Dual optical elastography detects TGF - β -induced alterations in the biomechanical properties of skin scaffolds

The skin's mechanical properties are tightly regulated. Various pathologies can affect skin stiffness, and understanding these changes is a focus in tissue engineering. Ex vivo skin scaffolds are a robust platform for evaluating the effects of various genetic and molecular interactions on the skin. Transforming growth factor-beta ( $\mathrm{TGF}\text{-}\beta$ ) is a critical signaling molecule in the skin that can regulate the amount of collagen and elastin in the skin and, consequently, its mechanical properties.

This study investigates the biomechanical properties of bio-engineered skin scaffolds, focusing on the influence of $\mathrm{TGF}\text{-}\beta$ , a signaling molecule with diverse cellular functions.

The $\mathrm{TGF}\text{-}\beta$ receptor I inhibitor, galunisertib, was employed to assess the mechanical changes resulting from dysregulation of $\mathrm{TGF}\text{-}\beta$ . Skin scaffold samples, grouped into three categories (control, $\mathrm{TGF}\text{-}\beta$ -treated, and $\mathrm{TGF}\text{-}\beta$ + galunisertib-treated), were prepared in two distinct culture media-one with aprotinin (AP) and another without. Two optical elastography techniques, namely wave-based optical coherence elastography (OCE) and Brillouin microscopy, were utilized to quantify the biomechanical properties of the tissues.

Results showed significantly higher wave speed (with AP, $p<0.001$ ; without AP, $p<0.001$ ) and Brillouin frequency shift (with AP, $p<0.001$ ; without AP, $p=0.01$ ) in $\mathrm{TGF}\text{-}\beta$ -treated group compared with the control group. The difference in wave speed between the control and $\mathrm{TGF}\text{-}\beta$ + galunisertib with ( $p=0.10$ ) and without AP ( $p=0.36$ ) was not significant. Moreover, the $\mathrm{TGF}\text{-}\beta$ + galunisertib-treated group exhibited lower wave speed without and with AP and reduced Brillouin frequency shift than the $\mathrm{TGF}\text{-}\beta$ -treated group without AP, further strengthening the potential role of $\mathrm{TGF}\text{-}\beta$ in regulating the mechanical properties of the samples.

These findings offer valuable insights into $\mathrm{TGF}\text{-}\beta$ -induced biomechanical alterations in bio-engineered skin scaffolds, highlighting the potential of OCE and Brillouin microscopy in the development of targeted therapies in conditions involving abnormal tissue remodeling and fibrosis.