This journal is © The Royal Society of Chemistry 2021 J. Mater. Chem. B, 2021, 9, 7205–7215 | 7205 Cite this: J. Mater. Chem. B, 2021, 9, 7205 Hyaluronic acid drives mesenchymal stromal cell-derived extracellular matrix assembly by promoting fibronectin fibrillogenesis† Marisa Assunça ˜ o, ab Chi Him Kendrick Yiu, ab Ho-Ying Wan, ab Dan Wang, abcd Dai Fei Elmer Ker, abcd Rocky S. Tuan ab and Anna Blocki * abc Hyaluronic acid (HA)-based biomaterials have been demonstrated to promote wound healing and tissue regeneration, owing to the intrinsic and important role of HA in these processes. A deeper understanding of the biological functions of HA would enable better informed decisions on applications involving HA-based biomaterial design. HA and fibronectin are both major components of the provisional extracellular matrix (ECM) during wound healing and regeneration. Both biomacromolecules exhibit the same spatiotemporal distribution, with fibronectin possessing direct binding sites for HA. As HA is one of the first components present in the wound healing bed, we hypothesized that HA may be involved in the deposition, and subsequently fibrillogenesis, of fibronectin. This hypothesis was tested by exposing cultures of mesenchymal stromal cells (MSCs), which are thought to be involved in the early phase of wound healing, to high molecular weight HA (HMWHA). The results showed that treatment of human bone marrow derived MSCs (bmMSCs) with exogenous HMWHA increased fibronectin fibril formation during early ECM deposition. On the other hand, partial depletion of endogenous HA led to a drastic impairment of fibronectin fibril formation, despite detectable granular presence of fibronectin in the perinuclear region, comparable to observations made under the well-established ROCK inhibition- mediated impairment of fibronectin fibrillogenesis. These findings suggest the functional involvement of HA in effective fibronectin fibrillogenesis. The hypothesis was further supported by the co-alignment of fibronectin, HA and integrin a5 at sites of ongoing fibronectin fibrillogenesis, suggesting that HA might be directly involved in fibrillar adhesions. Given the essential function of fibronectin in ECM assembly and maturation, HA may play a major enabling role in initiating and propagating ECM deposition. Thus, HA, as a readily available biomaterial, presents practical advantages for de novo ECM-rich tissue formation in tissue engineering and regenerative medicine. Introduction HA is a key biomacromolecule of the ECM and is composed of repeating glucuronic acid and N-acetylglucosamine disaccharides [–b(1,4)-GlcUA-b(1,3)-GlcNAc–] n . About 0.02% of a person’s bodyweight can be attributed to HA, which is abundantly present in many tissues such as the skin. It has a fast turn-over rate (30% per day) and is upregulated during tissue remodelling. 1 Its cell- and histocompatibility, as well as intrinsic role in tissue development and repair 2 make HA a biopolymer of choice in a vast range of biomaterials designed to limit fibrosis, accelerate wound healing, and augment functional recovery. 3–7 Missinato and colleagues showed that the difference between achieving regeneration versus scarring relied on the availability of HA in sufficient amounts throughout the wound healing process. 8 Biological processes, such as cellular pro- liferation, migration and differentiation, as well as inflammatory processes and the extent of fibrosis are influenced by HA as a function of its molecular weight (size) and the physiological context. 6 Upon tissue injury, HMWHA originating from blood, platelets and the surrounding damaged tissue is released into a Institute for Tissue Engineering and Regenerative Medicine, The Chinese University of Hong Kong (CUHK), Shatin, Hong Kong SAR, China. E-mail: anna.blocki@cuhk.edu.hk b School of Biomedical Sciences, CUHK, Shatin, Hong Kong SAR, China c Department of Orthopaedics & Traumatology, Faculty of Medicine, CUHK, Shatin, Hong Kong SAR, China d Key Laboratory for Regenerative Medicine, Ministry of Education, School of Biomedical Sciences, Faculty of Medicine, The Chinese University of Hong Kong, Shatin, Hong Kong SAR, China † Electronic supplementary information (ESI) available: Fig. S1. See DOI: 10.1039/ d1tb00268f Received 9th February 2021, Accepted 4th March 2021 DOI: 10.1039/d1tb00268f rsc.li/materials-b Journal of Materials Chemistry B PAPER Published on 05 March 2021. Downloaded on 9/16/2021 11:26:35 AM. View Article Online View Journal | View Issue