Influence of age on thirst and fluid intake

Independently living older adults (over the age of 65 yr) consume adequate volumes of fluids on a daily basis. However, when challenged by fluid deprivation, a hyperosmotic stimulus, or exercise in a warm environment (all of which combine hypovolemia and hyperosmolality), older adults exhibit decreased thirst sensation and reduced fluid intake. Full fluid restoration eventually occurs, but full restoration of fluid balance is slowed. The aging process alters important physiological control systems associated with thirst and satiety. Recent evidence suggests that older men and women (i) have a higher baseline osmolality and thus a higher osmotic operating point for thirst sensation (with little or no change in sensitivity), and (ii) exhibit diminished thirst and satiety in response to the unloading (hypovolemia) and loading (hypervolemia) of baroreceptors. A diminished sensation of thirst in the elderly relative to young adults is generally absent when a volume stimulus is absent, despite higher baseline plasma osmolalities. Compared with the elderly, there are scant data associated with homeostatic control of thirst in children. Nonhomeostatic control of thirst and drinking behavior may likewise be different for children (as it is for the elderly), as compared with young adults; however, little empirical data exist on this topic. Children rarely exhibit voluntary dehydration for activities lasting 45 min or less; however, drink flavoring and sodium chloride are important promoters of drinking in active children.

The impact of 3-dimensional reconstructions on operation planning in liver surgery

BACKGROUND

Operation planning in liver surgery depends on the precise understanding of the 3-dimensional (D) relation of the tumor to the intrahepatic vascular trees. To our knowledge, the impact of anatomical 3-D reconstructions on precision in operation planning has not yet been studied.

HYPOTHESIS

Three-dimensional reconstruction leads to an improvement of the ability to localize the tumor and an increased precision in operation planning in liver surgery.

DESIGN

We developed a new interactive computer-based quantitative 3-D operation planning system for liver surgery, which is being introduced to the clinical routine. To evaluate whether 3-D reconstruction leads to improved operation planning, we conducted a clinical trial. The data sets of 7 virtual patients were presented to a total of 81 surgeons in different levels of training. The tumors had to be assigned to a liver segment and subsequently drawn together with the operation proposal into a given liver model. The precision of the assignment to a liver segment according to Couinaud classification and the operation proposal were measured quantitatively for each surgeon and stratified concerning 2-D and different types of 3-D presentations.

RESULTS

The ability of correct tumor assignment to a liver segment was significantly correlated to the level of training (P<.05). Compared with 2-D computed tomography scans, 3-D reconstruction leads to a significant increase of precision in tumor localization by 37%. The target area of the resection proposal was improved by up to 31%.

CONCLUSION

Three-dimensional reconstruction leads to a significant improvement of tumor localization ability and to an increased precision of operation planning in liver surgery.

The current state of congenital tracheal stenosis

Congenital tracheal stenosis (CTS) is an uncommon condition that has challenged pediatric surgeons for decades. Patients with CTS can present with a wide spectrum of symptoms and varying degrees of severity. In addition, a variety of techniques have been devised to repair this malformation. A review of these procedures and our suggestions for clinical standards and practice guidelines will be presented in this paper. A retrospective review of the literature on CTS from 1964 to 31 March, 2006. There is not one standard technique for the repair of CTS, as individualized approach to each patient and airway lesion is necessary to optimize patient management; nevertheless there is a consensus about segmental resection and anastomosis being best for short segment stenosis while slide tracheoplasty is most effective for the long-segment ones. Conservative management is also an option for select group of patients with careful and close follow up. Survival following surgery over the years has improved, but mortality remained high, particularly in a specific subset of patients presenting at the age less than 1 month with associated cardiac malformations. In conclusion, CTS remains a significant challenge for pediatric surgeons. Additional research is required to improve our understanding of the pathogenesis of CTS, and to develop evidence-based treatment protocols for the entire spectrum of presentation including conservative management.

Tandem conjugate reduction-aldol cyclization using Stryker's reagent

[see reaction]. Conjugate reduction by Stryker's reagent to form copper enolates, followed by intramolecular aldol cyclization, successfully generated five- and six-membered carbocycles in one pot efficiently. This tandem reaction is generally diastereoselective and provides good yields of the beta-hydroxyketones without any dehydration at low temperatures.

Heart and combined heart-kidney transplantation in patients with concomitant renal insufficiency and end-stage heart failure

In patients with end-stage heart failure (ESHF) who are candidates for isolated heart transplant (HRT), dialysis dependence (DD) is considered an indication for combined heart-kidney transplantation (HKT). HKT remains controversial in ESHF transplant candidates with nondialysis-dependent renal insufficiency (NDDRI). Using United Network for Organ Sharing data, we examined the cumulative incidences of transplant and mortality in patients with DD and NDDRI waitlisted for HKT or HRT. In all groups, 3-month waitlist mortality was dismal: 31% and 21% for HRT- and HKT-listed patients with DD and 12% and 7% for HRT- and HKT-listed patients with NDDRI. Five-year posttransplant survival was improved in HKT recipients compared with HRT recipients for both patients with DD (73% vs. 51%, p<0.001) and NDDRI (80% vs. 69%, p<0.001). Likewise, multivariable analysis associated HKT with better outcomes than HRT in HKT-listed patients, although both improved survival. These data argue strongly for HKT in ESHF transplant candidates with DD. However, in patients with NDDRI, HKT must be weighed against the possibility of renal recovery with isolated HRT. Whether HRT (followed by a staged kidney transplant in patients who do not recover renal function after HRT), as opposed to HKT, maximizes organ benefit for patients with NDDRI and ESHF requires assessment. Nevertheless, given their dismal waitlist outcomes and excellent posttransplant results, we suggest that patients with DD and NDDRI with ESHF be considered for early listing and transplant.

Recognition of cello-oligosaccharides by a family 17 carbohydrate-binding module: an X-ray crystallographic, thermodynamic and mutagenic study

The crystal structure of the Clostridium cellulovorans carbohydrate-binding module (CBM) belonging to family 17 has been solved to 1.7 A resolution by multiple anomalous dispersion methods. CBM17 binds to non-crystalline cellulose and soluble beta-1,4-glucans, with a minimal binding requirement of cellotriose and optimal affinity for cellohexaose. The crystal structure of CBM17 complexed with cellotetraose solved at 2.0 A resolution revealed that binding occurs in a cleft on the surface of the molecule involving two tryptophan residues and several charged amino acids. Thermodynamic binding studies and alanine scanning mutagenesis in combination with the cellotetraose complex structure allowed the mapping of the CBM17 binding cleft. In contrast to the binding groove characteristic of family 4 CBMs, family 17 CBMs appear to have a very shallow binding cleft that may be more accessible to cellulose chains in non-crystalline cellulose than the deeper binding clefts of family 4 CBMs. The structural differences in these two modules may reflect non-overlapping binding niches on cellulose surfaces.

The influence of cannabidiol and delta 9-tetrahydrocannabinol on cobalt epilepsy in rats

The mechanisms of the anticonvulsant activity of cannabidiol (CBD) and the central excitation of delta 9-tetrahydrocannabinol (delta 9-THC) were investigated electrophysiologically with conscious, unrestrained cobalt epileptic rats. The well-known antiepileptics, trimethadione (TMO), ethosuximide (ESM), and phenytoin (PHT), were included as reference drugs. Direct measurements were made of spontaneously firing, epileptic potentials from a primary focus on the parietal cortex and convulsions were monitored visually. ESM and TMO decreased the frequency of focal potentials, but PHT and CBD exerted no such effect. Although CBD did not suppress the focal abnormality, it did abolish jaw and limb clonus; in contrast, delta 9-THC markedly increased the frequency of focal potentials, evoked generalized bursts of polyspikes, and produced frank convlusions. 11-OH-delta 9-THC, the major metabolite of delta 9-THC, displayed only one of the excitatory properties of the parent compound: production of bursts of polyspikes. In contrast to delta 9-THC and its 11-OH metabolite, CBD, even in very high doses, did not induce any excitatory effects or convulsions. The present study provides the first evidence that CBD exerts anticonvulsant activity against the motor manifestations of a focal epilepsy, and that the mechanism of the effect may involve a depression of seizure generation or spread in the CNS.

NS6180, a new K(Ca) 3.1 channel inhibitor prevents T-cell activation and inflammation in a rat model of inflammatory bowel disease

BACKGROUND AND PURPOSE

The K(Ca) 3.1 channel is a potential target for therapy of immune disease. We identified a compound from a new chemical class of K(Ca) 3.1 inhibitors and assessed in vitro and in vivo inhibition of immune responses.

EXPERIMENTAL APPROACH

We characterized the benzothiazinone NS6180 (4-[[3-(trifluoromethyl)phenyl]methyl]-2H-1,4-benzothiazin-3(4H)-one) with respect to potency and molecular site of action on K(Ca) 3.1 channels, selectivity towards other targets, effects on T-cell activation as well as pharmacokinetics and inflammation control in colitis induced by 2,4-dinitrobenzene sulfonic acid, a rat model of inflammatory bowel disease (IBD).

KEY RESULTS

NS6180 inhibited cloned human K(Ca) 3.1 channels (IC(50) = 9 nM) via T250 and V275, the same amino acid residues conferring sensitivity to triarylmethanes such as like TRAM-34. NS6180 inhibited endogenously expressed K(Ca) 3.1 channels in human, mouse and rat erythrocytes, with similar potencies (15-20 nM). NS6180 suppressed rat and mouse splenocyte proliferation at submicrolar concentrations and potently inhibited IL-2 and IFN-γ production, while exerting smaller effects on IL-4 and TNF-α and no effect on IL-17 production. Antibody staining showed K(Ca) 3.1 channels in healthy colon and strong up-regulation in association with infiltrating immune cells after induction of colitis. Despite poor plasma exposure, NS6180 (3 and 10 mg·kg(-1) b.i.d.) dampened colon inflammation and improved body weight gain as effectively as the standard IBD drug sulfasalazine (300 mg·kg(-1) q.d.).

CONCLUSIONS AND IMPLICATIONS

NS6180 represents a novel class of K(Ca) 3.1 channel inhibitors which inhibited experimental colitis, suggesting K(Ca) 3.1 channels as targets for pharmacological control of intestinal inflammation.

Socioeconomic impact of osteoarthritis in Hong Kong: utilization of health and social services, and direct and indirect costs

OBJECTIVE

To determine the direct and indirect cost of osteoarthritis (OA) according to disease severity, and to estimate the total cost of the disease in Hong Kong.

METHODS

This study is a retrospective, cross-sectional, nonrandom, cohort design, with subjects stratified according to disease severity based on functional limitation and the presence or absence of joint prosthesis. Subjects were recruited from primary care, geriatric medicine, rheumatology, and orthopedic clinics. There were 219 patients in the mild disease category, 290 patients in the severe category, and 65 patients with joint replacement. A questionnaire gathered information on demographic and socioeconomic characteristics, function limitation, use of health and social services, and effect on occupation and living arrangements over the previous 12 months. Costs were calculated as direct and indirect.

RESULTS

Low education and socioeconomic class were associated with more severe disease. OA affected family or close relationships in 44%. The average cost incurred as a result of side effects of medication is similar to the average cost of medication itself. Excluding joint replacement, the direct costs ranged from Hong Kong (HK) dollar $11,690 to $40,180 per person per year and indirect costs, HK $3,300-$6,640. The direct costs are comparable to those reported in Western countries; however, the ratio of direct to indirect costs is much higher than 1, in contrast to the greater indirect versus direct costs reported in whites. The total cost expressed as a percentage of gross national product is also much lower in Hong Kong.

CONCLUSIONS

The socioeconomic impact of OA in the Hong Kong population is comparable to Western countries, but the economic burden is largely placed on the government, with patients having relatively low out-of-pocket expenditures.

Antiplatelet and antiproliferative effects of SCH 51866, a novel type 1 and type 5 phosphodiesterase inhibitor

SCH 51866 is a potent and selective PDE1 and PDE5 inhibitor. The antiplatelet, antiproliferative, and hemodynamic effects of SCH 51866 were compared with those of E4021, a highly selective PDE5 inhibitor. SCH 51866 inhibited PDE1 and PDE5 isozymes with a 50% inhibitory concentration (IC50) of 70 and 60 nM, respectively. SCH 51866 and E4021 inhibited washed human platelet aggregation induced by collagen with an IC50 of 10 and 4 microM, respectively, and attenuated (p < 0.05) the adhesion of 111indium-labeled platelets to the nylon filament-injured rat aorta. The doses of SCH 51866 and E4021 that inhibited platelet adhesion caused significant increases in platelet cyclic guanosine monophosphate (cGMP; p < 0.05). SCH 51866 (1-10 mg/kg, p.o. twice daily) but not E4021 (3-30 mg/kg, p.o twice daily) inhibited neointima formation in the carotid arteries of spontaneously hypertensive rats (SHRs) subjected to balloon angioplasty. Moreover, SCH 51866 (0.3-10 mg/kg, p.o.) elicited dose-dependent reduction in blood pressure in SHRs, whereas E4021 (3-30 mg/kg, p.o.) did not affect blood pressure in SHRs. In conclusion, the data suggest that inhibition of PDE1 and PDE5 isozymes by SCH 51866 exerts antiplatelet and vascular protective effects. In comparison, inhibition of PDE5 alone by E4021 exhibited antiplatelet effects without affecting neointima formation.

A rhodium carbene cyclization-cycloaddition cascade strategy toward the pseudolaric acids

A rhodium carbene intramolecular cyclization-cycloaddition cascade was employed as the key reaction in the synthesis of the nucleus of the cytotoxic diterpenoids pseudolaric acids A and B.

2-Bromoethanesulfonate affects bacteria in a trichloroethene-dechlorinating culture

Long-term exposure to 2-bromoethanesulfonate (BES), an agent known to inhibit methanogenesis, altered the bacterial community structure of an anaerobic enrichment culture that reductively dechlorinated trichloroethene (TCE). BES did not hinder the dechlorination of TCE or other chlorinated ethenes as previously reported, although different intermediates and end products were observed.

Glycodelin in reproductive endocrinology and hormone-related cancer

Glycodelin is an endocrine-regulated glycoprotein that has significant effects on immune cells, apoptosis, reproduction, cell adhesion, differentiation and cancer. In reproduction, glycodelin contributes to capacitation and immunoprotection of spermatozoa, and it modulates sperm-oocyte binding, acrosome reaction and implantation. In endocrine-related cancer, the differentiation inducing effects of glycodelin are accompanied by growth restriction of malignant cells, decreased expression of oncogenes, increased expression of tumour suppressor genes and morphological reversion of the malignant phenotype. This review features these properties and clinical connections, highlighting the role of glycosylation in biological actions.

Immunohistochemical identification of Campylobacter fetus in natural cases of bovine and ovine abortions

An immunohistochemistry (IHC) procedure for the detection of Campylobacter fetus antigens using an avidin-biotin complex technique was performed on formalin fixed bovine and ovine fetal tissues from 26 natural cases of Campylobacter spp. abortion (four ovine and 22 bovine). The species of Campylobacter isolated included C. fetus ssp. venerealis from 13 bovine fetuses, C. fetus ssp. fetus from two ovine and one bovine fetus, Campylobacter jejuni from seven bovine fetuses, Campylobacter lari from two ovine fetuses and an unspeciated Campylobacter species in one bovine fetus. Histologic lesions identified in the aborted fetuses included placentitis, serositis, pneumonia, gastroenteritis, hepatitis and encephalitis. Campylobacter fetus antigens were identified by IHC in 13 of 13 bovine fetuses from which C. fetus ssp. venerealis was isolated and in two of two ovine fetuses from which C. fetus ssp. fetus was isolated. The IHC stains were negative in tissues from seven bovine fetuses from which C. jejuni was isolated, one bovine fetus infected with C. fetus ssp. fetus, one bovine fetus infected with the unspeciated Campylobacter and two ovine fetuses infected with C. lari. In positive cases, the IHC stain most frequently identified bacteria in the lung and gastrointestinal tract. The C. fetus IHC procedure performed on formalin fixed tissues is a practical tool for the diagnosis of natural cases of ovine and bovine abortion caused by C. fetus.

Beta-adrenoceptor subtypes and the opening of plasmalemmal K(+)-channels in trachealis muscle: electrophysiological and mechanical studies in guinea-pig tissue

1. Mechanical and electrophysiological studies of guinea-pig isolated trachealis have been made with the objectives of: (a) identifying which of the beta-adrenoceptor subtypes mediates the opening of plasmalemmal K(+)-channels, (b) gaining further insight into the properties of the novel, long-acting beta-adrenoceptor agonist, salmeterol and (c) clarifying the role of K(+)-channel opening in mediating the relaxant actions of agonists at beta-adrenoceptors. 2. Noradrenaline (10 nM-100 microM) caused a concentration-dependent increase in the rate of beating of guinea-pig isolated atria. The selective beta 1-adrenoceptor blocking drug, CGP 20712A (100 nM-10 microM) caused concentration-dependent antagonism of noradrenaline. The selective beta 2-adrenoceptor blocking drug, ICI 118551, also produced concentration-dependent antagonism of noradrenaline, but only when used in concentrations greater than 300 nM. 3. Cromakalim (100 nM-10 microM), isoprenaline (1-100 nM), procaterol (0.1-30 nM), salbutamol (1 nM-1 microM), salmeterol (1-100 nM) and theophylline (1 microM-1 mM) each caused concentration-dependent suppression of the spontaneous tone of guinea-pig isolated trachealis. 4. ICI 118551 (10 nM-1 microM) antagonized isoprenaline, procaterol and salmeterol in suppressing the spontaneous tone of the isolated trachea. The antagonism was concentration-dependent. In contrast, ICI 118551 (1 microM) antagonized neither cromakalim nor theophylline. CGP 20712A (up to 1 microM) failed to antagonize cromakalim, isoprenaline, procaterol, salmeterol or theophylline. In trachea treated with indomethacin (2.8 microM) and carbachol (10 microM), salmeterol (1 microM) antagonized the effects of isoprenaline but not aminophylline. 5. Intracellular electrophysiological recording from guinea-pig isolated trachealis showed that the relaxant effects of cromakalim (10 microM), isoprenaline (100 nM), procaterol (10 nM) and salbutamol(10 nM- 1 microM) were accompanied by the suppression of spontaneous electrical slow waves and by cellular hyperpolarization. In contrast, the relaxant effects of salmeterol (10 nM- 1 microM) were not accompanied by significant cellular hyperpolarization.6. CGP 20712A (1 microM) inhibited the hyperpolarization but not the relaxation induced by isoprenaline(100 nM). In contrast ICI 118551 (100 nM) inhibited both the hyperpolarization and the relaxation induced by isoprenaline (100 nM). Neither CGP 20712A (1 microM) nor ICI 118551 (100 nM) inhibited the hyperpolarization induced by cromakalim (10 microM). Salmeterol (1 microM) inhibited the hyperpolarization induced by isoprenaline (100 nM) but not that induced by cromakalim (10 microM).7. It is concluded that activation of either beta l- or beta 2-adrenoceptors can promote the opening of K+-channels in the trachealis plasmalemma. The poor ability of salmeterol to hyperpolarize trachealis muscle reflects neither its selectivity in activating beta 2-adrenoceptors as opposed to beta 1-adrenoceptors nor a non-specific action in stabilizing the cell membrane. Instead, it may reflect low intrinsic efficacy of the drug at beta 2-adrenoceptors. The opening of plasmalemmal K+-channels plays a supportive rather than a crucial role in mediating the tracheal relaxant actions of agonists at beta-adrenoceptors.

Specificity and affinity of substrate binding by a family 17 carbohydrate-binding module from Clostridium cellulovorans cellulase 5A

The C-terminal carbohydrate-binding module (CBM17) from Clostridium cellulovorans cellulase 5A is a beta-1,4-glucan binding module with a preference for soluble chains. CBM17 binds to phosphoric acid swollen Avicel (PASA) and Avicel with association constants of 2.9 (+/-0.2) x 10(5) and 1.6 (+/-0.2) x 10(5) M(-1), respectively. The capacity values for PASA and Avicel were 11.9 and 0.4 micromol/g of cellulose, respectively. CBM17 did not bind to crystalline cellulose. CBM17 bound tightly to soluble barley beta-glucan and the derivatized celluloses HEC, EHEC, and CMC. The association constants for binding to barley beta-glucan, HEC, and EHEC were approximately 2.0 x 10(5) M(-1). Significant binding affinities were found for cello-oligosaccharides greater than three glucose units in length. The affinities for cellotriose, cellotetraose, cellopentaose, and cellohexaose were 1.2 (+/-0.3) x 10(3), 4.3 (+/-0.4) x 10(3), 3.8 (+/-0.1) x 10(4), and 1.5 (+/-0.0) x 10(5) M(-1), respectively. Fluorescence quenching studies and N-bromosuccinimide modification indicate the participation of tryptophan residues in ligand binding. The possible architecture of the ligand-binding site is discussed in terms of its binding specificity, affinity, and the participation of tryptophan residues.

An optical and microPET assessment of thermally-sensitive liposome biodistribution in the Met-1 tumor model: Importance of formulation

The design of delivery vehicles that are stable in circulation but can be activated by exogenous energy sources is challenging. Our goals are to validate new imaging methods for the assessment of particle stability, to engineer stable and activatable particles and to assess accumulation of a hydrophilic model drug in an orthotopic tumor. Here, liposomes were injected into the tail vein of FVB mice containing bilateral Met-1 tumors and imaged in vivo using microPET and optical imaging techniques. Cryo-electron microscopy was applied to assess particle shape prior to injection, ex vivo fluorescence images of dissected tissues were acquired, excised tissue was further processed with a cell-digest preparation and assayed for fluorescence. We find that for a stable particle, in vivo tumor images of a hydrophilic model drug were highly correlated with PET images of the particle shell and ex vivo fluorescence images of processed tissue, R(2)=0.95 and R(2)=0.99 respectively. We demonstrate that the accumulation of a hydrophilic model drug is increased by up to 177 fold by liposomal encapsulation, as compared to accumulation of the drug at 24 hours.

Genetically engineered live attenuated influenza A virus vaccine candidates

We have generated new influenza A virus live attenuated vaccine candidates by site-directed mutagenesis and reverse genetics. By mutating specific amino acids in the PB2 polymerase subunit, two temperature-sensitive (ts) attenuated viruses were obtained. Both candidates have 38 degrees C shutoff temperatures in MDCK cells, are attenuated in the respiratory tracts of mice and ferrets, and have very low reactogenicity in ferrets. Infection of mice or ferrets with either mutant conferred significant protection from challenge with the homologous wild-type virus. Three tests for genetic stability were used to assess the propensity for reversion to virulence: 14 days of replication in nude mice, growth at 37 degrees C in tissue culture, and serial passage in ferrets. One candidate, which contains mutations intended to reduce the ability of PB2 to bind to cap structures, was stable in all three assays, whereas the second candidate, which contains mutations found only in other ts strains of influenza virus, lost its ts phenotype in the last two assays. This approach has therefore enabled the creation of live attenuated influenza A virus vaccine candidates suitable for human testing.

Establishment of a capillary-cumulus model to study the selection of sperm for fertilization by the cumulus oophorus

BACKGROUND

Spermatozoa have to traverse the cumulus oophorus before fertilization in vivo. Evidence suggests that the cumulus oophorus plays an important role in the fertilization process. We describe the establishment of a capillary-cumulus oophorus model with which to study the action of cumulus mass on the function of human spermatozoa.

METHODS

Human cumulus oophorus was aspirated into a glass capillary. Spermatozoa were allowed to pass through the cumulus mass in the capillary from one end of the capillary. The spermatozoa that had traversed the mass were collected at the other end of the capillary and underwent sperm function analyses.

RESULTS

Compared with those spermatozoa cultured in medium alone, spermatozoa exposed to the cumulus mass were more likely to have normal morphology, be capacitated and acrosome reacted, with a distinct motility pattern and better zona-binding capacity.

CONCLUSION

A novel in vitro model for spermatozoa penetration through the cumulus oophorus was established. The model can be applied to investigate the effect of the cumulus oophorus on sperm functions.

Mesolimbic and striatal dopamine receptor supersensitivity: prophylactic and reversal effects of L-prolyl-L-leucyl-glycinamide (PLG)

Functional supersensitivity of mesolimbic and striatal dopamine receptors has been suggested to contribute to the pathogenesis of schizophrenia and tardive dyskinesia. Using the rodent model of chronic administration of the neuroleptic haloperidol, we investigated the possible desensitizing effects of a tripeptide structurally unrelated to dopamine agonists, L-prolyl-L-leucyl-glycinamide (PLG) on mesolimbic and striatal dopaminergic receptor supersensitivity. Administration of PLG either prior to or after chronic haloperidol, inhibited the supersensitivity of dopamine receptors. The results have implications for pharmacological intervention in preventing tardive dyskinesia and relapse psychosis of schizophrenia.

Let-7 derived from endometrial extracellular vesicles is an important inducer of embryonic diapause in mice

Embryonic diapause is a maternally controlled phenomenon. The molecule controlling the onset of the phenomenon is unknown. We demonstrated that overexpression of microRNA let-7a or incubation with let-7g-enriched extracellular vesicles from endometrial epithelial cells prolonged the in vitro survival of mouse blastocysts, which developed into live pups after having been transferred to foster mothers. Similar to in vivo dormant blastocysts, let-7-induced dormant blastocysts exhibited low level of proliferation, apoptosis, and nutrient metabolism. Let-7 suppressed c-myc/mTORC1 and mTORC2 signaling to induce embryonic diapause. It also inhibited ODC1 expression reducing biosynthesis of polyamines, which are known to reactivate dormant embryos. Furthermore, the overexpression of let-7 blocked trophoblast differentiation and implantation potential of human embryo surrogates, and prolonged survival of human blastocysts in vitro, supporting the idea that embryonic diapause was an evolutionary conserved phenomenon. In conclusion, let-7 is the main factor inducing embryonic diapause.