In-vitro model reveals a role for mechanical stretch in the remodeling response of lymphatic muscle cells.

Objective Using primary LMCs in vitro, we sought to characterize the impact of LMC remodeling on their functional and molecular response to mechanical loading and culture conditions. Methods Primary "wounded leg" LMCs were derived from the hindlimb of three sheep who underwent lymphatic injury 6 weeks prior, while "control leg" LMCs were derived from the contralateral, unwounded, limb. Function of the LMCs was characterized in response to media of variable levels of serum (10% vs 0.2%) and glucose (4.5 vs 1 g/L). Functional and proteomic data were evaluated in LMCs exposed to cyclic stretch (0.1 Hz, 7.5% elongation) for 1 week. Results LMCs were sensitive to changes in serum levels, significantly reducing overall activity and collagen synthesis under low serum conditions. LMCs from the remodeled vessel had higher baseline levels of metabolic activity but not collagen synthesis. Cyclic loading induced cellular alignment perpendicular to the axis of stretch and alterations in signaling pathways associated with metabolism. Remodeled LMCs had consistently higher levels of metabolic activity and were more resistant to strain-induced apoptosis. Conclusions LMCs exist on a functional spectrum, becoming more active in response to stretching and maintaining phenotypic remodeling in response to local lymphatic/tissue damage.