Objective To investigate the expression of thymosin ?4 in the foreskin,normal skin(except the foreskin),hypertrophic scar,and keloid,and its relationship to pathological scars.Methods In situ hybridization was applied to detect the expression of thymosin ?4 mRNA [With the probe of BM005698(EST) gene marked by digoxin] in four groups: foreskin,normal skin(except the foreskin),hypertrophic scar,and keloid.Both qualitative and semi-quantitative analysis were performed.Results Thymosin ?4 mRNA was expressed in all the four groups.The proportion of thymosin ?4 mRNA expression in the keloid was 2/10,which was 25% of that in the foreskin(8/10),and was 28.6% of that in the normal skin(7/10).The positive rate of thymosin ?4 mRNA expression in the dermis was higher than that in the epidermis;and was high in fibroblasts,intravascular endothelial cells,and macrophages.The mean OSD of the positive samples was 0.03?0.01 in the keloids,which was significantly lower than that in the normal skins(0.09?0.03) and hypertrophic scars(0.09?0.02)(P=0.000 for both).Compared with the normal skins,the expression increased by 231.5%(P