Epithelial character and morphologic diversity of cell cultures from human amniotic fluids examined by immunofluorescence microscopy and gel electrophoresis of cytoskeletal proteins

Airway tissue engineering for congenital laryngotracheal disease

Regenerative medicine offers hope of a sustainable solution for severe airway disease by the creation of functional, immunocompatible organ replacements. When considering fetuses and newborns, there is a specific spectrum of airway pathologies that could benefit from cell therapy and tissue engineering applications. While hypoplastic lungs associated with congenital diaphragmatic hernia (CDH) could benefit from cellular based treatments aimed at ameliorating lung function, patients with upper airway obstruction could take advantage from a de novo tissue engineering approach. Moreover, the international acceptance of the EXIT procedure as a means of securing the precarious neonatal airway, together with the advent of fetal surgery as a method of heading off postnatal co-morbidities, offers the revolutionary possibility of extending the clinical indication for tissue-engineered airway transplantation to infants affected by diverse severe congenital laryngotracheal malformations. This article outlines the necessary basic components for regenerative medicine solutions in this potential clinical niche.

Murine amniotic fluid stem cells contribute mesenchymal but not epithelial components to reconstituted mammary ducts

Introduction

Amniotic fluid harbors cells indicative of all three germ layers, and pluripotent fetal amniotic fluid stem cells (AFSs) are considered potentially valuable for applications in cellular therapy and tissue engineering. We investigated whether it is possible to direct the cell fate of AFSs in vivo by transplantation experiments into a particular microenvironment, the mammary fat pad. This microenvironment provides the prerequisites to study stem cell function and the communication between mesenchymal and epithelial cells. On clearance of the endogenous epithelium, the ductal tree can be reconstituted by the transfer of exogenously provided mammary stem cells. Analogously, exogenously provided stem cells from other tissues can be investigated for their potential to contribute to mammary gland regeneration.

Methods

We derived pluripotent murine AFSs, measured the expression of stem cell markers, and confirmed their in vitro differentiation potential. AFSs were transplanted into cleared and non cleared fat pads of immunocompromised mice to evaluate their ability to assume particular cell fates under the instructive conditions of the fat-pad microenvironment and the hormonal stimulation during pregnancy.

Results

Transplantation of AFSs into cleared fat pads alone or in the presence of exogenous mammary epithelial cells caused their differentiation into stroma and adipocytes and replaced endogenous mesenchymal components surrounding the ducts in co-transplantation experiments. Similarly, transplantation of AFSs into fat pads that had not been previously cleared led to AFS-derived stromal cells surrounding the elongating endogenous ducts. AFSs expressed the marker protein α-SMA, but did not integrate into the myoepithelial cell layer of the ducts in virgin mice. With pregnancy, a small number of AFS-derived cells were present in acinar structures.

Conclusions

Our data demonstrate that the microenvironmental cues of the mammary fat pad cause AFSs to participate in mammary gland regeneration by providing mesenchymal components to emerging glandular structures, but do not incorporate or differentiate into ductal epithelial cells.

Three-dimensional maps of all chromosomes in human male fibroblast nuclei and prometaphase rosettes

Studies of higher-order chromatin arrangements are an essential part of ongoing attempts to explore changes in epigenome structure and their functional implications during development and cell differentiation. However, the extent and cell-type-specificity of three-dimensional (3D) chromosome arrangements has remained controversial. In order to overcome technical limitations of previous studies, we have developed tools that allow the quantitative 3D positional mapping of all chromosomes simultaneously. We present unequivocal evidence for a probabilistic 3D order of prometaphase chromosomes, as well as of chromosome territories (CTs) in nuclei of quiescent (G0) and cycling (early S-phase) human diploid fibroblasts (46, XY). Radial distance measurements showed a probabilistic, highly nonrandom correlation with chromosome size: small chromosomes-independently of their gene density-were distributed significantly closer to the center of the nucleus or prometaphase rosette, while large chromosomes were located closer to the nuclear or rosette rim. This arrangement was independently confirmed in both human fibroblast and amniotic fluid cell nuclei. Notably, these cell types exhibit flat-ellipsoidal cell nuclei, in contrast to the spherical nuclei of lymphocytes and several other human cell types, for which we and others previously demonstrated gene-density-correlated radial 3D CT arrangements. Modeling of 3D CT arrangements suggests that cell-type-specific differences in radial CT arrangements are not solely due to geometrical constraints that result from nuclear shape differences. We also found gene-density-correlated arrangements of higher-order chromatin shared by all human cell types studied so far. Chromatin domains, which are gene-poor, form a layer beneath the nuclear envelope, while gene-dense chromatin is enriched in the nuclear interior. We discuss the possible functional implications of this finding.

Inheritance of gene density-related higher order chromatin arrangements in normal and tumor cell nuclei

A gene density-related difference in the radial arrangement of chromosome territories (CTs) was previously described for human lymphocyte nuclei with gene-poor CT #18 located toward the nuclear periphery and gene-dense CT #19 in the nuclear interior (Croft, J.A., J.M. Bridger, S. Boyle, P. Perry, P. Teague, and W.A. Bickmore. 1999. J. Cell Biol. 145:1119-1131). Here, we analyzed the radial distribution of chromosome 18 and 19 chromatin in six normal cell types and in eight tumor cell lines, some of them with imbalances and rearrangements of the two chromosomes. Our findings demonstrate that a significant difference in the radial distribution of #18 and #19 chromatin is a common feature of higher order chromatin architecture in both normal and malignant cell types. However, in seven of eight tumor cell lines, the difference was less pronounced compared with normal cell nuclei due to a higher fraction of nuclei showing an inverted CT position, i.e., a CT #18 located more internally than a CT #19. This observation emphasizes a partial loss of radial chromatin order in tumor cell nuclei.

Non-random radial higher-order chromatin arrangements in nuclei of diploid human cells

A quantitative comparison of higher-order chromatin arrangements was performed in human cell types with three-dimensionally (3D) preserved, differently shaped nuclei. These cell types included flat-ellipsoid nuclei of diploid amniotic fluid cells and fibroblasts and spherical nuclei of B and T lymphocytes from peripheral human blood. Fluorescence in-situ hybridization (FISH) was performed with chromosome paint probes for large (#1-5) and small (#17-20) autosomes, and for the two sex chromosomes. Other probes delineated heterochromatin blocks of numerous larger and smaller human chromosomes. Shape differences correlated with distinct differences in higher order chromatin arrangements: in the spherically shaped lymphocyte nuclei we noted the preferential positioning of the small, gene dense #17, 19 and 20 chromosome territories (CTs) in the 3D nuclear interior--typically without any apparent connection to the nuclear envelope. In contrast, CTs of the gene-poor small chromosomes #18 and Y were apparently attached at the nuclear envelope. CTs of large chromosomes were also preferentially located towards the nuclear periphery. In the ellipsoid nuclei of amniotic fluid cells and fibroblasts, all tested CTs showed attachments to the upper and/or lower part of the nuclear envelope: CTs of small chromosomes, including #18 and Y, were located towards the centre of the nuclear projection (CNP), while the large chromosomes were positioned towards the 2D nuclear rim. In contrast to these highly reproducible radial arrangements, 2D distances measured between heterochromatin blocks of homologous and heterologous CTs were strikingly variable. These results as well as CT painting let us conclude that nuclear functions in the studied cell types may not require reproducible side-by-side arrangements of specific homologous or non-homologous CTs. 3D-modelling of statistical arrangements of 46 human CTs in spherical nuclei was performed under the assumption of a linear correlation between DNA content of each chromosome and its CT volume. In a set of modelled nuclei, we noted the preferential localization of smaller CTs towards the 3D periphery and of larger CTs towards the 3D centre. This distribution is in clear contrast to the experimentally observed distribution in lymphocyte nuclei. We conclude that presently unknown factors (other than topological constraints) may play a decisive role to enforce the different radial arrangements of large and small CTs observed in ellipsoid and spherical human cell nuclei.

Immunohistochemical identification and characterization of a special type of desmin-producing stromal cells in human placenta and other fetal tissues

An unusual type of stromal cells has been found to be abundantly present in chorionic villi of human placenta of gestational weeks 6, 17, 35-42 and in tissues of early stages of fetal development (gestational weeks 16-21). These mesenchymal cells are loosely arranged throughout the villous interior and contain the intermediate filament (IF) proteins vimentin and desmin; however the smooth muscle (sm) markers sm-alpha-actin and sm-myosin are absent. Typical myoid stromal cells that are positive for both desmin and sm-alpha-actin also occur in this tissue but are restricted to certain dispersed cell clusters associated with blood vessels. Similar disperse desmin-positive, sm-alpha-actin-negative stromal cells have also been identified, although more sparsely, in the chorionic plate of the placenta and in other diverse fetal tissues such as the interstitium of the kidney, of testis and epididymis, and in cells surrounding Hassall bodies of thymus. The biological nature of these desmin-containing but sm-alpha-actin-negative stromal cells is discussed in relation to myoid cell differentiation. It is emphasized that despite their synthesis of considerable amounts of desmin they cannot be considered myogenic as the occurrence of desmin in the cells may represent an isolated expression of an individual IF protein gene, independent of the synthesis of other muscle proteins.

Epithelial-mesenchymal transitions during cell culture of primary thyroid tumors?

Fibroblast contamination of epithelial tumor cell cultures is of great concern when examining tumor cells in vitro for specific biochemical and cytogenetic changes. The observations of normal karyotypes in thyroid tumor cell cultures have raised the concern of whether residual tissue fibroblasts might obscure the cytogenetic analysis of transformed epithelial cells. We have characterized early passaged thyroid tumor cells to examine the proportions of epithelial and fibroblastic cell types. Cells were analyzed by immunocytology using antibodies recognizing the thyroid prohormone thyroglobulin, epithelial cytokeratins, and vimentin, a mesenchyme marker. Tumors consisted of one follicular adenoma and five papillary carcinomas. When examined by day 15 in culture, all cells contained filaments composed of vimentin, which most likely represents an adaptation to culture conditions. Double immunofluorescence staining for thyroglobulin and cytokeratin revealed the presence of not only epithelial but also spindle-like fibroblastoid cells possessing thyroid epithelial cell markers. The results suggest that in thyroid tumor cultures there is a unique cell type intermediate between epithelial and mesenchyme phenotypes that must be considered when performing cytogenetic analysis.

Restrictive dermopathy: a lethal congenital skin disorder

Restrictive dermopathy is a recently described lethal congenital disorder of the skin with an autosomal recessive mode of inheritance. The rigidity of the skin impairs fetal movements in utero and causes arthrogryposis, as well as highly characteristic facial features and pulmonary hypoplasia. We report two cases of restrictive dermopathy in prematurely born infants, describe the typical pathological findings and discuss this disorder in the context of the fetal akinesia/hypokinesia deformation sequence.

Distribution of chromosome 18 and X centric heterochromatin in the interphase nucleus of cultured human cells

In situ hybridization of human chromosome 18 and X-specific alphoid DNA-probes was performed in combination with three dimensional (3D) and two dimensional (2D) image analysis to study the interphase distribution of the centric heterochromatin (18c and Xc) of these chromosomes in cultured human cells. 3D analyses of 18c targets using confocal laser scanning microscopy indicated a nonrandom disposition in 73 amniotic fluid cell nuclei. The shape of these nuclei resembled rather flat cylinders or ellipsoids and targets were preferentially arranged in a domain around the nuclear center, but close to or associated with the nuclear envelope. Within this domain, however, positionings of the two targets occurred independently from each other, i.e., the two targets were observed with similar frequencies at the same (upper or lower) side of the nuclear envelope as those on opposite sides. This result strongly argues against any permanent homologous association of 18c. A 2D analytical approach was used for the rapid evaluation of 18c positions in over 4000 interphase nuclei from normal male and female individuals, as well as individuals with trisomy 18 and Bloom's syndrome. In addition to epithelially derived amniotic fluid cells, investigated cell types included in vitro cultivated fibroblastoid cells established from fetal lung tissue and skin-derived fibroblasts. In agreement with the above 3D observations 18c targets were found significantly closer (P less than 0.01) to the center of the 2D nuclear image (CNI) and to each other in all these cultures compared to a random distribution derived from corresponding ellipsoid or cylinder model nuclei. For comparison, a chromosome X-specific alphoid DNA probe was used to investigate the 2D distribution of chromosome X centric heterochromatin in the same cell types. Two dimensional Xc-Xc and Xc-CNI distances fit a random distribution in diploid normal and Bloom's syndrome nuclei, as well as in nuclei with trisomy X. The different distributions of 18c and Xc targets were confirmed by the simultaneous staining of these targets in different colors within individual nuclei using a double in situ hybridization approach.

Chediak-Higashi syndrome in the cat: prenatal diagnosis by evaluation of amniotic fluid cells

Chediak-Higashi syndrome (CHS) is an autosomal recessive disease in humans, cats, and 8 other species. The homology of CHS in humans and cats has been demonstrated. Since human CHS is a progressive, serious, and eventually fatal disease, a method for prenatal diagnosis would be desirable. This study was designed to determine whether CHS could be diagnosed prenatally by examination of amniotic fluid cells. The amniotic fluid samples were obtained from CHS and control cat fetuses on the 45th day of gestation and cultures of cells were established. Because the underlying enzyme deficiency in CHS has not been identified, it was necessary to use a secondary manifestation of the syndrome in these studies. The secondary manifestation used was the characteristic enlargement of lysosomes associated with the disease. The lysosomes of these cells were stained by acid phosphatase histochemistry and the diameter of the largest lysosome in each cell was measured by light microscopy with a calibrated ocular micrometer. The diameters of the largest lysosomes in cells of normal fetuses ranged from 0.5 to 7.0 micron (means ranged from 0.9 to 1.8 micron), whereas the diameter of the largest lysosomes in the cells of CHS fetuses ranged from 0.5 to 30 microns (means ranged from 6.4 to 12.8 microns). The approximate t-test for independent samples with unequal variances disclosed that the largest acid phosphatase-positive lysosomes in amniotic fluid cells of CHS cat fetuses were significantly larger than the lysosomes in the cells of normal cat fetuses (P less than 0.0001). This information should, by extrapolation, provide the basis for the prenatal diagnosis of human CHS by amniocentesis.

Rearrangements of desmosomal and cytoskeletal proteins during the transition from epithelial to fibroblastoid organization in cultured rat bladder carcinoma cells

Changes of cell morphology and the state of differentiation are known to play important roles in embryogenesis as well as in carcinogenesis. Examples of particularly profound changes are the conversions of epithelial to mesenchymal cells; i.e., the dissociation of some or all polygonal, polar epithelial cells and their transformation into elongate, fibroblastoid cells of high motility. As an in vitro model system for such changes in cell morphology, we have used cell cultures of the rat bladder carcinoma-derived cell line NBT-II which, on exposure to inducing medium containing a commercial serum substitute (Ultroser G), show an extensive change in their organization (epithelial-mesenchymal transition): the junctions between the epithelial cells are split, the epithelial cell organization is lost, and the resulting individual cells become motile and assume a spindle-like fibroblastoid appearance. Using immunofluorescence microscopy and biochemical protein characterization techniques, we show that this change is accompanied by a redistribution of desmosomal plaque proteins (desmoplakins, desmoglein, plakoglobin) and by a reorganization of the cytokeratin and the actin-fodrin filament systems. Moreover, intermediate-sized filaments of the vimentin type are formed in the fibroblastoid cells. We demonstrate that the modulation of desmosomal proteins, specifically an increase in soluble desmoplakins, is a relatively early event in cell dissociation and in epithelial-mesenchymal transition. In this process, a latent period of 5 h upon addition of inducing medium precedes the removal of these desmosomal components from the plasma membrane. The transition, which is reversible, is dependent on continued protein synthesis and phosphorylation but not on the presence of the inducing medium beyond the initial 2-h period. We discuss the value of this experimental system as a physiologically relevant approach for studying the regulation of the assembly and disassembly of desmosomes and other intercellular adhesion structures, and as a model of the conversion of cells from one state of differentiation into another.

Double in situ hybridization in combination with digital image analysis: a new approach to study interphase chromosome topography

Double in situ hybridization with mercurated and biotinylated chromosome specific DNA probes in combination with digital image analysis provides a new approach to compare the distribution of homologous and nonhomologous chromosome targets within individual interphase nuclei. Here we have used two DNA probes representing tandemly repeated sequences specific for the constitutive heterochromatin of the human chromosomes 1 and 15, respectively, and studied the relative arrangements of these chromosome targets in interphase nuclei of human lymphocytes, amniotic fluid cells, and fibroblasts, cultivated in vitro. We have developed a 2D-image analysis approach which allows the rapid evaluation of large numbers of interphase nuclei. Models to test for a random versus nonrandom distribution of chromosome segments are discussed taking into account the three-dimensional origin of the evaluated 2D-distribution. In all three human diploid cell types the measurements of target-target and target-center distances in the 2D-nuclear image revealed that the labeled segments of the two chromosomes 15 were distributed both significantly closer to each other and closer to the center of the nuclear image than the labeled chromosome 1 segments. This result can be explained by the association of nucleolus organizer regions on the short arm of chromosome 15 with nucleoli located more centrally in these nuclei and does not provide evidence for a homologous association per se. In contrast, evaluation of the interphase positioning of the two chromosome 1 segments fits the random expectation in amniotic fluid and fibroblast cells, while in experiments using lymphocytes a slight excess of larger distances between these homologous targets was occasionally observed. 2D-distances between the labeled chromosome 1 and 15 segments showed a large variability in their relative positioning. In conclusion our data do not support the idea of a strict and permanent association of these homologous and nonhomologous targets in the cell types studied so far.

The distribution of intermediate filament proteins, actin and desmoplakins in human placental tissue as revealed by polyclonal and monoclonal antibodies

The distribution of intermediate filament proteins (cytokeratin, vimentin, desmin), actin, and desmoplakins in various placental compartments was studied by immunofluorescence microscopy using polyclonal and monoclonal antibodies. Trophoblast cells (cytotrophoblast, syncytiotrophoblast, isolated trophoblast cells, trophoblastic giant cells) were strongly stained by all types of cytokeratin antibodies. Antibodies to desmoplakins revealed the presence of desmosomes at all membranes, except the basal membrane of cytotrophoblast cells, and at the basal as well as the lumen-oriented membrane of the syncytiotrophoblast. After disappearance of the cytotrophoblast cell layer the distribution of desmosomes in the syncytiotrophoblast was unaltered. Isolated trophoblast cells contained desmosomes around their entire circumference. Amnion epithelial cells were heterogeneous with respect to cytokeratin composition as revealed, for example, by polyclonal antibodies with a broad range of cytokeratin reactivity and by monoclonal antibodies to cytokeratin No. 18. With the latter, a heterogeneous staining of amnion epithelial cells was achieved. Desmosomes (spots reactive with desmoplakin antibodies) were present at the lateral membranes of the amnion epithelial cells. In addition, vimentin filaments were coexpressed in these cells. Large vessels of the chorionic plate and stem villi showed thick walls consisting of vimentin-, desmin- and actin-positive cells. They were surrounded by mantles rich in vimentin-, desmin- and actin-positive cells, resembling myofibroblasts. This indicates that these cells may play a role in villous contractility and modulation of the intervillous space with effect on both maternal and fetal placental circulation.

Restrictive dermopathy: a newly recognized autosomal recessive skin dysplasia

A brother and sister from consecutive pregnancies had rigid and tightly adherent skin in association with generalized contractures, unusual facies, pulmonary hypoplasia, an abnormal placenta, and a short umbilical cord. Both died shortly after birth. Pathologic examination of the skin by light and electron microscopy showed structural abnormalities of the epidermis, dermis, and subcutaneous fat. An abnormal pattern of keratin proteins was determined biochemically using extracted epidermal proteins. Autopsy showed a normal spinal cord and muscle histology. It is postulated that the defective skin severely restricted movement and secondarily led to the other abnormalities. Familial occurrence is most consistent with autosomal recessive transmission. These patients and the primary skin defect are discussed within the framework of the Fetal Akinesia or Hypokinesia Deformation Sequence.

Expression of epidermal keratins and filaggrin during human fetal skin development

The major structural proteins of epithelia, the keratins, and the keratin filament-associated protein, filaggrin, were analyzed in more than 50 samples of human embryonic and fetal skin by one-dimensional SDS PAGE and immunoblotting with monoclonal and polyclonal antibodies. Companion samples were examined by immunohistochemistry and electron microscopy. Based on structural characteristics of the epidermis, four periods of human epidermal development were identified. The first is the embryonic period (before 9 wk estimated gestational age), and the others are within the fetal period: stratification (9-14 wk), follicular keratinization (14-24 wk), and interfollicular keratinization (beginning at approximately 24 wk). Keratin proteins of both the acidic (AE1-reactive, type I) and the basic (AE3-reactive, type II) subfamilies were present throughout development. Keratin intermediate filaments were recognized in the tissue by electron microscopy and immunohistochemical staining. Keratins of 50 and 58 kD were present in the epidermis at all ages studied (8 wk to birth), and those of 56.5 and 67 kD were expressed at the time of stratification and increased in abundance as development proceeded. 40- and 52-kD keratins were present early in development but disappeared with keratinization. Immunohistochemical staining suggested the presence of keratins of 50 and 58 kD in basal cells, 56.5 and 67 kD in intermediate cells, and 40 and 52 kD in the periderm as well as in the basal cells between the time of stratification and birth. Filaggrin was first detected biochemically at approximately 15 wk and was localized immunohistochemically in the keratinizing cells that surround hair follicles. It was identified 8-10 wk later in the granular and cornified cell layers of keratinized interfollicular epidermis. These results demonstrate the following. An intimate relationship exists between expression of structural proteins and morphologic changes during development of the epidermis. The order of expression of individual keratins is consistent with the known expression of keratins in simple vs. stratified vs. keratinized epithelia. Expression of keratins typical of stratified epithelia (50 and 58 kD) precedes stratification, and expression of keratins typical of keratinization (56.5 and 67 kD) precedes keratinization, which suggests that their expression marks the tissue commitment to those processes. Because only keratins that have been demonstrated in various adult tissues are expressed during fetal development, we conclude that there are no "fetal" keratins per se.(ABSTRACT TRUNCATED AT 400 WORDS)

Intermediate filament cytoskeleton of amnion epithelium and cultured amnion epithelial cells: expression of epidermal cytokeratins in cells of a simple epithelium

Using immunofluorescence microscopy and two-dimensional gel electrophoresis, we compared the cytoskeletal proteins expressed by human amnion epithelium in situ, obtained from pregnancies of from 10-wk to birth, with the corresponding proteins from cultured amnion epithelial cells and cultures of cells from the amniotic fluid of 16 week pregnancies. Epithelia of week 16 fetuses already display tissue-specific patterns of cytokeratin polypeptides which are similar, although not identical, to those of the corresponding adult tissues. In the case of the simple amnion epithelium, a complex and characteristic complement of cytokeratin polypeptides of Mr 58,000 (No. 5), 56,000 (No. 6), 54,000 (No. 7), 52,500 (No. 8), 50,000 (No. 14), 46,000 (No. 17), 45,000 (No. 18), and 40,000 (No. 19) is present by week 10 of pregnancy and is essentially maintained until birth, with the addition of cytokeratin No. 4 (Mr 59,000) and the disappearance of No. 7 (Mr 54,000) at week 16 of pregnancy. In full-term placentae, the amnion epithelium displays two morphologically distinct regions, i.e., a simple and a stratified epithelium, both of which express the typical amnion cytokeratin polypeptides. However, in addition the stratified epithelium also synthesizes large amounts of special epidermal cytokeratins such as No. 1 (Mr 68,000), 10 (Mr 56,500), and 11 (Mr 56,000). In culture amnion epithelial cells obtained from either 16-wk pregnancies or full-term placentae will continue to synthesize the amnion-typical cytokeratin pattern, except for a loss of detection of component No. 4. This pattern is considerably different from the cytokeratins synthesized by cultures of cells from amniotic fluids (cytokeratins No. 7, 8, 18, and 19, sometimes with trace amounts of No. 17) and from several so-called "amnion epithelial cell lines." In addition, amnion epithelial cells in situ as well as amnion epithelial cell cultures appear to be heterogeneous in that they possess some cells that co-express cytokeratins and vimentin. These observations lead to several important conclusions: In contrast to the general concept of recent literature, positively charged cytokeratins of the group No. 4-6 can be synthesized in a simple, i.e., one-layered epithelium. The change from simple to stratified amnion epithelium does not require a cessation of synthesis of cytokeratins of the simple epithelium type, but in this case keratins characteristic of the terminally differentiated epidermis (No. 1, 10, and 11) are also synthesized.(ABSTRACT TRUNCATED AT 400 WORDS)