At the base of every hair follicle, a small group of cells called the dermal papilla acts as the control center for hair production. Composed of connective cells, this structure regulates the hair’s growth cycle, size, and shape. The dermal papilla directs the activities of the surrounding epithelial cells, which are the building blocks of the hair shaft. The health of the dermal papilla ultimately determines the characteristics of the hair produced.
The Dermal Papilla’s Role in the Hair Growth Cycle
The dermal papilla orchestrates the hair growth cycle, which has three main phases. The first and longest is anagen, the growth period. During anagen, the dermal papilla signals cells in the hair matrix to produce the hair shaft. This process relies on a rich network of blood vessels within the papilla to supply the oxygen and nutrients needed for synthesizing keratin, the main protein in hair.
Following the anagen phase, the dermal papilla initiates the catagen phase. In this transitional stage, cell division in the matrix halts, and the lower part of the follicle regresses. The dermal papilla then moves upward, detaching from the base of the follicle. If this migration fails, the hair cycle can terminate and lead to hair loss.
The final phase is telogen, where the hair shaft is held in place but is no longer growing. The dermal papilla remains dormant near a region of stem cells known as the bulge. At the end of telogen, the dermal papilla signals these stem cells to reinitiate the anagen phase. This stimulates the formation of a new hair bulb that engulfs the dermal papilla and produces a new hair, pushing the old one out.
How the Dermal Papilla Contributes to Hair Loss
In androgenetic alopecia (pattern hair loss), the dermal papilla is a primary factor in hair thinning. This hereditary condition is dependent on androgens, specifically dihydrotestosterone (DHT). In individuals with a genetic predisposition, the dermal papilla cells in certain scalp follicles contain a high number of receptors for these androgens.
When DHT binds to these receptors, it alters the production of growth-regulating factors within the dermal papilla. This change affects the behavior of hair-producing cells. The signals from the androgen-affected dermal papilla cause the hair follicle to shrink, a process known as follicular miniaturization, which is the hallmark of this condition.
Follicular miniaturization alters the hair growth cycle. The anagen (growth) phase becomes shorter, while the telogen (resting) phase may lengthen. With each cycle, the affected follicle produces a finer, shorter, and less pigmented hair. Over time, the dermal papilla itself shrinks, and the follicle may become so small it produces only a tiny hair or stops producing hair, leading to baldness.
Therapies Targeting the Dermal Papilla
Many hair loss treatments influence the dermal papilla to counteract miniaturization. Minoxidil, a topical medication, is thought to function by improving blood flow to the follicle. This enhanced circulation delivers more oxygen and nutrients to the dermal papilla and is also believed to prolong the anagen phase by activating potassium channels in follicle cells.
Platelet-Rich Plasma (PRP) therapy involves injecting a concentration of a patient’s own growth factors into the scalp. This treatment aims to rejuvenate dermal papilla cells by stimulating their proliferation and promoting follicle vascularization. By supplying growth factors, PRP therapy can counteract the signals that lead to follicle shrinkage and encourage a healthier growth phase.
Low-Level Laser Therapy (LLLT) is an approved treatment for androgenetic alopecia that uses specific wavelengths of light to stimulate cellular activity in the follicle. The proposed mechanism involves energizing dermal papilla cells and promoting the reentry of resting follicles into the growth phase. Enhancing the metabolic function of these cells can increase the anagen phase’s duration and prevent premature follicle regression.
Future of Dermal Papilla Research
Future hair loss treatments focus on advanced manipulations of the dermal papilla, with a primary research area being dermal papilla cell (DPC) culture and implantation. This experimental approach, sometimes called “hair cloning,” involves isolating DPCs from a person’s healthy hair follicles. These cells are then multiplied in a laboratory to generate a large population.
The goal of this research is to inject these cultured DPCs back into the scalp. The hypothesis is that these implanted cells can induce the formation of new hair follicles or rejuvenate existing miniaturized ones. Animal studies have shown that implanting cultured dermal cells can generate new, cycling hair follicles.
Translating this success to humans has proven challenging, and this therapy remains in the clinical trial phase. A primary challenge is maintaining the hair-inducing properties of DPCs during culture, as the cells tend to lose their function when grown in a 2D lab environment. Researchers are now experimenting with 3D spheroid cultures, which better mimic the natural microenvironment of the dermal papilla, to preserve their regenerative capacity.