Hindawi Publishing Corporation Evidence-Based Complementary and Alternative Medicine Volume 2013, Article ID 780504, 12 pages http://dx.doi.org/10.1155/2013/780504 Research Article Modulation of Cell Cycle Profile by Chlorella vulgaris Prevents Replicative Senescence of Human Diploid Fibroblasts Tayyebeh Saberbaghi, 1 Firouz Abbasian, 2 Yasmin Anum Mohd Yusof, 1 and Suzana Makpol 1 1 Department of Biochemistry, Faculty of Medicine, Universiti Kebangsaan Malaysia, Jalan Raja Muda Abdul Aziz, 50300 Kuala Lumpur, Malaysia 2 Department of Microbiology, Science and Research Branch, Islamic Azad University, P.O. Box 14155/4933. 3, Tehran, Iran Correspondence should be addressed to Suzana Makpol; suzanamakpol@yahoo.com Received 6 November 2012; Revised 28 January 2013; Accepted 28 January 2013 Academic Editor: Hyung-In Moon Copyright © 2013 Tayyebeh Saberbaghi et al. his is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In this study, the efects of Chlorella vulgaris (CV) on replicative senescence of human diploid ibroblasts (HDFs) were investigated. Hot water extract of CV was used to treat HDFs at passages 6, 15, and 30 which represent young, presenescence, and senescence ages, respectively. he level of DNA damage was determined by comet assay while apoptosis and cell cycle proile were determined using FACSCalibur low cytometer. Our results showed direct correlation between increased levels of damaged DNA and apoptosis with senescence in untreated HDFs ( < 0.05). Cell cycle proile showed increased population of untreated senescent cells that enter G0/G1 phase while the cell population in S phase decreased signiicantly ( < 0.05). Treatment with CV however caused a signiicant reduction in the level of damaged DNA and apoptosis in all age groups of HDFs ( < 0.05). Cell cycle analysis showed that treatment with CV increased signiicantly the percentage of senescent HDFs in S phase and G2/M phases but decreased the population of cells in G0/G1 phase ( < 0.05). In conclusion, hot water extract of Chlorella vulgaris efectively decreased the biomarkers of ageing, indicating its potential as an antiageing compound. 1. Introduction Regardless of the persons’ oicial age, senescence is asso- ciated with appearance of age-related phenotypes, decline in protein homeostasis, and accumulation of DNA damage which alters individual lifespan. he theories of ageing can be classiied into two broad categories, namely, the genetic and stochastic theories [1]. he genetic theories postulated that ageing process is under the control of the same genes responsible for running the life cycle program [2]. However, the stochastic theories rely on the accumulation of cell damages and their ineicient repair as the main reason of ageing [3]. In other words, we can do nothing with ageing based on the genetic theories, but it is reversible based on the stochastic theories by improving the cellular defense system or decreasing cell damages. Based on the free radical theory of ageing, accumulation of free radicals over times leads to cellular damages and progressive deterioration of cells functions, tissues, and organ systems [4]. Due to their instability, the free radicals will attack the neighboring molecules to balance their unpaired electrons. Free radicals can be produced intrinsically through normal metabolic processes or extrinsically from exogenous agents [5, 6]. he mitochondria, for instance, are major contributors of reactive oxygen species (ROS) in the cells [4], and any dysfunction in this organelle can result in energy shortage and other cellular deiciency that inally give rise to age-related disorders such as muscular and neurological degeneration, heart failure, strokes, and other degenerative diseases and inally death. herefore, introducing natural or synthetic compounds with antioxidant properties may be beneicial to protect cells or tissues against oxidative damage which may result in age- related diseases as well as promoting longevity. Previous study showed that antioxidant activity of resveratrol in grapes and tocotrienol in palm oil extends lifespan [7–10].