Platelet Rich Plasma (PRP)
PRP has attracted attention because it contains a variety of growth factors, and is widely used in maxillofacial surgery, orthopedics, plastic surgery, ophthalmology and other fields. In 2006, Uebel et al. first tried to pretreat the follicular units to be transplanted with PRP and observed that compared with the scalp control area, the PRP-treated hair transplant area survived 18.7 follicular units/cm2, while the control group survived 16.4 follicular units. /cm2, the density increased by 15.1%. Therefore, it is speculated that the growth factors released by platelets may act on the stem cells of the hair follicle bulge, stimulate the differentiation of stem cells and promote the formation of new blood vessels.
In 2011, Takikawa et al. applied normal saline, PRP, heparin-protamine microparticles combined with PRP (PRP&D/P MPs) to subcutaneous injection of AGA patients to set up controls. The results showed that the cross-sectional area of the hair in the PRP group and the PRP&D/P MPs group was significantly increased, the collagen fibers and fibroblasts in the hair follicles were proliferated under the microscope, and the blood vessels around the hair follicles were proliferated.
PRP is rich in platelet-derived growth factors. These essential proteins regulate cell migration, attachment, proliferation, and differentiation, promote the accumulation of extracellular matrix, and many growth factors actively promote hair growth: growth factors in PRP interact with hair follicles. The combination of bulge stem cells induces the proliferation of hair follicles, generates follicular units, and promotes hair regeneration. In addition, it can activate the downstream cascade reaction and promote angiogenesis.
Current Status of PRP in the Treatment of AGA
There is still no consensus on the preparation method and platelet enrichment factor of PRP; the treatment regimens vary in the number of treatments, interval time, retreatment time, injection method, and whether combined drugs are used.
Mapar et al. included 17 male patients with stage IV to VI (Hamilton-Norwood staging method), and the results showed no difference between PRP and placebo injections, but the study only carried out 2 injections, and the number of treatments was too small. The results are open to question. ;
Gkini et al found that patients with lower stage showed higher responsiveness to PRP treatment; this view was confirmed by Qu et al, which included 51 male and 42 female patients with stage II-V in men and I in women ~ Stage III (staging is Hamilton-Norwood and Ludwig staging method), the results show that PRP treatment has statistically significant differences in patients with different stages of men and women, but the efficacy of low stage and higher stage is better, so the researchers recommend II , Stage III male patients and stage I female patients were treated with PRP.
Effective Enrichment Factor
The differences in the preparation methods of PRP in each study led to different enrichment folds of PRP in each study, most of which were concentrated between 2 and 6 times. Platelet degranulation releases a large number of growth factors, regulates cell migration, attachment, proliferation and differentiation, stimulates hair follicle cell proliferation, tissue vascularization, and promotes the accumulation of extracellular matrix. At the same time, the mechanism of microneedling and low-energy laser therapy is considered to be a Produces controlled tissue damage and stimulates the natural platelet degranulation process, which determines the product quality of PRP depends on its biological activity. Therefore, it is crucial to explore the effective concentration of PRP. Some studies believe that PRP with an enrichment fold of 1-3 times is more effective than a higher enrichment fold, but Ayatollahi et al. used PRP with an enrichment concentration of 1.6 times for treatment, and the results showed that the treatment of AGA patients was ineffective, and believed that PRP The effective concentration should be 4~7 times.
Number of Treatments, Interval Time and Retreatment Time
The studies of Mapar et al. and Puig et al. both obtained negative results. The number of PRP treatments in these two study protocols was 1 and 2 times, respectively, which were lower than other studies (mostly 3-6 times). Picard et al. found that the efficacy of PRP reached its peak after 3 to 5 treatments, so they believed that more than 3 treatments might be necessary to improve the symptoms of hair loss.
The Gupta and Carviel analysis found that most of the existing studies had treatment intervals of 1 month, and due to the limited number of studies, the results of treatment with monthly PRP injections were not compared with other injection frequencies, such as weekly PRP injections.
A study by Hausauer and Jones  showed that subjects who received monthly injections had a greater improvement in hair count compared to the frequency of injections every 3 months (P<0.001); Schiavone et al.  concluded that, Treatment should be repeated 10 to 12 months after the end of the course of treatment; Gentile et al. followed up for 2 years, the longest follow-up time among all studies, and found that some patients relapsed at 12 months (4/20 cases), and in 16 patients Symptoms are more pronounced in months.
In Sclafani’s follow-up, it was found that the efficacy of the patients decreased significantly 4 months after the end of the course of treatment. Picard et al. referred to the results and gave the corresponding treatment advice: after the conventional interval of 3 treatments of 1 month, the treatment should be performed every 3 times. Monthly intensive treatment. However, Sclafani did not explain the platelet enrichment ratio of the preparations used in the treatment process. In this study, 8-9 ml of platelet-rich fibrin matrix preparations were prepared from 18 ml of peripheral blood (the extracted PRP was added to a CaCl2 vacuum tube, and the fibrin glue was placed in a fibrin glue. injection before formation), we believe that the enrichment fold of platelets in this preparation may be far from sufficient, and more evidence is needed to support it.
Most of the injection methods are intradermal injection and subcutaneous injection. The researchers discussed the effect of administration method on the curative effect. Gupta and Carviel recommended subcutaneous injection. Some researchers use intradermal injection. Intradermal injection can delay the entry of PRP into the blood, reduce the metabolic rate, prolong the time of local action, and maximize the stimulation of the dermis to promote hair growth. and depth are not the same. We recommend that the Nappage injection technique should be strictly used when performing intradermal injections to exclude the influence of injection differences, and we recommend that patients shave their hair short to observe the direction of the hair, and adjust the needle insertion angle appropriately according to its growth direction so that the needle tip can reach around the hair follicle , thereby increasing the local PRP concentration in the hair follicle. These suggestions on injection methods are for reference only, as there are no studies that directly compare the advantages and disadvantages of various injection methods.
Jha et al. used PRP combined with microneedling and 5% minoxidil combined therapy to show good efficacy in both objective evidence and patient self-evaluation. We still face challenges in standardizing treatment regimens for PRP. Although most studies use qualitative and quantitative methods to assess symptom improvement after treatment, such as terminal hair count, vellus hair count, hair count, density, thickness, etc., the methods of assessment vary widely; in addition, the preparation of PRP There is no uniform standard in terms of method, adding activator, centrifugation time and speed, platelet concentration, etc.; treatment regimens vary in the number of treatments, interval time, retreatment time, injection method, and whether to combine medication; the selection of samples in the study is not Stratification by age, gender, and degree of alopecia further blurred the evaluation of PRP treatment effects. In the future, more large-sample self-controlled studies are still needed to clarify various treatment parameters, and further stratified analysis of factors such as patient age, gender, and degree of hair loss can be gradually improved.
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Post time: Aug-02-2022