Epithelial cell biology最新文献

Adult mouse mammary epithelial cells were isolated and grown in combination with mesenchyme from the following sources: embryonic preputial gland, foot skin, tail skin, genital tubercle skin, mammary gland, and neonatal uterus, vagina and urinary bladder. Following 1 month of in vivo cultivation of the tissue recombinants as grafts underneath the renal capsule of normal female or hyperprolactinaemic (pituitary-grafted) hosts, the specimens were analysed histologically and immunocytochemically for the expression of milk proteins, smooth muscle actin, and cytokeratins. Mesenchymal effects on adult mammary epithelium varied with the source of the mesenchyme and the hormonal status of the host. In normal female hosts preputial gland mesenchyme induced extensive mammary epithelial growth and ductal branching morphogenesis with epithelial differentiation and ductal pattern being comparable to that observed in homotypic recombinants composed of mammary gland mesenchyme plus adult mammary epithelium. Other mesenchymes (from foot, tail, genital tubercle and uterus) preserved ductal morphology and normal epithelial differentiation, but elicited minimal epithelial growth and branching morphogenesis in adult mammary epithelium. In association with urogenital sinus, vaginal or bladder mesenchymes ductal branching morphogenesis of the mammary epithelium was absent or greatly distorted and the epithelium exhibited a stratified cuboidal phenotype even though considerable epithelial growth had occurred. In hyperprolactinaemic hosts (which received a pituitary graft) epithelial growth, alveolar morphogenesis, and synthesis of casein and milk fat globule protein was stimulated in all tissue recombinants although to different extents. Alveolar morphogenesis and milk protein expression were extensive in tissue recombinants prepared with mesenchyme from embryonic mammary gland, preputial gland, tail skin and urinary bladder, but were minimal in tissue recombinants prepared with foot or genital tubercle skin. Few milk-protein-positive alveoli formed in tissue recombinants composed of mammary epithelium combined with urogenital sinus or vaginal mesenchyme, even following growth in pituitary-grafted hosts. These findings demonstrate: (1) that adult mammary epithelial cells are responsive to the growth-promoting influences of heterotypic embryonic and neonatal mesenchymes; (2) that mammary growth and branching morphogenesis are induced to variable extents by different mesenchymes; (3) that fibrous (non-adipose) mesenchymes are effective inducers of mammary epithelial development; and (4) that the ability to form alveoli and produce milk proteins in adult mammary epithelial cells is critically dependent upon the nature of the connective tissue environment.

Uterine mesenchyme from newborn (0-day) rats was grown in association with epithelia from the adult cornea, urinary bladder, oesophagus, mammary gland, 1-day skin, and 1-day uterus. Following 1 month of growth, the differentiation of uterine mesenchyme into actin-positive smooth muscle cells was assessed immunocytochemically with antibodies to smooth muscle actin. Whereas grafts of uterine mesenchyme produced only small amounts of myometrium, all types of epithelia induced extensive myometrial differentiation in the uterine mesenchyme, which indicates that this effect is non-specific. The role of cell-cell interactions in the morphological patterning of smooth muscle layers was assessed by analysing tissue recombinants composed of adult prostatic epithelium (PRE) plus mesenchyme of the urogenital sinus (UGM), or seminal vesicle (SVM), or adult bladder epithelium (BLE) plus UGM or SVM. Prostatic ducts developed in all of these tissue recombinants (UGM + BLE, SVM + BLE, UGM + PRE and SVM + PRE). When UGM was used (UGM + PRE and UGM + BLE recombinants), actin-positive smooth muscle cells became organized into thin sheaths resembling the prostatic pattern. Conversely, when SVM was grown in association with PRE or BLE, the induced prostatic ducts were surrounded by thick layers of smooth muscle cells exhibiting the seminal vesicle pattern of organization. Smooth muscle cells were unorganized in grafts of SVM or UGM alone. These observations suggest that in male urogenital glands the mesenchyme dictates the spatial organization of the smooth muscle layers.(ABSTRACT TRUNCATED AT 250 WORDS)

We have identified a minor population of crypts in small intestine which do not appear to export cells to villi. These crypts can be observed in whole-mounts of small intestine prepared from C57BL/6J<-->SWR mouse aggregation chimaeras stained with a peroxidase conjugate of the lectin Dolichos biflorus agglutinin (DBA-Px). In preparations where by chance the C57BL/6J epithelium (positive staining) forms only a minor component of the chimaera, occasional crypts occur which are isolated from larger patches of C57BL/6J epithelium and are surrounded by SWR (non-staining) epithelium. Fifty-one of 383 isolated C57BL/6J crypts (13%) did not appear to export cells to villi, although the crypt mouth is surrounded by a small patch of C57BL/6J epithelium on the intervillus gut floor.

We have used immunoblotting to compare expression of type I keratins in two strains of normal human epidermal keratinocytes (v and u) and their HPV16-transformed derivatives (vp and up). The levels of keratins 14 and 17 were similar in all four cell strains, whereas keratins 18 and 19 were more abundant in vp and up than in the normal parental keratinocytes. Keratin 13 was more abundant in the transformed cells than in the parentals; in addition, expression in v was higher than in u, and expression in vp was higher than in up, suggesting strain-specific variation in expression. Keratin 16 was the only keratin to be more highly expressed in v and u than in vp and up; this is consistent with the reduced capacity of the transformants for stratification and terminal differentiation. Double-label immunofluorescence of vp and up showed that more cells expressed involucrin than keratin 16. We conclude that HPV16 transformation results in marked changes in keratin expression. The increased expression of keratin 18, a keratin that is normally expressed in simple epithelia, fits well with reports of increased keratin 18 expression in invasive squamous cell carcinomas of skin and other keratinocyte-derived tumours.

The specific migration pathways which epithelial cells take as they migrate through the human villus is unknown, although there have been several speculations. The well-known phenomenon of 'gastric metaplasia' in the human duodenum is readily demonstrable by the diastase periodic acid Schiff (dPAS) method. However, there is no general agreement on whether the origin of this cell lineage is the villus epithelial cells or proliferative crypt cells. Using serial sections, model building and computer-aided three-dimensional reconstruction we have followed the pathway of migration of these metaplastic cells in human duodenal villi and report: (1) that these cells migrate in straight lines; (2) that migration is in relatively tight cohorts or migration streams; (3) that a single vestibule can supply cells to more than one villus; and (4) that the cell lineage has a complex origin, deriving either from Brunner's gland duct epithelium or from basal buds growing out of the crypts of Lieberkühn.

This study demonstrates the dual regulation by somatostatin of vasoactive intestinal peptide (VIP)-stimulated and forskolin-stimulated cyclic AMP accumulation by isolated rat intestinal epithelial cells. Somatostatin non-competitively inhibited (IC50 = 1 microM) the stimulatory effect of VIP on cyclic AMP accumulation, suggesting that the two neuropeptides act through separate receptors. The cyclic AMP accumulation produced by forskolin (a diterpene that stimulates directly the catalytic subunit of adenylate cyclase) was also inhibited by somatostatin in a dose-dependent manner. However, somatostatin did not modify the stimulatory effect of VIP on adenylate cyclase activity in a membrane preparation from the same cells, making it difficult to explain the mechanism of somatostatin action at this level. The data presented here suggest that somatostatin may play a physiological role in the regulation of nutrient absorption and the release of gut hormones or exocrine secretions by intestinal epithelial cells through the modulation of cyclic AMP production.

Among extrinsic modulators of keratinization are certain hormones and vitamins, which makes them potentially important pharmacological tools for treatment of keratinization disorders. Vitamin D3 and vitamin A, and their metabolites, promote and inhibit keratinization, respectively. We have shown that retinoic acid, via its nuclear receptor, directly suppresses the expression of the keratin genes which are markers of keratinocyte differentiation. Here we present evidence that 1,25(OH)2 vitamin D3 and its nuclear receptor do not directly regulate keratin gene expression. Co-transfection of a vector expressing the nuclear receptor for vitamin D3 with responder DNA constructs containing keratin gene promoters had no effect on the level of activity of keratin gene promoters either in the presence or in the absence of vitamin D3. We conclude that vitamin D3, unlike retinoic acid, modifies keratin synthesis indirectly, by changing the differentiation phenotype of the keratinocyte.

Surveillance of skin cancer is important to evaluate prevention programmes and to monitor the effect of stratospheric ozone depletion. Evidence available from a limited number of studies suggests that incidence rates of basal cell carcinoma and squamous cell carcinoma have been increasing for at least two decades. In white populations in the United States, Canada and Australia, average annual increases of 3%-7% for basal cell carcinoma and 2%-8% for squamous cell carcinoma have been observed, though variation in ascertainment levels or changes in treatment practices during the study periods may have contributed to these apparent changes in incidence patterns.

Techniques that allowed the successful serial subcultivation of human keratinocytes into sheets of epithelium suitable for grafting have made possible a variety of clinical applications for cultured epithelium. Following the first description of this technique in 1981 to treat third-degree burns, cultured keratinocytes derived from a small biopsy of the patient's normal skin (autografts) have been used in centres throughout the world to provide permanent wound coverage for extensive burns. Over the years, applications have expanded to include the treatment of leg ulcers and blistering skin disorders. A further development in this field has been the use of cultured epithelium derived not from the patients own skin, but from an allogeneic donor (cultured allograft). Cultured allografts have also been widely used in the treatment of burns, leg ulcers, the donor sites for split-thickness grafts, and other dermatological disorders. These allografts seem to act as a potent stimulus to wound healing, but do not survive permanently on the wound bed. Their postulated mechanism of action is through release of multiple cytokines that stimulate epithelialization from the wound periphery as well as from adnexal elements within the wound bed. Allograft application is a simple outpatient procedure which involves no discomfort for the patient. No skin biopsy is necessary and cryo-preservation of grafts for future use is possible.