Sulfation degree of glycosaminoglycans triggers distinct cytoskeleton organisation in mesenchymal stem cells

Glycosaminoglycans (GAGs) comprise the closest cellular environment: they are building
\nelements of the ECM and can be also found on cells surface. Their biological activity depends
\non several parameters among which the negative charge is of prime importance[1]. This
\ncharge is generally associated with the presence of sulfate groups (-OSO3H). Sulfation is
\na dynamic modification: it can occur at various positions within the glycan and different
\nsulfation patterns have been identified for the same organs and cells during their
\ndevelopment. However, the mechanisms of coding and transferring information by
\nthese functionalities are not yet complete understood, mainly because of (i)the complex
\nphysiological microenvironment in which GAGs interactions occur and (ii)the inability to access
\nhomogeneous GAGs[2].
\nIn this work, we propose model surfaces bearing GAGs with different sulfation degree as
\nplatform to investigate the pathways by which mesenchymal stem cells (MSCs) sense and
\nrespond to this peculiar functionality: the -OSO3H. We have selected two natural GAGs for this
\nstudy: hyaluronic acid (HA) because it is the only non-sulfated glycan and heparin (HEP) as it is
\nthe GAG with the highest degree of sulfation. To obtain a larger range of sulfation degrees, we
\nhave also prepared a synthetic analogue of HA with a sulfation degree of 1.4 (sHA). All these
\nGAGs were covalently bonded to aminothiols deposited on gold surfaces. MSCs, both from
\nbone marrow and adipose tissue, adhered well to all surfaces. Formation of focal adhesions
\nwas observed after only 1h of culture for bone marrow derived MSCs regardless the used
\nsubstrate. The presence of –OSO3H groups induced different morphology and cytoskeleton
\norganisation: formation of longer filopodia and well pronounced actin fibers were visible for
\nthe MSCs from both sources. Moreover, cells were more spread after 24h in contact with –
\nOSO3H containing surfaces. Cells behaved similarly on both sulfated surfaces (sHA and HEP)
\nand differences in cell morphology were less obvious: higher sulfation degree induced less
\nlamellipodia formation while filopodia number and length increased.
\nIn summary, the present study provides evidence that sulfation degree of GAGs triggers
\ndistinct cytoskeleton organisation in mesenchymal stem cells that may be related with the
\ndifferentiation of those cells. However, further studies at the molecular level about the exact
\nmechanism of these processes need to be carried out.