In vivoassessment of mechanical properties during axolotl development and regeneration using confocal Brillouin microscopy

Abstract

In processes such as development and regeneration, where large cellular and tissue rearrangements occur, cell fate and behavior are strongly influenced by tissue mechanics. While most well-established tools probing mechanical properties require an invasive sample preparation, confocal Brillouin microscopy captures mechanical parameters optically with high resolution in a contact-free and label-free fashion. In this work, we took advantage of this tool and the transparency of the highly regenerative axolotl to probe its mechanical properties in vivo for the first time. We mapped the Brillouin frequency shift with high resolution in developing limbs and regenerating digits, the most studied structures in the axolotl. We detected a gradual increase in the cartilage Brillouin frequency shift, suggesting decreasing tissue compressibility during both development and regeneration. Moreover, we were able to correlate such increase with the regeneration stage, which was undetected with fluorescence microscopy imaging. The present work evidences the potential of Brillouin microscopy to unravel the mechanical changes occurring in vivo in axolotls, setting the basis to apply this technique in the growing field of epimorphic regeneration.

Small leucine-rich proteoglycans inhibit CNS regeneration by modifying the structural and mechanical properties of the lesion environment

“…ν is proportional to the square root of 𝑀', which describes a material's elastic deformability under a distinct type of mechanical loading (i.e., longitudinal compressibility). Notably, ν has been shown in vivo to be sensitive to changes in the mechanical properties of the ECM during both physiological and pathological processes (41)(42)(43). We acquired Brillouin images of the region in the spinal lesion site through which the regenerating axons preferentially grow at 1 dpl (Fig.…”

Cartilage mechanobiology during limb growth

“…Likewise, in the study by Riquelme-Guzmán et al, it was shown that the elastic contrast of the limb, which is a function of the longitudinal modulus and water content, experiences an increase with both developmental age and during digit regeneration. 59 It is essential to note that the "longitudinal modulus" (M), determined through Brillouin microscopy, is highly dependent on water content and remains insensitive to changes in stiffness, conventionally measured by the Young's modulus (E) of the matrix. 60 As growing tissues exhibit high water content, M proves to be an inadequate measure for matrix stiffness.…”