Phytohaemagglutinin induced mitotic stimulation of epithelial cells in organ culture of adult human skin

ORGAN CULTURE OF ADULT HUMAN SKIN

Proliferation and differentiation of the epidermis in organ culture of adult human skin by the sponge matrix method were studied histologically and autoradiographically, and the following results were obtained: 1) On the first day of culture, mitotic figures were already observable in the epidermis. The outgrowth of epidermal cells at the margins of the explants started. On the second day, there was transformation to a zone that will be referred to as the newly formed stratum corneum in the upper epidermis. 2) On the third and fourth days, the increased growth of epidermal cells caused thickening of the epidermis. Simultaneously, Malpighian cells progressively differentiated into a cornified layer. 3) On and after the fifth day, the basospinous cell layer was reduced in thickness in most of explants. On the ninth and tenth days, DNA synthesis in the basal layer was still obvious, although the epidermis showed a thickness of only one or two cells overlaid with a large number of horny layers. 4) In the culture medium supplemented with corticosteroid, the epidermal growth was slightly depressed with lessened formation of stratum corneum in the early stages of culture as compared with the explants cultured in the basic medium. The reduction of the basospinous layer was scarcely notable after the fifth day. Even after 10-11 days, epidermal cells were well preserved and their stratified squamous architecture was less disorganized. It seemed that corticosteroid could prolong the survival of adult human skin in vitro. These findings indicate that this culture technique could be used as a model for organ culture of adult human skin.

Lectins

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Approach to the mechanism of Zajdela's hepatoma cell growth inhibition induced by concanavalin A and phytohaemagglutinin

Cell growth of tumour ascites cells was inhibited by concanavalin A, phytohaemagglutinin and Ricinus lectin at 2-100 micrograms/ml. As expected, the Ricinus lectin inhibited the protein synthesis estimated by leucine incorporation and decreased thymidine incorporation, whereas concanavalin A and phytohaemagglutinin stimulate the uptake and the incorporation of both leucine and thymidine, and thus, synthesis of protein and DNA. These results suggest that different mechanisms are involved in the hepatoma cell growth inhibition by the lectins. This difference was not related to the kinetic characteristics of the lectin interactions with the cells which represent a first and necessary step. It was showed that concanavalin A and phytohaemagglutinin as well as chloroquine inhibited the 14C-labelled asialofetuin degradation. We can conclude that Ricinus lectin present a toxic effect whereas both concanavalin A and phytohaemagglutinin show an anti-protease activity.

Embryo cell surfaces--lectin binding and cell proliferation

The interaction between chick embryo fibroblasts and various lectins has been studied at different stages of embryo development. There is evidence that Robinia lectin, Dolichos lectin, and Concanavalin A decrease cell number and proportion of cells incorporating [3H] thymidine in case of 8- and 10-day-old chick embryo fibroblasts, whereas they stimulated the proliferation of 16-day-old embryo cells. No effect was noticed in 12-day cells. These results suggest that some cell surface changes occur during embryo development. The site number of Dolichos lectin remains the same during embryo development, and the affinity constant decreases. The site number of Robinia lectin and Concanavalin A decreases from the 8th to the 12th day of development, and slowly increases on the 16-day cells, the affinity constant remaining rather constant. The results indicate that the age-dependent effect of lectin on embryo cells could not be directly related to the number of lectin-binding sites. Competitive binding experiments revealed that Dolichos receptor sites were distincts from binding sites of Robinia lectin and Concanavalin A, and Robina receptor sites distinct from those of concanavalin A. Lectin effects on embryo fibroblasts were very specific as determined by inhibitory assays.

Growth response to lectins in chick embryo cells at different stages of development

We report here the effect of Robinia lectin and Concanavalin A on fibroblasts and liver cells from chick embryos between the 8th and the 20th day of development. This was observed in vitro after different times of cultivation. There is evidence that these lectins decrease cell number in cultures from young embryo cells but that they stimulate the proliferation of older embryo cells. The optimum concentration of either lectin was 3 mug/ml. No effect was observed on 12- and 14-day cells at the different concentrations of lectin used. The agglutination of fibroblasts by these lectins regularly decreased from the 8th to the 16th day of development. Liver cells however were agglutinated at no stage. These results could perhaps be explained in terms of cell surface changes either during the course of ontogeny or as a result of lectin treatment.

Inhibition of the in vivo effects of concanavalin-A on mammalian epidermis by alpha-methyl-D-glucopyranoside

Concanavalin-A (Con-A) injected intradermally into newborn rats produces inhibition of granular-cell formation, accumulation of spinous cells, glycogen deposition, and a decrease followed by an increase in the number of basal cells in DNA synthesis. These changes were maximal with a dose of 0.1 mg Con-A, although 0.005, 0.01, and 0.05 mg caused some epidermal changes. The Con-A effects were partially blocked when 0.1 ml of 0.3 or 0.1 M alpha-methyl-D-glucopyranoside (alphaMG) solution was injected 2 hr after 0.1 mg Con-A and completely inhibited by injection of 0.1 ml of 3.0 M alphaMG solution. The inhibitory effects were not seen after injection of 0.1 ml of 3.0 M N-acetyl-galactosamine saline solution, or 0.1 ml normal saline. Injection of alphaMG alone did not cause any changes in epidermal cells. These results indicate that specific sugar inhibits Con-A effects on mammalian epidermis in vivo.

Cell growth and thymidine incorporation changes induced by Dolichos lectin in embryo fibroblasts at various stages of differentiation

We report here the effect of Dolichos lectin on chick embryo fibroblasts from embryos between 6th and 16th day of development. There is evidence that Dolichos lectin decreases cell number and proportion of cells incorporating tritium labelled thymidine in case of chick embryo fibroblasts of 6th, 8th and 10th day of development. Dolichos lectin stimulated the proliferation of 16-day old embryo cells. No effect was noticed on 12-day embryo cells at different concentrations of Dolichos lectin used. This lectin is specifically inhibited by N-acetyl-D-galactosamine and anti-Dolichos lectin serum. The difference in response by cells during different stages of embryonic development could perhaps be explained as some regulatory changes occurring on the cell surface.

Cell migration and DNA synthesis in organ culture of human skin

Cell migration and DNA synthesis in organ cultured skin were studied. Cell migration leads to the formation of a new epithelial layer around the free edges of the dermis. No significant DNA synthesis occurs in this newly formed epithelium. In contrast, DNA synthesis in the original epidermis is maintained throughout the period of culture as shown by the uptake of radioactive thymidine. Addition of hydrocortisone to the culture medium increases cell migration, and phytohaemagglutinin, while dramatically stimulating mitotic activity, suppresses cell migration. These results show that an increase in epithelial cell division is accompanied by diminished cell migration whereas an increase in cell migration occurs in the presence of a decrease in epithelial cell division. The behavaiour of skin in organ culture during the first 48-72 h can be compared with that seen in wound healing.