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Keywords:

  • human embryonic stem cell;
  • extracellular matrix;
  • basement membrane;
  • laminin;
  • integrin;
  • B-CAM/Lutheran;
  • adhesion;
  • defined cultures

Abstract

To reveal the functional intrinsic niche of human embryonic stem cells (hESC) we examined the production of basement membrane (BM) proteins and the presence of their receptors in feeder-free cell culture conditions. In addition, we investigated binding of hESCs to purified human BM proteins and identified the receptors mediating these contacts. Also, we tested whether purified human laminin (Lm) isoforms have a role in hESC self-renewal and growth in short-term cultures. The results show that hESCs synthesize Lm α1 and Lm α5 chains together with Lm β1 and γ1 chains suggesting the production of Lms-111 and -511 into the culture medium and deposits on cells. hESCs contain functionally important integrin (Int) subunits, Int β1, α3, α6, α5, β5 and αV, as well as the Lm α5 receptor, Lutheran (Lu) glycoprotein and its truncated form, basal cell adhesion molecule (B-CAM). In cell adhesion experiments, Int β1 was crucial for adhesion to most of the purified human BM proteins. Lu/B-CAM mediated adhesion to Lm-511 together with Int α3β1, and was essential for the adhesion of hESCs to embryonic feeder cells. Adhesion to Lm-411 was mediated by Int α6β1. Lm-511 supported hESC growth in defined medium equally well as Matrigel. These results provide consequential information of the biological role of BM in hESCs, warranting further investigation of BM biology of human pluripotent stem cells.