Normal human epidermal keratinocytes are the major cell type in the epidermis composed of multiple layers that form the outermost covering of the skin. Cultivation of keratinocytes has been extensively used to treat burns, chronic wounds, and other de ...
Normal human epidermal keratinocytes are the major cell type in the epidermis composed of multiple layers that form the outermost covering of the skin. Cultivation of keratinocytes has been extensively used to treat burns, chronic wounds, and other defects such as vitiligo as well as to investigate differentiation stages of the cell. Although animal-derived materials act as an important resource to promote cell proliferation and growth, they could impose significant health risk on patients with contamination of infectious agents such as viruses, prions, and mycoplasma. To avoid disadvantages of using animal-derived materials, studies for development of cell culture-derived biopharmaceuticals have been focused on the substitution or removal of animal-derived components among media. Protein hydrolysates have been used to supplement basal medium as an additional source of nutrients including amino acids, oligopeptides, lipids, and trace elements for the fortification of cell proliferation or productivity. In an effort to search the feasibility of use of plant protein hydrolysates on the cell growth, we investigated the effect of plant protein hydrolysates on characteristics of keratinocytes growth and assessed whether soy protein hydrolysates might substitute partly or fully for animal-derived component such as bovine pituitary extracts (BPE). When control medium containing animal derived components such as BPE was supplemented with soy hydrolysates, cell density increased up to 104~120% of the control medium. The result clearly showed that soy protein hydrolysates such as Bacto soytone and Soy hydrolysate could be an excellent source of nutrient and have a growth-stimulating activity. Supplementation of Soy hydrolysates (1 g/l) or Bacto soytone (2 g/l) to keratinocytes culture medium containing BPE inhibited expression of early and terminal differentiation markers in the cells and also helped the cells to maintain small cell size that might indicate undifferentiated state. However, extent of proliferation and differentiation of the cell in the medium without BPE is not better than that with BPE. These imply that the hydrolysates alone might be insufficient to stimulate cell proliferation and to inhibit differentiation of keratinocytes in the absence of BPE.
All-trans retinoic acid (atRA) modulates the growth of a variety of cells and plays an important role in the chemoprevention of many human malignancies. In this present work, effect of atRA was investigated on proliferation and morphological changes of the cell, expression of mRNA and protein of NGF, expression of two classes of NGF receptor (p75 and TrkA). Together with stimulatory or inhibitory effect of RA on expression of NGF and NGF receptors, modulation of survival or apoptosis of keratinocytes during UV-B irradiating conditions was also investigated in the presence of atRA. This study showed that treatment of the cells with low concentration of atRA (i.e., 10-8 and 10-7 M) stimulated cell growth and DNA synthesis after 48 h, although the treatment with a higher concentration (10-5 M) inhibited cell division and DNA synthesis. atRA modulates also apoptotic and antiapoptotic effect via up-regulation or down-regulation of NGF, TrkA, and p75. Treatment with high concentration (10-5 M) of atRA repressed apoptosis by increasing the expression of NGF and TrkA in UVB-irradiated keratinocytes. On the other hand, low concentration of atRA (10-8 and 10-7 M) stimulated apoptosis by both increasing the expression of p75 and decreasing the expression of NGF and TrkA in UVB-irradiated keratinocytes. This present study also showed that, when treated with various concentrations of atRA, apoptosis did not occur in the non-irradiated keratinocytes. These results indicate that atRA affects survival and apoptosis of human normal keratinocytes by regulating expression of many factors including NGF, TrkA, and p75.