What makes your hair curl? An AgResearch hint: it’s not eating your crusts

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Shall we curl it …. or leave it straight? 

Heaps of money have been spent on making our hair curly or taming it straight but scientists haven’t been sure what makes our hair curl in the first place.

New Zealand scientists have set about trying to find out by examining merino sheep to learn what’s behind the spring in their locks.

They found different cell types on either side of the strands, with small cells on the inside of the curl and longer cells on the outside. So rather than some cells growing faster than others, they found the type of cell is important to curls.

They think their discovery could help in developing new products for taming our tresses.

The work was supported by Kao Corporation and by AgResearch through its Integrated Wool Sciences Programme (Ministry of Business Innovation & Employment, Science Strategic Investment Fund).

It is being reported today (HERE) by scimex.

Duane Harland, from AgResearch, says there were two competing theories about what makes hair curl naturally.

Individual hairs are made up of two different cell types – paracortical cells (which are packed with parallel keratin fibres) and orthocortical cells (which are packed with twisted keratin fibres).

One theory suggested that the longer orthocortical cells would line the outer side of the curve, with paracortical cells lining the inner side. The alternative theory suggested there were more cells on the outer side of the curl, because the cells on that side of the hair follicle divided more, increasing the number of cells in the outer curve of the curl.

“But most of these theories have very limited or indirect evidence to back them up,” says Harland.

Having worked with Japan’s Kao Corporation cosmetics company to learn more about the structure of human hair, Jolon Dyer and Stefan Clerens teamed up with Shinobu Nagase, Takashi Itou and Kenzo Koike to get to grips with the knotty problem of what makes hair curly.

But because human hair is too coarse to analyse its cell structure, the team turned to fine curly merino sheep wool. They explain that the chemistry, structure and growth of all hair is essentially the same, so the lessons learned from sheep’s wool will apply to human hair also.

Knowing the exact origin of the merino sheep whose wool was used in the study,
David Scobie clipped a few full length locks from the winter coats of each animal before Harland, James Vernon and Joy Woods spent hours painstakingly cleaning and preparing over seven hundred 0.5 cm snippets from the base of individual fibres.

Great care was taken to make sure they 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.

The fibres were dried on a vibrating surface to ensure they didn’t pick up any additional kinks.

Harland describes how manoeuvring the snippets onto microscope slides took a steady nerve.

“Grabbing the snippets with fine forceps was not an option because they were easily damaged…so we used the electrostatic force on the tip of fine forceps to accurately position them.”

The team 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.

After months of counting and measuring the cells on the inside and outside of each curly snippet, the team could see that the shorter paracortical cells lined the inside of the curve, while the longer orthocortical cells were located on the outside of the curl. Hence the curl was produced by the arrangement of the different cell types and not cells dividing more often on one side of the hair follicle to produce more cells on the outside of the curl.

“We have established clearly that cell type is important, as is cell length,” Harland says.

The same should hold true for human hair.

The global hair-care market is estimated to be worth over $85 billion. The team therefore is optimistic that its discovery could contribute to the design of novel hair products.

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