Bruce Enzmann is a rising junior at Johns Hopkins University, majoring in Materials Science & Engineering with a concentration in biomaterials. This summer, Bruce is working in Dr. Jason Burdick’s Polymeric Biomaterials Laboratory with Dr. Claudia Loebel to analyze patterns of nascent matrix with respect to properties of three-dimensional hydrogels. After graduation, Bruce plans to pursue a PhD in biomedical engineering to develop translational regenerative medicine.
Image Analysis to Examine Spatial Properties of the Pericellular Matrix within 3D Hydrogels
Biomaterials, such as hydrogels, can be engineered with biophysical cues that enable the study of three-dimensional microenvironments that simulate aspects of native extracellular matrix and modulate cellular functions such as differentiation and matrix deposition. Recent data showed that the accumulation of deposited matrix in the pericellular region influences the interactions between cells and their engineered hydrogel environment; however, little is known about the spatial localization and density of newly secreted (nascent) matrix at the cell-hydrogel interface. Using a metabolic labeling technique, we fluorescently labeled nascent proteins deposited by bovine chondrocytes within 7 days upon encapsulation in covalently crosslinked 5 kPa and 20 kPa hyaluronic acid hydrogels. To examine spatial properties of these nascent proteins, we used ImageJ to generate nascent protein intensity profiles and developed new analysis tools to quantify nascent protein area and average intensity. Our results show significant increases in nascent protein area and intensity around chondrocytes embedded within 5 kPa hydrogels compared to 20 kPa hydrogels. These findings suggest that secreted matrix within 5 kPa hydrogels distributes further into the hydrogel, whereas the more densely crosslinked 20 kPa hydrogels restrict nascent matrix distribution. Moreover, lower nascent protein average intensity and area within 20 kPa hydrogels indicate that densely crosslinked hydrogels reduce nascent protein deposition. Ongoing work is analyzing the effect of culture time and local mechanical properties on nascent matrix deposition and distribution. We anticipate that these results have implications on hydrogel design for applications in tissue engineering and regenerative medicine.