Yingtai: PRP in Hair Loss Treatment
Hair plays a significant role in personal appearance and self-perception. The history of treating hair loss dates back to 1500 BC. The ancient Egyptians first described a therapy for hair loss in the Ebers Papyrus, which involved a mixture of snake and crocodile fat, iron, and lead applied topically. In the 1850s, a mixture of cold Indian tea and fresh lemon juice was widely used in British colonies to treat hair loss. Since the mid-twentieth century, modern methods such as medication and surgical hair transplantation have become popular. Minoxidil, initially an antihypertensive drug, and finasteride, used for benign prostatic hyperplasia, are now the standard治疗方案 for hair loss. However, their efficacy varies and is related to the duration of use. Hair transplantation was first described in 1939 by Japanese dermatologist Dr. Shoji Okuda and later popularized in the United States by Dr. Norman Orentreich, becoming a surgical treatment option for hair loss. Today, hair loss treatment in the United States alone has become a $3.5 billion industry, expected to reach $5.5 billion within the next decade. Most hair loss treatments target patients with pattern hair loss. Male pattern hair loss (MPHL), also known as androgenetic alopecia (AGA), affects 85% of men. Androgens, particularly testosterone and dihydrotestosterone (DHT), cause follicular miniaturization in androgen-sensitive areas of the scalp, leading to the transformation of dense terminal hairs into sparse vellus hairs. The first areas affected are the frontal hairline and the top of the scalp. Female pattern hair loss (FPHL) affects about 40% of women. Due to the controversial role of androgens in female hair loss, FPHL is no longer classified as a form of AGA. The pattern of hair loss in women is different from that in men, with FPHL mainly presenting as diffuse hair loss, but the frontal hairline usually remains unchanged. Typically, Hamilton-Norwood system (for men) or Ludwig system (for women) is used to classify pattern hair loss, to assess the severity of hair loss and compare treatment effects. In addition to pattern hair loss, other forms of hair loss can also be treated. Alopecia areata (AA) is an autoimmune hair loss common in children, affecting any part of the body, presenting as patchy hair loss. The prevalence of AA is 0.1-0.2%, and the lifetime incidence is 1.7%, much lower than pattern hair loss. Telogen effluvium, tinea capitis, trichotillomania, and androgen-dependent female hair loss are relatively less common, and these forms of hair loss have different presentations and treatment methods. As our understanding of the types and causes of hair loss deepens, hair loss treatments are also continuously evolving.
In the mid-1920s, with the booming development of cell-based and regenerative medicine, PRP was first used for hair loss treatment. PRP, known for its anti-inflammatory properties in postoperative wound healing, is well-known to oral and maxillofacial surgeons, periodontists, and orthopedic doctors. PRP products contain a high concentration of platelets, which, when activated, release cellular regeneration factors to stimulate cell proliferation and increase collagen formation. Due to the advantages of PRP, such as being derived from the patient, minimally invasive treatment, short recovery time after treatment, and few side effects, it has become increasingly popular in the treatment of hair loss. In this chapter, we will explore the mechanism of action of PRP in hair loss, indications for PRP hair loss treatment, preparation and administration of PRP, and treatment effects, focusing on the efficacy of PRP in pattern hair loss. To understand the role of PRP in hair loss treatment, one must first understand the hair follicle life cycle. Simply put, hair follicle growth is cyclical: (1) Anagen phase, the stage of hair follicle regeneration and growth; (2) Catagen phase, the most physiologically active stage of hair follicles, where hair growth and production are at their highest; (3) Telogen phase, the stage of hair follicle degeneration and slowed growth; (4) Exogen phase, the stage where the hair follicle is dormant. Throughout life, the hair follicle will go through this cycle multiple times. In AGA, when the androgen-sensitive areas of the scalp are exposed to testosterone and DHT, the hair follicle life cycle changes. Androgens prevent hair follicle growth by prolonging the telogen phase and causing follicular miniaturization. The role of androgens in female pattern hair loss is unclear, but it also manifests as similar non-scarring follicular miniaturization. PRP is believed to extend the hair follicle life cycle and prevent follicular miniaturization. However, the exact mechanism of PRP in hair growth is not fully understood. It is known that platelet activation releases a series of growth factors, including Platelet-Derived Growth Factor (PDGF), Transforming Growth Factor-beta (TGF-β), Fibroblast Growth Factor (FGF), Epidermal Growth Factor (EGF), Vascular Endothelial Growth Factor (VEGF), Hepatocyte Growth Factor (HGF), and Insulin-like Growth Factor (IGF-1), which promote hair follicle growth and block apoptosis signals. Some growth factors have specific roles in the hair follicle life cycle. EGF and HGF accelerate the progression of the hair follicle life cycle to the anagen phase, while IGF-1 is necessary to maintain the anagen phase. In addition, these factors can directly affect dermal papilla cells in the scalp. The dermal papilla layer contains multipotent stem cells that can differentiate into hair follicles, and the growth factors released by PRP can promote cell transcription gene expression, leading to the proliferation and differentiation of dermal papilla stem cells.
PRP can also indirectly improve hair follicle health by promoting scalp angiogenesis, with VEGF playing an important role in this process. This conclusion has been confirmed by animal and human studies. A stable blood supply is crucial for the initiation of the hair follicle anagen phase and the development of new hair follicles, and poor vascularization can be observed in the scalp tissue of AGA patients. Therefore, PRP can directly lead to hair growth by increasing the survival and proliferation of stem cells in the dermal papilla and indirectly by promoting angiogenesis.
Patient Evaluation and Selection
Patient evaluation begins with a comprehensive medical history and clinical examination. Understanding the duration, severity, pattern, and related symptoms of hair loss is crucial for distinguishing different forms of hair loss. Questions to determine the type of hair loss include whether the hair is sparse or balding, whether it falls from the roots or breaks, whether it is pattern hair loss or alopecia areata. A history of metabolic, infectious, endocrine, and autoimmune diseases, as well as medication, psychosocial, nutritional, and family history, can provide additional information to differentiate different forms of hair loss. A comprehensive medical history also helps identify patients with contraindications for PRP, such as patients with platelet abnormalities or those who cannot have blood drawn due to local infection for PRP collection for hair loss treatment.
Clinical examination should include an assessment of the entire scalp and hair in other areas of the body. Special attention should be paid to the pattern and distribution of hair loss. In addition, the assessment of hair quality and density should cover multiple areas, including the frontal hairline, frontal area, temporal area, and top. A magnifying glass should be used to check for scarring to distinguish between scarring and non-scarring forms of hair loss. The pull test can assess the ease of hair loss and fragility. The quality and density of hair outside the scalp are also important. Patients can be asked and examined for changes in eyebrows, facial hair, or body hair. Hair loss or thinning outside the scalp indicates a possible systemic disease and should be further evaluated. The process and diagnosis of hair loss patterns are beyond the scope of this chapter. Before treatment, patients should be informed of possible complications and side effects. Since PRP is derived from the patient and the treatment is minimally invasive, side effects are rare. A few patients may experience headaches and erythema and edema at the injection site after the procedure.
Preparation and Administration
Currently, there is no standard PRP product for hair loss treatment. PRP products can be roughly divided into four categories based on the concentration of platelets, fibrin, and white blood cells: Pure PRP (P-PRP), Leukocyte-Rich PRP (L-PRP), Pure Platelet-Rich Fibrin (P-PRF), and Leukocyte-Rich Platelet-Rich Fibrin (L-PRF). P-PRP and L-PRP are the two most commonly used formulations in hair loss treatment. Some protocols use activators, such as thrombin and calcium chloride, to increase the concentration of growth factors. However, it is crucial to maintain platelet stability and reduce activation before injection to obtain the maximum benefit. To balance platelet activation and stability, anticoagulants such as heparin are often added to the formulation. Moreover, higher concentrations of platelets do not necessarily produce better results; beyond a certain concentration, angiogenesis may be impaired. One study reported an effective therapeutic concentration of 1.5×10^6 platelets/uL, which is about 2 to 6 times the baseline enrichment. To standardize the protocol and optimize treatment outcomes, further exploration of the impact of different formulations, activators, and platelet concentrations on hair loss treatment is needed. The administration technique for PRP varies among clinicians. PRP can be injected intradermally or subcutaneously. The dosage, area of administration, number of treatments, and frequency are usually determined by the physician based on the severity of hair loss. Most reports choose 1 to 6 treatments with intervals ranging from 1 week to 3 months. Improvements in hair density and quality are usually noticeable within 3 months after the completion of treatment. Patient treatment outcomes have been reported in numerous studies, showing the positive effects of PRP in hair loss, especially in pattern hair loss. Many studies have conducted non-invasive or minimally invasive sampling of PRP treatment areas and analyzed the results, finding that after PRP treatment, there is a significant improvement in hair density and diameter in patients with AGA. Although the number of PRP treatments varies among studies, most patients have achieved satisfactory results after multiple treatments over 3 months. Gkini et al. also found that patients with Hamilton-Norwood grades II-III showed more significant improvements in hair thickness with PRP treatment than those with grades V-VII. The treatment effect is better in areas with vellus hairs than in areas without hair. Therefore, patients with mild hair loss and more vellus hairs respond better to the treatment and are more suitable for PRP treatment. Conversely, two studies found no improvement in hair density and thickness after PRP treatment. Mapar et al. conducted a scalp area study on 19 male patients with AGA and found no difference between the scalp areas treated with PRP and those treated with saline placebo. It is worth noting that Mapar's treatment protocol included only 2 treatments, once a month, which is far less than most studies reporting positive results. Puig et al. conducted a large study on female patients with pattern hair loss treated with PRP and found no significant improvement in hair count or hair quality index. These studies emphasize the need for standardized clinical trials to optimize patient selection and treatment protocols.
Although the efficacy of PRP in hair loss treatment remains controversial, patient satisfaction with the treatment is high. Many studies have assessed patient-centered indicators, including self-perceived hair quality and density, hair loss rate, and overall satisfaction with the treatment. Between 75% and 90% of patients self-assessed that their hair loss has been completely improved, and about 65% of patients believe that the quantity, quality, and appearance of their hair have improved. The overall patient satisfaction is greater than 7/10. Quality of life (QOL) has become an important indicator to consider whether a medical procedure is recommended, especially when assessing cosmetic surgery. The high satisfaction of patients has encouraged the rapid development of PRP in the field of hair loss treatment. PRP is often used to compare with other forms of hair loss treatment. Verma et al. followed up with 30 patients for 6 months to compare the efficacy of PRP with minoxidil. The study found that PRP performed better than minoxidil in quantitative indicators (such as the pull test) and patient-centered self-assessment and overall satisfaction. Minoxidil is a topical medication for hair loss that needs to be applied twice daily to the balding area. Patient compliance with this treatment regimen varies greatly. In addition, there are many adverse reactions to using minoxidil, the most common being scalp irritation and hypertrichosis, with occasional headaches and dizziness. Finasteride is an oral medication used to treat AGA and also has many side effects, including loss of libido and sexual dysfunction. In contrast, PRP has fewer side effects and higher patient compliance due to fewer treatment sessions. Moreover, when PRP is used in combination with hair transplantation, especially follicular unit extraction (FUE), the efficacy is also enhanced. A scalp area study and a randomized controlled trial both found that patients who received PRP combined with FUE had higher hair graft density after surgery than those who used FUE alone, proving the feasibility of PRP as an adjuvant treatment for hair transplantation.
In summary, PRP is a new biotechnology derived from the patient and has the advantages of fewer side effects and lower cost compared to hair transplantation, and it has become widely popular as an injection method in the field of hair loss treatment. Unlike minoxidil and finasteride, PRP does not need to be used for life. Unlike hair transplantation, PRP does not depend on the patient's existing donor hair volume and is less likely to form scars. However, the selection of patient indications, the preparation of PRP, and the details of injection operations have not been well studied, and there are no guidelines for regulation.
Currently, most of the understanding of PRP's mechanism of action comes from its widespread application in wound healing, and the application of PRP as a treatment for hair loss is still controversial. Most studies focus on male pattern hair loss, and few studies pay attention to female hair loss. The application of PRP in other forms of hair loss has not been studied. Although early studies have limitations, such as being based on a small number of patients, different treatment protocols and assessment forms in different studies, and a few studies also found no significant improvement in hair loss after PRP treatment, more studies have recognized the positive efficacy of PRP in hair loss treatment, and generally believe that the application of PRP in hair repair is beneficial. Finally, PRP as a treatment for hair loss is rapidly becoming popular. Patients are increasingly pursuing fast and convenient cosmetic methods. PRP shows great advantages. However, to standardize and further study the efficacy of PRP hair repair, larger-scale studies are needed.
