Localization of alkaline phosphatase and Ca2+-ATPase in the cat placenta

Endotheliochorial placental glycosylation reflects evolutionary divergence between Felidae species (Felis catus and Panthera leo) and Canidae (Canisfamiliaris)

Endotheliochorial cat (Felis catus) and lion (Panthera leo) term placentae and one 6 week placenta (term 60-63 days) from a dog (Canis familiaris) were stained with a panel of 24 lectins to compare glycosylation at the feto-maternal interface. Glycan expression in lion and cat placentae was very similar apart from the occurrence of terminal α-galactose in the lion trophoblast. The dog differed in several respects, particularly in the trophoblast, consistent with species-specific glycotypes differing according to the degree of their evolutionary divergence. The data suggest that evolutionary effects on the glycotype are most readily observed in trophoblast.

Lectin histochemistry reveals two cytotrophoblast differentiation pathways during placental development in the feline (Feliscatus)

INTRODUCTION

Placental glycosylation has been examined on eight feline placentae ranging from approximately 15 to 60 days post-conception as little is known about changes in glycan distribution in this species.

METHODS

Specimens were resin embedded and lectin histochemistry was applied to semi-thin sections using a panel of 24 lectins and an avidin-biotin revealing system.

RESULTS

Abundant tri-tetraantennary complex N-glycan and α-galactosyl residues found in the syncytium in early pregnancy were greatly reduced in mid-pregnancy, though retained at the invasion front in the syncytium (N-glycan) or cytotrophoblast layer (αGal). Some other glycans were also uniquely present in invading cells. Abundant polylactosamine was found in the infolding basal lamina of syncytiotrophoblast and the apical villous cytotrophoblast membrane. Syncytial secretory granules often clustered near the apical membrane abutting maternal vessels. Decidual cells selectively expressed β-galactosyl residues throughout pregnancy and highly branched N-glycan levels increased over time.

DISCUSSION

Glycan distribution changes significantly over pregnancy, probably relating to the development of transport and invasive properties of trophoblast which in the endotheliochorial placenta reaches the level of the maternal vessels. Highly branched complex N-glycans, often associated with invasive cells, N-Acetylgalactosamine and terminal α-galactosyl residues are present at the invasion front abutting the junctional zone of the endometrium. Abundant polylactosamine on the syncytiotrophoblast basal lamina may reflect the presence of specialised adhesive interactions, while clustering of glycosylated granules apically is probably associated with secretion and absorption of material via maternal vasculature. It is suggested that lamellar and invasive cytotrophoblast represent distinct differentiation pathways. 246 words.

Alkaline phosphatase: a potential biomarker for stroke and implications for treatment

Stroke is the fifth leading cause of death in the U.S., with more than 100,000 deaths annually. There are a multitude of risks associated with stroke, including aging, cardiovascular disease, hypertension, Alzheimer's disease (AD), and immune suppression. One of the many challenges, which has so far proven to be unsuccessful, is the identification of a cost-effective diagnostic or prognostic biomarker for stroke. Alkaline phosphatase (AP), an enzyme first discovered in the 1920s, has been evaluated as a potential biomarker in many disorders, including many of the co-morbidities associated with stroke. This review will examine the basic biology of AP, and its most common isoenzyme, tissue nonspecific alkaline phosphatase (TNAP), with a specific focus on the central nervous system. It examines the preclinical and clinical evidence which supports a potential role for AP in stroke and suggests potential mechanism(s) of action for AP isoenzymes in stroke. Lastly, the review speculates on the clinical utility of AP isoenzymes as potential blood biomarkers for stroke or as AP-targeted treatments for stroke patients.

An Immunohistochemical Assay to Detect Trophoblasts in Frozen Feline Placenta

The placenta, a fetal endocrine organ, is composed of subpopulations of trophoblasts, including cytotrophoblasts, and syncytiotrophoblasts. Trophoblastic populations can be distinguished based upon their expression of cytokeratin. The purpose of the current study was to develop an immunohistochemistry (IHC) method to identify trophoblasts selectively in frozen feline placental tissue using antibodies specific for cytokeratin. The mouse monoclonal antibody anti-human pan-cytokeratin AE1/AE3 and a commercial detection system were used. Nonspecific immunoreactivity was encountered that could not be eliminated with altered blocking methods. The nonspecific reactivity was attributed to the goat anti-mouse/rabbit immunoglobulin G (IgG) peroxidase polymer included in the commercial kit. Alternatively, a polyclonal rabbit anti-cow cytokeratin wide spectrum screening antibody with goat anti-rabbit IgG polyclonal secondary antibody was used to detect cytokeratin in feline placental tissue. The IHC procedure eliminated nonspecific immunoreactivity while specifically labeling cytokeratin. This new approach provides an IHC method to identify trophoblasts specifically in feline placenta.

Glycosylation at the fetomaternal interface in hemomonochorial placentae from five widely separated species of mammal: is there evidence for convergent evolution?

Hemomonochorial placentation occurs in diverse species. We have examined placental glycosylation in five widely separated mammals with this type of placentation--lesser hedgehog tenrec (Echinops telfairi), spotted hyena (Crocuta crocuta), nine-banded armadillo (Dasypus novemcinctus), human (Homo sapiens) and guinea pig (Cavia porcellus)--in order to assess whether evolutionary convergence to the hemomonochorial state is accompanied by a similar convergence of glycan expression. Placentae from 2 E. telfairi, 3 C. crocuta, 1 D. novemcinctus, 4 womenand 1 C. porcellus were fixed and processed into epoxy resin. Binding of twenty-three lectins was assessed using a semiquantitative ranking system. The trophoblast apical/microvillous membrane of all five species showed marked similarities in glycosylation. In the N-linked series, there were abundant bi/tri-antennary complex chains, while the non-bisected variants were much scarcer. All species had plentiful N-acetyl lactosamine sequences; at chain termini, binding to Galbeta1,4GlcNAc and Galbeta1,3GalNAc sequences was greatly enhanced after neuraminidase treatment. In all species, terminal NeuNAcalpha2,3 residues were detected. The tenrec had unusually abundant terminal N-acetyl galactosamine. The basal plasma membrane/basal lamina showed glycosylation patterns distinct from the microvillous membrane in each case, indicating chemical diversity of the two opposite faces of trophoblast. Similar classes of glycan at the hemochorial interface suggest conservation of function. The observed lectin binding patterns suggest broad similarities of glycosylation that may have arisen by convergent evolution.

Extracellular Matrix Components and Matrix Degrading Enzymes in the Feline Placenta during Gestation

In the endotheliochorial placenta of the cat, the maternal surface epithelium and parts of the connective tissue have to be removed to bring the fetal blood vessels in close contact to the maternal capillaries. The composition of the extracellular matrix (ECM) in the feline uterus is not known and it is still not clear if and which parts of the maternal ECM persist during gestation in the placental labyrinth. We demonstrated various extracellular matrix components (collagen types I, III, IV, and laminin) and matrix metalloproteinases (MMP-1, -2, -13) using immunohistochemistry and studied the distribution of intermediate filaments (vimentin, cytokeratin) and alpha-smooth muscle actin (SMA) in the placental girdle on specimens of different stages of gestation. Collagen types I and III were mainly present in the fetal chorionic lamellae whereas diminished in the maternal placental labyrinth part. Collagen IV and laminin were expressed in fetal basement membranes and mesenchyme. Maternal endothelial cells and stromal cells showed a positive immunoreaction for anti-collagen type IV and laminin. MMP-2 was identified in the maternal stroma, including decidual cells. Endothelia of maternal blood vessels within the labyrinth contained MMP-1, -2 and -13, probably associated with angiogenesis. In the trophoblast MMP-1 and -13 were demonstrated. Maternal stem vessels were accompanied by a thick layer of syncytiotrophoblast. Around these vessels, collagen type I and SMA were present in a periendothelial region between the endothelium and the trophoblast. These findings indicate that a strictly regulated balance between ECM deposition and ECM degradation in the feline placental labyrinth is necessary for proper placental development and function.

System beta and system A amino acid transporters in the feline endotheliochorial placenta

There is no knowledge of the transport mechanisms by which solutes cross the cat placenta or any other endotheliochorial placenta. Here, we investigated whether the amino acid transport systems beta and A are present in the cat placenta using a placental fragment uptake technique. Data were compared with studies in the human placenta, in which the presence of these two transport systems has been well established. A time course of [(3)H]taurine (substrate for system beta) and [(14)C]MeAIB (nonmetabolizable substrate for system A) uptake was determined in the term cat and human placental fragments in the presence and absence (choline substituted) of Na(+), and further studies were carried out over 15 min. Taurine uptake into both cat and human placenta fragments was found to be Na(+) and Cl(-) dependent, and Na(+)-dependent taurine uptake was blocked by excess beta-alanine. MeAIB uptake was found to be Na(+) dependent, and Na(+)-dependent MeAIB uptake was blocked by excess MeAIB or glycine. Western blotting and immunohistochemistry performed on cat and human placenta showed expression of TAUT and ATA2 (SNAT2), proteins associated with system beta and system A activity, respectively. This study therefore provides the first evidence of the presence of amino acid transport systems beta and A in the cat placenta.