Biomedical Engineering Reference
In-Depth Information
environmentforseededligamentfibroblaststoproliferateandorga-
nize in response to mechanical stimulation.
26
However, the utility
of collagen gels was limited by their inferior mechanical proper-
ties. Fibrous silk and collagen scaffolds were subsequently adopted
in order to provide the necessary mechanical competence of the
developing ligaments throughout the
in vitro
cultivation and fol-
lowing implantation
in vivo
. Conventional electrospinning produces
randomly oriented nanofibers; however, the authors made use of a
rotating target to achieve electrospun fiber alignment. The fibers
were then seeded with HLF to study the influence of alignment
on HLF behavior. Their results demonstrated that HLF were spin-
dle shaped, oriented in the direction of nanofibers, and showed
enhancementinthesynthesisofECMproteins(collagen)onaligned
nanofibers compared with randomly oriented nanofibers. In addi-
tion, the authors also studied the effect of the direction of mechani-
cal stimuli on the ECM produced by HLF. For this study the authors
seeded HLF on PU nanofibers that were parallel, vertically aligned
to the strain direction, and randomly oriented. The results demon-
strated that HLF were more sensitive to strain in the longitudinal
direction. Therefore, this study concluded that aligned nanofibrous
scaffolds showedpromise foruse in ligament tissueengineering.
24
12.3.4
Nerve Grafts
Nerve damage debilitates thousands of Americans each year and
leads to problems such as paralysis. In addition to the phys-
ical and emotional outcomes, financial burdens amounting to
nearly $7 billion in the United States alone are associated with
nerve injury (American Paralysis Association, 1997). In fact, nearly
50,000peripheralnerverepairprocedureswereperformedin1995
(National Center for Health Statistics, 1995). Nerve injuries can
occurinthespinalcordinthecentralnervoussystemor,morecom-
monly, in nerve bundles in the peripheral nervous system. Nerve
injury can result from mechanical, thermal, chemical, or patho-
logical mechanisms. In the nervous system, degeneration of neu-
rons or glial cells or any unfavorable change in the ECM of neural
tissue can lead to a wide variety of clinical disorders. Peripheral
nerve injuries resulting from trauma, diseases, or tumor surgery
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