Purpose of review
The interstitium represents the fluid, proteins, solutes, and extracellular matrix comprising the microenvironment of tissues. We here review attempts to characterize the levels and composition of lipoproteins in human interstitial fluid, and identify potentially important questions for future research.
Despite the high relevance of understanding how lipoproteins enter and exit the interstitial compartment, and how they interact with extracellular and cellular molecules, scientific progress in this field has been rather slow. This is partly due to methodological difficulties, both regarding how to obtain representative samples and how to perform appropriate measurements to compare patient cohorts and to evaluate responses to treatment. Predominant techniques include peripheral lymph cannulation and suction blister creation, both of which have inherent advantages and disadvantages. Detailed studies comparing the effects of long-term incubation of serum and lymph lipoproteins are compatible with the view that HDL in interstitial fluid takes up free cholesterol from cells and transfers it into the circulation.
Studies of the concentration, composition, functionality, and turnover of interstitial fluid lipoproteins will be of great future interest for understanding how tissue cholesterol metabolism is regulated, and how different diseases link to increased risk for development of atherosclerosis.