The pathophysiologic basis for wound healing and cutaneous regeneration - Biomaterials for Treating Skin Loss - page 42

Table 4.1 Fundamental similarities and differences between scar and
regenerated skin

Repair/scar formation Regeneration

Intact epidermis Yes Yes

Adnexa Absent Present

Rete ridges Absent Present

Basement membrane Present Present

Fibroblast orientation Parallel to epidermis Quasi-random

Myofibroblast presence More pronounced Less pronounced

(contractile fibroblast)
Collagen organization Parallel Quasi-random

Collagen I to collagen III ratio > 4:1 1:4

Vascular orientation Perpendicular to Parallel to epidermis;

epidermis; ill-defined well-defined plexus

plexus and capillary loops and capillary loops

Relative tensile strength 70-80% 100%

Function Suboptimal Normal

Table 4.2 Potential 'essential ingredients' for regeneration

Required for regeneration

Sterile environment No

Inhibition of platelet activation Yes

Inhibition of inflammatory response Yes

Inhibition of growth factors TGF- β 3 , PDGF and FGF Yes

Inhibit fibroblast differentiation to myofibroblast Yes

Inhibition of wound contraction Yes

Source of epidermal and mesenchymal stem cells Yes

HOX B13 and PRX-2 gene expression Yes

Surgical conversion to full-thickness wound Yes

Dermal regeneration template (pore size 20-125 µm) Yes

smaller set of criteria (which minimally overlap with the regeneration set.) It is
important to note that although the conditions required for regeneration and
repair are diametrically opposed, they are not necessarily mutually exclusive.
However, fundamental differences between repair and regeneration (such as
spatial orientation of cellular and acellular elements, as well as wound contrac-
tion) allow the inclusion of conditions (that oppose repair) in a list of 'essential
ingredients' needed to induce regeneration. Table 4.2 contains a set of potential
requirements necessary for the healing response to proceed towards the regen-
erative pathway.