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

Abstract

Significance: 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.

Aim: 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.

Approach: 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: 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.

Conclusions: 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.

Keywords: Brillouin microscopy; bioengineered skin; elasticity; optical coherence elastography; tissue scaffold.