For more than two decades, methods for the non-invasive exploration of cutaneous microcirculation have been mainly based on optical microscopy and laser Doppler techniques. In this review, we discuss the advantages and drawbacks of these techniques. Although optical microscopy-derived techniques, such as nailfold videocapillaroscopy, have found clinical applications, they mainly provide morphological information about the microvessels. Laser Doppler techniques coupled with reactivity tests are widespread in the field of microvascular function research, but many technical issues need to be taken into account when performing these tests. Post-occlusive reactive hyperemia and local thermal hyperemia have been shown to be reliable tests, although their underlying mechanisms are not yet fully understood.Acetylcholine and sodium nitroprusside iontophoresis, despite their wide use as specific tests of endothelium-dependent and -independent function, respectively, show limitations. The influence of the skin site, recording conditions, and the way of expressing data are also reviewed.Finally, we focus on promising tools such as laser speckle contrast imaging.Key words: microcirculation, capillaroscopy, laser Doppler, laser speckle, iontophoresis, local thermal hyperemia, post-occlusive hyperemia WHY AND HOW TO ASSESS SKIN MICROVASCULAR FUNCTION?Since the development of methods allowing the study of microcirculation, microvascular dysfunction has been associated with several vascular diseases as well as in aging [100]. The role of generalized microvascular dysfunction in the pathophysiology or as a consequence of these diseases has also been questioned. Indeed, patients with impaired coronary microvascular function also have evidence of impaired peripheral microvascular function, suggesting a generalized disorder in the regulation of the microvasculature [120]. Similar findings have been reported of correlated abnormalities between cutaneous and retinal microvasculature in diabetic patients [20].As the skin is readily accessible, it provides an appropriate site to assess peripheral microvascular reactivity. Moreover, recent technological advances have provided simple and non-invasive methods to assess skin microvascular function. Therefore, human cutaneous circulation could be used as a surrogate marker of systemic microvascular function in various diseases. However, this raises the issue of how representative the microcirculation in the skin is to the microcirculation in other organs. To date, the skin has been used as a model of microcirculation to investigate vascular mechanisms in a variety of diseases, including

No abstract