Biomedical Engineering Reference
In-Depth Information
Structural components of ligaments and tendon are similar but their
characteristics may differ. Fibroblasts structure and size varies in ligament and
tendon. Even diameter of collagen fi bril, ratio of collagen type I to type III may
vary [276] .
Ligaments surround joints and bind them together by acting as a connecting
bridge between two bones. They help to strengthen and stabilize joints, permitting
movement only in certain directions. Thus, any excessive movement of ligament
or movement in wrong direction can result in ligament rupture and bone injury
[277]. When the injury causes total detachment of the ligament from the bone, an
insertion surgery is recommended. Untreated injuries lead to unstable joints and
excessive load on cartilage, which may progress into osteoarthritis [278-280]. It is
important to note that ligaments present in the same joint can differ from each
other in terms of regenerative capacity [272,281] Medial collateral ligament
(MCL) has better capacity to heal, whereas anterior crucial ligament (ACL), once
ruptured, cannot undergo self-repair. Thus, ACL, if injured, leads to disability
because of its poor healing capacity. This is primarily because of the lack of vascu-
lature and limited availability of nutrients to the damaged tissue from synovial
fl uid (depending on the severity of injury) [272,281].
Autografts and allografts have been explored for the reconstruction of ACL
[282]. Non-biodegradable grafts, and even collagen grafts, could not successfully
repair and replace damaged ligaments as they were mechanically unstable and
could not perform the biochemical and physiological function [283].
Unlike ACL, tendons have the capacity of self repair; however, when the
defect is too large (that is, beyond self repair), partial or total replacement is the
only available option [284].
The drawback associated with the aforementioned strategies has led to
the implementation of tissue-engineering approaches for ligament and tendon
repair.
13.5.2.4.1 POTENTIAL CELL SOURCES FOR LIGAMENT AND TENDON TISSUE
ENGINEERING. Autologous tissue specifi c cells are the gold standard for cell
therapy. Ligaments have a dense ECM and low population of cells makes their
isolation diffi cult [285,286]. Therefore, alternative cell sources have been explored
for ligament-tissue engineering. As stated in the previous sections, MSCs have the
potential to differentiate into variety of cell types of mesenchymal lineage, and
thus, are also capable of differentiating into ligament fi broblasts [287] . Wantanabe
et al. demonstrated that when MSCs from transgenic rats were injected into MCL
of wild type rat, MSCs migrated to the injury site of ligament in three days, and
after 28 days of study, it was found that the MSCs had differentiated into MCL
fi broblast-like cells following adaptation to the environment [288]. Previous
studies have demonstrated that when MSCs were used for tendon repair, there
was an increase in ultimate stress, modulus and strain energy density when trans-
planted in a collagen matrix [270]. MSCs have an added advantage of ease-of-
expansion in cell culture. Thus, MSCs can be used as a potential cell source for
ligament and tendon repair.
Search WWH ::
Custom Search