Elastin is a connective tissue protein which allows the tissues of the body to return to their original shape after distortion or stretching. Elastin fibres can be of varying size and diameter and are particularly well seen histologically in sites such as the lung, heart, blood vessels and the dermis.
Histological demonstration of elastin fibres (or lack of them) are important in diagnostic pathology for conditions such as arteriosclerosis, temporal arteritis and elastosis. Fine elastic fibres are not so easily seen on standard haemtoxylin and eosin (H+E) staining therefore special stains which demonstrate elastin clearly are vital.
There are many elastin special stain techniques such as Weigert-Type, Orcein, Aldehyde-Fuchsin and Verhoeff’s. The most common is Verhoeff’s technique of staining elastin due to its quick method and strong elastin colour result. Below is the author’s favoured method for demonstrating elastin which is a version of the Verhoeff’s.
Verhoeff’s solution – (5ml 5% alcoholic haematoxylin) + (2ml 10% aqueous ferric cholride) + (2ml Lugol’s iodine) MAKE IMMEDIATELY PRIOR TO USE.
Note – Lugol’s iodine = 2g potassium iodine dissolved in ~4ml of distilled water, then dissolve 1g iodine, then make up to 100ml.
2 % aqueous ferric chloride
Van Gieson counterstain = (100ml saturated aqueous picric acid) + (1% aqueous acid fuchsin), boil for 3 mins then filter.
1. Take sections to water.
2. Stain with Verhoeff’s solution for 15-20 mins
3. Wash well in tap water
4. Differentiate in 2% aqueous ferric chloride until only elastin fibres remain darkly stained.
5. Wash in tap water for 5 mins.
6. Counterstain with Van Gieson for 3 mins.
7. Dehydrate, clear and mount.
– aim for slight under-differentiation as the Van Gieson stain will continue the differentiation though more slowly.
– dehydrate quickly as alcohol can leach some of the Van Gieson stain from the section. You can accelerate dehydration by blotting the section with filter paper.
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