Last updated March 21, 2018 at 8:20 am
A New Zealand group may have cracked the mystery of what causes curly hair by looking at the curliest of all – sheep.
This may sound like the start of an Australian joke, but New Zealand scientists have turned to sheep to try to discover why some people have naturally curly hair.
And it’s a fair enough reason. Human hair is too coarse to study easily at the cellular level but fine Merino wool isn’t: and it has essentially the same chemistry, structure and growth patterns.
According to Dr Duane Harland, a Senior Scientist with AgResearch, there have been two competing theories about what makes some hairs curly.
One has it that there are more cells on the outer side of a curl, because the cells on that side of the hair follicle have divided more.
The other is related to the fact that individual hairs are made up of two cell types – paracortical cells (packed with parallel keratin fibres) and orthocortical cells (packed with twisted keratin fibres). The argument is that the longer orthocortical cells line the outer side of the curve, with paracortical cells lining the inner side.
Quite literally putting hair under the microscope
Putting these theories to the test involved first painstakingly cleaning and preparing more than 700 0.5 cm snippets from the base of individual wool fibres. This included drying them on a vibrating surface to ensure they didn’t pick up any additional kinks.
“We had to go to great lengths to make sure we were measuring the natural curvature programmed in during fibre development and not curvature imposed later while the wool was on the sheep’s back or during washing and processing,” Harland said.
Manoeuvring the snippets onto microscope slides also was far from straightforward. Grabbing them with fine forceps wasn’t an option because they are easily damaged, so the researchers used the electrostatic force on the tip of fine forceps.
They then measured the curvature of each wool snippet before staining it and transferring it to a confocal microscope to reveal the curl’s cell structure.
And the answer? The cell type theory wins.
The team could clearly see shorter paracortical cells lining the inside of the curve, while longer orthocortical cells were located on the outside.
Their hope is that the findings will be of value in the $85 billion global hair care market .”The improved knowledge of how features of hair contribute to its outward appearance and physical characteristics is essential background,” Harland said.
The paper published in Journal of Experimental Biology.
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