Epithelial-mesenchymal interaction during lung development: the effect of mesenchymal mass.
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Animals↗
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Results for “mesenchyme”
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Karyorrhexis and karyolysis of mesenchymal cells in the intestinal epithelium of amphibians and mammals with evidence for successful differentiation of some mesenchymal cells into epithelial cells.
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Ambystoma↗
Epithelial-mesenchymal interactions: mesenchymal specificity.
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Ameloblasts↗
Epithelial-mesenchymal interactions in differentiation of stomach epithelium in fetal mice.
Epithelial-mesenchymal interactions during development of the forestomach and glandular stomach in fetal mice were investigated by recombination experiments in vitro. Stomach epithelium could not survive when cultivated alone, but its development was supported by the presence of homologous or heterologous mesenchyme. The developmental fate of the epithelium was not affected by recombination with heterologous mesenchyme, but the expression of epithelial differentiation was influenced by the type of mesenchyme. The rate of keratinization of the forestomach epithelium was significantly greater on recombination with homologous mesenchyme than on recombination with heterologous mesenchyme. Moreover, the rate of formation of glandular structures in the glandular stomach epithelium was significantly greater on recombination with 16.5-day stomach mesenchyme than on recombination with 14.5- or 18.5-day stomach mesenchyme.
Animals↗
De novo induction of a gene product during heterologous epithelial--mesenchymal interactions in vitro.
Mesenchymal specification of epithelial cytodifferentiation and morphogenesis has been considered to be a general feature of various epithelial-mesenchymal interacting systems (e.g., salivary gland, mammary gland, feather, hair, and tooth morphogenesis). In contrast, we have demonstrated that a mesenchyme can be induced by a heterologous epithelium to synthesize in quantity a specific gene product(s) unorthodox to the organ from which the mesenchyme was taken. Stage 22-23 avian limb bud epithelium induced 17-day embryonic mouse tooth mesenchyme to differentiate into cartilage. Peptide analysis (cyanogen bromide cleavage after purification of extracted collagen chains) demonstrated that heterologous tissue recombinations produced type II collagen [alpha(II)](3) (i.e., cartilage-type) in addition to type I collagen [alpha(I)](2)alpha(2). Intact or reconstituted mouse molar tooth organs synthesized type I collagen and type I trimer [alpha(I)](3) collagen. Immunohistochemical criteria using anti-type II collagen antibodies identified type II collagen in cartilage-like matrix within the mesenchymal component of heterologous tissue recombinants. Cartilage has never been described during in vivo or in vitro tooth tissue differentiation or associated with the pathology of dental papilla mesenchyme. These results support the hypothesis that epithelial-mesenchymal interactions during embryonic development can selectively induce de novo synthesis of unique gene products.
Animals↗
The influence of local environment on the organization of mesenchyme cells.
Limb, somite, and neural crest mesenchyme from quail embryos were implanted orthotopically and heterotopically into chick hosts to ascertain the relative importance of the local environment on mesenchyme migration. It was found that mesenchyme behavior is strongly influenced by the environment. Normally non-migratory, limb mesenchyme is capable of spreading like sclerotome when placed in the somite region. A somite placed in the limb acquires an appearance typical of limb mesenchyme. Neural crest placed in the limb migrates only along the co-implanted neural tube or axons growing out from it. The orthotopic transplantations showed that quail mesenchyme behaves normally in chick embryos. Furthermore, it was observed in the orthotopic transplants that there was no intermingling of quail and chick cells even at the edge of the graft. This result indicates that cells within mesenchyme are normally not locomotory; rather, the mesenchyme "migrates" by spreading and expansion of the tissue as a unit in response to local influences.
Animals↗
Evolutionary fingerprints of epithelial-to-mesenchymal transition.
Mesenchymal plasticity has been extensively described in advanced epithelial cancers; however, its functional role in malignant progression is controversial1-5. The function of epithelial-to-mesenchymal transition (EMT) and cell plasticity in tumour heterogeneity and clonal evolution is poorly understood. Here we clarify the contribution of EMT to malignant progression in pancreatic cancer. We used somatic mosaic genome engineering technologies to trace and ablate malignant mesenchymal lineages along the EMT continuum. The experimental evidence clarifies the essential contribution of mesenchymal lineages to pancreatic cancer evolution. Spatial genomic analysis, single-cell transcriptomic and epigenomic profiling of EMT clarifies its contribution to the emergence of genomic instability, including events of chromothripsis. Genetic ablation of mesenchymal lineages robustly abolished these mutational processes and evolutionary patterns, as confirmed by cross-species analysis of pancreatic and other human solid tumours. Mechanistically, we identified that malignant cells with mesenchymal features display increased chromatin accessibility, particularly in the pericentromeric and centromeric regions, in turn resulting in delayed mitosis and catastrophic cell division. Thus, EMT favours the emergence of genomic-unstable, highly fit tumour cells, which strongly supports the concept of cell-state-restricted patterns of evolution, whereby cancer cell speciation is propagated to progeny within restricted functional compartments. Restraining the evolutionary routes through ablation of clones capable of mesenchymal plasticity, and extinction of the derived lineages, halts the malignant potential of one of the most aggressive forms of human cancer.
Animals↗
Interaction between mesenchymal cells and the posterior iris epithelium in chicken embryos.
The iris anlage of 3--10 day old chicken embryos was studied by both light and electron microscopy. Serial semithin sections showed that some of the mesenchymal cells overlying the eye cup moved into the primitive eye cavity by the 3rd day of incubation. On the 4th day some of these cells came into close contact with the basement membrane of the dorsal iris epithelium. The bases of the epithelial cells were flat at this stage. Towards the 10th day they formed cytoplasmic processes which did not penetrate the basement membrane. Fine mesenchymal cytoplasmic processes and a large number of extracellular fibrils developed in the epithelial--mesenchymal interface. The fine mesenchymal processes came into close contact with the basement membrane of the posterior iris epithelium but did not penetrate it. Collagen-like material was observed within the cisternae of the rough ER of the mesenchymal cells at certain stages of development. Both, the mesenchymal cells and the collagen fibrils adjacent to the posterior iris layer disappeared by the 10th day when the entire iris epithelium was completely pigmented. The possible origin of the collagen fibrils and the differentiation of the posterior iris epithelium are discussed.
Animals↗
Histone gene transcripts in the cleavage and mesenchyme blastula embryo of the sea urchin, S. purpuratus.
Two distinct populations of histone gene transcripts have been identified in the sea urchin embryo. Both late cleavage and mesenchyme blastula stages contain histone transcripts which hybridize to a full-length histone repeat recombinant DNA, pCO1. The histone RNAs of the two stages, however, are dissimilar in sequence. While the transcripts of the cleavage embryo form well matched hybrids with the plasmid DNA which are relatively resistant to RNAase, the hybrids containing the mesenchyme blastula transcripts melt some 10 degrees C lower and are twice as sensitive to RNAase. Hybridization of the two RNA samples to the Hha I fragments of the histone DNA, or to segments of the histone repeat subcloned in other plasmids, shows that many regions scattered along the repeat are complementary to widely diverged transcripts in the mesenchyme blastula RNA. The two RNA populations consist predominantly of polysomal RNA sequences and are most probably mRNAs for the five histones. The mesenchyme blastula RNA sequences in both S. purpuratus and L. pictus form hybrids with pCO1 DNA that are less stable than those containing L. pictus cleavage RNA, indicating the wide divergence of the two histone RNA populations. The bulk of the histone genes in S. purpuratus appear to be of the type coding for the early mRNAs. Only a small percentage of the several hundred gene copies are candidates for the type coding for the late mRNAs. The melting characteristics of the hybrids and the sensitivity of RNAase provide an assay for the late embryonic histone genes. Of the total RNA labeled during a 10 min pulse in the cleavage embryo, histone transcripts represent approximately 9.7 and 6.5% of the radioactivity in S. purpuratus and L. pictus, respectively. These values fall to 0.57 and 1.4%, respectively, at the mesenchyme blastula stage. Although histone genes are transcribed during these two periods, the type of gene which is active is switched at some point prior to the mesenchyme blastula stage.
Animals↗
Nephroblastoma in the rat: histology of a spontaneous tumor, identity with respect to renal mesenchymal neoplasms, and a review of previously recorded cases.
The histology of a spontaneously occurring neoplasm of the rat kidney conforming to a classification of nephroblastoma is described and compared with that of N-nitrosodimethylamine-induced renal mesenchymal tumors. This rat nephroblastoma was an encapsulated epitheloid neoplasm with a uniform histologic pattern. Clumps of densely crowded, hyperchromatic cells frequently associated with central, well-differentiated ducts were supported by a less cellular, interconnecting stroma of loose areolar or mature fibrous connective tissue. Neoplastic cells were organized into primitive, ill-defined tubular formations. The neoplastic cell component strongly resembled metanephrogenic blastema. In contrast, the renal mesenchymal tumor was nonencapsulated and consisted of a heterogeneous mixture of connective tissue elements including fibroblast-like spindle cells, smooth muscle, and embryonic mesenchyme that engulfed and sequestered preexisting renal tubules and glomeruli. The separate morphologic identities and apparently unrelated existence of rat nephroblastoma and renal mesenchymal tumor were stressed. The rat nephroblastoma morphologically resembled the malignant epithelial component of human Wilms' tumor, whereas rat renal mesenchymal tumor appeared to have counter-parts in the mesenchymal component of Wilms' tumor and in congenital mesoblastic nephroma (leiomyomatous hamartoma) of infancy. The histologic descriptions of previously recorded occurrences of spontaneous and experimentally induced rat neoplasma classified as nephroblastoma or its synonyms were reevaluated in comparison to the present case. In all but four instances, in which sufficient histologic detail was provided in previous reports, a consistent histologic pattern emerged for this neoplasm in the rat.
9,10-Dimethyl-1,2-benzanthracene↗
Mechanisms of invasiveness of epithelial tumours: ultrastructure of the interactions of carcinoma cells with embryonic mesenchyme and epithelium.
Three different kinds of carcinoma cell, human breast tumours, mouse lung tumour and rat bladder tumours have been implanted into the developing chick wing to assay their invasive behaviour. We found that the majority of the carcinoma cells did not invade the mesenchyme but were positioned in the ectoderm. We examined the ultrasturcture of the interaction of the carcinoma cells with both the ectoderm and the mesenchyme to see if there are any differences. We found no specialized adhesive junctions between carcinoma cells and mesenchyme cells. In contrast, the carcinoma cells seem to be adhesive to the ectoderm cells; desmosomes between the two have been found and also frequent parallel alignment of membranes over long distances. This difference between the interaction of the carcinoma cells with the mesenchyme and the ectoderm may explain why the carcinoma cells can penetrate into the ectoderm but rarely do so into the mesenchyme. The carcinoma cells formed a smooth border with the mesenchyme even in the absence of a basal lamina. These results are discussed in relation to the mechanisms of invasion of epithelial tumours in vivo. In particular, the relative importance of the basal lamina, and cell adhesion within the tumour, in limiting invasiveness are assessed.
Animals↗
Metabolism of testosterone by the epithelium and mesenchyme of the rat urogenital sinus.
Testosterone metabolism was measured in separated epithelium and mesenchyme from the urogenital sinuses of 17- and 19-day-old male and female rat embryos and compared with testosterone metabolism in the intact sinus. Both the epithelium and the mesenchyme converted testosterone to 5 alpha-dihydrotestosterone. The epithelium produced much more androstanedione and androsterone but less 3 alpha, 17 beta-androstanediol than did the mesenchyme. The whole sinus synthesized all four metabolites, but in different proportions, producing relatively more androsterone than either of its two component tissues. These data suggest that androsterone is formed by the joint action of epithelium and mesenchyme. Metabolism of testosterone did not differ with sex or foetal age in either of the separated tissues or in the intact sinus, implying that the failure of urogenital mesenchyme from 19-day-old female foetuses to induce prostatic morphogenesis is not due to the loss of 5 alpha-reductase. It is suggested that this lack of inductive capacity may be attributable to a decline in androgen levels with age in female mesenchyme.
Androstane-3,17-diol↗
Acceleration of mammary cancer development by grafting of fetal mammary mesenchymes in C3H mice.
Transplantation of fetal mammary gland mesenchyme into mammary glands of 2-month-old syngeneic virgin mice resulted in focal re-enactment of events that normally occur probably during fetal and early postnatal development of the mammary gland. Portions of the recipient's mammary duct system in contact with the fetal mammary mesenchyme underwent branching and proliferation in a pattern resembling that of rudimentary mammary gland development. This process occurred in C3H mice regardless of whether or not the milk-transmitted mammary tumor virus (MTV-S) was present. In mice carrying MTV-S, mammary cancers of Types A and B appeared earlier and more frequently in the mammary glands that had received transplants of fetal mammary mesenchyme, compared with those in the glands that received no fetal mesenchyme. Some of the smaller cancers were shown to develop directly from portions of the mammary gland interacting with fetal mammary mesenchyme, without preformation of typical hyperplastic alveolar nodules. In C3H mice not carrying MTV-S, cancers did not appear in the similarly treated mammary glands. These facts suggest that non-hormonal and probably nonviral factors that stimulate focal proliferation in the mammary duct system resulting from transplantation of fetal mesenchymes eventually accelerate local development of mammary cancers.
Animals↗
Morphogenesis of the truncus arteriosus of the chick embryo heart: the formation and migration of mesenchymal tissue.
The appearance and migration of mesenchymal cushion tissue within the truncus arteriosus of the normal 2.5 to 6-day chick embryo heart was surveyed systemically with the light microscope. Series of cross-sections taken from replicate hearts at successive developmental stages allowed comparison of the following qualitative and quantitative aspects of early truncal morphogenesis. Mesenchyme within the truncus was derived from two distinct sources. The first mesenchyme appeared to migrate caudally into the cardiac jelly of the distal truncus from the nearby aortic arch region, coincident with slowing of the anterior elongation of the heart tube (Hamburger-Hamilton Stage 17-18). A second, separate mesenchymal population, derived from endocardium, began to fill the conus and proximal truncus in a radial direction, coicident with expansion of the bulbs cordis (Stage 12-19). The measured kinetics of relative cell numbers, distributions, and mitotic indices suggest substantial contributions from both sources. By Stage 26, the conotruncal region was filled with mesenchyme, which then condensed to form the anlagen of three future structures: the semilunar valves, the aorticopulmonary septum, and the tunica media of the great arteries.
Animals↗
Meningeal mesenchymal chondrosarcoma: report of 8 cases with review of the literature.
This paper reviews 8 personally examined cases of primary meningeal mesenchymal chondrosarcoma and 4 similar cases previously reported by others. The clinicopathologic features of these extraosseous intracranial and intraspinal examples are similar to those of other extraskeletal mesenchymal chondrosarcomas. The tumor occurred most often in the second and third decades, showed a moderate tendency to local recurrence (5 of 12 cases) and occasionally metastasized to the lungs (1 case). Both intracranial and intraspinal tumors occurred with equal frequency, but the former, probably due to the later onset of symptoms, had the worse prognosis. Microscopically, they are composed of primitive undifferentiated mesenchymal cells and frequently well-defined islands of hyaline cartilage. There is an apparent correlation between the frequency of mitotic figures and the likelihood of recurrence and metastasis. Electron microscopic study of one example revealed morphologic features similar to those previously described by others and supports the conclusion that the neoplastic cells represent primitive precartilaginous mesenchyme displaying focal cartilaginous differentiation.
Adolescent↗
Mucopolysaccharidosis type I, II, IIIA and V. Pathological and biochemical abnormalities in the neural and mesenchymal elements of the brain.
Histochemical and electron microscopic studies of the brains inclusive of the leptomeninges containing large blood vessels from 7 patients with mucopolysaccharidosis (MPS) I, II, IIIA and V showed marked increase in mesenchymal elements and the generalized presence of characteristic lesions around cerebral veins and arteries. The periadventitial space was greatly distended and filled with viscous fluid and numerous mononuclear cells containing large cytoplasmic vacuoles; these cells stained positively for glycosaminoglycans (GAG). In contrast, the neurons showed only a slight increase of GAG over the normal controls but contained an excessive amount of glycolipid-like material. The amount of GAG in the leptomeninges, inclusive of the large blood vessels, was 10.8, 6.5, 4.5 and 2.2 times greater in patients with MPS I, II, V and IIIA respectively, than the mean of unaffected controls. Dermatan sulfate (DS) accounted for most of the GAG increase in MPS I, II and V [mixed excretors of DS and heparan sulfate (HS)], and HS for the GAG increase in MPS IIIA (HS excretor). With the exception of the patient with MPS IIIA, whose GAG content and composition were the same in both the neural and mesenchymal elements, in all the other MPS types the mesenchymal elements contained more GAG, with a preponderance of DS. We conclude that the mesenchymal elements contribute substantially to the increased content of GAG in the brain and its coverings, mostly in the form of dermatan sulfate.
Adult↗
Regression of mouse mammary gland anlagen in recombinants of Tfm and wild-type tissues: testosterone acts via the mesenchyme.
In the male mouse, regression of the mammary gland anlagen is induced by testosterone during embryonic life. In the androgen-insensitive Tfm mouse, the gland anlagen are resistant to the testosterone action. To analyze cellular interactions in this process, we isolated the mammary gland anlagen from Tfm- and wild-type embryos. The epithelial buds were separated from the mesencyme by trypsin-pacreatin treatment. From the epithelial and mesenchymal components, reciprocal recombinations were prepared and cultivated on millipore filter in the presence of testosterone. In combination with androgen-insensitive Tfm- mesenchyme, the wild-type buds survived the action of testosterone. On the other hand, in combination with wild-type mesenchyme, the androgen-insensitive Tfm epithelial buds were destroyed. The results show that testosterone induces detachment and degeneration of the buds via the mesenchyme.
Animals↗
Isolation and transformation of primary mesenchymal cells of the chick embryo.
Pure primary mesenchymal cells from definitive streak stage chick embryos have been prepared free of epiblast and hypoblast cells. These cells have the potential in culture to differentiate into erythroid cells, beating heart muscle tissue, chondrocytes and epithelial cells. Transformation in vitro of pure primary mesenchymal cells by avian erythroblastosis virus (wt-AEV) and a temperature-sensitive mutant (ts34-AEV) gave rise to rapidly growing cells which remained largely undifferentiated, could be cloned in semi-solid medium and could be maintained for up to 3 months in culture. The majority of mesenchymal cells transformed by wt-AEV (MAE cells) are benzidine-negative. Gel electrophoresis of radioactively labeled cell proteins, immunoprecipitated with specific antisera against chicken hemoglobin, showed that MAE cell clones synthesize the alpha D, pi (or pi') and some unidentified "globin" polypeptide chains. Treatment of MAE cell clones with 1.0 mM n-butyrate stops cell proliferation reversibly and causes an increased synthesis of alpha D and pi (or pi') globin polypeptide chains. In certain clones of mesenchymal cells transformed by a temperature-sensitive mutant of the virus, ts34-AEV (MAE-ts34 cells), benzidine-positive cells can be induced by a shift from 37 degrees to 41 degrees C. The ability of the clone to undergo an increase in benzidine-positivity by temperature shift is decreased with the age of the clone. Different clones show a variable proportion of cells which are positive by immunofluorescence for both globin and chicken-specific histone H5. The alpha A and alpha D globin chains are synthesized in MAE-ts34 clones, but the ratios and quantities of these chains vary for different clones. Temperature shift made little difference in the types and quantities of globin chains synthesized; the increase in benzidine positivity is probably due to an increase in heme biosynthesis.
Alpharetrovirus↗