Surface morphology and mechanical properties of MDCK monolayers by atomic force microscopy

Jan H. Hoh, Cora Ann Schoenenberger

Research output: Contribution to journalArticle

Abstract

We describe the morphology and mechanical stability of the apical surface of MDCK monolayers by atomic force microscopy (AFM). Living cells could be imaged in physiological solution for several hours without noticeable deterioration. Cell boundaries appear as ridges that clearly demarcate neighboring cells. In some cases the nucleus of individual cells could be seen, though apparently only in very thin areas of the monolayer. Two types of protrusions on the surface could be visualized. Smooth bulges that varied in width from a few hundred nanometers to several micrometers, which appear to represent relatively rigid subapical structures. Another type of protrusion extended well above the membrane and was swept back and forth during the imaging. However, the microvilli that are typically present on the apical surface could not be resolved. For comparison, a transformed MDCK cell line expressing the K-ras oncogene was also examined. When cultured on solid substrata at low density, the R5 cells spread out and are less than 100 nm thick over large areas with both extensive processes and rounded edges. Many intracellular structures such as the nucleus, cytoskeletal elements and vesicles could be visualized. None of the intracellular structures seen in the AFM images could be seen by scanning electron microscopy. Both R5 cells and MDCK monolayers required imaging forces of >2 nN for good image contrast. Force measurements on the MDCK monolayers show that they are very soft, with an effective spring constant of ~0.002 N/m for the apical plasma membrane, over the first micrometer of deformation, resulting in a height deformation of approximately 500 nm per nanoNewton of applied force. The mechanical properties of the cells could be manipulated by addition of glutaraldehyde. These changes were monitored in real time by collecting force curves during the fixation reaction. The curves show a stiffening of the apical plasma membrane that was completed in ~1 minute. On the basis of these measurements and the imaging forces required, we conclude that deformation of the plasma membrane is an important component of the contrast mechanism, in effect 'staining' structures based on their relative rigidity.

Original languageEnglish (US)
Pages (from-to)1105-1114
Number of pages10
JournalJournal of Cell Science
Volume107
Issue number5
StatePublished - May 1994
Externally publishedYes

Fingerprint

Atomic Force Microscopy
Madin Darby Canine Kidney Cells
Cell Membrane
Transformed Cell Line
ras Genes
Glutaral
Microvilli
Cell Nucleus
Electron Scanning Microscopy
Cell Count
Staining and Labeling
Membranes

Keywords

  • AFM
  • Living cell
  • Viscoelasticity

ASJC Scopus subject areas

  • Cell Biology

Cite this

Surface morphology and mechanical properties of MDCK monolayers by atomic force microscopy. / Hoh, Jan H.; Schoenenberger, Cora Ann.

In: Journal of Cell Science, Vol. 107, No. 5, 05.1994, p. 1105-1114.

Research output: Contribution to journalArticle

Hoh, Jan H. ; Schoenenberger, Cora Ann. / Surface morphology and mechanical properties of MDCK monolayers by atomic force microscopy. In: Journal of Cell Science. 1994 ; Vol. 107, No. 5. pp. 1105-1114.
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