Results— Mutational analyses of KCNJ2 were performed in 57 unrelated probands showing typical (≥2 ATS features) and atypical (only 1 of the ATS features or CPVT) ATS. We identified 24 mutation carriers. Mutation-positive rates were 75% (15/20) in typical ATS, 71% (5/7) in cardiac phenotype alone, 100% (2/2) in periodic paralysis, and 7% (2/28) in CPVT. We divided all carriers (n=45, including family members) into 2 groups: typical ATS (A) (n=21, 47%) and atypical phenotype (B) (n=24, 53%). Patients in (A) had a longer QUc interval [(A): 695±52 versus (B): 643±35 ms] and higher U-wave amplitude (0.24±0.07 versus 0.18±0.08 mV). C-terminal mutations were more frequent in (A) (85% versus 38%, P<0.05). There were no significant differences in incidences of ventricular tachyarrhythmias. Functional analyses of 4 mutations found in (B) revealed that R82Q, R82W, and G144D exerted strong dominant negative suppression (current reduction by 95%, 97%, and 96%, respectively, versus WT at −50 mV) and T305S moderate suppression (reduction by 89%). Conclusions— KCNJ2 gene screening in atypical ATS phenotypes is of clinical importance because more than half of mutation carriers express atypical phenotypes, despite their arrhythmia severity.

Acetylcholine Mediates AMPK-Dependent Autophagic Cytoprotection in H9c2 Cells During Hypoxia/Reoxygenation Injury

Background: Acetylcholine (ACh), a neurotransmitter of vagal nerve, offers tolerance to ischemia/reperfusion injury. Given the regulation of autophagy in cardioprotection, this study was to examine the role of autophagy in ACh-elicited protection against hypoxia/reoxygenation (HR) injury. Methods: H9c2 cells were subjected to HR injury. Autophagy was determined by transmission electron microscopy, MDC staining and western blot. MTT kit, LDH and CK release, ATP content and TUNEL assay were used to evaluate cardiomyocytes injury. Atg7 and AMPK knockdown was performed with siRNA transfection. Results: Following 4, 8, 12 and 16 h reoxygenation, autophagosomes were decreased along with reduced cell viability. ACh during 4 h reoxygenation facilitated autophagy as evidence by increased autophagosomes and MDC labeling autophagic vacuoles. H9c2 cells treated with ACh also underwent a biochemical changes by increased ratio of LC3-II/LC3-I and autophagy flux (decreased p62), while muscarinic receptor antagonist atropine suppressed these effects. Induction of autophagy was correlated with enhanced cell survival and decreased apoptosis. Autophagy inhibition with chloroquine and Atg7 siRNA significantly attenuated ACh-induced cytoprotection. ACh-elicited autophagy activation could be related to increased AMPK phosphorylation and decreased mTOR phosphorylation. AMPK siRNA exhibited an elevation in mTOR phosphorylation and reduced the ratio of LC3-II/LC3-I. Importantly, AMPK knockdown desensitized H9c2 cells to ACh-mediated protection. Conclusions: These data provided first evidence that ACh-induced autophagy elicited cytoprotective effects through muscarinic receptor activated-AMPK-mTOR pathway, and suggested a novel mechanism of ACh-induced tolerance against HR injury.

Effects of Acute Administration of Ethanol on Experimental Arrhythmia

Many studies have shown that the relationship between alcohol consumption and most cardiovascular diseases is U-shaped, with nondrinkers and heavier drinkers having higher risks than moderate drinkers. However, the association between cardiac arrhythmias and acute alcohol consumption is not well understood. We set up several experimental arrhythmia animal models to examine the effects of acute administration of ethanol on arrhythmia. The results showed 0.4, 0.8 and 1.6 g/kg ethanol consumption obviously delayed the onset time of atrial fibrillation (AF) (P < 0.05 or P < 0.01) and increased the survival rates on acetylcholine-CaCl₂-induced AF in mice. Ethanol (0.4, 0.8 and 1.6 g/kg) consumption significantly delayed the onset time of ventricular tachycardia (VT), ventricular fibrillation (VF) and cardiac arrest (CA) (P < 0.01), and 0.4 and 0.8 g/kg ethanol consumption increased the survival rates on CaCl₂-induced arrhythmia in rats. Ethanol (0.4 g/kg) essentially increased the cumulative dosage of aconitine required to CA (P < 0.05), and 0.8 g/kg, 1.6 g/kg ethanol reduced the cumulative aconitine dosage to induce VT, VF and CA (P < 0.05 or P < 0.01) on aconitine-induced arrhythmia in rats. Ethanol (0.4, 0.8 and 1.6 g/kg) consumption remarkably increased the cumulative dosage of deslanoside to induce ventricualr premature contraction (P < 0.01) on deslanoside-induced arrhythmia in guinea pigs. Collectively, our results indicate that low concentrations of ethanol had anti-arrhythmic effect on experimental arrhythmia, and high concentrations of ethanol may aggravated the occurrence of experimental arrhythmia.

Cardioprotection by acetylcholine: A novel mechanism via mitochondrial biogenesis and function involving the PGC‐1α pathway

Mitochondrial biogenesis disorders appear to play an essential role in cardiac dysfunction. Acetylcholine as a potential pharmacologic agent exerts cardioprotective effects. However, its direct action on mitochondria biogenesis in acute cardiac damage due to ischemia/reperfusion remains unclear. The present study determined the involvement of mitochondrial biogenesis and function in the cardiopotection of acetylcholine in H9c2 cells subjected to hypoxia/reoxygenation (H/R). Our findings demonstrated that acetylcholine treatment on the beginning of reoxygenation improved cell viability in a concentration‐dependent way. Consequently, acetylcholine inhibited the mitochondrial morphological abnormalities and caused a significant increase in mitochondrial density, mass, and mitochondrial DNA (mtDNA) copy number. Accordingly, acetylcholine enhanced ATP synthesis, membrane potentials, and activities of mitochondrial complexes in contrast to H/R alone. Furthermore, acetylcholine stimulated the transcriptional activation and protein expression of peroxisome proliferator‐activated receptor co‐activator 1 alpha (PGC‐1α, the central factor for mitochondrial biogenesis) and its downstream targets including nuclear respiration factors and mitochondrial transcription factor A. In addition, acetylcholine activated phosphorylation of AMP‐activated protein kinase (AMPK), which was located upstream of PGC‐1α. Atropine (muscarinic receptor antagonist) abolished the favorable effects of acetylcholine on mitochondria. Knockdown of PGC‐1α or AMPK by siRNA blocked acetylcholine‐induced stimulating effects on mtDNA copy number and against cell injury. In conclusion, we suggested, acetylcholine as a mitochondrial nutrient, protected against the deficient mitochondrial biogenesis and function induced by H/R injury in a cellular model through muscarinic receptor‐mediated, AMPK/PGC‐1α‐associated regulatory program, which may be of significance in elucidating a novel mechanism underlying acetylcholine‐induced cardioprotection. J. Cell. Physiol. 228: 1238–1248, 2013.

Optimizing the Parameters of Vagus Nerve Stimulation by Uniform Design in Rats with Acute Myocardial Infarction

Vagus nerve stimulation (VNS) has been shown to improve left ventricular function and survival in rats with acute myocardial infarction (AMI), and this maneuver has also been adopted clinically for the treatment of patients with chronic heart failure (CHF). Recent in vitro and in vivo studies have suggested that VNS can modulate the level of pro-inflammatory factors. Despite the beneficial effects of VNS, the stimulation parameters for obtaining favorable outcomes appear highly variable. To optimize VNS parameters, we set up different stimulation protocols with different pulse width (1–2 ms), frequency (1–6 Hz), voltage (1–6 V) and duration (40–240 min) of VNS by uniform design (UD). Rats were divided into seven groups with (Group1–Group6) or without VNS (MI group). Our results demonstrate that (1) the parameter sets in Group1, Group2 and Group3 yield the best post-MI protection by VNS, while the protective role were not observed in Group4, Group5 and Group6; (2) baroreflex sensitivity and the α7 nicotinic acetylcholine receptor level were also increased in Group1, Group2 and Group3. (3) the parameter set in Group1 (G1:1 ms, 2 Hz, 3 V, 240 min) is judged the most optimal parameter in this study as rats in this group not only showed a reduced myocardial injury with better-preserved cardiac function compared with other groups, more important, but also exhibited minimal heart rate (HR) reduction. (4) the duration of VNS plays an important role in determining the protection effect of VNS. In conclusion, VNS displays a beneficial role in Group1, Group2 and Group3. Of note, the parameter set in Group1 provides the most optimal cardioprotective effect. These results may provide insight into development of novel treatment for ischemic heart diseases.

Ultra-slow voltage-dependent inactivation of the calcium current in guinea-pig and ferret ventricular myocytes.

L-type Ca2+ current, iCa, has been recorded in guinea-pig ventricular myocytes at 36° C using the whole cell patch clamp technique. Intracellular Ca2+ was buffered with ethylenebis(oxonitrilo)tetraacetate (EGTA). An increase in the rate of stimulation from 0.5 to 3 Hz resulted in an abrupt decrease in iCa in the first beat at the high rate, followed by a progressive decrease (τ approx. 7 s) over the next 30 s. The changes were not the result of Ca2+-dependent inactivation, because similar changes occurred with either Ba2+ or Na+ as the charge carrier. During 20-s voltage clamp pulses there was an ultra-slow phase of inactivation of Ba2+ or Na+ current through the Ca2+ channel (τ approx. 6 s at 0 mV). This was confirmed by applying test pulses after conditioning pulses of different duration: the Ba2+ current during the test pulse decreased progressively when the duration of the conditioning pulse was increased progressively to 20 s. Ultra-slow inactivation of Ba2+ current was voltage dependent and increased monotonically at more positive potentials. Recovery of Ba2+ current from ultra-slow inactivation occurred with a time constant of 3.7 s at −40 mV and 0.7 s at −80 mV. The gradual decrease in iCa on increasing the rate to 3 Hz may have been the result of the development of ultra-slow voltage-dependent inactivation.

Receptor kinase‐dependent desensitization of the muscarinic K+ current in rat atrial cells.

1. Activity of rat atrial muscarinic K+ channels has been measured in five configurations of the patch clamp technique. 2. In configurations in which the normal intracellular solution was lost, the slow phase of desensitization (a slow decline of channel activity during an exposure to ACh) was much reduced (or absent) and deactivation (on wash‐off of ACh) was slowed as compared with desensitization and deactivation in configurations in which normal intracellular solution was retained. This suggests that soluble intracellular regulators are involved in these processes. 3. When a G protein‐coupled receptor kinase (GRK2) was applied to the cytoplasmic surface of conventional outside‐out patches in the presence of ATP, the slow phase of desensitization was restored. In the absence of ATP, GRK2 failed to restore the slow phase. 4. It is concluded that (i) G protein‐coupled receptor kinase dependent phosphorylation of the muscarinic receptor is responsible for the slow phase of desensitization and (ii) a soluble factor (such as a GTPase activating protein or ‘GAP’) is responsible for normal rapid deactivation.

Characterization of ion channels in human preadipocytes

Ion channels participate in regulation of cell proliferation. However, though preadipocyte (the progenitor of fat cell) is a type of highly proliferating cells, ion channel expression and their role in proliferation is not understood in human preadipocytes. The present study was designed to characterize ion channels using whole‐cell patch clamp technique, RT‐PCR, and Western blotting. It was found that a 4‐aminopyridine‐ (4‐AP) sensitive transient outward K+ current (Ito) was present in a small population of (32.0%) cells, and an outward “noisy” big conductance Ca2+‐activated K+ current (IKCa) was present in most (92.7%) preadipocytes. The noisy current was inhibited by the big conductance IKCa channel blocker paxilline (1 µM), and enhanced by the Ca2+ ionophore A23187 (5 µM) and the big conductance IKCa channel activator NS1619 (10 µM). RT‐PCR and Western blot revealed the molecular identities (i.e., KCa1.1 and Kv4.2) of the functional ionic currents IKCa and Ito. Blockade of IKCa or Ito with paxilline or 4‐AP reduced preadipocyte proliferation, and similar results were obtained with specific siRNAs targeting to KCa1.1 and Kv4.2. Flow cytometric analysis showed ion channel blockade or knockdown of KCa1.1 or Kv4.2 with specific siRNA increased the cell number of G0/G1 phase. The present study demonstrates for the first time that two types of functional ion channel currents, Ito and big conductance IKCa, are present in human preadipocytes and that these two types of ion channels participate in regulating proliferation of human preadipocytes. J. Cell. Physiol. 218: 427–435, 2009.