Hennings H, Michael D, Cheng C, Steinert P, Holbrook K, Yuspa S H
Cell. 1980 Jan;19(1):245-54. doi: 10.1016/0092-8674(80)90406-7.
Modification of the ionic calcium concentration in the culture medium markedly alters the pattern of proliferation and differentiation in cultured mouse epidermal cells. When medium calcium is lowered to 0.05--0.1 mM, keratinocytes proliferate rapidly with a high growth fraction and do not stratify, but continue to synthesize keratin. The cells grow as a monolayer for several months and can be subcultured and cloned in low Ca++ medium. Ultrastructural examination of cells cultured under low Ca++ conditions reveals widened intercellular spaces, abundant microvilli and perinuclear organization of tonofilaments and cellular organelles. Desmosomes are absent. Epidermal cells growing as a monolayer in low Ca++ can be induced to terminally differentiate by adding calcium to the level normally found in the culture medium (1.2 mM). Cell-to-cell contact occurs rapidly and desmosomes form within 2 hr. The cells stratify by 1--2 days and terminally differentiate with cell sloughing by 3--4 days. After Ca++ addition, DNA synthesis decreases with a lag of 5--10 hr and is totally inhibited within 34 hr. In contrast, RNA and protein synthesis continue at 40--50% of the low Ca++ level at day 3, a time when many cells are detaching from the culture dish. Keratin synthesis is unaffected by the Ca++ switch.
培养基中离子钙浓度的改变显著影响培养的小鼠表皮细胞的增殖和分化模式。当培养基钙浓度降至0.05 - 0.1 mM时，角质形成细胞迅速增殖，生长分数高且不形成分层，但继续合成角蛋白。细胞以单层形式生长数月，可在低钙培养基中传代培养和克隆。在低钙条件下培养的细胞的超微结构检查显示细胞间隙增宽、微绒毛丰富，张力丝和细胞器呈核周排列。桥粒缺失。在低钙条件下以单层形式生长的表皮细胞可通过将钙添加至培养基中正常水平（1.2 mM）而被诱导终末分化。细胞间接触迅速发生，桥粒在2小时内形成。细胞在1 - 2天内分层，并在3 - 4天内伴随细胞脱落终末分化。添加钙后，DNA合成滞后5 - 10小时下降，并在34小时内完全被抑制。相反，在第3天，RNA和蛋白质合成以低钙水平时40 - 50%的速率继续，此时许多细胞正从培养皿上脱落。角蛋白合成不受钙转换的影响。
