Temporal Enzymatic Treatment to Enhance the Remodeling of Multiple Cartilage Microtissues into a Structurally Organized Tissue

Abstract

Scaffold‐free tissue engineering aims to recapitulate key aspects of normal developmental processes to generate biomimetic grafts. Although functional cartilaginous tissues have been engineered using such approaches, considerable challenges remain. Herein, the benefits of engineering cartilage via the fusion of multiple cartilage microtissues compared to using (millions of) individual cells to generate a cartilaginous graft is demonstrated. Key advantages include the generation of a richer extracellular matrix, more hyaline‐like cartilage phenotype, and superior shape‐fidelity. A major drawback of aggregate engineering is that individual microtissues do not completely (re)model and remnants of their initial architectures remain throughout the macrotissue. To address this, a temporal enzymatic (chondroitinase‐ABC) treatment is implemented to accelerate structural (re)modelling and is shown to support robust fusion between adjacent microtissues, enhance microtissue (re)modelling, and enable the development of a more biomimetic tissue with a zonally organised collagen‐network. Additionally, enzymatic treatment is shown to modulate matrix composition, tissue phenotype, and to a lesser extent, tissue mechanics. This work demonstrates that microtissue self‐organisation is an effective method for engineering scaled‐up cartilage grafts with a predefined geometry and near‐native levels of matrix accumulation. Importantly, key limitations associated with using biological building blocks can be alleviated by temporal enzymatic treatment during graft development.This article is protected by copyright. All rights reserved

Injectable MSC Spheroid and Microgel Granular Composites for Engineering Tissue

“…[ 63 ] Additionally, prior work with MSC spheroids exhibit comparable mechanical properties to our approach, but the lack of injectability and limited initial construct stabilization will limit clinical translation. [ 24,49,64,65 ] Although construct stability with spheroids can be introduced through seeding on macroporous lattice scaffolds, this approach is again not injectable and suffers from poor spheroid seeding and uniformity. [ 5,46,66 ] MSCs may also be encapsulated directly within microgels, supporting injectability, but this often results in fibrocartilage production and limited cell–cell contacts.…”

“…[ 48 ] To alleviate this issue, MSC or chondrocyte spheroids have been recently used for cartilage tissue engineering by packing spheroids alone, in the presence of enzymatic treatments, or with MEW scaffolds. [ 24,46,49 ] While these approaches are exceptional as implantable strategies, they all lack the ability to be injected and stabilized post‐injection. Thus, our granular composite approach that combines MSC spheroids and norbornene‐modified hyaluronic acid (NorHA) microgels into high cell dense granular composites (>200 million cells mL −1 ) will facilitate the formation of cartilage tissue that is guided by the stabilized granular hydrogel (Figure 1b).…”