Activation of a fibroblast-specific enhancer of the Pro alpha 2(I) collagen gene in tight-skin mice

Objective. Reporter transgenes were introduced into the type 1 tight-skin ( Tsk1/+) mouse model of scleroderma to test the hypothesis that fibroblast-s pecific genetic programs are activated in fibrosis. Methods. Transgenes harboring upstream fragments of the 5' flanking region of the mouse pro alpha2(I) collagen gene (Colla2), linked to a 400-bp minim al Colla2 promoter driving an Escherichia coli beta -galactosidase (LacZ) r eporter gene, were introduced into Tsk1/+ mice by breeding. Expression of t hese transgenes, which function as lineage-specific markers of fibroblast d ifferentiation, was compared between the Tsk-LacZ mice and non-Tsk litterma tes. Responsiveness of these constructs to the profibrotic cytokine, transf orming growth factor beta1 (TGF beta1), was investigated by transient trans fection of reporter constructs in tissue-culture cells. Results. There was significant activation of reporter genes harboring the u pstream enhancer in Tsk1/+ mice starting from 1 week of age. This was maxim al at 6 weeks old (mean +/- SD 237 +/- 24% of non-Tsk controls; P = 0.001). Recombinant TGF beta1 significantly activated reporter genes regulated by the upstream enhancer in transient transfection, and Tsk-LacZ fibroblasts s howed elevated LacZ expression in tissue culture. Conclusion. These data suggest that activating signals in Tsk1/+ mice may a ct via fibroblast-specific regulatory elements within the murine Colla2 gen e. Although TGF beta has been implicated in the pathogenesis of fibrosis, a nd reporter genes regulated by the upstream enhancer appear to be TGF beta responsive in vitro, our results suggest that fibroblast-specific pathways may also be involved.