NanoSIMS imaging shows increased amounts of accessible cholesterol on microvilli projections from cells. Image credit: Haibo Jiang and Stephen Young

A new imaging modality has enabled researchers from the University of California (Los Angeles) and the University of Western Australia to visualize cholesterol distribution in cells and tissues. Nanoscale secondary ion mass spectrometry (NanoSIMS) allowed the team to quantify a pool of cholesterol called “accessible cholesterol” on the cell surfaces.

While cholesterol is essential for maintaining the integrity of cellular plasma membranes, elevated levels of cholesterol in the blood represent a risk factor for coronary artery disease.

The accessible pool of cholesterol on the plasma membrane is thought to play a role in regulating production of cholesterol by cells and likely plays a role in the ability of cells to unload surplus cholesterol. Accessible cholesterol on cell surfaces can be detected with a cholesterol-binding protein from bacteria.

The researchers used the bacterial protein along with NanoSIMS imaging to reveal the uneven distribution of the accessible pool on a cell’s plasma membrane. This cholesterol is highly enriched on specialized projections from the plasma membrane called microvilli. The finding supports previous assumptions that microvilli play a role in moving cholesterol into and out of cells.

The imaging method could yield new strategies for lowering cholesterol levels in the blood or for optimizing the effects of existing cholesterol-lowering drugs. NanoSIMS will now be combined with novel biochemical approaches, to investigate cholesterol distribution and movement in multiple cell types.