ABSTRACT
Osteoarthritis (OA) is characterized by the irreversible breakdown of cartilage extracellular matrix (ECM).
Current regenerative strategies cannot fully restore the biomechanical functions of cartilage, as they do not
fully recapitulate the collagen fibrillar architecture of native ECM. This project will study the activities of the
regulatory fibril-forming type III collagen (collagen III) in directing cartilage matrix assembly and chondrocyte
mechanotransduction at different stages of post-natal growth, maintenance and disease. Our central
hypothesis is that collagen III regulates cartilage ECM biomechanics and chondrocyte mechanotransduction
through its effects on collagen fibril assembly and integrin switching, and that loss of collagen III increases
cartilage susceptibility to OA.
Specifically, we will elucidate the activities of collagen III in the formation and maintenance of cartilage (Aim 1),
in injury-induced cartilage degradation in OA (Aim 2), as well as in the neo-matrix assembly and chondrocyte
mechanotransduction (Aim 3). In Aim 1, we will determine if loss of collagen III impairs ECM fibril assembly,
pericellular matrix (PCM) integrity, chondrocyte mechanosensing and gene expression during the post-natal
growth and aging. In Aim 2, we will first determine if loss of collagen III accelerates cartilage degeneration and
OA progression in post-traumatic OA induced by the following destabilization of the medial meniscus surgery
(DMM model). We will then determine if collagen III delays the degradation of collagen II and aggrecan in
response to inflammatory factors known to drive OA progression. In Aim 3, we will first determine if collagen III
regulates the assembly of neo-matrix synthesized by chondrocytes cultured in 3D hydrogel under the
stimulation of dynamic loading. Next, we will delineate the effects of collagen III on regulating the integrin
switching of chondrocytes and downstream mechanosensitive pathways, with a focus on integrin α11. To
elucidate the role of collagen III in cartilage, a number of innovative approaches will be used. We generated a
novel inducible collagen III deficient (i.e., Col3a1F/+, Col3a1F/F) mouse model to study the dose-dependent
effects of collagen III by temporal targeting of collagen III in cartilage. We will apply a multidisciplinary analysis
paradigm that integrates atomic force microscopy (AFM)-nanomechanical tests, immunofluorescence imaging
and laser capture microdissection. These techniques will enable us to study the impact of collagen III on
cartilage composition, structure, mechanics and cell mechanotransduction, and to determine mechanisms by
which it regulates matrix remodeling and mechanosensation. Successful completion of this study will establish
collagen III as an essential constituent responsible for ECM structural integrity and cell mechanotransduction of
cartilage. Outcomes will provide a new basis for improving cartilage tissue engineering using collagen III-based
biomaterials and elucidate new collagen III-dependent mechanisms to serve as targets for OA intervention.
