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<p>Intervertebral disc (IVD) disorders can cause pain and disability for affected
individuals. A subset of IVD disorders are thought to originate in the nucleus pulposus
(NP) region of the IVD, due to alterations in tissue structure and composition with
age and injury. Cells of the NP undergo a phenotypic and behavioral shift with age,
changes that are thought to disrupt tissue homeostasis and lead to disc degeneration.
There is significant interest in developing biomaterials and strategies to revert
adult degenerate NP cells to healthy, young NP cell phenotypes with increased biosynthesis
and cell clustering. Studies demonstrate that healthy porcine NP cells interact with
laminin proteins through specific integrin subunits on soft substrates in a process
that regulates cell morphology and biosynthesis. The central hypothesis of this dissertation
is that the engagement of cell-surface adhesion receptors, using laminin-mimetic peptides
on a controlled stiffness material, can revert adult degenerate NP cellular phenotype
and behaviors to their healthy, biosynthetically active form.</p><p>In the first part
of this dissertation, integrin subunits used by adult degenerate human NP cells to
attach to laminin were revealed using flow cytometric analyses, function blocking
antibodies, and immunohistochemistry. Secondly, NP cell recognition peptides were
identified by screening laminin-mimetic peptides for cell attachment. Finally, human
NP cells were cultured on peptide functionalized polyacrylamide gels to examine the
effect of ligand and substrate stiffness in regulating adult human NP cell phenotype
and biosynthesis. </p><p>Findings reveal that adult human NP cells express and utilize
integrin subunits α3, α5, and β1 to attach to laminins, in contrast to integrin α6β1
found previously for healthy porcine NP cells. This difference between current and
previous findings likely arises from aging-associated difference in NP cells between
human and porcine tissues. Select laminin-mimetic peptides, chosen from the literature
and informed by NP cell integrin expression, were found to promote significant NP
cell attachment in a concentration dependent manner. Finally, a subset of laminin
mimetic peptides were found to promote a young NP cell phenotype by increasing cell
clustering on soft (0.3 kPa) and stiff (14 kPa) substrates as well as increasing proteoglycan
synthesis on soft substrates. </p><p>The studies presented in this dissertation demonstrate
that adult degenerate human NP cells attach to laminin proteins in an integrin dependent
manner. Furthermore, laminin-mimetic peptides are able to mediate human NP cell attachment
at levels comparable to full-length laminin, increase cell clustering when presented
on soft and stiff substrates, and can increase NP cell biosynthesis when presented
on soft substrates. Utilizing laminin-mimetic peptides may allow for the design of
biomaterials that promote a healthy young NP phenotype for a variety of disc therapies.</p>
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