posted on 2022-03-11, 11:15authored byMark Lemoine
Articular cartilage has limited self-healing capacity and damaged cartilage can lead
to osteoarthritis, and to the need for joint replacement surgery. Biomaterial based
scaffolds have shown limited potential to regenerate osteochondral tissue and
generally have insufficient mechanical properties to withstand the mechanically
demanding and dynamic joint environment. To overcome this limitation, the
primary research goal of this thesis was to develop reinforced collagen based
scaffolds for musculoskeletal tissue engineering, with focus on articular cartilage,
bone, and osteochondral tissue.
A process was initially developed in Chapter 2 to produce a range of 3D printed
polycaprolactone (PCL) scaffolds with high reproducibility. Optimized 3D printing
parameters resulted in a range of PCL scaffolds designs with different compressive
moduli and high porosities suitable for bone, cartilage, and osteochondral tissue
engineering. A multiple linear regression (MLR) model was developed that can be
used to predict the compressive modulus of future designs of 3D printed PCL
scaffolds, and to tune it for specific tissues to make suitable composite scaffolds
containing different ECM based matrices.
In Chapter 3, the PCL scaffold with mechanical properties optimized for cartilage
repair 2 was combined with a collagen type I and hyaluronic acid (CI-HyA) matrix, to
make a composite scaffold capable of directing MSC differentiation towards
chondrogenesis and having mechanical properties suitable for cartilage repair.
Sulphated glycosaminoglycan (sGAG) deposition by MSCs undergoing chondrogenic
differentiation in the developed composite CI-HyA scaffold led to increased
mechanical properties over culture time.
In Chapter 4, a PCL scaffold with a high compressive modulus developed in Chapter
2 was combined with a collagen type I and nano-hydroxyapatite (CI-nHA) matrix, to
make composite scaffolds with a composition that can promote MSC osteogenic
differentiation to regenerate bone. The composite CI-nHA scaffold sustained MSC
osteogenic differentiation and achieved an even calcium distribution throughout its 4
whole volume while having a compressive modulus suitable for bone tissue
engineering.
In Chapter 5, a composite scaffold for osteochondral repair was made by combining
the composite scaffolds developed in Chapter 3 and Chapter 4. These bi-layered
composite scaffolds were made with a novel one-step freeze drying technique
which achieved spatially defined CI-nHA and CI-HyA layers. The bi-layered
composite scaffold induced layer-specific MSC differentiation, with sGAG
deposition in the cartilage layer which spread to form a sGAG rich matrix over
culture time and an increased calcium deposition over culture time in the bone
layer, although the results suggested further optimization of the composition of the
cartilage layer was needed to minimize risk of calcification.
In Chapter 6 a refined cartilage layer consisting of collagen type I, type II and
hyaluronic acid was used in a reinforced tri-layered composite scaffold which also
contained an intermediate layer consisting of collage type I and hyaluronic acid to
reduce off-site calcification in the cartilage layer. The reinforced tri-layered
composite scaffold contained a compressive modulus gradient that resisted shear
forces and could be securely fixed in the articular joint. The layered matrix
composition led to layer-specific MSC differentiation with sGAG rich ECM being
deposited throughout the depth of the cartilage layer with calcium deposition
contained to the intermediate and bone layers.
In conclusion, the thesis has led to the development of a series of composite
scaffold systems based on 3D printed PCL designs which incorporated specific
collagen-based matrices with biochemical composition tailored to facilitate
cartilage, bone, and osteochondral regeneration. The scaffolds have demonstrated
potential to facilitate desired MSC differentiation and matrix formation in vitro, and
have the mechanical properties required to withstand the compression and shear
forces present in articulating joints suggesting can be used as off-the-shelf
treatments for regeneration cartilage, bone, or osteochondral defects, with the
potential to avoid or delay the need for joint replacement surgery.
Funding
ERC, Grant Agreement Number 788753, ERC-2017-ADG
AMBER (Science Foundation Ireland) SFI/12/RC/2278_P2
History
First Supervisor
Prof. John M. O'Bryne
Second Supervisor
Prof. Daniel J. Kelly
Third Supervisor
Prof. Fergal J. O'Brien
Comments
Submitted for the Award of Doctor of Philosophy to the Royal College of Surgeons in Ireland, 2021.
Published Citation
LeMoine M. Reinforced collagen based scaffolds for musculoskeletal tissue engineering [PhD Thesis] Dublin: Royal College of Surgeons in Ireland; 2021