Dr. Franziska Mitrach (Leipzig, DE), Anton Liebezeit (Leipzig, DE), Alexandra H. Springwald (Leipzig, DE), Maximilian Schmid (Leipzig, DE; Düsseldorf, DE), Dr. Sandra Hinkelmann (Leipzig, DE), Dr. Christian Wölk (Leipzig, DE), Prof. Dr. Michael C. Hacker (Leipzig, DE; Düsseldorf, DE), Prof. Dr. Michaela Schulz-Siegmund (Leipzig, DE)
Abstract text (incl. figure legends and references)
Objective: Bone tissue engineering using human mesenchymal stem cells (hMSCs) is a promising strategy to support regeneration of bone defects. Cultivation and differentiation in a three-dimensional environment preserves cell-cell interactions and results in enhanced biological functions. Here, we used cross-linked gelatin microparticles (cGM) that served for two purposes for regeneration of bone tissue: 1) as a cell-adhesive biomaterial to increase volume and diffusivity and 2) as a siRNA delivery system to decrease expression of anti-osteogenic factors. Methods: 10,000 hMSCs were aggregated with systematically varied amounts of cGM to form microtissues. We analyzed the impact of different cGM amounts on cell viability and osteogenic differentiation. To load siRNA onto cGM, we used oligomer-stabilized calcium phosphate nanoparticles (CaP-NP). In a previous project, those CaP-NP had been investigated for siRNA transfection and had been shown to provide high loading capacity [1]. We further determined silencing of the BMP-2 antagonist Chordin as a molecular target to improve osteogenic differentiation in presence of BMP-2. Silencing efficiencies were determined by using quantitative real-time PCR. Results: Cultivation of hMSCs with cGM significantly increased cell viability and osteogenic differentiation markers. The loading of cGM with Chordin siRNA-carrying CaP-NP resulted in a successful silencing of the anti-osteogenic target Chordin. This decreased Chordin expression led to a remarkably increased mineralization. Conclusion: Here, we present the concept of microtissues from hMSC and cGM to generate well differentiated bone-like tissues for regenerative purposes. As a cell-adhesive material, cGM increased cell viability and osteogenic differentiation of the microtissues. The loading with a Chordin siRNA via CaP-NP showed a successful silencing of Chordin with a strongly increased mineralization.
References: [1] Mitrach, F. et al.: Pharmaceutics 2022, 14(2): 326.