Table 1. Major findings from reports on skin repair in Postn^−/− mice.

	Elliott et al., 2012	Nishiyama et al., 2011	Ontsuka et al., 2012
Wound model	6 mm punch biopsy	3 mm punch biopsy	8 mm or 10 mm punch biopsy
Main effect	KO delay at D5 and D7	KO delay at D3, D5 and D7	KO delay at D3, D5, D7 and D11
Proposed in vivo cause	Myofibroblast differentiation	Re-epithelialization via keratinocyte proliferation	Fibroblast proliferation and migration
In vivo evidence	Reduced α-smooth muscle actin gene expression and immunoreactivity in KO	Measurements from H&E stained sections Reduced Ki-67 immunoreactivity around KO hair follicles	No data
In vitro support	Adult KO fibroblasts showed reduced: Force generation, Collagen gel contraction, α-smooth muscle actin immunofluorescence, α-smooth muscle actin protein	No data	Newborn KO fibroblasts show reduced proliferation KO MEFs show reduced migration
Rescue tool(s) (in vitro)	Recombinant full-length human periostin (R&D Systems) produced in a mouse myeloma cell line (NS0)	Expression vector for mouse periostin	Recombinant full-length mouse periostin (R&D Systems) produced in an insect ovarian cell line (Sf21) Expression vector for full-length mouse periostin
Rescue? (in vitro)	Adult KO fibroblasts showed restored: Collagen gel contraction, α-smooth muscle actin staining, α-smooth muscle actin protein. (Force generation not tested for rescue)	Conflicting results: Overexpression of Ms Postn in human keratinocyte cell line (HaCaT) resulted in no difference in cell number when cultured for 96 h. However, the same cells cultured for one week beyond confluence showed an increase in BrdU labeling.	Proliferation of newborn mouse fibroblasts (vector and recombinant) Proliferation of normal human dermal fibroblasts (recombinant)
Rescue tool (in vivo)	Recombinant full-length human periostin (R&D Systems) incorporated into an electrospun collagen scaffold	No in vivo rescue	Recombinant full-length mouse periostin (R&D Systems) added directly onto wounds
Rescue? (in vivo)	Increased α-smooth muscle actin immunoreactivity at D7 No wound closure kinetics	No in vivo rescue	Restored wound closure kinetics No evidence for mechanism
Additional findings	No difference in fibroblast migration No difference in re-epithelialization	Similar Ki-67 numbers in granulation tissue and migrating keratinocytes

Three recent studies on the role of periostin in skin repair have similarities in in vivo results. Yet, considerable differences in in vitro results and methodologies make it difficult to clearly define the mechanism through which periostin influences skin repair.