The role of dietary vitamin A in mechanisms of cataract development in the teleost lumpfish (Cyclopterus lumpus L)

Lumpfish (Cyclopterus lumpus L) are highly prone to cataract development in the wild and in culture. There is evidence that cataract in farmed fish is related to nutrition. However, both the nutrients and the mechanisms involved in cataract development in lumpfish are not clear. Here we investigated the mechanisms involved and the role of dietary vitamin A in cataract development in a cultured lumpfish population. Cultured lumpfish were fed three diets differing only in vitamin A supplementation level (5000, 15,000 and 120,000 IU/kg) over an 18-month period, and fish weight, cataract frequencies and severities were determined. Western blotting and immunohistochemistry were performed on lens tissue to measure the levels of oxidative stress, and apoptosis. The lowest levels of vitamin A significantly reduced cataract frequencies in adult lumpfish and resulted in less severe cataract and increased weight in males. Oxidative stress levels in the lens were positively correlated with vitamin A intake. Apoptosis was observed at high levels in lenses with severe cataract. Oxidative stress and apoptosis levels were the highest in regions of the lens with severe, advanced cataract pathology when compared to regions with no visible pathology. These results suggest that higher vitamin A intake contributes to cataract development through an oxidative stress pathway, and that both oxidative stress and apoptosis are involved in advanced stages of cataract in lumpfish.

Genetic Variants of the Beta-Adrenergic Receptor Pathways as Both Risk and Protective Factors for Retinopathy of Prematurity

PURPOSE

There is strong evidence that genetic factors influence retinopathy of prematurity (ROP), a neovascular eye disease. It has been previously suggested that polymorphisms in the genes involved in β-adrenergic receptor (ADRβ) pathways could protect against ROP. Antagonists for the ADRβ are actively tested in clinical trials for ROP treatment, but not without controversy and safety concerns. This study was designed to assess whether genetic variations in components of the ADRβ signaling pathways associate with risk of developing ROP.

DESIGN

An observational case-control targeted genetic analysis.

METHODS

A study was carried out in premature participants with (n = 30) or without (n = 34) ROP and full-term controls (n = 20), who were divided into a discovery cohort and a validation cohort. ROP was defined using International Classification of Retinopathy of Prematurity criteria (ICROP). Targeted sequencing of 20 genes in the ADRβ pathways was performed in the discovery cohort. Polymerase chain reaction (PCR)/restriction enzyme analysis for some of the discovered ROP-associated variants was performed for validation of the results using the validation cohort.

RESULTS

The discovery cohort revealed 543 bi-allelic variants within 20 genes of the ADRβ pathways. Ten single-nucleotide variants (SNVs) in 5 genes including protein kinase A regulatory subunit 1α (PRKAR1A), rap guanine exchange factor 3 (RAPGEF3), adenylyl cyclase 4 (ADCY4), ADCY7, and ADCY9 were associated with ROP (P < .05). The most significant SNV was found in PRKAR1A (P = .001). Multiple variants located in the 3'-untranslated region (3'UTR) of RAPGEF3 were also associated with ROP (P < .05). PCR/restriction enzyme analysis of the 3'UTR of RAPGEF3 methodologically validated these findings.

CONCLUSION

SNVs in PRKAR1A may represent protective factors whereas SNVs in RAPGEF3 may represent risk factors for ROP. PRKAR1α has previously been implicated in retinal vascular development whereas the RAPGEF3 product has a role in the maintenance of vascular barrier function, 2 processes important in ROP. Multicenter validation of these newly discovered risk factors could lead to valuable tools for predicting and preventing the development of severe ROP.

CD45 in ocular tissues during larval and juvenile stages and early stages of V. anguillarum infection in young lumpfish (Cyclopterus lumpus)

Immune responses to infectious diseases impacting lumpfish (Cyclopterus lumpus) eye tissue are only starting to be studied at a molecular and histopathological level. In this study, we extend our understanding of lumpfish sensory organ anatomy, of components of the lumpfish nasal and ocular immune system and the nature of the intraocular response to Vibrio anguillarum infection. We have evaluated the expression of cluster of differentiation (CD) 45 protein, a tyrosine phosphatase, in larval and juvenile lumpfish tissues in order to spatially survey ocular and related head structures that may participate in early stages of intraocular immune responses. We provide here a histological mapping of the larval lumpfish nasal chamber system since its connectively with the eye though mucosal epithelia have not been explored. These results build upon our growing understanding of the lumpfish intraocular immune response to pathogens, exemplified herein by experimental nasally delivered V. anguillarum infection. CD45 is developmentally regulated in lumpfish eyes and periocular anatomy with early expression appearing in larvae in corneal epithelium and in nasal structures adjacent to the eye. Normal juvenile and adult lumpfish eyes express CD45 in the corneal epithelium, in leukocyte cells within blood vessel lumens of the rete mirabile, choroid body and choriocapillaris vasculatures. Experimental nasally delivered V. anguillarum infection led to qualitative and quantitative changes in CD45 expression in head kidney renal tubule tissues by 7 days post infection (dpi). The same animals showed redistribution and upregulation of corneal epithelial CD45 expression, corneal epithelial dysplasia and an increased frequency of CD45⁺ cells in ocular vasculature. Interestingly, while CD45 upregulation and/or CD45⁺ cell infiltration into inner ocular and retinal tissues was not observed under this experimental scenario, subtle neural retinal changes were observed in infected fish. This work provides new fundamental knowledge on North Atlantic teleost visual systems and vision biology in general.

Novel segmentation algorithm for high-throughput analysis of spectral domain-optical coherence tomography imaging of teleost retinas

Spectral domain-optical coherence tomography (SD-OCT) has become an essential tool for assessing ocular tissues in live subjects and conducting research on ocular development, health, and disease. The processing of SD-OCT images, particularly those from non-mammalian species, is a labor-intensive manual process due to a lack of automated analytical programs. This paper describes the development and implementation of a novel computer algorithm for the quantitative analysis of SD-OCT images of live teleost eyes. Automated segmentation processing of SD-OCT images of retinal layers was developed using a novel algorithm based on thresholding. The algorithm measures retinal thickness characteristics in a large volume of imaging data of teleost ocular structures in a short time, providing increased accuracy and repeatability of SD-OCT image analysis over manual measurements. The algorithm also generates hundreds of retinal thickness measurements per image for a large number of images for a given dataset. Meanwhile, heat mapping software that plots SD-OCT image measurements as a color gradient was also created. This software directly converts the measurements of each processed image to represent changes in thickness across the whole retinal scan. It also enables 2D and 3D visualization of retinal thickness across the scan, facilitating specimen comparison and localization of areas of interest. The study findings showed that the novel algorithm is more accurate, reliable, and repeatable than manual SD-OCT analysis. The adaptability of the algorithm makes it potentially suitable for analyzing SD-OCT scans of other non-mammalian species.

Use of three-dimensional printing for adapting and optimizing smartphone ophthalmoscopy to existing SD-OCT instrumentation for rodent and teleost ocular research

Use of animal models for human vision research is now pervasive. To address a range of technical challenges, laboratories either modify existing equipment or purchase products that are purpose designed. Three-dimensional (3D) printing technology now allows the do-it-yourself capability to invent, innovate, and manufacture for a specific purpose. Ophthalmic imaging is often used with a range of other sophisticated experimental retinal imaging techniques, such as spectral domain optical coherence tomography (SD-OCT). The handheld smartphone camera and cost-effective, readily available professional-quality apps now allow accessible high-definition video ophthalmic image recording. However, to our knowledge, there are few reports of adapting smartphone ophthalmic imaging to existing experimental SD-OCT imaging instrumentation. This would offer better accuracy, reproducibility, and most importantly, precision. The objective of the present study was to use 3D printing to enhance the functionality and precision of existing SD-OCT instrumentation and smartphone-based ophthalmic imaging through construction of a custom 3D-printed assembly. The assembly can be controlled either manually or by the highly precise rodent stage of the SD-OCT instrument. Using this technical approach, 3D printing facilitated a novel methodology for high-quality ophthalmic imaging with low cost and ease of production either manually or by enhancing existing SD-OCT instrumentation.

CD10+ Cells and IgM in Pathogen Response in Lumpfish (Cyclopterus lumpus) Eye Tissues

Lumpfish (Cyclopterus lumpus), a North Atlantic “cleaner“ fish, is utilized to biocontrol salmon louse (Lepeophtheirus salmonis) in Atlantic salmon (Salmo salar) farms. Lumpfish require excellent vision to scan for and eat louse on salmon skin. The lumpfish eye immune response to infectious diseases has not been explored. We examined the ocular response to a natural parasite infection in wild lumpfish and to an experimental bacterial infection in cultured lumpfish. Cysts associated with natural myxozoan infection in the ocular scleral cartilage of wild adult lumpfish harbored cells expressing cluster of differentiation 10 (CD10) and immunoglobulin M (IgM). Experimental Vibrio anguillarum infection, which led to exophthalmos and disorganization of the retinal tissues was associated with disruption of normal CD10 expression, CD10⁺ cellular infiltration and IgM expression. We further describe the lumpfish CD10 orthologue and characterize the lumpfish scleral skeleton in the context of myxozoan scleral cysts. We propose that lumpfish develop an intraocular response to pathogens, exemplified herein by myxozoan and V. anguillarum infection involving novel CD10⁺ cells and IgM⁺ cells to contain and mitigate damage to eye structures. This work is the first demonstration of CD10 and IgM expressing cells in a novel ocular immune system component in response to disease in a teleost.

Ocular tissue changes associated with anterior segment opacity in lumpfish (Cyclopterus lumpus L) eye

Lumpfish use their vision to hunt prey or, in the case of aquaculture, to see and eat pelleted diets. A common anterior ocular opacity abnormality designated in the literature as "cataract" described in both farmed and wild lumpfish has not yet been characterized in detail at the pathobiological level. We describe here lens tissue changes associated with cataract in cultured and domesticated lumpfish. Methodology included gross observations, ophthalmoscopy and histology. Young adult cultured animals approaching 400 days post-hatch presented a range of anterior segment opacities associated with lenticular abnormalities observable at a histological level. Wild aged domesticated animals also displayed cataracts characterized mainly by abnormalities of the lens observed by both ophthalmoscopy and histology. Dysplastic lesions of the lens in one aged domesticated lumpfish were accompanied with both retinal and optic nerve degeneration. These novel naturally occurring anatomical changes in lumpfish present both commonalities and unique features associated with cataract in young adult cultured animals versus aged domesticated broodstock animals.

Novel characteristics of the cultured Lumpfish Cyclopterus lumpus eye during post-hatch larval and juvenile developmental stages

We systematically analysed the characteristics of the Cyclopterus lumpus eye and retina during cultured post-hatch developmental stages using gross observations, histology, immunohistochemistry, microscopy, fundus imaging and spectral domain optical coherence tomography retinal imaging. Post-hatch developing cultured C. lumpus eye and retinal tissues share a number of features typically conserved in other teleost fish. However, cultured C. lumpus possess some novel ocular and retinal features different from previous descriptions of other teleosts, including a prominent retractor lentis pigmented tissue closely associated with the vascular rete mirabile, peripherally located lobes of separate retinal tissue containing proliferative cells, extensive tapetum material of varying thickness, prominent fundus stripes and an elongated rod-shaped optic nerve stalk. Post-hatch developing cultured C. lumpus also developmentally regulate a protein homologous to alpha smooth-muscle actin in strikingly dense continuous bands in the plexiform layers of the retina. The novel features of the eye and retina of cultured C. lumpus described here could contribute to our understanding of fitness and survival of C. lumpus in a widely ranging habitat.

High rates of glucose utilization in the gas gland of Atlantic cod (Gadus morhua) are supported by GLUT1 and HK1b

The gas gland of physoclistous fish utilizes glucose to generate lactic acid that leads to the off-loading of oxygen from haemoglobin. This study addresses characteristics of the first two steps in glucose utilization in the gas gland of Atlantic cod (Gadus morhua). Glucose metabolism by isolated gas gland cells was 12- and 170-fold higher, respectively, than that in heart and red blood cells (RBCs) as determined by the production of (3)H2O from [2-(3)H]glucose. In the gas gland, essentially all of the glucose consumed was converted to lactate. Glucose uptake in the gas gland shows a very high dependence upon facilitated transport as evidenced by saturation of uptake of 2-deoxyglucose at a low extracellular concentration and a requirement for high levels of cytochalasin B for uptake inhibition despite the high efficacy of this treatment in heart and RBCs. Glucose transport is via glucose transporter 1 (GLUT1), which is localized to the glandular cells. GLUT1 western blot analysis from whole-tissue lysates displayed a band with a relative molecular mass of 52 kDa, consistent with the deduced amino acid sequence. Levels of 52 kDa GLUT1 in the gas gland were 2.3- and 33-fold higher, respectively, than those in heart and RBCs, respectively. Glucose phosphorylation is catalysed by hexokinase Ib (HKIb), a paralogue that cannot bind to the outer mitochondrial membrane. Transcript levels of HKIb in the gas gland were 52- and 57-fold more abundant, respectively, than those in heart and RBCs. It appears that high levels of GLUT1 protein and an unusual isoform of HKI are both critical for the high rates of glycolysis in gas gland cells.

Tubedown regulation of retinal endothelial permeability signaling pathways

Tubedown (Tbdn; Naa15), a subunit of the N-terminal acetyltransferase NatA, complexes with the c-Src substrate Cortactin and supports adult retinal homeostasis through regulation of vascular permeability. Here we investigate the role of Tbdn expression on signaling components of retinal endothelial permeability to understand how Tbdn regulates the vasculature and supports retinal homeostasis. Tbdn knockdown-induced hyperpermeability to Albumin in retinal endothelial cells was associated with an increase in the levels of activation of the Src family kinases (SFK) c-Src, Fyn and Lyn and phospho-Cortactin (Tyr421). The knockdown of Cortactin expression reduced Tbdn knockdown-induced permeability to Albumin and the levels of activated SFK. Inhibition of SFK in retinal endothelial cells decreased Tbdn knockdown-induced permeability to Albumin and phospho-Cortactin (Tyr421) levels. Retinal lesions of endothelial-specific Tbdn knockdown mice, with tissue thickening, fibrovascular growth, and hyperpermeable vessels displayed an increase in the levels of activated c-Src. Moreover, the retinal lesions of patients with proliferative diabetic retinopathy (PDR) associated with a loss of Tbdn expression and hyperpermeability to Albumin displayed increased levels of activated SFK in retinal blood vessels. Taken together, these results implicate Tbdn as an important regulator of retinal endothelial permeability and homeostasis by modulating a signaling pathway involving c-Src and Cortactin.

Osmotic pressure-adaptive responses in the eye tissues of rainbow smelt (Osmerus mordax)

PURPOSE

The rainbow smelt (Osmerus mordax), is a teleost fish, which avoids freezing by becoming virtually isosmotic with seawater. The effects that such massive changes in osmolarity have on both its visual system and its highly evolved and specialized circulation are not known. New knowledge about the osmotic adaptation of the rainbow smelt eye is highly relevant to the adaptation and survival of this species and to its ability to feed as a visual predator in the face of environmental pressures. Moreover, the molecular physiologic response of the smelt to osmotic stress might provide valuable insights into understanding and managing mammalian pathological hyperosmolarity conditions, such as diabetes. We undertook the present study to provide an initial assessment of gene expression in ocular vasculature during osmotic adaptation in rainbow smelt.

METHODS

Immunohistochemistry with species cross reactive antibodies was used to assess blood vessel protein expression in paraffin sections. Western blotting was used to further verify antibody specificity for orthologs of mammalian blood vessel proteins in rainbow smelt. Thermal hysteresis and the analysis of glycerol concentrations in vitreous fluid were used to assess the physiologic adaptive properties of cold stressed eyes.

RESULTS

Glycerol levels and osmotic pressure were significantly increased in the vitreal fluid of smelt maintained at <0.5 °C versus those maintained at 8-10 °C. Compared to the 8-10 °C adapted specimens, the rete mirabile blood vessels and connecting regions of the endothelial linings of the choroidal vessels of the <0.5 °C adapted specimens showed a higher expression level of Tubedown (Tbdn) protein, a marker of the endothelial transcellular permeability pathway. Expression of the zonula occludens protein ZO-1, a marker of the endothelial paracellular permeability pathway showed a reciprocal expression pattern and was downregulated in rete mirabile blood vessels and connecting regions in the endothelial linings of choroidal vessels in <0.5 °C adapted specimens. Smelt orthologs of the mammalian Tbdn and zoluna occludens protein 1 (ZO-1) proteins were also detected by western blotting using anti-mammalian antibodies raised against the same epitopes as those used for immunohistochemistry.

CONCLUSIONS

This work provides the first evidence that molecules known to play a role in ocular vascular homeostasis are expressed and may be differentially regulated during anti-freezing cold adaptation in smelt eyes. We propose a hypothesis that in a state of cold-induced hyperosmolarity, changes in ZO-1 expression are associated with the passage of small solutes from the plasma space to ocular fluid, while changes in Tbdn expression regulate the passage of proteins between the ocular fluid and plasma space. This work also provides fundamental insight into the mechanisms underlying the adaptation of the blood-retinal barrier to metabolically relevant compounds such as glycerol.

Tubedown associates with cortactin and controls permeability of retinal endothelial cells to albumin

Tubedown (Narg1, Tbdn), a member of the Nat1 family of proteins, associates with the acetyltransferase Ard1 and exerts an angiostatic function in adult retinal-blood-vessel homeostasis. The purpose of the present study was to gain a better understanding of the nature of the Tbdn protein complex and how it might exert a homeostatic influence on blood vessels. Immunoprecipitation of Tbdn from endothelial cells followed by gel electrophoresis and liquid-chromatography–tandem-mass-spectrometry identified the actin-cytoskeleton-binding protein cortactin as a co-immunopurifying species. Western blotting confirmed the association between Tbdn and cortactin. Immunofluorescence confocal microscopy revealed that Tbdn colocalizes with cortactin and F-actin in cytoplasmic regions and at the cortex of cultured endothelial cells. Because cortactin is known to regulate cellular permeability through its interaction with the actin cytoskeleton, a process that is crucial for endothelial cell homeostasis, the role of Tbdn on endothelial cell permeability was examined. Knockdown of Tbdn expression in endothelial cells led to the co-suppression of Ard1 protein expression and to a significant increase in cellular permeability measured by the transit of FITC-albumin across the cellular monolayer. Furthermore, the proliferative retinal neovascularization and thickening resulting from induction of Tbdn knockdown in endothelium in transgenic mice was associated with a significant increase in extravasation or leakage of albumin from abnormal retinal blood vessels in vivo. These results provide evidence that an association occurs between Tbdn and cortactin, and that Tbdn is involved in the regulation of retinal-endothelial-cell permeability to albumin. This work implicates a functional role for Tbdn in blood-vessel permeability dynamics that are crucial for vascular homeostasis.

Tubedown Expression Correlates with the Differentiation Status and Aggressiveness of Neuroblastic Tumors

PURPOSE

The discovery and validation of new prognostic factors and further refinement of risk group stratification are needed to improve clinical interpretation of neuroblastoma. Our laboratory isolated and characterized a developmentally regulated gene named TUBEDOWN against which we have raised a monoclonal antibody (OE5). Tubedown becomes down-regulated postnatally yet remains strongly expressed in some neuroblastomas. The purpose of this study is to define the utility of Tubedown expression as a new measure of the differentiation status and aggressiveness of neuroblastic tumors.

EXPERIMENTAL DESIGN

Tubedown protein expression was quantitatively assessed in neuroblastic tumors (neuroblastomas, ganglioneuroblastomas, and ganglioneuromas) and normal adrenal tissues using Western blot and OE5 immunohistochemistry. Regulation of Tubedown expression during retinoic acid-induced neuronal differentiation in neuroblastoma cell lines was assessed by Western blotting.

RESULTS

High levels of Tubedown expression are observed in tumors with significant neuroblastic component, unfavorable histopathology, advanced stage, high-risk group, and poor outcome. In contrast, more differentiated subsets of neuroblastic tumors, ganglioneuroblastomas with favorable histopathology and ganglioneuromas, express low levels of Tubedown. In vitro, marked retinoic acid-induced neuronal differentiation responses of neuroblastoma cells are associated with a significant decrease in Tubedown expression, whereas limited neuronal differentiation responses to retinoic acid were associated with little or no decrease in Tubedown expression.

CONCLUSIONS

Our results indicate that the levels of Tubedown expression are linked to the differentiation status and aggressiveness of neuroblastic tumors and represent an independent prognostic factor for neuroblastoma. Tubedown expression may be useful to more accurately define different neuroblastic tumor subsets and ultimately provide more adequate assessment and treatment for neuroblastoma patients.

Tubedown-1 (Tbdn-1) suppression in oxygen-induced retinopathy and in retinopathy of prematurity

PURPOSE

Identification of unique proteins involved in retinopathy of prematurity (ROP) may facilitate new and more effective diagnostic tools and molecular-based treatments for ROP. Tubedown-1 (Tbdn-1), a novel homeostatic protein which copurifies with an acetyltransferase activity, is expressed in normal retinal endothelium and is specifically suppressed in retinal endothelial cells from patients with proliferative diabetic retinopathy. Furthermore, recent in vivo knockdown studies in mice have revealed that Tbdn-1 is important for retinal blood vessel homeostasis and for preventing retinal neovascularization in adults. The purpose of the present study was to determine if the expression pattern of Tbdn-1 is altered during oxygen-induced retinal neovascularization in mice and in a specimen of stage 3 human ROP.

METHODS

Specimens of oxygen-induced retinal neovascularization in mice, and a single specimen of active stage 3 ROP were studied by immunohistochemistry and digital image analysis using antibodies raised against Tbdn-1 and other blood vessel markers.

RESULTS

The pattern of Tbdn-1 expression during the course of oxygen-induced retinal neovascularization in mice suggests a regulating role in neonatal retinopathy. Retinal lesions from oxygen-induced retinal neovascularization in mice display suppression of retinal endothelial Tbdn-1 protein expression in conjunction with an increase in expression of proliferating cell nuclear antigen (a marker of proliferation) and alpha smooth muscle actin (a marker of myofibroblastic cells). Abnormal blood vessels within vitreoretinal neovascular lesions in a human specimen of active stage 3 ROP did not show Tbdn-1 protein expression.

CONCLUSIONS

These results suggest that the loss of retinal endothelial Tbdn-1 expression may be a contributing factor in retinal blood vessel proliferation in ROP.

Conditional Knockdown of Tubedown-1 in Endothelial Cells Leads to Neovascular Retinopathy

PURPOSE

Identification of novel proteins involved in retinal neovascularization may facilitate new and more effective molecular-based treatments for proliferative retinopathy. Tubedown-1 (Tbdn-1) is a novel protein that shows homology to the yeast acetyltransferase subunit NAT1 and copurifies with an acetyltransferase activity. Tbdn-1 is expressed in normal retinal endothelium but is specifically suppressed in retinal endothelial cells from patients with proliferative diabetic retinopathy. The purpose of this study was to investigate the importance of Tbdn-1 expression in retinal blood vessels in vivo.

METHODS

A bitransgenic mouse model that enables conditional knockdown of Tbdn-1 specifically in endothelial cells was produced and studied using molecular, histologic, and immunohistochemical techniques and morphometric analysis.

RESULTS

Tbdn-1-suppressed mice exhibited retinal and choroidal neovascularization with intra- and preretinal fibrovascular lesions similar to human proliferative retinopathies. Retinal lesions observed in Tbdn-1-suppressed mice increased in severity with prolonged suppression of Tbdn-1. In comparison to normal retina, the retinal lesions displayed alterations in the basement membrane of blood vessels and in the distribution of glial and myofibroblastic cells. Moreover, the pathologic consequences of Tbdn-1 knockdown in endothelium were restricted to the retina and the choroid.

CONCLUSIONS

These results indicate that the maintenance of Tbdn-1 expression is important for retinal blood vessel homeostasis and for controlling retinal neovascularization in adults. Restoration of Tbdn-1 protein expression and/or activity may provide a novel approach for treating proliferative retinopathies.

Role of Cys41 in the N-terminal domain of lumican in ex vivo collagen fibrillogenesis by cultured corneal stromal cells

The keratan sulphate proteoglycan lumican regulates collagen fibrillogenesis to maintain the integrity and function of connective tissues such as cornea. We examined the role of a highly conserved cysteine-containing domain proximal to the N-terminus of lumican in collagen fibrillogenesis using site-specific mutagenesis to prepare plasmid DNA encoding wild-type murine lumican (Cys(37)-Xaa(3)-Cys(41)-Xaa-Cys-Xaa(9)-Cys) and a Cys-->Ser (C/S) mutant (Cys(37)-Xaa(3)-Ser(41)-Xaa-Cys-Xaa(9)-Cys). cDNAs were cloned into the pSecTag2A vector, and cultures of MK/T-1 cells (an immortalized cell line from mouse keratocytes) were transfected with the cDNAs. Stable transformants were selected and cloned in the presence of Zeocin. All stable transformants maintained a dendritic morphology and growth rate similar to those of parental MK/T-1 cells. Western blot analysis with anti-lumican antibody detected a 42 kDa lumican protein secreted into the culture medium of both wild-type and C/S mutant lumican cell lines. Ultrastructural analyses by transmission electron microscopy showed both cell lines to form a multi-layered stroma ex vivo, but the matrix assembled by the two cell lines differed. Compared with the mutant cell line, the wild-type cells assembled a more organized matrix with regions containing orthogonal collagen fibrils. In addition, the fibrils in the extracellular matrix formed by the mutant cell line exhibited alterations in fibril packing and structure. Immunostaining analysed by confocal microscopy showed a further difference in this matrix, with the marked occurrence of lumican and collagen I co-localization in the lumican wild-type cells, but a lack thereof in the lumican C/S mutant cells. The results indicate that the cysteine-rich domain of lumican is important in collagen fibrillogenesis and stromal matrix assembly.

Tubedown-1 in remodeling of the developing vitreal vasculature in vivo and regulation of capillary outgrowth in vitro

Tubedown-1 (tbdn-1) is a mammalian homologue of the N-terminal acetyltransferase subunit NAT1 of Saccharomyces cerevisiae and copurifies with an acetyltransferase activity. Tbdn-1 expression in endothelial cells becomes downregulated during the formation of capillary-like structures in vitro and is regulated in vivo in a manner which suggests a functional role in dampening blood vessel development. Here we show that tbdn-1 is expressed highly in the vitreal vascular network (tunica vasculosa lentis and vasa hyaloidea propria) during the pruning and remodeling phases of this transient structure. The vitreal blood vessels of mice harboring a targeted inactivation of TGF-beta2 fail to remodel and abnormally accumulate, a phenomenon reminiscent of the ocular pathology resembling persistent fetal vasculature (PFV) in humans. Since suppression of normal tbdn-1 expression has been previously observed in retinal vessel proliferation, we analyzed vitreal vascular changes and tbdn-1 expression in TGF-beta2(-/-) eyes. The nuclei of vitreal vessel endothelial cells in TGF-beta2(-/-) eyes express proliferating cell nuclear antigen (PCNA) and exhibit increased levels of active (P42/44)mitogen-activated protein kinase (phospho-(P42/44)MAPK), characteristics consistent with proliferative endothelial cells. In contrast to normal vitreal vessels, collagen IV expression exhibited a disorganized pattern in the TGF-beta2(-/-) vitreal vessels, suggesting vessel disorganization and possibly a breakdown of vessel basal laminae. Moreover, vitreal vessels of TGF-beta2(-/-) mice lack expression of pericyte markers (CD13, alpha smooth muscle actin) and show ultrastructural changes consistent with pericyte degeneration. The accumulating vitreal blood vessels of TGF-beta2(-/-) mice, while maintaining expression of the endothelial marker von Willebrand Factor, show a significant decrease in the expression of tbdn-1. We addressed the functional role of tbdn-1 in the regulation of vitreal blood vessels using an in vitro model of choroid-retina capillary outgrowth. Clones of the RF/6A fetal choroid-retina endothelial cell line showing suppression of tbdn-1 levels after overexpression of an antisense TBDN-1 cDNA display a significant increase in the formation of capillary-like structures in vitro compared with controls. These findings suggest that tbdn-1 inhibits capillary-like formation in vitro and may serve to dampen vitreal blood vessel formation preceding the regression of the vitreal vasculature during development. Our results also suggest that tbdn-1 may participate with TGF-beta2 in regulating normal development of the vitreal vasculature.

TGFbeta2 in corneal morphogenesis during mouse embryonic development

To examine the roles of TGFbeta isoforms on corneal morphogenesis, the eyes of mice that lack TGFbetas were analyzed at different developmental stages for cell proliferation, migration and apoptosis, and for expression patterns of keratin 12, lumican, keratocan and collagen I. Among the three Tgfb(-/-) mice, only Tgfb2(-/-) mice have abnormal ocular morphogenesis characterized by thin corneal stroma, absence of corneal endothelium, fusion of cornea to lens (a Peters'-like anomaly phenotype), and accumulation of hyaline cells in vitreous. In Tgfb2(-/-) mice, fewer keratocytes were found in stroma that has a decreased accumulation of ECM; for example, lumican, keratocan and collagen I were greatly diminished. The absence of TGFbeta2 did not compromise cell proliferation, nor enhance apoptosis. The thinner stroma resulting from decreased ECM synthesis may account for the decreased cell number in the stroma of Tgfb2 null mice. Keratin 12 expression was not altered in Tgfb2(-/-) mice, implicating normal corneal type epithelial differentiation. Delayed appearance of macrophages in ocular tissues was observed in Tgfb2(-/-) mice. Malfunctioning macrophages may account for accumulation of cell mass in vitreous of Tgfb2 null mice.

Suppressed expression of tubedown-1 in retinal neovascularization of proliferative diabetic retinopathy

PURPOSE

Retinal neovascularization occurring as a complication of diabetes mellitus can cause vision loss and blindness. The identification and study of novel genes involved in retinal angiogenesis may define new targets to suppress retinal neovascularization in diabetes and other ocular diseases. A novel acetyltransferase subunit, tubedown-1 (tbdn-1), has been isolated, the expression of which is regulated during blood vessel development. Tbdn-1 is not detected in most adult vascular beds but persists at high levels in the adult ocular vasculature. The purpose of this study was to gain insight into the possible role of tbdn-1 in retinal blood vessels by characterizing its expression patterns in adult homeostasis and in retinal neovascularization associated with diabetes.

METHODS

Western blot analysis and immunohistochemistry were performed to study the expression patterns of tbdn-1 during adult homeostasis in normal human retinas, in a model of choroid-retina endothelial capillary outgrowth in vitro, and in retinas showing neovascularization in patients with proliferative diabetic retinopathy (PDR).

RESULTS

In adults during homeostasis, tbdn-1 was expressed highly in normal endothelium of retinal and limbic blood vessels. Tbdn-1 was also expressed in RF/6A, a rhesus macaque choroid-retina-derived endothelial cell line. In an in vitro model system using the RF/6A cell line, tbdn-1 expression was downregulated during the outgrowth of these cells into capillary-like structures on a reconstituted basement membrane matrix. Similar to this in vitro model, tbdn-1 expression is specifically suppressed in the endothelial cells of blood vessels and capillary fronds in vivo in both the neural retinal tissue and in preretinal membranes in eyes of patients with PDR.

CONCLUSIONS

High levels of expression of tbdn-1 are associated with ocular endothelial homeostasis in adults. Conversely, low levels of tbdn-1 expression are associated with endothelial capillary outgrowth in vitro and retinal neovascularization in vivo. Because the tbdn-1 acetyltransferase subunit is a member of a family of regulatory enzymes that are known to control a range of processes, including cell growth and differentiation, through posttranslational modification, the current results support a hypothesis that tbdn-1 may be involved in maintaining homeostasis and preventing retinal neovascularization.

Retinopathy of prematurity

The majority of cases of ROP regress spontaneously, but better treatment methods are needed to prevent retinal detachment and other effects of ROP such as myopia. In the future, molecular mechanisms may be exploited to treat ROP.

MK/T-1, an immortalized fibroblast cell line derived using cultures of mouse corneal stroma

PURPOSE

Immortalized cell lines representing fibroblast cells from corneal stroma would facilitate studies of corneal cell biology and injury response.

METHODS

Primary cultures of cells derived from mouse corneal stroma were transfected with a human telomerase reverse transcriptase (hTERT) expression construct to maximize chances of cellular immortalization. A resulting cell line was analyzed for telomerase activity, cell growth characteristics, senescence and gene expression patterns. Specific responses to transforming growth factor beta (TGF-beta) were also analyzed.

RESULTS

An immortalized cell line was derived and was named MK/T-1. MK/T-1 cells show no signs of cellular senescence or transformation at over 100 passages. Telomerase activity was significantly higher in MK/T-1 cells as compared to the parental cell cultures. However, relative telomere length (RTL) in the MK/T-1 and parental cells was not significantly different. Senescence associated beta-galactosidase (SA-beta-Gal) activity was not detected in late passage MK/T-1 cells while the parental cells had already upregulated SA-beta-Gal at high levels by passage 9. The MK/T-1 cells express vimentin, tubulin, lumican, mimecan, decorin and collagen I, but not keratocan. Exposure of the MK/T-1 cells to TGF-beta induces the expression of smooth muscle alpha-actin (ASMA), the activation of MAP Kinase (p38-MAPK) and morphological changes consistent with cytoskeletal reorganization.

CONCLUSIONS

MK/T-1 cells represent an immortalized fibroblast cell line derived using cultures from corneal stroma cell preparations. Expression of hTERT may contribute to immortalization of the MK/T-1 cells by a mechanism other than increases in RTL. MK/T-1 cells may be a useful model in which to study the responses of corneal fibroblast cells to cytokines and other diverse environmental factors in vitro.

LIF transduces contradictory signals on capillary outgrowth through induction of stat3 and (P41/43)MAP kinase

The signaling pathways regulating blood vessel growth and development are not well understood. In the present report, an in vitro model was used to identify signaling pathways regulating capillary formation in embryonic endothelial cells. Basic fibroblast growth factor (bFGF) plus leukemia inhibitory factor (LIF) optimally stimulate the formation of capillary-like structures of the embryonic endothelial cell line IEM. LIF stimulation of IEM cells leads to activation of the Stat3 as well as the (P41/43)mitogen-activated protein kinase ((P41/43)MAPK) cascade, while bFGF does not activate Stat3 but does induce the (P41/43)MAPK cascade. Inhibition of Stat3 DNA-binding activity by expression of a dominant inhibitory Stat3 mutant increases the capillary outgrowth of the IEM cells induced by LIF. Increased Stat3 activity by overexpression of the wild-type Stat3 greatly reduced capillary outgrowth. In contrast, inhibition of the (P41/43)MAPK cascade using a MEK-1 inhibitor dramatically inhibits the LIF-induced capillary outgrowth. Moreover, the increased formation of capillary-like structures of the IEM cells mediated by Stat3 inhibition does not overcome the requirement for activation of the (P41/43)MAPK pathway for capillary outgrowth. Stat3 activity correlates with the LIF-induced expression of the negative feedback regulators of the Janus (JAK) family of tyrosine kinases, SOCS-1 and SOCS-3. These results provide evidence that Stat3 acts as a negative regulator of capillary outgrowth, possibly by increasing SOCS-1 or SOCS-3 expression. The contradictory signals stimulated by LIF could be necessary to control the intensity of the response leading to capillary outgrowth in vivo.

Tubedown-1, a novel acetyltransferase associated with blood vessel development

We have used an embryonic endothelial cell line (IEM cells) as an experimental system for identifying and characterizing new molecules which are regulated during blood vessel development. A novel gene isolated from IEM cells, tubedown-1 (tbdn-1), is expressed at high levels in unstimulated IEM cells and is downregulated during formation of capillary tube structures by the IEM cells induced by basic fibroblast growth factor (bFGF) and leukemia inhibitory factor (LIF) in vitro. Tbdn-1 is also downregulated in M1 myeloid leukemia cells after differentiation in response to LIF in vitro. Tbdn-1 is homologous to the yeast NAT-1 N-terminal acetyltransferases and encodes a novel protein of approximately 69 kDa associated with an acetyltransferase activity. Levels and distribution of tbdn-1 expression are regulated in both endothelial and hematopoietic cells during development in tissues such as the yolk sac blood islands, heart, and liver blood vessels. In the adult, tbdn-1 expression is low or undetected in most organs examined with the exception of the atrial endocardium, the endothelial and myeloid compartments of bone marrow, and the remodeling vascular bed of atretic ovarian follicles. The distribution and regulation of expression of tbdn-1 suggest that this novel acetyltransferase may be involved in regulating vascular and hematopoietic development and physiologic angiogenesis.

Embryonic vasculogenesis by endothelial precursor cells derived from lung mesenchyme

During development, the lung mesenchyme has a dynamic relationship with the branching airway. Embryonic lung mesenchyme is loosely packed and composed of indistinguishable cells, yet it is the source of vascular progenitors that will become endothelial cells, smooth muscle cells and fibroblasts. In the lung, vessel development in the periphery proceeds first through vasculogenesis, the migration and assembly of cells into a primitive network, and subsequently, through angiogenesis, the sprouting of vessels from this network. As a way to assess the cellular and molecular mechanisms of lung vascularization, we have isolated and cloned cell lines from mouse fetal lung mesenchyme (MFLM). Two of these MFLM cell lines, MFLM-4 and MFLM-91U, display characteristics of an endothelial lineage. RNA analysis demonstrates transcripts for the vascular endothelial growth factor receptors R1 and R2, the receptor tyrosine kinases, Tie-1 and Tie-2, as well as the Tie-2 ligands, Ang-1 and -2. The MFLM cell lines form extensive networks of capillary-like structures with lumens when cultured on a reconstituted basement membrane. In vivo, following blastocyst injection, the MFLM cells chimerize endothelium of the lung and areas of the heart vasculature. The results from these studies suggest that MFLM-4 and MFLM-91U, derived from embryonic lung mesenchyme, can function in vitro and in vivo as endothelial precursors and as models of cardiopulmonary vascularization. Dev Dyn 2000;217:11-23.

Differentiation responses of embryonic endothelium to leukemia inhibitory factor

The IEM cell line is a murine embryonic endothelial cell line that responds to combinations of basic fibroblast growth factor (bFGF) and leukemia inhibitory factor (LIF) by undergoing proliferation and vasculogenic differentiation in vitro and in vivo. Exposure to LIF and bFGF in vitro permits the IEM cells to specifically chimerize endothelium in vivo and recapitulate normal endothelial development after blastocyst injection. We report here that unmanipulated IEM cells form vascular neoplasias when injected into immunodeficient nude mice. Examination of IEM neoplasia following exposure in vitro to bFGF and LIF before injection into nude mice profoundly reduced or completely suppressed the neoplastic growth of IEM cells. Furthermore, this suppression was observed by treatment with LIF alone, while bFGF treatment did not significantly alter IEM neoplasia and did not modify the LIF-mediated suppression. Characterization of the IEM responses to LIF revealed that the LIF suppression of IEM neoplasia depended on how long the cells were exposed to LIF in vitro. The IEM cell response to LIF was associated with the specific activation of the transcription factor Stat3. Stat1 activation could not be detected in response to LIF, although it is expressed in IEM cells. Our results demonstrate that the LIF-induced differentiation of IEM cells involves suppression of IEM-derived neoplasia and is associated with the specific activation of Stat3.

Abnormal uterine stromal and glandular function associated with maternal reproductive defects in Hoxa-11 null mice

Here we describe in detail both the expression of Hoxa-11 in the wild-type mouse uterus and the defects resulting in maternal reproductive failure of Hoxa-11 null female mice. The Hoxa-11 gene is expressed at peak levels in uterine stromal cells during metestrus. Hoxa-11 transcripts were induced beginning on Day 2 of gestation in the stromal cells underlying the uterine epithelium and appeared in the secondary decidual zone between Days 6 and 8 of gestation. At early gestational stages, stromal, decidual, and glandular cell development were deficient in Hoxa-11 null uteri in comparison to wild-type as assessed by histology and immunohistochemical localization of the decidual cell marker epitope, stage-specific embryonic antigen-3 (SSEA-3). Both steroid-induced uterine stromal and glandular cell proliferation as well as oil-induced stromal decidualization after induction of pseudopregnancy were deficient in mutant uteri. Moreover, both Western blotting and immunohistochemistry demonstrated that the burst of glandular leukemia inhibitory factor (LIF) found in normal pregnant uteri at Day 4.5 of gestation was absent in Hoxa-11-deficient uteri. The LIF burst was also not observed in the uteri of bilaterally ovariectomized, hormonally stimulated Hoxa-11 mutants. These results demonstrate that the Hoxa-11 gene is required for normal uterine stromal cell and glandular differentiation during pregnancy, as is the presence of the steroid-induced glandular LIF burst initiating embryo implantation.

Induction of embryonic vasculogenesis by bFGF and LIF in vitro and in vivo

The de novo formation of blood vessels (vasculogenesis) is an integral part of embryogenesis. Elucidation of the role of cytokine cooperation in vasculogenesis may lead to a better understanding of organogenesis, blood vessel regulation during tumorigenesis, and tissue injury. We have used embryonic stem cells to derive an endothelial cell line, designated IEM, which expresses a range of endothelial markers, including Von Willibrand Factor VIII related antigen, vascular cell adhesion molecule, platelet-endothelial cell adhesion molecule (CD31), and receptors for acetylated low-density lipoprotein. More importantly, IEM cells can be induced upon exposure to combinations of basic fibroblast growth factor and leukemia inhibitory factor (LIF) to proliferate and undergo vasculogenesis in vitro, resulting in the formation of vascular tubes and microcapillary anastomoses. Moreover, exposure to both cytokines conditionally permits IEM cells to specifically chimerize microvascular endothelium in vivo following blastocyst injection. These results indicate that bFGF and LIF together contribute to the induction and support of embryonic vasculogenesis in an isolated endothelial cell line. Our results provide evidence that combined actions of bFGF/LIF may play a role in mechanisms controlling blood vessel development.

P-glycoprotein is expressed in the mineralizing regions of the skeleton

Using oligonucleotide primers specific for the human MDR 1 gene, we were able to identify a specific amplicon using RT-PCR from total bovine growth plate chondrocyte RNA. The identification of MDR mRNA in growth plate chondrocytes led us to examine the precise distribution of MDR P-glycoprotein in bone and cartilage. We applied two monoclonal antibodies (C219 and C494) to human fetal, neonatal, and childhood growth plates and bone. In growth plates, P-glycoprotein was detected at high levels in a perilacunar distribution in the calcifying zone and at lower levels in hypertrophic, but not proliferative or reserve zone, chondrocytes. P-glycoprotein was also observed in perichondrial chondrocytes, in perivascular chondrocytes and matrix in the fetal cartilage anlage, and in osteoblasts and the surface osteoid matrix of newly formed bone trabeculae in the primary spongiosa. The recently described chloride channel of P-glycoprotein suggests a potential role of P-glycoprotein in growth plate chondrocyte hypertrophy.

Immunological prevention of spontaneous early embryo resorption is mediated by non-specific immunosimulation

PROBLEM

Spontaneous early embryo resorption following implantation occurs in many species, but little is known regarding the causes or the prevention of early pregnancy failure. Embryo and fetal loss have widely been assumed to be due to maternal allospecific immune rejection. Alloimmunization therapy with paternal tissues has been successfully used in human and murine pregnancies to prevent early embryo demise. The mechanisms of this treatment have been assumed to be the induction of antigen specific, fetal "graft" enhancing antibodies and suppressor cells. The purpose of this study was to investigate the validity of this assumption.

METHOD

To investigate these general assumptions, female CBA/J mice were immunized with either specific or nonspecific antigens prior to mating with DBA/2 or Balb/c males. Further, a model system for the study of bacterial lipopolysaccharide (LPS) induced abortion was used to demonstrate the nature of antigen specific immune protection against abortion.

RESULTS

Whereas the administration of 1 microgram of LPS to CFW female x CFW male pregnant mice on day 7 of gestation induced complete fetal resorption, prior immunization with 20 micrograms of LPS completely prevented LPS induced abortion as long as the anti-LPS antibody titers remained above a threshold value of about 1/500. Therefore, early embryo loss could be induced by a bacterial infection and could be prevented by appropriate immunity to abortogenic factors. However, due to the short half-life of IgM antibodies, immunity to LPS was short-lived and the protective effect of LPS immunization against LPS induced abortion waned after 5 wk. Through the use of the CBA/J female x DBA/2 male model system to study spontaneous early embryo loss, previous vaccination of CBA/J female mice with Balb/c spleen cells expressing paternal MHC antigens, complete Freund's adjuvant (CFA) or LPS, all decreased the incidence of spontaneous resorption in subsequent pregnancies. Similarly, a previous mating with a Balb/c male prevented spontaneous embryo loss for a period of up to 6 wk. However, none of the immunotherapeutic vaccinations or matings had a permanent effect on CBA/J female x DBA/2 male embryo survival, which one would have expected if specific immune mediators were involved.

CONCLUSION

The results of this study indicated that the decrease in the incidence of spontaneous embryo resorption following alloimmunization was more likely to be due to nonspecific immunomodulatory effects on the immune system of the female mice, as opposed to specific antipaternal immunity. This may, in part, explain the placebo effects observed for alloimmunization therapy for human habitual pregnancy loss. The relevance of these results to the development of immunotherapy strategies for the prevention of habitual abortion is discussed.

Evaluation of the role of exogenous pathogens on the incidence of embryo loss during early pregnancy in mice

The mating of CBA/j female mice (H2k) by DBA/2j male mice (H2d) typically results in an elevated incidence of spontaneous embryo loss thus providing an ideal genetically controlled laboratory model for the study of the factors causing early embryo loss during pregnancy. There is now considerable data on the cells and factors involved in fetal resorption but little is known about the events which activate this process. While the activation of the maternal response to the fetal implant could have endogenous or genetic origins, a role for exogenous factors including microbial pathogens could also be involved. In order to investigate these possibilities, the reproductive success of CBA/j female x DBA/2j male matings in a conventional animal care facility were compared with matings in a specific pathogen free (SPF) animal facility. All animals housed under these conditions were routinely screened by immunoassay and culture, for the presence of a number of viral and bacterial pathogens of mice. The incidence of spontaneous embryo loss in specific pathogen free CBA female mice mated by DBA and other male strains was found to be virtually identical to that of CBA female mice infected with multiple viral pathogens and housed under otherwise identical conditions (non-SPF). However, the numbers of implantation per pregnancy was significantly greater in an SPF facility. Therefore, exposure of mating mice to exogenous viral and bacterial pathogens did not appear to alter the overall incidence of spontaneous embryo resorption. It was concluded that the immunomodulatory effects of infection by common murine pathogens neither augmented nor reduced post-implantation embryo losses.

Murine pregnancies predisposed to spontaneous resorption show alterations in the concentrations of leukotriene B4 and prostaglandin E2

Female CBA/J mice mated with DBA/2 males exhibit an increased spontaneous resorption rate (30-35%) in their first pregnancy. Second pregnancies show a decreased resorption rate (15-20%). In contrast, resorption in CBA/J females mated with BALB/c males (identical to DBA/2 at the H-2 major histocompatibility locus) occurs with a frequency of 5-10%. Resorption is preceded by fetoplacental infiltration of natural killer (NK)-like cells and a deficiency in a lipophilic NK-suppressive activity. The eicosanoids leukotriene B4 (LTB4) and prostaglandin E2 (PGE2) are known to modulate NK activity in vitro. We measured the concentrations of LTB4 and PGE2 in extracts of individual fetoplacental units at Day 8 of gestation from (1) primigravid CBA/J x DBA/2 resorption-prone matings (RES); (2) second CBA/J x DBA/2 matings (SEC); and (3) primigravid CBA/J x BALB/c control matings (CON). We detected a significant decrease in the mean concentration of LTB4 in RES fetoplacental units (176.4 +/- 11.8 pg/ml; n = 42) compared with CON and SEC fetoplacental units (570.2 +/- 45.5 pg/ml; n = 21 and 420.2 +/- 59.5 pg/ml; n = 39, respectively). To confirm that the LTB4 deficiency is associated with decreased NK suppression in RES matings, we supplemented RES extracts, in vitro, with exogenous LTB4 (0-500 pg/ml). The effect of the addition of LTB4 to RES extracts was biphasic. Addition of LTB4 in the range of 30-125 pg/ml increased the extract's NK suppressive capacity, whereas LTB4 alone either stimulated NK activity or was without effect. These results suggest a critical role for LTB4 in averting NK-mediated early spontaneous fetal resorption.

Expression of tumor necrosis factor alpha in the developing nervous system

We present evidence that tumor necrosis factor alpha (TNF-alpha) is transiently expressed at specific times during embryogenesis in precisely defined areas of the nervous system in two different classes of vertebrates. In murine embryos, TNF-alpha was detected in the brain, neural tube and peripheral mixed spinal nerves. In the chick embryo, TNF-alpha was observed in the brain neuroepithelium and in the developing Purkinje neurons of the cerebellum. Western immunoblot analysis revealed that brain tissue from both mouse and chick embryos contained a 50 kDa protein showing immunoreactivity with anti-TNF-alpha antibody. These results suggest that TNF-alpha participates in the normal development of the vertebrate brain and spinal cord.

Lipopolysaccharide-induced fetal resorption in mice is associated with the intrauterine production of tumour necrosis factor-alpha

Certain strains of mice display an increased frequency of fetal resorption, but little is known about the effector mechanisms involved. We have examined the events associated with lipopolysaccharide (LPS)-induced fetal resorption in mice. Administration of 25 micrograms LPS on Day 12 of gestation resulted in the appearance of tumour necrosis factor-alpha (TNF-alpha) in the amniotic fluid and fetal resorption. Levels of LPS-induced TNF-alpha were reduced by 90% after pretreatment with the TNF-alpha-suppressing drug pentoxifylline (PXF). Treatment of pregnant mice during early gestation with 0.1 micrograms LPS resulted in fetoplacental resorption which was maximal when the LPS was given on Day 8. Resorption induced by 0.1 micrograms LPS on Day 8 of gestation was significantly reduced by pretreatment with PXF. Infiltration of asialo-GM1-positive cells was observed in the decidual-ectoplacental cone area of embryonic units from LPS-treated mice. In addition, treatment with anti-AGM1 antiserum prevented the LPS-induced resorption. Our results suggest that TNF-alpha and asialo-GM1-positive cells are involved in LPS-induced fetal resorption.

Resorption of CBA/J x DBA/2 mouse conceptuses in CBA/J uteri correlates with failure of the feto-placental unit to suppress natural killer cell activity

Lipid extraction was used to study the natural killer (NK) suppressive activity of individual feto-placental units. Normal pregnancies showed a lipophilic NK cell suppressive factor that was gestational day specific. Feto-placental units from CBA/J x DBA/2 pregnancies were deficient in the NK cell suppressive factor when compared to normal CBA/J x BALB/c pregnancies. The frequency of non-suppressive feto-placental units from CBA/J x DBA/2 pregnancies correlated with the frequency of feto-placental units infiltrated with NK cells and the frequency of spontaneous resorption. Our results implicate a deficiency of NK suppressive activity in the feto-placental unit as a contributing factor in spontaneous fetal resorption.

Morphometric analysis of the histology of spontaneous fetal resorption in a murine pregnancy

Immunopathology of the spontaneous resorption phenomenon in the CBA x DBA/J murine model was explored using morphometric analysis. Accompanying the previously reported presence of natural killer (NK) cells in resorptive feto-placental units we find major changes in tissue morphology indicating that early infiltration of the feto-placental unit by maternal leukocytes plays a direct role with NK cells in fetal demise. Total number of cell nuclei per field and total nuclear area per field were significantly elevated in feto-placental units containing abnormally increased NK cell presence before detectable resorption as early as day 7 of gestation. This difference persisted throughout all stages of early gestation up to and including the final resorption event at day 10 to 12. Increases in cell density were also detected in areas of the embryonic unit not associated with NK infiltration. These results demonstrate that the spontaneous resorption phenomenon in this model involves: (i) Early (day 7-8) cellular infiltration of the decidual-ectoplacental cone junction associated with the presence in this area of NK cells. (ii) Late (day 8-9) cellular infiltration of the ectoplacental cone.

Infiltrating decidual natural killer cells are associated with spontaneous abortion in mice

Immunohistochemistry was used to study a murine model which spontaneously aborts at a frequency of 25 to 30%. Our results show that natural killer (NK) cells are not only the predominant infiltrating cells in aborting feto-placental units, but that they also appear in a similar proportion of feto-placental units before abortion is detectable. The frequency of feto-placental units with significantly elevated NK infiltrates corresponds to the subsequent abortion frequency, indicating a causal relationship. Immunization of the mother with BALB/C splenocytes prevents these NK infiltrates and decreases the abortion frequency to normal levels. These results suggest for the first time that maternal NK cells may have an instrumental role in the etiology of spontaneous abortion.