Active transforming growth factor-β in wound repair: Determination using a new assay

Transforming growth factor (TGF)-beta regulates wound repair and scarring in an isoform-specific fashion. TGF-beta is produced in a latent form, and its activation is a critical regulatory step controlling the bioactivity of this growth factor. To date, it has been impossible to determine latent TGF-beta activation in vivo due to a lack of quantitative assays. We describe here a semiquantitative modification of the plasminogen activator inhibitor-1/luciferase bioassay (PAI/L assay) for TGF-beta, which we used to determine active and latent TGF-beta isoforms in frozen sections of rat wound tissue. We found that significant amounts of latent TGF-beta were rapidly activated upon wounding (38% of the total TGF-beta at 1 hour after wounding). A second peak of active TGF-beta (17% of total) occurred at 5 days after wounding. The predominant isoforms were TGF-beta1 and -2 with only minor amounts of TGF-beta3 present. This is the first TGF-beta bioassay allowing semiquantitative determination of active and latent isoforms present in vivo, and our results document the significance and temporal regulation of latent TGF-beta isoform activation in wound repair.