YKL-40 Is Differentially Expressed in Human Embryonic Stem Cells and in Cell Progeny of the Three Germ Layers

Abstract

The secreted glycoprotein YKL-40 participates in cell differentiation, inflammation, and cancer progression. High YKL-40 expression is reported during early human development, but its functions are unknown. Six human embryonic stem cell (hESC) lines were cultured in an atmosphere of low or high oxygen tension, in culture medium with or without basic fibroblast growth factor, and on feeder layers comprising mouse embryonic fibroblasts or human foreskin fibroblasts to evaluate whether hESCs and their progeny produced YKL-40 and to characterize YKL-40 expression during differentiation. Secreted YKL-40 protein and YKL-40 mRNA expression were measured by enzyme-linked immunosorbent assay (ELISA) and quantitative RT-PCR. Serial-sectioned colonies were stained for YKL-40 protein and for pluripotent hESC (OCT4, NANOG) and germ layer (HNF-3β, PDX1, CD34, p63, nestin, PAX6) markers. Double-labeling showed YKL-40 expression in OCT4-positive hESCs, PAX6-positive neuroectodermal cells, and HNF-3β-positive endodermal cells. The differentiating progeny showed strong YKL-40 expression. Abrupt transition between YKL-40 and OCT4-positive hESCs and YKL-40-positive ecto- and neuroectodermal lineages was observed within the same epithelial-like layer. YKL-40-positive cells within deeper layers lacked contact with OCT4-positive cells. YKL-40 may be important in initial cell differentiation from hESCs toward ectoderm and neuroectoderm, with retained epithelial morphology, whereas later differentiation into endoderm and mesoderm involves a transition into the deeper layers of the colony.

Serum YKL-40 in Risk Assessment for Colorectal Cancer: A Prospective Study of 4,496 Subjects at Risk of Colorectal Cancer

“…YKL-40 plays several roles in different biologic processes such as inflammation, cell proliferation and differentiation, angiogenesis, apoptosis, and regulation of extracellular tissue remodeling (3,(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20), processes important for the progression of cancer growth and metastatic potential (21). YKL-40 upregulates VEGF expression and blockade of YKL-40 activity decreases tumor growth, angiogenesis, and metastasis in xenografted SCID mice (13)(14)(15).…”

“…YKL-40 is a highly conserved glycoprotein produced by cancer cells (including colorectal cancer cells), macrophages and neutrophils (3) and by fetal and embryonic stem cells (9,10). IL6 and hypoxia stimulate YKL-40 synthesis (11,12).…”

“…YKL-40 regulates VEGF and plays a role in angiogenesis (13)(14)(15), and inflammation (3,16), including inflammationassociated carcinogenic changes of colonic epithelial cells (17,18). Furthermore, YKL-40 participates in activation of Akt signaling pathways in these cells (19), in apoptosis (20), in cell proliferation and differentiation (9,10), and in regulation of extracellular tissue remodeling (3), all processes that are important for cancer growth and dissemination (21). Recently, it has been demonstrated that YKL-40 regulates cellular and tissue responses via IL13 receptor a2 (22).…”

Brain Barriers and a Subpopulation of Astroglial Progenitors of Developing Human Forebrain Are Immunostained for the Glycoprotein YKL-40

“…Hence, findings based on human samples are very important in order to understand normal brain development and disorders of the central nervous system. So far, YKL-40 has been described particularly in diverse pathological conditions and promoted as a factor with profound implications for both diagnostic and therapeutic applications (Prakash et al 2013), whereas the general role of YKL-40 in developmental biology has been largely ignored, with a few exceptions (Johansen et al 2007;Brøchner et al 2012). In order to elucidate its possible functions during brain development, we have focused on YKL-40 protein and its mRNA expression in human embryonic and fetal forebrain.…”

From Pluripotency to Early Differentiation of Human Embryonic Stem Cell Cultures Evaluated by Electron Microscopy and Immunohistochemistry

“…However, what has not really been emphasized so far, is the lack of EMT in the initial differentiation of epiblast cells directly into the remaining ecto-and neuroectodermal germ layer -an in vivo process of Epiblast-ectodermal transformation (EET) corresponding to an in vitro process of ESC-ectodermal transformation. In a previous in vitro study of regional differences in the expression of markers during differentiation of hESC lines (LRB001-004), we noticed a distinct and direct transformation from undifferentiated OCT4 positive hESCs to SSEA1-positive fully differentiated epithelial cells (Laursen et al, 2007), and in a very recent investigation of six different LRB-cell lines we observed a similar abrupt transformation between OCT4-positive hESC regions and areas with either ectodermal p63-positive cells or neuroectodermal nestinpositive cells, while a direct transition into either meso-or endodermal marker positive cells, was not seen (Brøchner et al, 2011). In the present in vitro study we found an OCT4-postive epithelial-like cell type with a well-defined junctional complex facing the outside compartment which strongly resemble an in vivo embryonic epiblast cell type, whereas the pluripotent cells without junctional complexes in the central compartment of early cultures resemble an ICM-like cell type.…”