PROJECT SUMMARY
The overall goal of this project is to develop a physiologically relevant in vitro test bed of fibrotic scar after
spinal cord injury (SCI) and identify novel therapeutic targets to improve SCI treatment outcomes. SCI is a
devastating traumatic condition that inflicts the affected individuals with permanent sensorimotor deficits and
socioeconomic burdens. The well-known pathological landscape of SCI consists of glial scar rich in neuro-
inhibitory chondroitin sulfate proteoglycans (CSPGs) deposited by reactive astrocytes. However, little attention
has been given to the collagen and fibronectin-rich, neuro-inhibitory fibrotic scar despite documented evidences.
Existing studies suggest that perivascular mesenchymal cells such as pericytes are primarily responsible for
depositing collagen-rich fibrotic scar. In fibrotic pathologies, pericytes transition into myofibroblasts that deposit
fibrotic scar. However, the detailed mechanism of pericyte-mediated fibrotic scar formation after SCI is unclear.
A specific focus of this proposal is to evaluate the effects of transforming growth factor beta (TGF-¿1)
and collagen fiber assembly on fibrotic scar deposition by pericytes. TGF-¿1 is a well-known cytokine behind
pericyte-myofibroblast transition, and its levels are upregulated after SCI at a time point (5-7 days post injury)
that coincides with increased fibrotic scar deposition. In addition, pathologic collagen fiber organization has been
documented in patient samples. Further, PI has recently shown that this pathologic collagen fiber assembly can
be mimicked in vitro by modulating collagen hydrogel crosslinking temperature. Pathologic collagen fiber
assembly drives myofibroblast differentiation via Rho-associated coiled-coil-forming protein kinase (ROCK)-
mediated enhanced mechanosensing. However, the role of collagen fiber and TGF-¿1 on pericytes, fibrotic scar
formation after SCI and subsequent neurite outgrowth remain unclear.
To this end, we hypothesize that TGF-¿1 and pathological collagen fiber network promote pericyte
dissociation from vasculature and fibrotic scar deposition after SCI. To test our hypothesis, we will
bioengineer three-dimensional (3D) SCI fibrotic scar test beds via spinal cord decellularization and temperature-
controlled collagen fiber assembly methods. Endothelial cells, pericytes and astrocytes will be cultured in this
3D test beds. Individual effects of collagen fiber assembly (Aim 1) and TGF-¿1 (Aim 2) on pericyte-myofibroblast
transition, fibrotic and glial scars deposition, and neurite infiltration will be assessed. The combined effects of
TGF-¿1 and collagen fibers will be determined in Aim 3. ROCK inhibitor Y27632 and TGF-¿1 receptor inhibitor
SB431542 will be used to disrupt collagen fiber and TGF-¿1 effects, respectively. The outcomes of this study
will provide an insight into the role of SCI physicochemical cues on fibrotic scar deposition and astrocyte
response. In particular, this research will highlight the importance of understanding fibrotic scar, not just glial
scar, on SCI progression. Further, undergrad and grad student participations in this line of research will help
educate future scientists and engineers in fundamental and applied biomedical research.