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EMBRYONIC STEM CELLS

Putative Role of Hyaluronan and Its Related Genes, HAS2 and RHAMM, in Human Early Preimplantation Embryogenesis and Embryonic Stem Cell Characterization

Meenakshi Choudhary^a,b,c, Xin Zhang^a,b, Petra Stojkovi^a,b, Louise Hyslop^a,b,c, George Anyfantis^a,b, Mary Herbert^a,b,c, Alison P. Murdoch^a,b,c, Miodrag Stojkovi^a,b, Majlinda Lako^a,b

^aNorth East Institute for Stem Cell Research and
^bInstitute of Human Genetics, University of Newcastle, International Centre for Life, Newcastle, United Kingdom;
^cNewcastle Fertility Centre at Life, Bioscience Centre, International Centre for Life, Newcastle upon Tyne, United Kingdom

Key Words. Human embryo • Embryonic stem cell • Hyaluronan • HAS2 • RHAMM • Small interfering RNA

Correspondence: Majlinda Lako, Ph.D., M.Sc., B.Sc., International Centre for Life, Central Parkway, Newcastle upon Tyne NE1 3BZ, United Kingdom. Telephone: 00-44-191-241-8688 or 00-44-191-241-8695; Fax: 00-44-191-241-8666; e-mail: Majlinda.Lako{at}ncl.ac.uk; Miodrag Stojkovic, Centro de Investigación, Príncipe Felipe, Valencia, Spain. Telephone: 00-34-963289680; Fax: 00-34-963289701; e-mail: mstojkovic{at}cipf.es

Received on April 23, 2007; accepted for publication on August 31, 2007.

First published online in STEM CELLS EXPRESS  September 13, 2007.


Human embryonic stem cells (hESC) promise tremendous potential as a developmental and cell therapeutic tool. The combined effort of stimulatory and inhibitory signals regulating gene expression, which drives the tissue differentiation and morphogenetic processes during early embryogenesis, is still very poorly understood. With the scarcity of availability of human embryos for research, hESC can be used as an alternative source to study the early human embryogenesis. Hyaluronan (HA), a simple hydrating sugar, is present abundantly in the female reproductive tract during fertilization, embryo growth, and implantation and plays an important role in early development of the mammalian embryo. HA and its binding protein RHAMM regulate various cellular and hydrodynamic processes from cell migration, proliferation, and signaling to regulation of gene expression, cell differentiation, morphogenesis, and metastasis via both extracellular and intracellular pathways. In this study, we show for the first time that HA synthase gene HAS2 and its binding receptor RHAMM are differentially expressed during all stages of preimplantation human embryos and hESC. RHAMM expression is significantly downregulated during differentiation of hESC, in contrast to HAS2, which is significantly upregulated. Most importantly, RHAMM knockdown results in downregulation of several pluripotency markers in hESC, induction of early extraembryonic lineages, loss of cell viability, and changes in hESC cycle. These data therefore highlight an important role for RHAMM in maintenance of hESC pluripotency, viability, and cell cycle control. Interestingly, HAS2 knockdown results in suppression of hESC differentiation without affecting hESC pluripotency. This suggests an intrinsic role for HAS2 in hESC differentiation process. In accordance with this, addition of exogenous HA to the differentiation medium enhances hESC differentiation to mesodermal and cardiac lineages.

Disclosure of potential conflicts of interest is found at the end of this article.

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