Background: Cell signaling pathways underlying wound repair are under extensive investigation; however, there is still a poor understanding of the mechanisms orchestrating these processes. Hox genes, which are a subgroup of homeobox genes, encode for a family of transcription factors that play a critical role in tissue migration and cell differentiation during embryogenesis and may also serve as master regulatory genes of postnatal wound repair. We have developed a fetal excisional wound healing model whereby mid-gestational wounds heal in a regenerative manner while late-gestational wounds display scar formation. We theorize that Hoxd3 and Hoxd8 will be differentially expressed in mid- and late-gestational wounds compared with normal skin.
Materials and methods: Pregnant FVB mice underwent hysterotomy at mid (E15)- or late (E18)-gestational time points, and 3-mm excisional wounds were made on the dorsum of each fetus. Wound samples (w) were collected at the site of injury as well as near wound normal skin (nwc) on the same fetus. Control (c) skin samples were also obtained from unwounded adjacent fetuses. Samples were harvested at 3 and 6 h and real-time polymerase chain reaction was performed for Hoxd3 and Hoxd8 and normalized to glyceraldehyde-3-phosphate dehydrogenase. Data were analyzed by analysis of variance with statistical significance of P < 0.05.
Results: Hoxd3 levels were increased in all of the mid-gestational groups, with a significant increase at 3 h compared with late-gestational control groups. In the 3-h time group, Hoxd8 is increased in mid-gestational wounds compared with late-gestational control skin. This is repeated in the 6-h time group, where Hoxd8 is increased in mid-gestational wounds compared with all groups. Also, Hoxd8 in the mid-gestational near wound controls is significantly greater than that in the late-gestational near wound control and control groups.
Conclusions: These data suggest that Hoxd3 is constitutively expressed in the skin of mid-gestational mice. However, Hoxd8 expression is increased in the mid-gestational wounds compared with normal control groups and late gestational wounds, suggesting that it may play a role in scarless wound repair.