Regenerative Tissue Engineering of Tendon Using Fetal and Adult Fibroblast-Seeded Scaffolds
Restoration of hand and upper extremity function following tendon injures
is largely dependent on the reestablishment of the gliding mechanism between
the tendon and its surrounding tissue. Post surgical scarring that hinders
gliding remains the most problematic aspect of tendon repair. Extensive
experimental evidence exists that fetal tissue in the early to mid-gestational
age responds to injury in a fundamentally different manner than adult tissue.
In general, fetal wound healing occurs at a faster rate and in the absence
of scar formation. Importantly, lack of scar formation in fetal tissues
has been attributed to the absence of a substantial inflammatory response
following injury, obviating the reparative fibrotic response seen in adult
tissue. A non-scarring fetal healing response has been observed in skin,
articular cartilage, nerve, bone, and tendon injury models. Further more,
injured fetal tendon tissue transplanted into an adult environment retains
its regenerative healing pattern, suggesting that this scarless pattern
is intrinsic to the fetal tendon tissue and not the fetal environment. Harnessing
the processes that control the regenerative healing response in fetal animals
may enable us to modulate the fibrotic response observed in adults, leading
to significant improvement in the clinical treatment of traumatic tendon
injuries.
Research is currently being conducted in our laboratory to determine if
fetal skin fibroblast cells seeded on a bioabsorbable scaffold in an adult
tendon defect will lead to improved elastic and viscoelastic biomechanical
properties compared to adult tendon defects implanted with adult skin cells
seeded on the same bioabsorbable scaffold. Our hypothesis is that the implantation
of fetal skin fibroblast-bioabsorbable scaffold composites into adult tendon
defects will lead to regenerative healing in a manner intrinsic to fetal
tissue, with rapid regeneration of normally aligned collagen fibers, minimal
inflammatory cell infiltration, minimal granulation tissue formation, and
an absence of scar.
To test this hypothesis skin fibroblast cells will be isolated, plated in monolayer and maintained until confluent. The cells will then be transfected with a plasmid encoding the enhanced green fluorescent protein for later identification of seeded cells. Current research is being conducted to determine the optimal seeding density for the bio-scaffold.
Once this has been completed, mice will be divided into three time points,
3, 6 and 12 weeks post-surgery. The surgical procedure uses a 0.75 mm diameter
biopsy punch to create a full thickness partial (60%) width transaction
in the patellar tendon. After the partial tenotomy is created in the tendon,
a cell-scaffold composite matching the defect in size, shape, and thickness
will be sewn directly into the tenotomy site. At the described time points,
mice will be sacrificed and their tendons excised. The tendons will then
be mechanically tested or sectioned for histological analysis. The results
from this study will offer information on tendon healing by fetal cells
in an adult environment.