Collagen Type I and II Blend Hydrogels for Articular Carilage Tissue Engineering
Claire E Kilmer
10.25394/PGS.8986613.v1
https://hammer.purdue.edu/articles/thesis/Collagen_Type_I_and_II_Blend_Hydrogels_for_Articular_Carilage_Tissue_Engineering/8986613
<p>Osteoarthritis (OA) is a debilitating condition that affects
over 27 million Americans and is defined by degradation in articular cartilage
extracellular matrix. Patients suffer from pain and stiffness in the joints
associated with the onset of OA. Tissue that is damaged by OA is a major health
concern since cartilage tissue has a limited ability to self-repair due to the
lack of vasculature in cartilage and low cell content. Tissue engineering seeks
to repair damaged cartilage by introducing an optimized combination of cells,
scaffold, and bioactive factors that can be transplanted into a patient. </p>
<p>Collagen type II is a promising material to repair cartilage
defects since it is a major component of articular cartilage and plays a key
role in chondrocyte function. This work harnesses the biological activity of
collagen type II and the superior mechanical properties of collagen type I by
characterizing gels made of collagen type I and II blends (1:0, 3:1, 1:1, 1:3,
and 0:1). The collagen blend hydrogels were able to incorporate both types of
collagen, chondroitin sulfate (CS), and hyaluronic acid. Cryo-scanning electron
microscopy images showed that the 3:1 ratio of collagen type I to type II gels
had a lower void space percentage (36.4%) than the 1:1 gels (46.5%). The
complex modulus was larger for the 3:1 gels (G* = 5.0 Pa) compared to the 1:1
gels (G* = 1.2 Pa). The 3:1 blend consistently formed gels with superior
mechanical properties compared to the other blends and showed the potential to
be implemented as a scaffold for articular cartilage engineering.</p>
<p>Building on the characterization work, this study examined
the chondrogenic differentiation of bone marrow-derived mesenchymal stem cells
(MSCs) embedded within a 3:1 collagen type I to II blend (Col I/II) hydrogel or
an all collagen type I (Col I) hydrogel. Glycosaminoglycan (GAG)
production in Col I/II hydrogels was statistically higher than in Col I
hydrogels or pellet culture, and these results suggested that adding collagen
type II promoted GAG production. Col I/II hydrogels had statistically lower
alkaline phosphatase (AP) activity than pellets cultured in chondrogenic
medium. The ability of MSCs encapsulated in Col I/II hydrogels to repair
cartilage defects was investigated by creating<i> </i>two defects in the femurs of rabbits. After 13 weeks,
histochemical staining suggested that Col I/II blend hydrogels provided
favorable conditions for cartilage repair. Histological scoring revealed a
statistically higher cartilage repair score for the Col I/II hydrogels compared
to either the Col I hydrogels or empty defect controls. Results from this study
suggest that there is clinical value in the cartilage repair capabilities of
our Col I/II hydrogel with encapsulated MSCs.</p>
<p>There are many examples of collagen hydrogels with incorporated
CS here the addition of CS has been shown to improve scaffolds for articular
cartilage tissue engineering. Our final study investigated the use of CS with
attached collagen binding peptides to retain, without the use of chemical
crosslinking, matrix molecules and better recapitulate aspects of native
cartilage in a Col I/II hydrogel with encapsulated MSCs. The number of SILY peptides attached to a CS backbone was
varied to create 3 different molecules: CS-10SILY, CS-15SILY, and CS-20SILY, with
10, 15, and 20 denoting the number of SILY peptides attached to CS. As CS
retention, average fibril diameter, and mechanical properties are altered by
the addition of different CS-SILY molecules, the physical properties of the
desired Col I/II hydrogel can be tuned by adjusting the amount of SILY peptides
attached to the CS backbone. In addition, the scaffolds that contained
CS-10SILY, CS-15SILY, and CS-20SILY had higher GAG production which suggests
better differentiation of MSCs into chondrocytes in scaffolds that contain a
CS-SILY molecule. Taken together, these results suggested that the addition of
a CS-SILY molecule to a Col I/II hydrogel with encapsulated MSCs has the
potential to promote cartilage repair.</p>
2019-10-16 17:46:47
extracellular matrix
fibrillogenesis
osteoarthritis
rabbit model
chondrogenic differentiation
Biomaterials