Leveraging Multi-Material Bioprinting to Examine the Effect of Architecture on Mesenchymal Stem Cell-Laden Constructs’ Tissue Integration within an Ex Vivo Osteochondral Explant Model

Abstract

Novel bioprinted constructs for osteochondral tissue engineering were fabricated to study the effect of multi-material architecture on encapsulated human mesenchymal stem cells’ tissue-specific matrix deposition and integration into an ex vivo porcine osteochondral explant model. Two extrusion fiber architecture groups with differing transition regions and degrees of bone- and cartilage-like bioink mixing were employed. The gradient fiber (G-Fib) architecture group showed an increase in chondral integration over time, 18.5 ± 0.7 kPa on Day 21 compared to 9.55 ± 1.6 kPa on Day 1 for the required peak push-out force, and the segmented fiber (S-Fib) architecture group did not, which corresponded to the increase in sulfated glycosaminoglycan deposition noted only in the G-Fib group and the staining for cellularity and tissue-specific matrix deposition at the fiber-defect boundary. Conversely, the S-Fib architecture was associated with significant mineralization over time, but the G-Fib architecture was not. Notably, both fiber groups also had similar chondral integration as a re-inserted osteochondral tissue control. While architecture did dictate differences in the cells’ responses to their environment, architecture was not shown to distinguish a statistically significant difference in tissue integration via fiber push-out testing within a given time point or explant region. Use of this three-week osteochondral model demonstrates that these novel bioink formulations support the fabrication of cell-laden constructs that integrate into explanted tissue as capably as natural tissue and encapsulate osteochondral matrix-producing cells, and it also highlights the important role that spatial architecture plays in the engineering of multi-phasic tissue environments.

Funding Information: The authors acknowledge support from the National Science Foundation Graduate Research Fellowship Program (MLB, HAP), the National Institute of Dental and Craniofacial Research (F31 DE030333, KJH), the Baylor College of Medicine Medical Science Training Program (KJH), and the National Institutes of Health (P41 EB023833).

Declaration of Interests: The authors declare that they have no other known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Keywords: bioprinting, extrusion, multi-material, gradient, bioinks, osteochondral, hMSC, explant, tissue integration