[Expression and function of sphingosine kinases 1 and 2 in human keloid fibroblasts]

To study the expression and function of sphingosine kinase (SphK) 1 and SphK2 in human keloid fibroblasts.

Specimens of keloid and surrounding normal skin were collected from 12 patients with keloid during operation. Primary fibroblasts were isolated, cultured, and randomly divided into 3 groups: normal skin group, keloid group, and keloid with transforming growth factor (TGF)-beta1 group cultured with TGF-beta1 for 48 h. Immunofluorescence technique was used to detect the location of SphK1 and SphK2 protein. Real-time PCR and Western blotting were used to measure the mRNA and protein expression levels of SphK1 and SphK2.

Sphk1 protein was localized primarily in the nuclei of the fibroblasts, and Sphk2 protein was detected both in the cytoplasm and nuclei in the 3 groups. The mRNA and protein levels of Sphk1 in the keloid group were (0.0608 +/- 0.0190) and (0.8308 +/- 0.1093) respectively, both significantly higher than those of the normal skin group [(0.0383 +/- 0.0147) and (0.6800 +/- 0.1126) respectively, both P < 0.05], but significantly lower than those of the keloid fibroblasts with TGF-beta1 group [(0.0790 +/- 0.0280), P < 0.05, and (1.4267 +/- 0.1938), P < 0.01]. There was no significant differences in the Sphk2 mRNA and protein levels among these 3 groups (all P > 0.05).

Sphk1 plays a leading role in keloid pathogenesis. The SphK1 mRNA and protein levels are increased by TGF-beta1 stimulation in keloid fibroblasts, perhaps indicating that Sphk1 is involved in TGF-beta signal transduction pathway.