AIM: To study the expression of collagen I and transcription factor specificity protein 1 (Sp1), a transforming growth factor-beta 1 (TGF-beta 1) downstream target, and reveal the impact of the TGF-beta 1-Sp1 signaling pathway on collagen remodeling in myopic sclera. METHODS: Seventy-five 1-week-old guinea pigs were randomly divided into normal control, form deprivation myopia (FDM), and self-control groups. FDM was induced for different times using coverage with translucent latex balloons and FDM recovery was performed for 1wk after 4wk treatment; then, changes in refractive power and axial length were measured. Immunohistochemistry and reverse transcription-polymerase chain reaction were used to evaluate dynamic changes in collagen I and Sp1 expression in the sclera of guinea pigs with emmetropia and experimental myopia, and the relationship between collagen I and Sp1 levels was analyzed. RESULTS: In the FDM group, the refractive power was gradually changed (from 2.09 +/- 0.30 D at week 0 to -1.23 +/- 0.69 D, -4.17 +/- 0.59 D, -7.07 +/- 0.56 D, and -4.30 +/- 0.58 D at weeks 2, 4, 6, and 1wk after 4wk, respectively; P<0.05), indicating deepening of myopia. The axial length was increased (from 5.92 +/- 0.39 mm at week 0 to 6.62 +/- 0.36 mm, 7.30 +/- 0.34 mm, 7.99 +/- 0.32 mm, and 7.41 +/- 0.36 mm at weeks 2, 4, 6, and 1wk after 4wk; P<0.05). The mRNA and protein expression of Sp1 and collagen I in the sclera of the FDM group was lower than that of the control groups (P<0.05), and the reduction was eye-coverage time-dependent. Furthermore, correlation between Sp1 and collagen I down-regulation in the myopic sclera was observed. CONCLUSION: Our data indicate that transcription factor Sp1 may be involved in the regulation of type I collagen synthesis/degradation during myopic sclera remodeling, suggesting that TGF-beta 1 signaling plays a role in the development and progression of myopia.