Sulfated hyaluronan alters fibronectin matrix assembly and promotes osteogenic differentiation of human bone marrow stromal cells

Abstract

Extracellular matrix (ECM) composition and structural integrity is one of many factors that influence cellular differentiation. Fibronectin (FN) which is in many tissues the most abundant ECM protein forms a unique fibrillary network. FN homes several binding sites for sulfated glycosaminoglycans (sGAG), such as heparin (Hep), which was previously shown to influence FN conformation and protein binding. Synthetically sulfated hyaluronan derivatives (sHA) can serve as model molecules with a well characterized sulfation pattern to study sGAG-FN interaction. Here is shown that the low-sulfated sHA (sHA1) interacts with FN and influences fibril assembly. The interaction of FN fibrils with sHA1 and Hep, but not with non-sulfated HA was visualized by immunofluorescent co-staining. FRET analysis of FN confirmed the presence of more extended fibrils in human bone marrow stromal cells (hBMSC)-derived ECM in response to sHA1 and Hep. Although both sHA1 and Hep affected FN conformation, exclusively sHA1 increased FN protein level and led to thinner fibrils. Further, only sHA1 had a pro-osteogenic effect and enhanced the activity of tissue non-specific alkaline phosphatase. We hypothesize that the sHA1-triggered change in FN assembly influences the entire ECM network and could be the underlying mechanism for the pro-osteogenic effect of sHA1 on hBMSC.

Engineered Sulfated Polysaccharides for Biomedical Applications

“…Analysis of TNAP activity, a marker for early osteogenic differentiation, was significantly increased for sHA treated cultures. [353] This result was in agreement with earlier studies that described the pro-osteogenic effect of sHA on hBMSCs within collagen-based matrices. [351,355] As referred to in a previous section, osteogenic differentiation of hBMSCs into osteoblasts was also observed when culturing cells osteogenic medium conditioned with sHA and dexamethasone.…”

“…[ 351 ] To further characterize the underlying cellular mechanisms, sHA interaction with fibronectin, as a major interaction partner of GAGs in the ECM and a key player in the commitment of MSCs to osteoblast lineage, [ 352 ] has been investigated. [ 353 ] It has previously been shown that heparin‐induced conformational changes of fibronectin within the ECM promote hMSC osteogenic differentiation. [ 352 ] Here, it was shown that while both sHA and heparin affected fibronectin conformation, only sHA increased fibronectin levels and led to thinner fibrils and later only sHA showed pro‐osteogenic effect, pointing the probable involvement of fibronectin regulated osteogenic effects.…”

Role of Fibronectin in Primary Open Angle Glaucoma

“…However, some studies have shown a more direct interaction. For instance, synthetic hyaluronan was found to increase fibronectin levels in differentiated human bone marrow stromal cells in culture, which further supports the observation that hyaluronan regulates fibronectin levels [59]. In addition, it also appears to affect fibril formation since the fibronectin fibrils assembled were thinner and their overall level deceased in the presence of the synthetic hyaluronan.…”

Sulfated hyaluronic acid and dexamethasone possess a synergistic potential in the differentiation of osteoblasts from human bone marrow stromal cells

“…7,24 Nevertheless, minor ECM components were altered in their abundance by SH and Dex, for example, FN was induced in secretion, forming thinner fibrils after SH treatment independently on Dex as well as enhancing the ECM assembly and thereby assisting the osteogenic differentiation. 25 THPS2 and POSTN were in elevated abundance after SH and SH/Dex treatment in all analyzed compartments, indicating a continuously induced synthesis, secretion, and ECM association of these proteins by SH. Both matricellular proteins are known for their roles as extracellular linkers, contributing to the ECM assembly and remodeling, cell adhesion as well as growth factor binding.…”