Enhancing skin epidermal stability - Biomaterials for Treating Skin Loss - page 131

cell differentiation. Growth factors may mediate hyaluronic acid-induced cell
locomotion. For example, TGF- 1 upregulates hyaluronic acid expression and the

receptor RHAMM, hence promoting fibroblast motility (Yang et al. , 1993). The
stimulatory effect of hyaluronic acid on granulation tissue formation is complex.
Hyaluronic acid is known to have pro-angiogenic effects (West et al ., 1985) with
biodegradants from hyaluronic acid increasing angiogenesis (Anthony et al .,
2006).
Hyaluronic acid has a wide range of healthcare applications. This versatility is
in part due to the ease with which hyaluronic acid-based biopolymers can be
processed. Following esterification, the material can be processed into a number of
formulations such as membranes, sponges or microspheres by lyophilising, spray
drying or extrusion. HA fibres can be used to produce gauzes, ropes or non-woven
materials. It is used to repair cartilage in orthopaedic surgery, in ophthalmology as
a replacement for lost vitreous fluid during cataract or lens surgery, in dermatology
and plastic surgery for augmentation, to fill facial wrinkles cosmetically, to
produce microspheres for drug delivery, in surgery and chronic and acute wound
healing, topical gel delivery of drugs and vascular regeneration (Lepidi et al .,
2006).

β

9.3.1 Effect of hyaluronic acid and Laserskin ® on

epidermal stability

Laserskin ® is unique amongst the current epithelial delivery systems and its
development addresses a number of the factors that adversely affect the stability
and usefulness of epithelial autografts. The physical properties of Laserskin ® mean
that cells can proliferate and migrate through the material's interstices and struc-
tural components formed by the cells can be incorporated into the network. In
addition to providing a conduit for cell migration and proliferation, the laser cut
holes allow drainage of wound exudate. The supporting nature of the sheet also
enhances ease of handling during surgical application and the transparent nature of
the membrane means the wound can be observed during dressing changes.
Other advantages of the use of Laserskin ® as a delivery system for keratinocytes
over the use of fully confluent, layered, differentiated epidermal sheets is that they
can be produced in a shorter space of time, saving up to 1 week, which is of
particular advantage in the treatment of acute burn injuries (Pianigiani et al ., 1999;
Chan et al ., 2001). Sub-confluent keratinocytes delivered in this way are also in a
more proliferative state which may increase the rate of epidermal closure. Growing
cells on a biocompatible delivery sheet also overcomes one of the major problems
associated with the use of cultured epithelial autografts, which is the use of
enzymatic dislodgement, commonly dispase, to remove the sheets from the
surface of the tissue culture flasks. Dispase causes damage to the basal cell layer
and a loss of laminin 5 laid down by epithelial cells during culture occurs which
may adversely affect epidermal stability (Yamato et al ., 2001). With Laserskin ® ,