Skin Research Institute Singapore, Singapore.
Food and Bio-based Products Group, AgResearch, Crown Research Institute, Lincoln, New Zealand.
Exp Dermatol. 2019 May;28(5):517-527. doi: 10.1111/exd.13898.
Human recorded history is littered with attempts to improve the perceived appearance of scalp hair. Throughout history, treatments have included both biological and chemical interventions. Hair "quality" or "perceived appearance" is regulated by multiple biological intervention opportunities: adding more hairs by flipping follicles from telogen to anagen, or delaying anagen follicles transiting into catagen; altering hair "apparent amount" by modulating shaft diameter or shape; or, in principle, altering shaft physical properties changing its synthesis. By far the most common biological intervention strategy today is to increase the number of hairs, but to date this has proven difficult and has yielded minimal benefits. Chemical intervention primarily consists of active material surface deposition to improve shaft shine, fibre-fibre interactions and strength. Real, perceptible benefits will best be achieved by combining opportunity areas across the three primary sciences: biology, chemistry and physics. Shaft biogenesis begins with biology: proliferation in the germinative matrix, then crossing "Auber's Critical Line" and ceasing proliferation to synthesize shaft components. Biogenesis then shifts to oxidative chemistry, where previously synthesized components are organized and cross-linked into a shaft. We herein term the crossing point from biology to chemistry as "The Orwin Threshold." Historically, hair biology and chemistry have been conducted in different fields, with biological manipulation residing in biomedical communities and hair shaft chemistry and physics within the consumer care industry, with minimal cross-fertilization. Detailed understanding of hair shaft biogenesis should enable identification of factors necessary for optimum hair shaft production and new intervention opportunities.
人类有记载的历史充斥着各种改善头皮毛发外观的尝试。纵观历史，治疗方法包括生物和化学干预。头发的“质量”或“外观感知”受到多种生物干预机会的调节：通过将毛囊从休止期翻转到生长期来增加更多的毛发，或延迟进入退行期的生长期毛囊；通过调节轴直径或形状来改变头发“明显数量”；或者，原则上可以改变轴的物理性质，从而改变其合成。到目前为止，最常见的生物干预策略是增加头发数量，但迄今为止，这一策略证明是困难的，并且只带来了最小的益处。化学干预主要包括活性物质表面沉积以改善轴的光泽、纤维间相互作用和强度。通过结合三大主要科学领域的机会领域，将最好地实现真正可感知的益处：生物学、化学和物理学。轴发生始于生物学：在生发基质中增殖，然后跨越“奥伯的关键线”并停止增殖以合成轴成分。然后发生生物发生转移到氧化化学，先前合成的成分在那里被组织并交联成轴。我们在此将从生物学到化学的交点称为“欧文阈值”。从历史上看，头发生物学和化学一直是在不同的领域进行的，生物操纵存在于生物医学社区，而毛发轴的化学和物理则存在于消费护理行业，几乎没有交叉。对毛发轴发生的详细了解应该能够识别出产生最佳毛发轴所需的因素，并为新的干预机会提供依据。
