Fig. 3

HMF morphology in mTG hydrogels. a HMFs encapsulated in compliant, moderate and stiff hydrogels were examined for differences in cell morphology during the culture period. At day 1, HMFs in all tested mTG concentrations appeared rounded and started to spread, forming elongated spindle-like morphologies at day 3. At day 5, HMFs in compliant and moderate hydrogels assumed a more spindle-like morphology while HMFs in stiff hydrogels appeared to have a larger cell body with thicker cellular protrusions. After 7 days in culture, HMFs in compliant and moderate hydrogels retained their spindle-like morphology from day 5, but occupied a greater area of the hydrogel. HMFs in stiff mTG hydrogels still exhibited a large cell body with multiple large cellular protrusions at day 7, an observation similar to that for day 5. b HMF morphology was quantified based on the circularity where 0 indicates an elongated structures and 1 indicates a perfect circle. Overall, HMFs became more elongated during the culture period in each of the mTG hydrogels. For stiff hydrogels, HMF morphology didn’t change much after day 3 of culture. Comparing hydrogel conditions, HMFs were more elongated in stiff hydrogels at days 1 and 3, compliant hydrogels at day 5 and moderate hydrogels at day 7. ^* p ≤ 0.05; ^** p ≤ 0.01; ^*** p ≤ 0.001