Biofabrication of spatially organised tissues by directing the growth of cellular spheroids within 3D printed polymeric microchambers

Abstract

Successful tissue engineering requires the generation of human scale implants that mimic the structure, composition and mechanical properties of native tissues. Here, we report a novel biofabrication strategy that enables the engineering of structurally organised tissues by guiding the growth of cellular spheroids within arrays of 3D printed polymeric microchambers. With the goal of engineering stratified articular cartilage, inkjet bioprinting was used to deposit defined numbers of mesenchymal stem cells (MSCs) and chondrocytes into pre-printed microchambers. These jetted cell suspensions rapidly underwent condensation within the hydrophobic microchambers, leading to the formation of organised arrays of cellular spheroids. The microchambers were also designed to provide boundary conditions to these spheroids, guiding their growth and eventual fusion, leading to the development of stratified cartilage tissue with a depth-dependant collagen fiber architecture that mimicked the structure of native articular cartilage. Furthermore, the composition and biomechanical properties of the bioprinted cartilage was also comparable to the native tissue. Using multi-tool biofabrication, we were also able to engineer anatomically accurate, human scale, osteochondral templates by printing this microchamber system on top of a hypertrophic cartilage region designed to support endochondral bone formation and then maintaining the entire construct in long-term bioreactor culture to enhance tissue development. This bioprinting strategy provides a versatile and scalable approach to engineer structurally organised cartilage tissues for joint resurfacing applications.

From Shape to Function: The Next Step in Bioprinting

“…This effect was due to the fact that the narrower angles facilitated cell aggregation at the corners of the pores improving cell aggregation and cell–cell contact, effectively inducing the formation of hepatic spheroids throughout the printed scaffold . Likewise, high densities of chondrocytes bioprinted into porous polycaprolactone (PCL) microchambers were shown to lead to aggregation into spheroids, which grew over time from the depth of the microchamber to its surface, depositing a vertically aligned network of collagen fibers, mimicking the orientation observed in native cartilage …”

“…[195] Likewise, high densities of chondrocytes bioprinted into porous polycaprolactone (PCL) microchambers were shown to lead to aggregation into spheroids, which grew over time from the depth of the microchamber to its surface, depositing a vertically aligned network of collagen fibers, mimicking the orientation observed in native cartilage. [201] A combination of pore size and pore geometry can also be exploited to indirectly induce alignment of cells placed within the pore. Printed nerve guides made of GelMA and PEGDA blends, mimicking the orientation of axonal bundles in the spinal cord, were shown to induce the alignment of neurons recruited in vivo and of neural progenitor cells (NPCs) seeded preimplantation, a feature that was not observed when NPCs were injected in a spinal cord injury site simply within a fibrin glue gel.…”

Recent Advances in Enabling Technologies in 3D Printing for Precision Medicine

“…To recapitulate physiologically relevant 3D structures, technologies that enable the fabrication of heterogeneous constructs with various compositions are needed. Traditional extrusion platforms equipped with multiple printheads have successfully fabricated human scale constructs with vascular channel networks and multiple cell and material types . Multimaterial fabrication platforms have also been leveraged for the development of patient‐specific in vitro models .…”

“…Traditional extrusion platforms equipped with multiple printheads have successfully fabricated human scale constructs with vascular channel networks and multiple cell and material types. [40,66,67] Multimaterial fabrication platforms have also been leveraged for the development of patient-specific in vitro models. [51,54,[68][69][70] These systems provide single-step, automated fabrication processes for spatially controlled, heterogeneous structures.…”

Direct-Write Bioprinting Approach to Construct Multilayer Cellular Tissues

“…Usually, in hydrogel-free systems, cell aggregates or tissue spheroids are accurately positioned through one of most common bioprinting approaches, such as inkjet (Daly and Kelly, 2019), laser guidance (Barron et al, 2004), and extrusion bioprinting (Norotte et al, 2009;Jakab et al, 2010;Pourchet et al, 2017). In the meantime, there is some efforts to directly deposit cell suspension into pre-define patterns (Xu et al, 2005;Calvert, 2007), but to the best of our knowledge, controlling layer by layer the position as well as density and uniformity of seeded cells into 3D structures was not yet optimized.…”