Stein, S.; Braid, L.

Basement membrane, the specialized extracellular matrix (ECM) that compartmentalizes endothelial and epithelial cells, is the final frontier in bioengineering. The fibrillar collagens (Col I and Col III) of the interstitial matrix are commonly used for tissue modeling, but the networking collagens that scaffold the basement membrane (human Col IV and Col VI) remain elusive. Commercial hydrogels like Matrigel that simulate basement membrane are ill-defined, dilute, variable and contain murine proteins. Here, we investigated whether human mesenchymal stromal cells (MSCs) could be used to produce 3D basement membrane scaffolds amenable to decellularization and downstream applications in bioengineering. Using a xeno-free, process, MSCs from placenta, umbilical cord, bone marrow and adipose tissues were cultivated as adherent multilayers or free-floating spheroids. Matrix assembly was assessed daily by fluorescence imaging and western blot, revealing de novo, systematic, matrix development. Notably, these scaffolds were rich in basement membrane-specific components Col IV and Col VI. Interestingly, we observed that MSCs produce distinct combinations of Col IV alpha chains and other matrix components depending on their tissue of origin. Ongoing work aims to combine this intrinsic Col IV patterning with other strategic process parameters to refine basement membrane composition to resemble target tissues, and to develop assays for processes like angiogenesis that incorporate relevant matrix biology as a variable and readout.