The restoration of dentine-pulp complex remains a challenge for dentists; nonetheless, it has been poorly addressed. An ideal system should modulate the host response, as well as enable the recruitment, proliferation and differentiation of relevant progenitor cells. Herein was proposed a photocrosslinkable hydrogel system based on hyaluronic acid (HA) and platelet lysate (PL). PL is a cocktail of growth factors (GFs) and cytokines involved in wound healing orchestration, obtained by the cryogenic processing of platelet concentrates, and was expected to provide the HA hydrogels specific biochemical cues to enhance pulp cells' recruitment, proliferation and differentiation. Stable HA hydrogels incorporating PL (HAPL) were prepared after photocrosslinking of methacrylated HA (Met-HA) previously dissolved in PL, triggered by the Ultra Violet activated photoinitiator Irgacure 2959. Both the HAPL and plain HA hydrogels were shown to be able to recruit cells from a cell monolayer of human dental pulp stem cells (hDPSCs) isolated from permanent teeth. The hDPCs were also seeded directly over the hydrogels (5 × 10 cells/hydrogel) and cultured in osteogenic conditions. Cell metabolism and DNA quantification were higher, in all time-points, for PL supplemented hydrogels (p < 0,05). Alkaline phosphatase (ALPL) activity and calcium quantification peaks were observed for the HAPL group at 21 days (p < 0,05). The gene expression for ALPL and COLIA1 was up-regulated at 21 days to HAPL, compared with HA group (p < 0,05). Within the same time point, the gene expression for RUNX2 did not differ between the groups. Overall, data demonstrated that the HA hydrogels incorporating PL increased the cellular metabolism and stimulate the mineralized matrix deposition by hDPSCs, providing clear evidence of the potential of the proposed system for the repair of damaged pulp/dentin tissue and endodontics regeneration.

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Hyaluronic acid (HA)-based hydrogels have been widely used as cell culture substrates, adhesives and fillers for clinical therapeutics, and drug delivery vehicles, with promising results. Due to the limited mechanical properties, degradation rates, and biological activity of HA, it is important that HA be chemically modified, cross-linked or reinforced with specific components to confer a versatile range of viscoelastic and biophysical cues. Herein, we present a toolbox comprising of a class of in situ cross-linkable hydrogels encompassing a blend of three components: HA, cellulose nanocrystals (CNCs) and tropoelastin (TROPO). The resulting hydrogels confer tenable mechanical and biological properties which benefit from the merits of the individual components. Incorporation of CNCs enhanced the hydrogel’s stability against hydrolytic and enzymatic degradation, due to the chemical integration of the nanoparticles within the HA mesh. Additionally, the incorporation of TROPO enhanced elasticity and resilience. Finally, the developed hydrogels demonstrated a positive in vitro biological response as they were able to support and promote the adhesion, viability and growth of the seeded fibroblasts. These results demonstrate a feasible approach for the production of hydrogels exhibiting key structural stability, biological response and improved elastic resilience that can be advantageously explored in acellular and cellular tissue engineering strategies for the regeneration of various tissues, such as the vocal fold.

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