Follicular penetration and targeting.

Area of Science:

• Dermatology
• Hair Research
• Pharmacokinetics

Background:

• Historically, intercellular penetration was considered the primary route for topical substances.
• Recent research highlights the significant role of follicular penetration, particularly for targeting specific cells like nestin-expressing follicular bulge cells.

Purpose of the Study:

• To investigate the role of hair follicles as reservoirs for topical substance penetration.
• To explore the influence of the follicular infundibulum state (open vs. closed) on penetration.
• To examine the potential of nestin-expressing hair follicle stem cells in forming neuronal and vascular networks during hair follicle cycling.

Main Methods:

• Utilizing differential stripping technology to determine the reservoir volume of hair follicles.
• Experimental investigations differentiating penetration into open versus closed hair follicles.
• Analysis of hair follicle cycling, neuronal, and vascular networks.

Main Results:

• Hair follicles serve as efficient reservoirs for topical substance penetration and targeting.
• Penetration of topical substances is restricted to open hair follicles.
• Nestin-expressing hair follicle stem cells possess the potential for neurogenesis and angiogenesis during anagen initiation.

Conclusions:

• Follicular penetration is a critical pathway for topical applications, offering targeted delivery potential.
• The state of the follicular infundibulum (open/closed) dictates the success of follicular penetration.
• Hair follicle stem cells play a role in vascular and neuronal network formation during hair cycling, relevant for therapeutic targeting.