Material properties in regenerating axolotl limbs using inverse finite element analysis

Area of Science:

• Regenerative Biology
• Biophysics
• Developmental Biology

Background:

• The extracellular matrix mechanical properties are crucial for skeletal development and tissue regeneration.
• Studying regenerating tissues offers insights into cellular mechanical environments and matrix maturation.
• Axolotl limb regeneration provides a model to investigate these dynamic changes.

Purpose of the Study:

• To quantify the viscoelastic material properties of regenerating axolotl forelimbs at distinct regeneration stages.
• To correlate changes in mechanical properties with glycosaminoglycan (GAG) content during limb regrowth.
• To understand the evolving mechanical signals experienced by cells during skeletal regeneration.

Main Methods:

• Viscoelastic material properties were determined using stress-relaxation indentation tests.
• Two-term Prony series viscoelastic inverse finite element analysis was applied to obtain material parameters.
• Glycosaminoglycan (GAG) content was measured using a 1,9-dimethyl methylene blue assay.

Main Results:

• Instantaneous and equilibrium shear moduli significantly increased during limb regeneration.
• Short-term stress relaxation time decreased, while long-term stress relaxation time was lowest in fully-grown limbs.
• GAG content increased in fully-grown limb cartilage compared to earlier regeneration stages (27 and 41 days post-amputation).

Conclusions:

• The mechanical environment of regenerating cells changes significantly during axolotl limb regrowth.
• Quantifying mechanical property changes is vital for linking cellular matrix production to tissue-level mechanical signaling.
• These findings contribute to understanding the interplay between mechanical forces and skeletal development in regeneration.