H. Zlotnick (Philadelphia, US)
University of PennsylvaniaPresenter Of 1 Presentation
16.2.5 - Magneto-responsive hydrogel recapitulates cartilage-like cell distribution in engineered tissue
Abstract
Purpose
Instructive biomaterials may guide cell position and phenotype to engineer cartilage tissue with native-like depth dependent properties. In this study, an FDA-approved paramagnetic MRI contrast agent, Gadodiamide (Gd), was combined with a hyaluronic acid (HA) solution to create a cytocompatible magneto-responsive hydrogel. We investigated the movement of mesenchymal stem cells (MSCs) within this material under brief exposure to a static magnetic field and the biologic activity of these cells after positioning, to generate tissue constructs with a cell template similar to that of native cartilage.
Methods and Materials
Construct fabrication: A 1% w/v methacrylated HA solution (20 million bovine MSCs/mL) with 0.05% Lithium phenyl-2,4,6-trimethylbenzoylphosphinate, and 200mM Gd, was cast inside a polydimethylsiloxane ring (4mm inner diameter, 1.3mm thickness) on a glass slide (Fig.1A). After 0-minutes, 2-minutes, or 5-minutes of exposure to a static magnetic field (0.28-0.34T), the solution was UV crosslinked. Constructs (n = 8) were cultured for 15 days in chemically defined media with 10ng/mL TGFβ3. Cell distribution/matrix staining: After 9 days of culture, samples were processed, paraffin embedded, and sectioned for labeling of cell nuclei (DAPI) and matrix. Cell viability: Cell viability and metabolism was assessed throughout culture using the live/dead kit and the Alamar blue assay.
Results
With increased exposure to the magnetic field, cells moved away from the surface of the construct closest to the magnet, creating a depth-dependent cartilage-like cell distribution (Fig.1B). Transient exposure to Gd had no deleterious effects on cell viability or metabolism, as assessed by live/dead staining, and Alamar blue assays (Fig.1C,D). By 15 days of culture, all constructs showed similar healthy metabolic activity and matrix staining that reflected the original positioning of cells (Fig. 1D,1E).
Conclusion
The developed magneto-responsive hydrogel eliminates the need for potentially harmful intracellular magnetic tags currently used for magnetic field-based cell positioning, and produces a cartilage-like cell template within a single material.