Human Hair Production by Scalp Samples Grafted onto Nude Mice: Biochemical Data on Normal Human Hair and the Genetic Defect Trichothiodystrophy

The study demonstrated a laboratory model using nude mice to continuously produce human hair by grafting human scalp samples, including those from a fetus with trichothiodystrophy (TTD). The amino acid composition of hair from these grafts was similar to that of the original human scalp, with TTD samples showing a significant decrease in cysteine and moderate decreases in threonine and proline, alongside increases in other amino acids. These changes indicated a reduction in high sulfur proteins and a relative increase in keratins. The transformation of lanugo hairs into terminal hairs and normal melanization in grafts suggested that keratin and HSP gene expression, as well as melanogenesis regulation, were independent of systemic host factors. This model was proposed as a clinically relevant tool for studying normal and abnormal gene expression in hair follicles.