Biomedical subjects

T Ma

Publications and source records attributed to T Ma.

At least 37 records · Page 2Linked to original sources

PubMed2001

Oxygen tension influences proliferation and differentiation in a tissue-engineered model of placental trophoblast-like cells.

A considerable oxygen gradient exists in vivo, which exerts regulatory effects on tissue development and function. The objective of this study was to evaluate the feasibility of controlling cell proliferation and differentiation by regulating oxygen tension in a tissue-engineered bioreactor model. The effects of oxygen tension on proliferation and differentiation of first-trimester human trophoblast cells (known as ED(27) cells) were studied in a fiber-bed perfusion bioreactor system in which cells were grown in polyethylene terephthalate (PET) nonwoven fibrous matrix. By varying the oxygen tension between 2% and 20%, differential responses of trophoblasts in their proliferation and differentiation activities were observed. There was no significant difference in the rates of glucose consumption and lactate production, and lactate dehydrogenase (LDH) level in the culture media for both 2% and 20% oxygen tension cultures, indicating that cell metabolic activities were not limited by low oxygen tension. However, 2% oxygen stimulated cell proliferation but impeded the secretion of a functional hormone, 17beta-estradiol. In contrast, 20% oxygen tension reduced cell proliferation, but yielded higher hormone secretion. A step change in oxygen tension from 2% to 20% caused cells in the bioreactor to increase 17beta-estradiol secretion and shifted cell cycle from proliferation to differentiation, which were verified with the expression levels of cyclin B1 and p27(kip1). However, no significant response to a change from 6% to 20% oxygen tension was observed. It is concluded that changes in oxygen tension can be an effective strategy to control cell cycle and long-term tissue development. This work also demonstrated the important role of oxygen tension in regulating placental trophoblast tissue development and the feasibility of using the bioreactor under well-controlled physiological environment for tissue engineering applications.

Bioreactors↗

PubMed2001

Human cord cell hematopoiesis in three-dimensional nonwoven fibrous matrices: in vitro simulation of the marrow microenvironment.

Current hematopoietic culture systems mainly utilize two-dimensional devices with limited ability to promote self-renewal of early progenitors. In vivo-like three-dimensional (3-D) culture environments might be conducive to regulating stem cell proliferation and differentiation similar to in vivo hematopoiesis. The few 3-D cultures reported in the literature either produced few progenitors or provided little information about microenvironment. In this study, we constructed a 3-D hematopoietic microenvironment composed of nonwoven matrix and human cord blood (CB) cells to simulate the marrow microenvironment and expand cord progenitors. Nonwoven polyethylene terephthalate (PET) fabric with defined microstructure was used as the 3-D scaffold and the PET surface was modified by hydrolysis to improve cell adhesion. Different cell organizations were formed in a 3-D matrix in a developmental manner, from individual cells and cells bridging between fibers to large cell aggregates. Both stromal and hematopoietic cells were distributed spatially within the scaffold. Compared to two-dimensional (2-D) CD34(+) cell culture, 3-D culture produced 30-100% higher total cells and progenitors without exogenous cytokines. With thrombopoietin and flt-3/flk-2 ligand, it supported two- to three-fold higher total cell number (62.1- vs. 24.6-fold), CD34(+) cell number (6.8- vs. 2.8-fold) and colony-forming unit (CFU) number for 7-9 weeks (n = 6), indicating a hematopoiesis pathway that promoted progenitor production. Culture in 3-D nonwoven matrices enhanced cell-cell and cell-matrix interactions and allowed 3-D distribution of stromal and hematopoietic cells. The formation of cell aggregates and higher progenitor content indicated that the spatial microenvironment in 3-D culture played an important role in promoting hematopoiesis. This 3-D culture system can be used as an in vitro model to study stem cell or progenitor behavior, and to achieve sustained progenitor expansion.

Biocompatible Materials↗

PubMed2001

Defective dietary fat processing in transgenic mice lacking aquaporin-1 water channels.

Immunocytochemistry showed expression of aquaporin-1 (AQP1) water channels at sites involved in dietary fat processing, including intrahepatic cholangiocytes, gallbladder, pancreatic microvascular endothelium, and intestinal lacteals. To determine whether AQP1 has a role in dietary fat digestion and/or absorption, mice were placed on a diet that contained 50% fat. Whereas wild-type mice (3-3.5 wk of age, 10-12 g) gained 49 +/- 5% (SE, n = 50) body weight in 8 days, and heterozygous mice gained 46 +/- 4%, AQP1 null mice gained only 4 +/- 3%; weights became similar after return to a 6% fat diet after 6 days. The null mice on a high-fat diet acquired an oily appearance, developed steatorrhea with increased stool triglyceride content, and manifested serum hypotriglyceridemia. Supplementation of the high-fat diet with pancreatic enzymes partially corrected the decreased weight gain in null mice. Absorption of [(14)C]oleic acid from small intestine was not affected by AQP1 deletion, as determined by blood radioactivity after duodenal infusion. Lipase activity in feces and small intestine was remarkably greater in AQP1 null than wild-type mice on low- and high-fat diets. Fluid collections done in older mice (that are less sensitive to a high-fat diet) by ductal cannulation showed threefold increased pancreatic fluid flow in response to secretin/cholecystokinin, but volumes, pH, and amylase activities were affected little by AQP1 deletion, nor were bile flow rates and bile salt concentrations. Together, these results establish a dietary fat misprocessing defect in AQP1 null mice.

Age Factors↗

PubMed2001

[Eyelid reconstruction with a reversal flow axial preauricular island flap based on the supraorbital artery].

OBJECTIVE: In order to find an ideal flap to reconstruct the eyelid defect, we have explored the possibilities to reconstruct eyelid with a reversal flow axial preauricular island flap based on the supraorbital artery. METHODS: According to Chen's theory on "reversal flow axial flap", we designed and applied the reversal flow axial preauricular island flap based on the supraorbital artery, which could nourish the flap by anastomotic branches between the supraorbital artery and the frontal branch of the superficial temporal artery. RESULTS: We have successfully reconstructed 7 cases of eyelid defect with this method since 1997. The size of the flaps ranged from 4.0 cm x 2.4 cm to 2.0 cm x 1.8 cm and good result were revealed with 1-2 years follow up. CONCLUSIONS: The flap has a stable and reliable blood supplying. It is an ideal flap to reconstruct the eyelid defect for texture and color similarity of the eyelid and preauricular skin.

Adolescent↗

PubMed2001

[The application of genetic engineering to the petroleum biodesulfurization].

The developed course and reaction mechanisms of petroleum biodesulfurization were introduced. The recent development of genetic engineering technology, which used in desulfuration strain's construction, reconstruction and other fields, was summarized emphatically. Its current research situation internal and overseas and the developing prospect were simply analyzed, and our research designs were submitted.

Biodegradation, Environmental↗

PubMed2000

Effects of pore size in 3-D fibrous matrix on human trophoblast tissue development.

The effects of pore size in a 3-D polyethylene terephthalate (PET) nonwoven fibrous matrix on long-term tissue development of human trophoblast ED27 cells were studied. Thermal compression was used to modify the porosity and pore size of the PET matrix. The pore size distributions in PET matrices were quantified using a liquid extrusion method. Cell metabolic activities, estradiol production, and cell proliferation and differentiation were studied for ED27 cells cultured in the thermally compressed PET matrices with known pore structure characteristics. In general, metabolic activities and proliferation rate were higher initially for cultures grown in the low-porosity (LP) PET matrix (porosity of 0.849, average pore size of 30 microm in diameter) than those in the high-porosity (HP) matrix (porosity of 0.896, average pore size of 39 microm in diameter). However, 17beta-estradiol production and cell differentiation activity in the HP matrix surpassed those in the LP matrix after 12 days. The expression levels of cyclin B1 and p27kip1 in cells revealed progressively decreasing proliferation and increasing differentiation activities for cells grown in PET matrices. Also, difference in pore size controlled the cell spatial organization in the PET matrices and contributed to the tissue development in varying degrees of proliferation and differentiation. It was also found that cells grown on the 2-D surface behaved differently in cell cycle progression and did not show increased differentiation activities after growth had stopped and proliferation activities had lowered to a minimal level. The results from this study suggest that the 3-D cell organization guided by the tissue scaffold is important to tissue formation in vitro.

Blotting, Western↗

PubMed2000

Cell cycle-regulated phosphorylation of p220(NPAT) by cyclin E/Cdk2 in Cajal bodies promotes histone gene transcription.

Cyclin E/Cdk2 acts at the G1/S-phase transition to promote the E2F transcriptional program and the initiation of DNA synthesis. To explore further how cyclin E/Cdk2 controls S-phase events, we examined the subcellular localization of the cyclin E/Cdk2 interacting protein p220(NPAT) and its regulation by phosphorylation. p220 is localized to discrete nuclear foci. Diploid fibroblasts in Go and G1 contain two p220 foci, whereas S- and G2-phase cells contain primarily four p220 foci. Cells in metaphase and telophase have no detectable focus. p220 foci contain cyclin E and are coincident with Cajal bodies (CBs), subnuclear organelles that associate with histone gene clusters on chromosomes 1 and 6. Interestingly, p220 foci associate with chromosome 6 throughout the cell cycle and with chromosome 1 during S phase. Five cyclin E/Cdk2 phosphorylation sites in p220 were identified. Phospho-specific antibodies against two of these sites react with p220 within CBs in a cell cycle-specific manner. The timing of p220 phosphorylation correlates with the appearance of cyclin E in CBs at the G1/S boundary, and this phosphorylation is maintained until prophase. Expression of p220 activates transcription of the histone H2B promoter. Importantly, mutation of Cdk2 phosphorylation sites to alanine abrogates the ability of p220 to activate the histone H2B promoter. Collectively, these results strongly suggest that p220(NPAT) links cyclical cyclin E/Cdk2 kinase activity to replication-dependent histone gene transcription.

Amino Acid Sequence↗

PubMed2000

Comparison of G-protein activation in the brain by mu-, delta-, and kappa-opioid receptor agonists in mu-opioid receptor knockout mice.

Mice lacking the mu-opioid receptor gene have been developed by a gene knockout procedure. In this study, the activity of opioid receptor coupled G-proteins was examined to investigate whether there is a change in the extent of coupling for mu, delta-, and kappa-opioid receptors in mu-opioid receptor knockout mice. Selective agonists of mu- (DAMGO), delta- (DPDPE), and kappa- (U-69,593) opioid receptors stimulated [(35)S]GTPgammaS binding in the caudate putamen and cortex of wild-type mice. In contrast, only U-69,593 stimulated [(35)S]GTPgammaS binding in these regions of mu-opioid receptor knockout mice. These results confirmed the absence of G-protein activation by a mu-opioid receptor agonist in mu-opioid receptor knockout mice, and demonstrated that coupling of the kappa-opioid receptor to G-proteins is preserved in these mice. However, G-protein activation by the delta-opioid receptor agonist, DPDPE, was reduced in the mu-opioid receptor knockout mice, at least in the brain regions studied using autoradiography.

Alleles↗

PubMed2000

Role of aquaporins in alveolar fluid clearance in neonatal and adult lung, and in oedema formation following acute lung injury: studies in transgenic aquaporin null mice.

Aquaporin (AQP) water channels provide a major pathway for osmotically driven water movement across epithelial and microvascular barriers in the lung. We used mice deficient in each of the three principal lung aquaporins, AQP1, AQP4 and AQP5, to test the hypothesis that aquaporins are important in neonatal lung fluid balance, adult lung fluid clearance and formation of lung oedema after acute lung injury. Wet-to-dry weight ratios (W/D) in lungs from wild-type mice decreased from 7.9 to 5.7 over the first hour after spontaneous delivery. AQP deletion did not significantly affect W/D at 45 min after birth. Alveolar fluid clearance was measured in living ventilated mice in which 0.5 ml saline containing radiolabelled albumin was instilled into the airspaces. Fluid clearance was 17.4 % in 15 min and inhibited >90 % by amiloride, but clearance was not affected by AQP deletion. W/D was measured in established models of acute lung injury - acid aspiration and thiourea administration. Two hours after intratracheal administration of HCl, W/D increased from 3.7 to 7.5 but was not affected by AQP deletion. Three hours after intraperitoneal infusion of thiourea, W/D increased to 5.5 and marked pleural effusions appeared, but there were no differences in wild-type and AQP knockout mice. Hyperoxic subacute lung injury was induced by 95 % oxygen. Neither mean survival (143 h) nor W/D at 65 h (5.1) were significantly affected by AQP deletion. Despite their role in osmotically driven lung water transport, aquaporins are not required for the physiological clearance of lung water in the neonatal or adult lung, or for the accumulation of extravascular lung water in the injured lung.

Acids↗

PubMed2000

Involvement of mu-opioid receptors in potentiation of apomorphine-induced climbing behavior by morphine: studies using mu-opioid receptor gene knockout mice.

The present study examined the hypothesis that mu-opioid receptors contribute to a behavioral stimulation produced by stimulation of dopamine receptors by comparing responses in mu-opioid receptor knockout and wild type mice. Apomorphine-induced climbing behavior was augmented by 65%, in wild type mice, but not in mu-knockout, following subcutaneous administration of morphine (15 mg/kg). Moreover, pretreatment with either naloxone (an opioid receptor antagonist) or haloperidol (a mixed D(1)/D(2) receptor antagonist) eliminated the enhancement by morphine of climbing behavior in wild type mice. These results indicate that expression of mu-opioid receptors plays an important role in the enhancement of climbing behavior induced by the dopamine receptor agonist, apomorphine. Furthermore, this augmentation is mediated by interaction between dopamine and mu-opioid receptors.

Analgesics, Opioid↗

PubMed2000

Nephrogenic diabetes insipidus in mice lacking aquaporin-3 water channels.

Aquaporin-3 (AQP3) is a water channel expressed at the basolateral plasma membrane of kidney collecting-duct epithelial cells. The mouse AQP3 cDNA was isolated and encodes a 292-amino acid water/glycerol-transporting glycoprotein expressed in kidney, large airways, eye, urinary bladder, skin, and gastrointestinal tract. The mouse AQP3 gene was analyzed, and AQP3 null mice were generated by targeted gene disruption. The growth and phenotype of AQP3 null mice were grossly normal except for polyuria. AQP3 deletion had little effect on AQP1 or AQP4 protein expression but decreased AQP2 protein expression particularly in renal cortex. Fluid consumption in AQP3 null mice was more than 10-fold greater than that in wild-type litter mates, and urine osmolality (<275 milliosmol) was much lower than in wild-type mice (>1,200 milliosmol). After 1-desamino-8-d-arginine-vasopressin administration or water deprivation, the AQP3 null mice were able to concentrate their urine partially to approximately 30% of that in wild-type mice. Osmotic water permeability of cortical collecting-duct basolateral membrane, measured by a spatial filtering optics method, was >3-fold reduced by AQP3 deletion. To test the hypothesis that the residual concentrating ability of AQP3 null mice was due to the inner medullary collecting-duct water channel AQP4, AQP3/AQP4 double-knockout mice were generated. The double-knockout mice had greater impairment of urinary-concentrating ability than did the AQP3 single-knockout mice. Our findings establish a form of nephrogenic diabetes insipidus produced by impaired water permeability in collecting-duct basolateral membrane. Basolateral membrane aquaporins may thus provide blood-accessible targets for drug discovery of aquaretic inhibitors.

Amino Acid Sequence↗

PubMed2000

HeLa cells are phenotypically limiting in cyclin E/CDK2 for efficient human papillomavirus DNA replication.

Human papillomaviral (HPV) origin-containing plasmids replicate efficiently in human 293 cells or cell extracts in the presence of HPV origin-recognition protein E2 and replication initiation protein E1, whereas cervical carcinoma-derived, HPV-18-positive HeLa cells or cell extracts support HPV DNA replication poorly. We recently showed that HPV-11 E1 interacts with cyclin/cyclin-dependent kinase (cdk) complexes through an RXL motif and is a substrate for these kinases. E1 mutations in this motif or in candidate cdk phosphorylation sites are impaired in replication, suggesting a role for cdks in HPV replication. We now demonstrate that one limiting activity in HeLa cells is cyclin E/CDK2. Purified cyclin E/CDK2 or cyclin E/CDK3 complex, but not other cdks, partially complemented HeLa cell extracts. Cyclin E/CDK2 expression vectors also enhanced transient HPV replication in HeLa cells. HeLa cell-derived HPV-18 E1 protein is truncated at the carboxyl terminus but can associate with cyclin E/CDK2. This truncated E1 was replication-incompetent and inhibited cell-free HPV replication. These results indicate that HeLa cells are phenotypically limiting in cyclin E/CDK2 for efficient HPV replication, most likely due to sequestration by the endogenous, defective HPV-18 E1 protein. Further analyses of the regulation of HPV E1 and HPV replication by cyclin E may shed light on the roles of cyclin E/CDK2 in cellular DNA replication.

CDC2-CDC28 Kinases↗

PubMed2000

Partial correction of the urinary concentrating defect in aquaporin-1 null mice by adenovirus-mediated gene delivery.

The feasibility of water channel gene delivery to kidney tubules and microvessels was evaluated by delivery of an adenovirus encoding aquaporin 1 (AQP1-Ad5) to transgenic AQP1 null mice. In wild-type mice, AQP1 is expressed in kidney proximal tubule, thin descending limb of Henle, and descending vasa recta, where urine osmolality (Uosm) increases from 1000-1500 mOsm (before) to 2500-3500 mOsm after 36 hr of water deprivation. Uosm in AQP1 null mice remains nearly fixed at 650-750 mOsm. AQP1-Ad5 (with a CMV promoter) was generated and purified. Infection of CHO cells gave strong uniform AQP1 expression with plasma membrane localization and eightfold increased water permeability over noninfected cells. AQP1-Ad5 was delivered to 20 to 25-g AQP1 null mice by tail vein infusion (0-10(10) PFU). At 3-7 days, AQP1 protein expression was strongest in liver (approximately 20 microg of AQP1 protein per liver) and next strongest in kidney, with expression in proximal tubule apical and basolateral membranes, and renal microvessels. Functional analysis showed increased water permeability in apical membrane vesicles from proximal tubule. AQP1 expression was not detected in glomerulus, limb of Henle, or collecting duct. In water-deprived null mice receiving 5 x 10(9) PFU of AQP1-Ad5, Uosm increased by up to 510 mOsm (mean increase, 225 +/- 24 mOsm; n = 33 mice). Whereas the control null mice became lethargic and lost 34.2 +/- 0.6% body weight, the virus-treated mice remained relatively active and lost 32.3 +/- 0.7% body weight. Viral DNA and AQP1 transcript were detected in kidney and liver of null mice up to 17 weeks after virus infusion; partial correction of the urinary concentrating defect persisted for 3-5 weeks. These results demonstrate partial functional correction of a urinary concentrating defect by adenoviral delivery of the AQP1 gene.

Adenoviridae↗

PubMed2000

Carbon dioxide permeability of aquaporin-1 measured in erythrocytes and lung of aquaporin-1 null mice and in reconstituted proteoliposomes.

Measurements of CO(2) permeability in oocytes and liposomes containing water channel aquaporin-1 (AQP1) have suggested that AQP1 is able to transport both water and CO(2). We studied the physiological consequences of CO(2) transport by AQP1 by comparing CO(2) permeabilities in erythrocytes and intact lung of wild-type and AQP1 null mice. Erythrocytes from wild-type mice strongly expressed AQP1 protein and had 7-fold greater osmotic water permeability than did erythrocytes from null mice. CO(2) permeability was measured from the rate of intracellular acidification in response to addition of CO(2)/HCO(3)(-) in a stopped-flow fluorometer using 2',7'-bis-(2-carboxyethyl)-5-(and -6)-carboxyfluorescein (BCECF) as a cytoplasmic pH indicator. In erythrocytes from wild-type mice, acidification was rapid (t((1)/(2)), 7.3 +/- 0.4 ms, S.E., n = 11 mice) and blocked by acetazolamide and increasing external pH (to decrease CO(2)/HCO(3)(-) ratio). Apparent CO(2) permeability (P(CO(2))) was not different in erythrocytes from wild-type (0.012 +/- 0.0008 cm/s) versus null (0.011 +/- 0.001 cm/s) mice. Lung CO(2) transport was measured in anesthetized, ventilated mice subjected to a decrease in inspired CO(2) content from 5% to 0%, producing an average decrease in arterial blood pCO(2) from 77 +/- 4 to 39 +/- 3 mm Hg (14 mice) with a t((1)/(2)) of 1.4 min. The pCO(2) values and kinetics of decreasing pCO(2) were not different in wild-type versus null mice. Because AQP1 deletion did not affect CO(2) transport in erythrocytes and lung, we re-examined CO(2) permeability in AQP1-reconstituted liposomes containing carbonic anhydrase (CA) and a fluorescent pH indicator. Whereas osmotic water permeability in AQP1-reconstituted liposomes was >100-fold greater than that in control liposomes, apparent P(CO(2)) (approximately 10(-3) cm/s) did not differ. Measurements using different CA concentrations and HgCl(2) indicated that liposome P(CO(2)) is unstirred layer-limited and that HgCl(2) slows acidification because of inhibition of CA rather than AQP1. These results provide direct evidence against physiologically significant AQP1-mediated CO(2) transport and establish an upper limit to the CO(2) permeability through single AQP1 water channels.

Animals↗

PubMed2000

Tear secretion by lacrimal glands in transgenic mice lacking water channels AQP1, AQP3, AQP4 and AQP5.

The expression of three aquaporin (AQP)-type water channels has been reported in the lacrimal gland: AQP5 in the apical membranes of acinar and duct cells, AQP4 in the basolateral membranes of acinar cells, and AQP1 in microvascular endothelia. Recent experiments indicate that water movement through AQP5 in the salivary gland is important in saliva secretion. To investigate the role of aquaporins in lacrimal gland function, basal and pilocarpine-stimulated tear secretion was compared in wildtype mice and knockout mice lacking AQP1, AQP4 and AQP5, as well as AQP3, which was found here to be expressed in the basolateral membrane of acinar cells. Tear fluid was collected in anesthetized mice using microcapillary tubes before and at 4 min intervals after pilocarpine administration. Tear fluid volumes were (in microliter per 4 min, S.E.): 0.69 +/- 0.06 (wildtype mice), 0.70 +/- 0.07 (AQP1 -/-), 0.81 +/- 0.13 (AQP3 -/-), 0.62 +/- 0.14 (AQP4 -/-), and 0.78 +/- 0.09 (AQP5 -/-) (differences not significant). Chloride concentrations (average 155 +/- 13 mM) measured by a fluorescence assay were also not different in tear fluid collected from wildtype vs aquaporin null mice. These findings provide direct evidence against an essential role for aquaporins in lacrimal gland fluid secretion. The requirement for aquaporins in salivary but not lacrimal gland secretion, may involve the substantially slower fluid secretion rate across lacrimal gland acinar cells.

Animals↗

PubMed2000

Aquaporin-4 deletion in mice reduces brain edema after acute water intoxication and ischemic stroke.

Cerebral edema contributes significantly to morbidity and death associated with many common neurological disorders. However, current treatment options are limited to hyperosmolar agents and surgical decompression, therapies introduced more than 70 years ago. Here we show that mice deficient in aquaporin-4 (AQP4), a glial membrane water channel, have much better survival than wild-type mice in a model of brain edema caused by acute water intoxication. Brain tissue water content and swelling of pericapillary astrocytic foot processes in AQP4-deficient mice were significantly reduced. In another model of brain edema, focal ischemic stroke produced by middle cerebral artery occlusion, AQP4-deficient mice had improved neurological outcome. Cerebral edema, as measured by percentage of hemispheric enlargement at 24 h, was decreased by 35% in AQP4-deficient mice. These results implicate a key role for AQP4 in modulating brain water transport, and suggest that AQP4 inhibition may provide a new therapeutic option for reducing brain edema in a wide variety of cerebral disorders.

Animals↗

PubMed2000

Role of aquaporin-4 in airspace-to-capillary water permeability in intact mouse lung measured by a novel gravimetric method.

The mammalian peripheral lung contains at least three aquaporin (AQP) water channels: AQP1 in microvascular endothelia, AQP4 in airway epithelia, and AQP5 in alveolar epithelia. In this study, we determined the role of AQP4 in airspace-to-capillary water transport by comparing water permeability in wild-type mice and transgenic null mice lacking AQP1, AQP4, or AQP1/AQP4 together. An apparatus was constructed to measure lung weight continuously during pulmonary artery perfusion of isolated mouse lungs. Osmotically induced water flux (J(v)) between the airspace and capillary compartments was measured from the kinetics of lung weight change in saline-filled lungs in response to changes in perfusate osmolality. J(v) in wild-type mice varied linearly with osmotic gradient size (4.4 x 10(-5) cm(3) s(-1) mOsm(-1)) and was symmetric, independent of perfusate osmolyte size, weakly temperature dependent, and decreased 11-fold by AQP1 deletion. Transcapillary osmotic water permeability was greatly reduced by AQP1 deletion, as measured by the same method except that the airspace saline was replaced by an inert perfluorocarbon. Hydrostatically induced lung edema was characterized by lung weight changes in response to changes in pulmonary arterial inflow or pulmonary venous outflow pressure. At 5 cm H(2)O outflow pressure, the filtration coefficient was 4.7 cm(3) s(-1) mOsm(-1) and reduced 1.4-fold by AQP1 deletion. To study the role of AQP4 in lung water transport, AQP1/AQP4 double knockout mice were generated by crossbreeding of AQP1 and AQP4 null mice. J(v) were (cm(3) s(-1) mOsm(-1) x 10(-5), SEM, n = 7-12 mice): 3.8 +/- 0. 4 (wild type), 0.35 +/- 0.02 (AQP1 null), 3.7 +/- 0.4 (AQP4 null), and 0.25 +/- 0.01 (AQP1/AQP4 null). The significant reduction in P(f) in AQP1 vs. AQP1/AQP4 null mice was confirmed by an independent pleural surface fluorescence method showing a 1.6 +/- 0.2-fold (SEM, five mice) reduced P(f) in the AQP1/AQP4 double knockout mice vs. AQP1 null mice. These results establish a simple gravimetric method to quantify osmosis and filtration in intact mouse lung and provide direct evidence for a contribution of the distal airways to airspace-to-capillary water transport.

Animals↗

PubMed2000

Role of water channels in fluid transport studied by phenotype analysis of aquaporin knockout mice.

Aquaporin-type water channels are expressed widely in mammalian tissues, particularly in the kidney, lung, eye and gastrointestinal tract. To define the role of aquaporins in organ physiology, we have generated and analysed transgenic mice lacking aquaporins (AQP) 1, 3, 4 and 5. Multiple phenotype abnormalities were found in the null mice. For example, in kidney, deletion of AQP1 or AQP3 produced marked polyuria whereas AQP4 deletion produced only a mild concentrating defect. Deletion of AQP5, the apical membrane water channel in the salivary gland, caused defective saliva production. Deletion of AQP1 or AQP5, water channels in lung endothelia and epithelia, resulted in a 90% decrease in airspace-capillary water permeability. In the brain, deletion of AQP4 conferred marked protection from brain swelling induced by acute water intoxication and ischaemic stroke. The general paradigm that has emerged from these phenotype studies is that aquaporins facilitate rapid near-isosmolar transepithelial fluid absorption/secretion, as well as rapid vectorial water movement driven by osmotic gradients. However, we have found many examples in which the tissue-specific expression of an aquaporin is not associated with any apparent phenotypic abnormality. The physiological data on aquaporin null mice suggest the utility of aquaporin blockers and aquaporin gene replacement in selected human diseases.

Animals↗