Biomedical Engineering Reference
In-Depth Information
8.2.3
Scarless Healing of Wounds in the Oral Mucosa of Adults
The oral (palatal) mucosa is often harvested for use as the equivalent of a skin graft
in oral surgical procedures in humans. As with the harvesting of skin autografts,
removal of mucosal grafts by excision leads to “donor” sites, i.e., deep wounds at
the harvested site (Jung et al. 2013). It has been persistently reported that wounds
in the oral mucosa of mice closed with greatly reduced scar or even lack of scar
formation (Schrementi et al. 2008; Mak et al. 2009; Wong et al. 2009; Larjava et al.
2011; Glim et al. 2013).
Studies in oral mucosal wounds in the swine showed that the levels of TGFβ1
and TGFβ1 expression were lower than in control skin wounds (Schrementi et al.
2008). Another study of the wounded oral mucosa with the same swine model found
evidence that oral mucosal wounds contracted significantly less than skin wounds
(Mak et al. 2009).
In conclusion, oral mucosal wounds contracted significantly less than skin
wounds while also being relatively scarless. Such wounds also showed evidence
of reduced expression of the cytokine which is required for differentiation of myo-
fibroblasts, the contractile cells considered to be primarily responsible for wound
contraction (Hinz et al. 2012) (Myofibroblast differentiation is described further
briefly).
8.2.4
Scarless Healing in the Axolotl
Among vertebrates the adult axolotl (
Ambystoma mexicanum
) is uniquely capable
to regenerate amputated limbs and other body parts (Lévesque et al. 2010), includ-
ing full-thickness excisional skin wounds (Seifert et al. 2012).
Studies of skin wound healing in the adult axolotl have shown that alpha smooth
muscle actin (αSMA), a protein characteristic of myofibroblasts, was absent.
TGFβ1, which is required for expression of the αSMA phenotype in fibroblasts,
was only transiently expressed during wound healing (Lévesque et al. 2007, 2010).
The observed absence of myofibroblasts, contractile cells that drive contraction
in wounds (Hinz et al. 2012), and the reduced presence of TGFβ1 are indirect evi-
dence for reduction or absence of contraction in axolotl skin wounds.
8.3
Cell and Tissue Morphology During Spontaneous Wound
Contraction
Contraction can be measured either as force or as deformation, the result of ap-
plication of a balanced force. Measurements of contractile forces in wounds have
appeared very rarely in the literature, a testament to the inherent difficulty in mak-
ing such measurements. The contraction force required to close a skin wound in the
rabbit thorax was measured to be about 0.1 N (Higton and James 1964).
