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The development of biomimetic scaffolds for osteochondral tissue engineering
Articular cartilage (AC) is a soft tissue lining the ends of the bones in our joints. Even minor lesions in AC cause pain, impaired mobility and can develop to osteoarthritis (OA), a disease affecting millions of adults worldwide. Within damaged or diseased synovial joints, such as the knee, this damage can penetrate to the underlying bone, creating an osteochondral (OC) defect. OC defect repair remains a significant clinical challenge and necessitates unique tissue engineering strategies. In the recent years, there has been an increased interest in the use of decellularized extracellular matrix (ECM) derived scaffolds as they contain structural and soluble biomolecules supportive of tissue and organ regeneration. While ECM-based materials tend to be highly biocompatible and promote a pro-regenerative immune response, a number of studies have demonstrated that the specific tissue from which the ECM is extracted plays a crucial role in instructing the differentiation of infiltrating cells, helping to direct the type of new tissue formed. In the field of orthopaedic tissue engineering, ECM extracted from articular cartilage (AC) and growth plate (GP) has previously been used to generate scaffolds with chondro- and osteo-inductive properties, respectively. While the direct use of such decellularized ECMs is highly promising, clinical translation is hindered by a number of key challenges. Firstly, the mechanical properties of ECM derived scaffolds are commonly insufficient for use in high load bearing region such as synovial joints. Secondly, the internal architecture of such scaffolds is typically not conducive to facilitate rapid cellular infiltration. In addition, the architecture of such scaffolds needs to be carefully designed as it plays a role in directing cell differentiation and the organization of the resulting tissue. Thirdly, the different physicochemical treatments used during the decellularization of ECM can deplete it of its resident growth factors, thus diminishing its capacity to support tissue-specific differentiation. The overall aim of this thesis is to develop a biomimetic ECM derived scaffold that can spatially direct the differentiation of adult stem cells. The specific aims are (i) to characterise the ECM proteome of AC and GP tissues, (ii) to develop scaffolds mimicking the composition of these tissues, (iii) to engineer scaffolds recapitulating aspects of the native tissue architecture to promote the recruitment of infiltrating cells and to direct their organization and differentiation, and (iv) to evaluate its potential for cartilage, bone and osteochondral tissue engineering in vitro and in vivo. In this thesis, it is demonstrated that the cartilaginous ECM of AC and GP contain distinct soluble factors that may play important roles in promoting stable chondrogenesis and endochondral bone respectively. The ECM of AC contained factors such as Gremlin-1 (GREM1), transforming growth factor-?; induced (TGBI) and frizzle-related protein (FRZB), critical for maintaining cartilage homeostasis; while GP ECM contained osteolectin (CLEC11A), s100a10, collagenase 13 (MMP13) and osteonectin (SPARC), which are known to be integral to joint and long bone development. The chosen AC ECM factors and GP ECM factors were supplemented in the media to assess their effect on chondrogenesis and osteogenesis of MSCs. Based on this analysis, GREM1 was further studied to assess its effect on cartilage tissue deposition by MSCs in an optimised scaffold model, which was made of the collagenous fraction of pepsin-solubilised AC ECM. A novel freeze-drying process combining directional freeze-casting and annealing process was developed to fabricate an AC ECM derived scaffolds with tailored pore size and anisotropic microarchitecture. Increased pore size enhanced cell infiltration, while an anisotropic architecture enabled oriented matrix deposition mimicking aspects of the collagen architecture of articular cartilage. Finally, it was possible to develop a bilayered scaffold made up of AC ECM and bone ECM for osteochondral tissue engineering applications, that was able to support spatially defined MSC differentiation in vitro and the development of spatially distinct tissues in vivo. The results of the preclinical studies in a caprine model, although preliminary, would appear to demonstrate that the scaffolds can promote more consistent repair of osteochondral defects, particularly in animals with a low endogenous capacity for spontaneous bone regeneration.
Keyword(s): Osteochondral; Tissue engineering; Freeze-drying; Extracellular matrix; Scaffold
Publication Date:
Type: Doctoral thesis
Peer-Reviewed: Yes
Language(s): English
Institution: Trinity College Dublin
Citation(s): D?AZ PAYNO, PEDRO JOSE, The development of biomimetic scaffolds for osteochondral tissue engineering, Trinity College Dublin.School of Engineering, 2020
Publisher(s): Trinity College Dublin. School of Engineering. Discipline of Mechanical & Manuf. Eng
Supervisor(s): Kelly, Daniel
First Indexed: 2020-09-17 06:19:18 Last Updated: 2020-10-30 07:14:20