Transforming growth factor-beta1, -beta2, and -beta3 in vivo: effects on normal and mitomycin C-modulated conjunctival scarring.

Purpose: To compare the effects of the three human isoforms of transforming growth factor (TGF)-beta in vivo using a mouse model of conjunctival scarring, both in normal eyes and after treatment with MMC, with a view to delineating the role of this growth factor in glaucoma filtration surgery.
Methods: Application of recombinant human TGF-beta was assessed in a prospective, randomized study of mouse conjunctival scarring, in which subconjunctival TGF-beta1, -beta2, and -beta3 (all 10(-9) M) were compared with control (phosphate-buffered saline [PBS] carrier) and mitomycin C (MMC; 0.4 mg/ml) treatment at 6 hours, and 1, 3, and 7 days after surgery (six eyes/treatment/time point). Effects of TGF-beta2 on eyes previously treated with MMC were also assessed. Histologic studies of enucleated eyes were performed to analyze development of the scarring response, extracellular matrix deposition, and the inflammatory cell profile.
Results: All three isoforms of TGF-beta behaved in a similar manner in vivo, being associated with a rapid-onset and exaggerated scarring response compared with control and MMC treatment. TGF-beta-treated eyes showed evidence of an earlier peak in inflammatory cell activity (P < 0.05) and increased collagen type III deposition (P < 0.05). TGF-beta2 treatment significantly stimulated scarring after MMC application (P < 0.05).
Conclusions: TGF-beta1, -beta2, and -beta3 appear to have similar actions in vivo and stimulate the conjunctival scarring response. Application of TGF-beta2 modified the effects of MMC. All TGF-beta isoforms may be potent modulators of the conjunctival scarring response. These studies indicate that TGF-beta2 may naturally modify the antiscarring effects of antimetabolites such as MMC in glaucoma filtration surgery.