Distinct membrane mechanical properties of human mesenchymal stem cell determined using laser optical tweezers

¹ Univeristy of Illinois
² University of Illinois

^* To whom correspondence should be addressed. E-mail: mcho{at}uic.edu.

Submitted on September 2, 2005
Revised on October 24, 2005
Accepted on 28 November 2005

	Abstract

The therapeutic efficacy of mesenchymal stem cells (MSCs) in tissue engineering and regenerative medicine is determined by their unique biological, mechanical, and physicochemical characteristics that are yet to be fully explored. Cell membrane mechanics, for example, has been shown to critically influence MSC differentiation. In the present study, we used laser optical tweezers to measure the membrane mechanics of human MSCs and terminally differentiated fibroblasts by extracting tethers from the outer cell membrane. The average tether lengths were 10.6 ± 1.1 (hMSC) and 3.0 ± 0.5 µm (fibroblasts). The tether extraction force did not increase during tether formation, which suggests existence of a membrane reservoir intended to buffer membrane tension fluctuations. Cytoskeleton disruption resulted in a 4-fold tether length increase in fibroblasts but had no effect in hMSCs, indicating weak association between the cell membrane and hMSC actin cytoskeleton. Cholesterol depletion, known to decrease lipid bilayer stiffness, caused an increase in the tether length both in fibroblasts and hMSCs, as does the treatment of cells with DMSO. We postulate that while fibroblasts use both the membrane rigidity and membrane-cytoskeleton association to regulate their membrane reservoir, hMSCs cytoskeleton has only a minor impact on the stem cell membrane mechanics.

Key Words: laser optical tweezers, membrane mechanics, membrane reservoir, membrane-cytoskeleton association, mesenchymal stem cell

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