Traumatic spinal cord injuries (SCI) are debilitating
injuries
affecting twenty-seven million people worldwide and cause functional
impairments. Despite decades of research and medical advancements,
current treatment options for SCI remain limited, in part due to the
complex pathophysiology of spinal cord lesions including cellular
transformation and extracellular matrix (ECM) remodeling. Recent studies
have increased focus on fibrotic scarring after SCI, and yet much
remains unclear about the impact of fibrotic scarring on SCI lesion
progression. Here, using collagen and decellularized spinal cord-based
composite hydrogels, a three-dimensional (3D) cell culture model mimicking
the fibrous core of spinal cord lesions was implemented to investigate
its influence on the surrounding astrocytes. To mimic the fibrotic
milieu, collagen fibril thickness was tuned using previously established
temperature-controlled casting methods. In our platforms, astrocytes
in fibro-mimetic hydrogels exhibited increased levels of activation
markers such as glial fibrillary acidic protein and N-cadherin. Furthermore,
astrocytes in fibro-mimetic hydrogels deposited more fibronectin and
laminin, further hinting that astrocytes may also contribute to fibrotic
scarring. These markers were decreased when Rho-ROCK and integrin
β1 were inhibited via pharmacological inhibitors. Mechanistic
analysis of Yes-associated protein reveals that blocking integrin
β1 prevents mechanosensing of astrocytes, contributing to altered
phenotypes in variable culture conditions. In the presence of these
inhibitors, astrocytes increased the secretion of brain-derived neurotrophic
factor, and a greater degree of dorsal root ganglia neurite infiltration
into the underlying hydrogels was observed. Altogether, this study
presents a novel tissue-engineered platform to study fibrotic scarring
after SCI and may be a useful platform to advance our understanding
of SCI lesion aggravation.
