Biomedical Engineering Reference
In-Depth Information
and expulsion [ 63 , 70 ]. Synthetic materials may also generate wear debris or toxic
leachables due to incomplete in situ curing, which in the long term may adversely
affect adjacent disc and neurologic tissue. Additionally, none of the synthetic
implants attempt to regenerate healthy host NP tissue.
8 Tissue Engineering
The field of tissue engineering (TE) has been developed in part in response to
chronic organ and tissue donor shortages. TE has been broadly defined by
Laurencin as “the application of biological, chemical, and engineering principles
toward the repair, restoration, or regeneration of living tissue by using biomaterials,
cells, and factors alone or in combination.” [ 71 ]. Nerem elaborates that TE utilizes
“living cells, manipulated through their extracellular environment or even geneti-
cally, to develop biological substitutes for implantation into the body and/or to
foster the remodeling of tissue in some other active manner. The purpose is to either
either repair, replace, maintain, or enhance the function of a particular tissue or
organ” [ 72 ]. In general, the foundation of any TE strategy lies within the ability of
healthy cells to induce the de novo production and subsequent maintenance of an
ECM. Clinically speaking, this strategy aims to produce healthy tissue with which
to restore damaged or diseased tissues in hopes of recapitulating normal structure
and function. Although TE does not always allege to address underlying pathology,
one can speculate that the regeneration of a living tissue surrogate may be advanta-
geous compared to implanting synthetic materials alone in that the tissue surrogate
may possess the ability to remodel, integrate, and respond to the physiologic
environment in which it is placed.
In the last 20 years, significant interest has been raised in utilizing TE strategies
to mitigate the progression of IDD. Theoretical advantages of such approaches as
outlined by Halloran et al. include “the use of degradable polymers, less invasive
surgical procedures, preservation of native tissue, non-preclusion of future spinal
surgery and multi-level disc treatments” [ 73 ]. Effects of IDD are initially manifest
within the centrally located, hydrophilic NP, which when left unaddressed may
progress to affect the remainder of the IVD and adjacent spinal structures. In
response to this issue, researchers are developing TE strategies that aim to replace
the degenerate NP in symptomatic patients with mild to moderate IDD in an attempt
to mitigate its progression. The following sections provide details on the use of cells
and biopolymeric scaffolds in attempts at IVD regeneration.
8.1 Cell Sourcing for Tissue Engineering of the NP
For IVD applications, a suitable cell source must be identified for the following
reasons. First, dramatic reductions in viable cell number are typically observed in
Search WWH ::




Custom Search