Nsun2 coupling with RoRγt shapes the fate of Th17 cells and promotes colitis.

T helper 17 (Th17) cells are a subset of CD4+ T helper cells involved in the inflammatory response in autoimmunity. Th17 cells secrete Th17 specific cytokines, such as IL-17A and IL17-F, which are governed by the master transcription factor RoRγt. However, the epigenetic mechanism regulating Th17 cell function is still not fully understood. Here, we reveal that deletion of RNA 5-methylcytosine (m5C) methyltransferase Nsun2 in mouse CD4+ T cells specifically inhibits Th17 cell differentiation and alleviates Th17 cell-induced colitis pathogenesis. Mechanistically, RoRγt can recruit Nsun2 to chromatin regions of their targets, including Il17a and Il17f, leading to the transcription-coupled m5C formation and consequently enhanced mRNA stability. Our study demonstrates a m5C mediated cell intrinsic function in Th17 cells and suggests Nsun2 as a potential therapeutic target for autoimmune disease.

Targeted therapy of atherosclerosis by pH-sensitive hyaluronic acid nanoparticles co-delivering all-trans retinal and rapamycin.

Atherosclerosis, the leading cause of death in the elderly worldwide, is typically characterized by elevated reactive oxygen species (ROS) levels and a chronic inflammatory state at the arterial plaques. Herein, pH-sensitive nanoparticles (HRRAP NPs) co-delivering all-trans retinal (ATR), an antioxidant linked to hyaluronic acid (HA) through a pH-sensitive hydrazone bond, and rapamycin (RAP), an anti-atherosclerotic drug loaded into the nanoparticle core, are developed for targeted combination therapy of atherosclerosis. In this way, HRRAP NPs might simultaneously reduce ROS levels via ATR antioxidant activity and reduce inflammation via the anti-inflammatory effect of RAP. In response to mildly acidic conditions mimicking the lesional inflammation in vitro, HRRAP NPs dissociated and both ATR and RAP were effectively released. The developed HRRAP NPs effectively inhibited pro-inflammatory macrophage proliferation, and displayed dose- and time-dependent specific internalization by different cellular models of atherosclerosis. Also, HRRAP NP combination therapy showed an efficient synergetic anti-atherosclerotic effect in vitro by effectively inhibiting the inflammatory response and oxidative stress in inflammatory cells. More importantly, HR NPs specifically accumulated in the atherosclerotic plaques of apolipoprotein E-deficient (ApoE-/-) mice, by active interaction with HA receptors overexpressed by different cells of the plaque. The treatment with HRRAP NPs remarkably inhibited the progression of atherosclerosis in ApoE-/- mice which resulted in stable plaques with considerably smaller necrotic cores, lower matrix metalloproteinase-9, and decreased proliferation of macrophages and smooth muscle cells (SMCs). Furthermore, HRRAP NPs attenuated RAP adverse effects and exhibited a good safety profile after long-term treatment in mice. Consequently, the developed pH-sensitive HRRAP NP represent a promising nanoplatform for atherosclerosis combination therapy.

Vagal-α7nAChR signaling is required for lung anti-inflammatory responses and arginase 1 expression during an influenza infection.

Vagal circuit-α7 nicotinic acetylcholine receptor (α7nAChR, coded by Chrna7) signaling can modulate lung proinflammatory responses. Arginase 1 (ARG1) plays a crucial role in the resolution of lung inflammation. However, whether vagal-α7nAChR signaling can regulate lung inflammation and ARG1 expression during an influenza infection is elusive. Here, we found that lung and spleen IL-4+ cells and lung ARG1 expression were reduced; however, bronchoalveolar lavage (BAL) protein and leukocytes and lung inflammatory cytokines were increased in PR8 (A/Puerto Rico/8/1934, H1N1)-infected vagotomized mice when compared to the control. In PR8-infected α7nAChR-deficient mice, lung Arg1, Il10, and Socs3 expression and BAL Ly6C+CD206+ cells were reduced. PR8-infected Chrna7+/+ recipient mice reconstituted with Chrna7-/- bone marrow had a lower survival as compared to PR8-infected Chrna7+/+ recipient mice reconstituted with Chrna7+/+ bone marrow. Mechanistically, the activation of α7nAChR by its agonist GTS-21 could enhance IL-4-induced Arg1 expression, reduced Nos2, and TNF-α expression in PR8-infected bone marrow-derived macrophages (BMDM). Stimulation with IL-4 increased phosphorylation of STAT6 and activation of α7nAChR increased STAT6 binding with the ARG1 promoter and relieved IL-4-induced H3K27me3 methylation by increasing JMJD3 expression in PR8-infected BMDM. Inhibition of JMJD3 increased H3K27me3 methylation and abolished α7nAChR activation and IL-4 induced ARG1 expression. Activation of α7nAChR also reduced phosphorylation of AKT1 and contained FOXO1 in the nucleus. Knockdown of Foxo1a reduced α7nAChR activation and IL-4 induced Arg1 expression in PR8-infected BMDM. Therefore, vagal-α7nAChR signaling is a novel therapeutic target for treating lung inflammatory responses during an influenza infection.

PDK1 Regulates the Maintenance of Cell Body and the Development of Dendrites of Purkinje Cells by pS6 and PKCγ.

3-Phosphoinositide-dependent protein kinase-1 (PDK1) plays a critical role in the development of mammalian brain. Here, we investigated the role of PDK1 in Purkinje cells (PCs) by generating the PDK1-conditional knock-out mice (cKO) through crossing PV-cre or Pcp2-cre mice with Pdk1fl/fl mice. The male mice were used in the behavioral testing, and the other experiments were performed on mice of both sexes. These PDK1-cKO mice displayed decreased cerebellar size and impaired motor balance and coordination. By the electrophysiological recording, we observed the reduced spontaneous firing of PCs from the cerebellar slices of the PDK1-cKO mice. Moreover, the cell body size of PCs in the PDK1-cKO mice was time dependently reduced compared with that in the control mice. And the morphologic complexity of PCs was also decreased after PDK1 deletion. These effects may have contributed to the reduction of the rpS6 (reduced ribosomal protein S6) phosphorylation and the PKCγ expression in PDK1-cKO mice since the upregulation of pS6 by treatment of 3-benzyl-5-((2-nitrophenoxy) methyl)-dihydrofuran-2(3H)-1, the agonist of mTOR1, partly rescued the reduction in the cell body size of the PCs, and the delivery of recombinant adeno-associated virus-PKCγ through cerebellar injection rescued the reduced complexity of the dendritic arbor in PDK1-cKO mice. Together, our data suggest that PDK1, by regulating rpS6 phosphorylation and PKCγ expression, controls the cell body maintenance and the dendritic development in PCs and is critical for cerebellar motor coordination.SIGNIFICANCE STATEMENT Here, we show the role of 3-phosphoinositide-dependent protein kinase-1 (PDK1) in Purkinje cells (PCs). The ablation of PDK1 in PCs resulted in a reduction of cell body size, and dendritic complexity and abnormal spontaneous firing, which attributes to the motor defects in PDK1-conditional knock-out (cKO) mice. Moreover, the ribosomal protein S6 (rpS6) phosphorylation and the expression of PKCγ are downregulated after the ablation of PDK1. Additionally, upregulation of rpS6 phosphorylation by3-benzyl-5-((2-nitrophenoxy) methyl)-dihydrofuran-2(3H)-1 partly rescued the reduction in cell body size of PCs, and the overexpression of PKCγ in PDK1-KO PCs rescued the reduction in the dendritic complexity. These findings indicate that PDK1 contributes to the maintenance of the cell body and the dendritic development of PCs by regulating rpS6 phosphorylation and PKCγ expression.

Lymphomatoid gastropathy: one case report and literatures review / 中华血液学杂志

Objective: To report the first case of lymphomatoid gastropathy in China, and to demonstrate the clinical characteristics, diagnostic approach, treatment and prognosis in this kind of patients. Methods: One patient was diagnosed as lymphomatoid gastropathy at Peking Union Medical College Hospital, and her clinical characteristics, lab data, treatment and follow-up outcomes were reviewed. Results: A case of a 51-year-old female was presented, who underwent esophagogastroduodenoscopy (EGD) due to slight epigastric discomfort. EGD revealed multiple ulcers and erosions. Biopsies showed atypical lymphocytes infiltration with CD3(+), CD56(+), CD20(-), CD8(-), TIA(+), Granzyme B(-) and Ki-67 (75%). Epstein-Barr virus-encoded RNA in situ hybridization was negative. Four months later, repeated EGD examination showed regression of the lesions without specific treatment. Conclusion: Lymphomatoid gastropathy was a unique disease entity mimicking NK/T-cell lymphomas in pathology, with the quite different profile of treatment and prognosis. It's important to consider this issue during the differential diagnosis to avoid any excessive treatment.

NDR Kinases Are Essential for Somitogenesis and Cardiac Looping during Mouse Embryonic Development.

Studies of mammalian tissue culture cells indicate that the conserved and distinct NDR isoforms, NDR1 and NDR2, play essential cell biological roles. However, mice lacking either Ndr1 or Ndr2 alone develop normally. Here, we studied the physiological consequences of inactivating both NDR1 and NDR2 in mice, showing that the lack of both Ndr1/Ndr2 (called Ndr1/2-double null mutants) causes embryonic lethality. In support of compensatory roles for NDR1 and NDR2, total protein and activating phosphorylation levels of the remaining NDR isoform were elevated in mice lacking either Ndr1 or Ndr2. Mice retaining one single wild-type Ndr allele were viable and fertile. Ndr1/2-double null embryos displayed multiple phenotypes causing a developmental delay from embryonic day E8.5 onwards. While NDR kinases are not required for notochord formation, the somites of Ndr1/2-double null embryos were smaller, irregularly shaped and unevenly spaced along the anterior-posterior axis. Genes implicated in somitogenesis were down-regulated and the normally symmetric expression of Lunatic fringe, a component of the Notch pathway, showed a left-right bias in the last forming somite in 50% of all Ndr1/2-double null embryos. In addition, Ndr1/2-double null embryos developed a heart defect that manifests itself as pericardial edemas, obstructed heart tubes and arrest of cardiac looping. The resulting cardiac insufficiency is the likely cause of the lethality of Ndr1/2-double null embryos around E10. Taken together, we show that NDR kinases compensate for each other in vivo in mouse embryos, explaining why mice deficient for either Ndr1 or Ndr2 are viable. Ndr1/2-double null embryos show defects in somitogenesis and cardiac looping, which reveals their essential functions and shows that the NDR kinases are critically required during the early phase of organogenesis.

The alteration of protein prenylation induces cardiomyocyte hypertrophy through Rheb-mTORC1 signalling and leads to chronic heart failure.

G protein-regulated cell function is crucial for cardiomyocytes, and any deregulation of its gene expression or protein modification can lead to pathological cardiac hypertrophy. Herein, we report that protein prenylation, a lipidic modification of G proteins that facilitates their association with the cell membrane, might control the process of cardiomyocyte hypertrophy. We found that geranylgeranyl diphosphate synthase (GGPPS), a key enzyme involved in protein prenylation, played a critical role in postnatal heart growth by regulating cardiomyocyte size. Cardiac-specific knockout of GGPPS in mice led to spontaneous cardiac hypertrophy, beginning from week 4, accompanied by the persistent enlargement of cardiomyocytes. This hypertrophic effect occurred by altered prenylation of G proteins. Evaluation of the prenylation, membrane association and hydrophobicity showed that Rheb was hyperactivated and increased mTORC1 signalling pathway after GGPPS deletion. Protein farnesylation or mTORC1 inhibition blocked GGPPS knockdown-induced mTORC1 activation and suppressed the larger neonatal rat ventricle myocyte size and cardiomyocyte hypertrophy in vivo, demonstrating a central role of the FPP-Rheb-mTORC1 axis for GGPPS deficiency-induced cardiomyocyte hypertrophy. The sustained cardiomyocyte hypertrophy progressively provoked cardiac decompensation and dysfunction, ultimately causing heart failure and adult death. Importantly, GGPPS was down-regulated in the hypertrophic hearts of mice subjected to transverse aortic constriction (TAC) and in failing human hearts. Moreover, HPLC-MS/MS detection revealed that the myocardial farnesyl diphosphate (FPP):geranylgeranyl diphosphate (GGPP) ratio was enhanced after pressure overload. Our observations conclude that the alteration of protein prenylation promotes cardiomyocyte hypertrophic growth, which acts as a potential cause for pathogenesis of heart failure and may provide a new molecular target for hypertrophic heart disease clinical therapy.

Akt-p53-miR-365-cyclin D1/cdc25A axis contributes to gastric tumorigenesis induced by PTEN deficiency.

Although PTEN/Akt signaling is frequently deregulated in human gastric cancers, the in vivo causal link between its dysregulation and gastric tumorigenesis has not been established. Here we show that inactivation of PTEN in mouse gastric epithelium initiates spontaneous carcinogenesis with complete penetrance by 2 months of age. Mechanistically, activation of Akt suppresses the abundance of p53, leading to decreased transcription of miR-365, thus causing upregulation of cyclin D1 and cdc25A, which promotes gastric cell proliferation. Importantly, genetic ablation of Akt1 restores miR-365 expression and effectively rescues gastric tumorigenesis in PTEN-mutant mice. Moreover, orthotopic restoration of miR-365 represses PTEN-deficient-induced hyperplasia. In human gastric cancer tissues, miR-365 reduction correlates with poorly differentiated histology, deep invasion and advanced stage, as well as the deregulation of PTEN, phosphorylated Akt, p53, cyclin D1 and cdc25A. These data demonstrate that the PTEN-Akt-p53-miR-365-cyclin D1/cdc25A axis serves as a new mechanism underlying gastric tumorigenesis, providing potential new therapeutic targets.

FSH acts on the proliferation of type A spermatogonia via Nur77 that increases GDNF expression in the Sertoli cells.

The molecular mechanism responsible for the regulation of GDNF in Sertoli cells remains largely unknown. In the present study, FSH induced the expression of Nur77 and GDNF in mouse testis tissue and human fetal Sertoli cells. Moreover, FSH increased the number of A spermatogonia co-cultured with Sertoli cells. In the additional assays, Nur77 was observed to directly regulate GDNF transcription. Furthermore, overexpression of Nur77 and siRNA-mediated knockdown of Nur77 affected levels of GDNF mRNA and protein in primary human fetal Sertoli cells. These results indicate that FSH-induced Nur77 regulates the expression of GDNF in Sertoli cells to stimulate the proliferation of A spermatogonia in vitro.

PDK1 plays a critical role in regulating cardiac function in mice and human.

BACKGROUND: PDK1 is an essential protein kinase that plays a critical role in mammalian development. Mouse lacking PDK1 leads to multiple abnormalities and embryonic lethality at E9.5. To elucidate the role of PDK1 in the heart, we investigated the cardiac phenotype of mice that lack PDK1 in the heart in different growth periods and the alteration of PDK1 signaling in human failing heart. METHODS: We employed Cre/loxP system to generate PDK1(flox/flox): α-MHC-Cre mice, which specifically deleted PDK1 in cardiac muscle at birth, and tamoxifen-inducible heart-specific PDK1 knockout mice (PDK1(flox/flox):MerCreMer mice), in which PDK1 was deleted in myocardium in response to the treatment with tamoxifen. Transmural myocardial tissues from human failing hearts and normal hearts were sampled from the left ventricular apex to analyze the activity of PDK1/Akt signaling pathways by Western blotting. RESULTS: PDK1(flox/flox): α-MHC-Cre mice died of heart failure at 5 and 10 weeks old. PDK1(flox/flox) -MerCreMer mice died of heart failure from 5 to 21 weeks after the initiation of tamoxifen treatment at 8 weeks old. We found that expression levels of PDK1 in human failing heart tissues were significantly decreased compared with control hearts. CONCLUSION: Our results suggest that PDK1 signaling network takes part in regulating cardiac viability and function in mice, and may be also involved in human heart failure disease.

[Changes of MAPK and Akt signaling pathways in hearts and placentas of aborted fetuses with congenital heart disease].

OBJECTIVE: To study the changes of MAPK and Akt signaling pathways in hearts and placentas of aborted fetuses with congenital heart disease (CHD), and investigate their roles in the pathogenesis of CHD. METHODS: Ten aborted fetuses with severe CHD (CHD group) and 7 gestational age-matched non-cardiac malformation aborted fetuses (control group) were enrolled. Western blot analysis was undertaken to assess the expression of p38, p38alpha, p-p38, MEF2, ERK, p-ERK, Akt, p-Akt(Ser473) and p-Akt(Thr308) in left ventricles and placentas of the fetuses, while semi-quantitative reverse transcription polymerase chain reaction analysis was used to detect the expression of p38alpha isoforms mRNA in hearts. RESULTS: Compared with the heart samples of the control group, the protein expression levels of p38 and its alpha isoform in 4 cases, p-p38 in 6 cases, MEF2 in 2 cases, p-ERK in 8 cases, Akt in 4 cases, p-Akt(Ser473) and p-Akt(Thr308) in 8 cases decreased, while the protein expression levels of p-p38 in 2 cases and p-Akt(Thr308) in 1 case increased. P-p38 protein level in 3 cases and p-ERK protein level in 2 cases decreased in placentas compared with the control group. The changes of protein expression of MAPK and Akt signaling pathway in hearts were not consistent with those in placentas in the CHD group. The expression of p38alpha isoform2 mRNA showed descent tendency in 4 heart samples with CHD, while the expression of other three p38alpha isoforms mRNA was reduced in only 1 sample compared with the control group. CONCLUSIONS: Dysfunction of MAPK and Akt signaling pathways is tissue-specific in aborted fetuses with CHD. The perturbed two signaling pathways in hearts may contribute to the pathogenesis of human CHD.

Life with a single isoform of Akt: mice lacking Akt2 and Akt3 are viable but display impaired glucose homeostasis and growth deficiencies.

To address the issues of isoform redundancy and isoform specificity of the Akt family of protein kinases in vivo, we generated mice deficient in both Akt2 and Akt3. In these mice, only the Akt1 isoform remains to perform essential Akt functions, such as glucose homeostasis, proliferation, differentiation, and early development. Surprisingly, we found that Akt2(-/-) Akt3(-/-) and even Akt1(+/-) Akt2(-/-) Akt3(-/-) mice developed normally and survived with minimal dysfunctions, despite a dramatic reduction of total Akt levels in all tissues. A single functional allele of Akt1 appears to be sufficient for successful embryonic development and postnatal survival. This is in sharp contrast to the previously described lethal phenotypes of Akt1(-/-) Akt2(-/-) mice and Akt1(-/-) Akt3(-/-) mice. However, Akt2(-/-) Akt3(-/-) mice were glucose and insulin intolerant and exhibited an approximately 25% reduction in body weight compared to wild-type mice. In addition, we found substantial reductions in relative size and weight of the brain and testis in Akt2(-/-) Akt3(-/-) mice, demonstrating an in vivo role for both Akt2 and Akt3 in the determination of whole animal size and individual organ sizes.

PKBalpha is required for adipose differentiation of mouse embryonic fibroblasts.

Protein kinase Balpha (PKBalpha) is a key regulator of metabolism, proliferation and differentiation. We have explored the role of PKBalpha in adipogenesis using wild-type and PKBalpha-knockout mouse embryonic fibroblasts (MEFs) and show that lack of PKBalpha prevents MEF differentiation into adipocytes. Expression of ectopic PKBalpha in PKBalpha-deficient cells restores adipogenesis. We identified 80 genes whose expression was upregulated in wild-type MEFs during adipogenesis but whose expression was significantly reduced in PKBalpha-deficient MEFs under the same conditions. Significantly, the regulator of adipogenesis Krüppel-like transcription factor 15 gene expression was downregulated in PKBalpha-deficient MEFs but could be restored by expressing an active PKBalpha in the deficient cells. The level of lipocalin 2, renin 1 and receptor-activity-modifying protein 3 genes expressed by adipose cells was also decreased in PKBalpha-deficient MEFs, and are inhibited by LY294002 treatment during early adipocyte differentiation of 3T3-L1 cells. The results underscore an essential role for PKBalpha in the transcriptional program required for adipogenesis.

Dosage-dependent effects of Akt1/protein kinase Balpha (PKBalpha) and Akt3/PKBgamma on thymus, skin, and cardiovascular and nervous system development in mice.

Akt/protein kinase B (PKB) plays a critical role in the regulation of metabolism, transcription, cell migration, cell cycle progression, and cell survival. The existence of viable knockout mice for each of the three isoforms suggests functional redundancy. We generated mice with combined mutant alleles of Akt1 and Akt3 to study their effects on mouse development. Here we show that Akt1-/- Akt3+/- mice display multiple defects in the thymus, heart, and skin and die within several days after birth, while Akt1+/- Akt3-/- mice survive normally. Double knockout (Akt1-/-) Akt3-/-) causes embryonic lethality at around embryonic days 11 and 12, with more severe developmental defects in the cardiovascular and nervous systems. Increased apoptosis was found in the developing brain of double mutant embryos. These data indicate that the Akt1 gene is more essential than Akt3 for embryonic development and survival but that both are required for embryo development. Our results indicate isoform-specific and dosage-dependent effects of Akt on animal survival and development.

Essential role of protein kinase B gamma (PKB gamma/Akt3) in postnatal brain development but not in glucose homeostasis.

Protein kinase B is implicated in many crucial cellular processes, such as metabolism, apoptosis and cell proliferation. In contrast to Pkb(alpha) and Pkb(beta)-deficient mice, Pkb(gamma)(-/-) mice are viable, show no growth retardation and display normal glucose metabolism. However, in adult Pkb(gamma)mutant mice, brain size and weight are dramatically reduced by about 25%. In vivo magnetic resonance imaging confirmed the reduction of Pkb(gamma)(-/-) brain volumes with a proportionally smaller ventricular system. Examination of the major brain structures revealed no anatomical malformations except for a pronounced thinning of white matter fibre connections in the corpus callosum. The reduction in brain weight of Pkb(gamma)(-/-) mice is caused, at least partially, by a significant reduction in both cell size and cell number. Our results provide novel insights into the physiological role of Pkb(gamma) and suggest a crucial role in postnatal brain development.

Identification and modulation of a caveolae-dependent signal pathway that regulates plasminogen activator inhibitor-1 in insulin-resistant adipocytes.

Plasminogen activator inhibitor-1 (PAI-1) plays an important role in the pathogenesis of obesity-driven type 2 diabetes mellitus and associated cardiovascular complications. Here, we show that perturbation of caveolar microdomains leads to insulin resistance and concomitant up-regulation of PAI-1 in 3T3L1 adipocytes. We present several lines of evidence showing that the phosphatidylinositol 3-kinase (PI3K) pathway negatively regulates PAI-1 gene expression. Insulin-induced PAI-1 gene expression is up-regulated by a specific inhibitor of PI3K. In addition, serum PAI-1 level is elevated in protein kinase Balpha-deficient mice, whereas it is reduced in p70 ribosomal S6 kinase 1-deficient mice. The PI3K pathway phosphorylates retinoblastoma protein (pRB), known to release free E2 (adenoviral protein) factor (E2F), which we have previously demonstrated to be a transcriptional repressor of PAI-1 gene expression. Accordingly, cell-penetrating peptides that disrupt pRB-E2F interaction, and thereby release free E2F, are able to suppress PAI-1 levels that are elevated during insulin-resistant conditions. This study identifies a caveolar-dependent signal pathway that up-regulates PAI-1 in insulin-resistant adipocytes and proposes a previously undescribed pharmacological paradigm of disrupting pRB-E2F interaction to suppress PAI-1 levels.

Protein kinase B alpha/Akt1 regulates placental development and fetal growth.

Protein kinase B alpha (PKB alpha/Akt1) is implicated in the regulation of metabolism, transcription, cell survival, angiogenesis, cell migration, growth, and tumorigenesis. Previously, it was reported that PKB alpha-deficient mice are small with increased neonatal mortality (Cho, H., Thorvaldsen, J. L., Chu, Q., Feng, F., and Birnbaum, M. J. (2001) J. Biol. Chem. 276, 38349-38352 and Chen, W. S., Xu, P. Z., Gottlob, K., Chen, M. L., Sokol, K., Shiyanova, T., Roninson, I., Wenig, W., Suzuki, R., Tobe, K., Kadowaki, T., and Hay, N. (2001) Genes Dev. 15, 2203-2208). Here we show that PKB alpha is widely expressed in placenta including all types of trophoblast and vascular endothelial cells. Pkb alpha-/- placentae display significant hypotrophy, with marked reduction of the decidual basalis and nearly complete loss of glycogen-containing cells in the spongiotrophoblast, and exhibit decreased vascularization. Pkb alpha-/- placentae also show significant reduction of phosphorylation of PKB and endothelial nitric-oxide synthase. These defects may cause placental insufficiency, fetal growth impairment, and neonatal mortality. These data represent the first evidence for the role of PKB alpha and endothelial nitricoxide synthase in regulating placental development and provide an animal model for intrauterine growth retardation.