青春之泉:科学家表示激活睡眠状态中的皮肤干细胞将抵御人体皮肤衰老,使人们容颜保持青春永驻
据英国每日邮报报道,目前,科学家最新研究表明,容貌青春永驻的秘密在于唤醒皮肤中“睡眠状态干细胞”。
一项计算机模型实验发现,伴随着人类逐渐衰老,我们将失去引发这些“万能细胞”再生受损皮肤的能力。英国和美国科学家称,这项创新性研究将有助于研制更好的美容治疗方法,使人们保持青春容颜。
科学家进行了一项复杂的虚拟仿真实验,测试了三种最易于接受的假设理论,验证人类皮肤在3年时间里如何再生。李新山(音译)博士说:“最佳解释理论是皮肤具有一定数量的‘睡眠状态干细胞’,它们位于皮肤最浅层,并不会经常分裂形成新的细胞。”
然而,如果皮肤受损,这些睡眠细胞将被唤醒修复皮肤受损部分,如果其它类型更成熟的皮肤细胞数量也持续减少,皮肤组织将在任何情况下持续再生。干细胞是人体的“万能细胞”,它将潜在成为许多不同类型的细胞。
李新山博士称,每次我们唤醒这些细胞,用于治疗伤口或者补充其它细胞,大量干细胞并不能返回进入睡眠模式,因此这种细胞的数量逐渐下降。这将解释为什么老年人皮肤伤口愈合缓慢,从某种程度上讲,伴随着我们年龄的增长,皮肤也将发生变化。通过更好地理解这种机制,很可能发现有效抵御人体皮肤衰老的方法。
人的一生之中不断地生长新的皮肤,同时脱落衰老皮肤组织,直到目前科学家们仍未达成一致观点解释其中的运行原理。这项英国谢菲尔德大学和宝洁公司玉兰油研发中心的研究人员共同完成这项实验,研究结果发布在近期出版的《自然科学报告》上。他们可能发现抵御皮肤衰老甚至是皮肤癌的有效方法。 (生物谷Bioon.com)
生物谷推荐英文摘要:
Scientific Reports doi:10.1038/srep01904
Skin Stem Cell Hypotheses and Long Term Clone Survival – Explored Using Agent-based Modelling
X. Li, A. K. Upadhyay, A. J. Bullock, T. Dicolandrea, J. Xu, R. L. Binder, M. K. Robinson, D. R. Finlay, K. J. Mills, C. C. Bascom, C. K. Kelling, R. J. Isfort, J. W. Haycock, S. MacNeil & R. H. Smallwood
Skin is the body's first line of defense against environmental hazards, forming a protective barrier for the surface of the body. It consists of an epidermis and a dermis separated by a basement membrane. Keratinocytes are the main building blocks of the epidermis. Under normal conditions, cells on the skin surface are continuously replaced by new cells generated in the basal layer. Cells leave the basal layer and differentiate upwards to comprise the stratum spinosum, stratum granulosum and stratum corneum. These upper layers mediate skin barrier function. The lifespan of keratinocytes and their differentiation into a barrier to prevent water loss and infection are precisely regulated in order to achieve coordinated self-renewal by a process called homeostasis.
Due to the dynamic nature of skin and the importance of its structural integrity, it is difficult to study the development of the tissue in vivo, as any disturbance in the epidermis (such as tape stripping or sodium dodecyl sulphate treatment) compromises the barrier function immediately and many of the experimental techniques used to study cell biology cannot ethically be carried out in man. Therefore, animal models and in vitro tissue engineered skin are commonly used as alternatives. Although these experiments provide a good representation of the human in vivo equivalent, the results are usually qualitative and difficult to interpret on a continuum basis, which hinders integrating new discoveries with previous research. Computer models on the other hand, are ideal tools for investigating individual cell behaviour by combining laboratory data and the existing literature. Agent-based models have been frequently used for studying a group of entities (or agents)1, 2, 3, such as keratinocytes, each with their unique properties4, 5. The behaviour of each agent is defined using a set of rules based on the experimental literature. Previous models of epithelial cells have been used in studying a wide range of applications, such as cell culture morphogenesis6, hierarchy of cells within the intestinal crypts7, 8, activation of hematopoietic stem cells9, the behaviour of sperm in the oviduct10, and modelling metabolic process in liver cells11. In particular, epithelial cells in the intestinal crypts are famous for their monoclonality, where a single stem cell lineage is thought to sustain the entire population in each crypt7, 8. This has been shown by Loeffler et al. (1997) through their 2D models by applying a stochastic symmetric division pattern to stem cells7. The model was later extended by Van Leeuwen et al. (1997) to investigate the process of mitosis and clonal expansion in the crypt8. In addition, agent-based models have also been used extensively to simulate tissue regeneration under pathological conditions, such as the remodelling of airway epithelium in asthma12, the acute inflammatory response13, elucidating possible mechanisms for psoriasis14, cancer cell invasion and tumour behaviour15, as well as a range of multi-scaled models aimed at bridging between changes at the cellular level with behaviours at the tissue and the organ levels1, 8, 12, 16, 17. These models allow one to explore alternative hypotheses inexpensively and for longer periods than are possible for in vitro experiments making them very useful for studying the dynamics of biological organisation.
In skin biology, epithelial homeostasis and self-renewal supported by regenerative cells is one of the most studied areas. As new data emerge hypotheses behind the behaviour of regenerative cells have also evolved over the past years. In particular, a series of recent publications18, 19 challenged the traditional view of a stem-transit amplifying (TA) cell population leading to the generation of an epithelial proliferation unit (EPU), which in turn sustains the renewal process in the tissue. By employing genetic labelling techniques, these studies followed colonies of regenerative cells over one year, and suggested an alternative hypothesis of division in the basal layer (see Figure 1). This hypothesis, described in Clayton et al. (2007)18, is in favour of a single proliferative progenitor cell population that sustains epithelial renewal by producing post mitotic basal cells in a stochastic process. The experiments however, provided insufficient evidence for slow-cycling stem cells as had previously been suggested. However, recent evidence20 suggests the existence of a hierarchical organisation consisting of both fast-cycling progenitor cells and slow-cycling stem cells in an attempt to consolidate the traditional stem-TA hypothesis with stochastic fate decision (hereon referred to as the “PAS” hypothesis, short for populational asymmetry with stem cells). All three hypotheses have been derived based on the observation of the dynamics of biological tissues over a steady state period of typically one year. Individually, each provides a sound mechanism that ensures the continuous regeneration during homeostasis. However, these hypotheses are derived from a collection of static snap-shots of tissues at regular intervals and hence provide a limited window of information within the lifespan of the tissue. A similar problem lies with the in vitro experiments, from which data can only be obtained over a few weeks. In contrast, these hypotheses can be used to generate rule sets which can run inexpensively using computer models, which can: (1) monitor the entire population over any numerical period; and (2) trace the development of individual lineages over years within the equivalent of days in computational time.