Fig. 3: Bicontinuous hydrogels introduce micro-interfaces that support rapid cell migration.

a Schematic of meniscal fibrochondrocyte (MFC) spheroid embedded within hydrogels and subsequent MFC migration over time. b Representative Z sections of a MFC spheroid (magenta) embedded within a 3 wt% GH bicontinuous hydrogel (gelatin-rich (GR) domain: green) over time. Inset (dotted blue border) is a single Z-section zoom-in highlighting cells along GR domain. Scale bar = 200 μm. c Representative maximum projection images (actin: magenta, Scale bar = 200 μm) at 3 days and d quantified outgrowth of MFCs over 3 days for spheroids embedded in hydrogels containing various GH content (0, 1, 3 wt%). n = 6 (Day 3:0%, Day 2:3%), 8 (Day 1:0%, Day 3:1%, Day 1: 3%), 9 (Day 2:0%, Day 1:1%, Day 3:3%) or 10 spheroids (Day 2:1%) from 2 biologically independent experiments. Day 2:0% vs. 3% ****p ≤ 0.0001; Day 2:1% vs. 3% ****p = 0.0001; Day 3:0% vs. 3%, Day 3:1% vs. 3%, ****p ≤ 0.0001; two-way ANOVA with Tukey post hoc. e Representative 3D migration tracks over 3 days, with track starting from plot origin (each cell track denoted with different color, n = 21–26 representative tracks per condition) and f quantified migration speeds of MFCs from spheroids embedded in hydrogels containing various GH content (0, 1, 3 wt%). n = 3 (0,3%) or 4 (1%) spheroids per condition from 1 biologically independent experiment. 0% vs. 1% ***p = 0.002; 0% vs. 3% ***p = 0.003; one-way ANOVA with Tukey post hoc. g Representative population-averaged mean squared displacement of cells over different time lags (starting from 30 h after spheroid embedding) computed from experimental (Exp) data and simulated (Sim) trajectories with exponential α, fitted based on MSD \(\propto {t}^{\alpha }\) in 3% GH hydrogels. n = 3 spheroids across 1 biologically independent experiment. h Representative experimental (Exp) and simulated (Sim) velocity magnitude profiles as a function of varying orientations relative to the primary axis \(\vec{{{{{{\bf{p}}}}}}}\) for 3% GH hydrogel across cells from one spheroid, in which purple circles denote the average magnitude of cell velocity in a specified direction. Inset shows that the primary axis is determined by the vector of cell trajectory over the period of migration. Data are mean ± s.d. Source data for (d, f–h) provided as a source data file.