Crescenzi M, Soddu S, Tatò F
Department of Cellular and Developmental Biology, University of Rome La Sapieza, Italy.
J Cell Physiol. 1995 Jan;162(1):26-35. doi: 10.1002/jcp.1041620105.
Different cell types (e.g., neurons, skeletal and heart myocytes, adipocytes, keratinocytes) undergo terminal differentiation, in which acquisition of specialized functions entails definitive withdrawal from the cell cycle. Such cells are distinct from quiescent (reversibly growth-arrested) cells, such as contact-inhibited fibroblasts. Terminally differentiated cells can not be induced to proliferate by means of growth factor stimulation or transduction of cellular oncogenes. An important first step toward defining the molecular basis for such unresponsiveness is to find a practical means to overcome the proliferative block. Furthermore, determining whether terminally differentiated, postmitotic cells still retain a potential competence for proliferation that can be reactivated would have important theoretical and practical implications. To address these questions, we exploited the properties of adenoviruses. These viruses can infect postmitotic cells and express E1A, a powerful activator of proliferation in reversibly growth-arrested cells. We infected terminally differentiated skeletal muscle cells and adipocytes with human adenovirus type 5 or 12, obtaining full reentry into the cell cycle, including DNA synthesis, mitosis, cytokinesis, and extended proliferation. Similar results were obtained with established cell lines and primary cells belonging to several species, from quail to humans. Genetic analysis indicated that the smaller splice product of E1A, E1A 12S, is sufficient to induce cell cycle reactivation in otherwise permanently nonmitotic cells. These results demonstrate that terminally differentiated cells retain proliferative potential and establish adenovirus as a convenient and powerful means to force such cells to reenter the cell cycle.
不同的细胞类型（如神经元、骨骼肌细胞、心肌细胞、脂肪细胞、角质形成细胞）会经历终末分化，在终末分化过程中，获得特定功能需要最终退出细胞周期。这类细胞与静止（可逆性生长停滞）细胞不同，比如接触抑制的成纤维细胞。终末分化细胞不能通过生长因子刺激或细胞癌基因转导被诱导增殖。确定这种无反应性的分子基础的重要第一步是找到克服增殖阻滞的实用方法。此外，确定终末分化的有丝分裂后细胞是否仍保留可被重新激活的增殖潜能具有重要的理论和实际意义。为了解决这些问题，我们利用了腺病毒的特性。这些病毒可以感染有丝分裂后细胞并表达E1A，E1A是可逆性生长停滞细胞中一种强大的增殖激活剂。我们用5型或12型人腺病毒感染终末分化的骨骼肌细胞和脂肪细胞，使其完全重新进入细胞周期，包括DNA合成、有丝分裂、胞质分裂以及持续增殖。从鹌鹑到人类的几个物种的已建立细胞系和原代细胞也得到了类似结果。基因分析表明，E1A的较小剪接产物E1A 12S足以在原本永久不分裂的细胞中诱导细胞周期重新激活。这些结果表明，终末分化细胞保留了增殖潜能，并确立了腺病毒是迫使这类细胞重新进入细胞周期的一种方便且强大的手段。
