Hair follicles are skin appendages with a complex structure and periodical self-renewal ability. The hair follicle cycle includes the anagen phase, catagen phase and telogen phase, and its orderly renewal is important to maintain hair growth. It is currently believed that Wnt, bone morphogenetic protein, and Notch signaling pathways are involved in regulating the hair follicle cycle. As research progresses, various regulatory mechanisms based on these signaling pathways have been gradually revealed, such as growth factors, non-coding RNAs, immune responses, etc. This review elaborates on the above molecular mechanisms and regulatory modalities, aiming to promote better understandingn of regulatory mechanisms underlying the hair follicle cycle and provide a theoretical reference for expanding treatment options for hair loss.

Objective:To investigate the role of umbilical cord mesenchymal stem cell (MSC) -derived nanovesicles in hair regeneration.Methods:(1) Nanovesicles were prepared by continuously extruding umbilical cord MSCs through polycarbonate membranes, and were identified using transmission electron microscopy and nanoparticle tracking analysis. (2) Six C57BL/6 female mice with full-thickness skin wounds were randomly divided into a nanovesicle group (subcutaneously injected with nanovesicles once at the wound margin) and a control group (subcutaneously injected with an equal volume of phosphate-buffered saline [PBS] at the wound margin) ; skin samples were collected on day 16 for hematoxylin-eosin (HE) staining to assess wound healing and hair follicle regeneration. (3) Human hair follicle dermal papilla cells (DPCs) were isolated using a two-step enzyme method; the uptake of PKH26-pre-labeled nanovesicles by DPCs was observed by fluorescence microscopy; the proliferative activity of DPCs co-cultured with nanovesicles was evaluated using cell counting kit-8 (CCK8) and 5-ethynyl-2'-deoxyuridine (EdU) assays. (4) Six healthy C57BL/6 female mice were randomly divided into two groups after anesthesia, and subcutaneously injected with either fluorescent dye DIR-pre-labeled nanovesicles or PBS; an in vivo imaging system was used to observe the uptake and metabolism of nanovesicles in the mouse skin. (5) Twenty-four C57BL/6 female mice with depilated backs were randomly divided into a nanovesicle group (subcutaneously injected with nanovesicles on days 0, 8, and 15) and a control group (subcutaneously injected with an equal volume of PBS at the same time points) ; skin samples were collected on days 4, 18, and 21 for HE staining to analyze differences in hair follicle cycling; transcriptome sequencing was performed on skin samples collected on day 4. Statistical analyses were conducted using the t test. Results:(1) Transmission electron microscopy showed that nanovesicles exhibited a spherical membranous structure with diameters of 141.3 ± 60.0 nm. (2) In 6 C57BL/6 female mice with full-thickness skin wounds, the wound area on day 12 was significantly smaller in the nanovesicle group (1.27 ± 0.50 mm 2) than in the control group (4.13 ± 1.03 mm 2, t = 4.34, P = 0.012). (3) Fluorescence microscopy revealed that nanovesicles were taken up by DPCs within 20 hours; the absorbance of DPCs was significantly higher in the nanovesicle group than in the control group ( t = 20.23, P < 0.001), and the percentage of EdU-positive cells was also significantly higher in the nanovesicle group (49.62% ± 6.45%) than in the control group (37.58% ± 3.42%, t = 3.69, P = 0.006). (4) In vivo imaging of the 6 C57BL/6 female mice showed strong fluorescence in the back of mice in the nanovesicle group on day 0, which markedly decreased by day 8, while no fluorescence was observed in the control group throughout the experiment. (5) Hair follicle cycle experiments on the 24 C57BL/6 female mice with depilated backs showed that the hair follicle length on day 4 after depilation was significantly longer in the nanovesicle group (368.00 ± 63.17 μm) than in the control group (266.90 ± 34.41 μm, t = 9.87, P < 0.001), and the hair bulb diameter was also significantly longer in the nanovesicle group (54.83 ± 10.32 μm) than in the control group (39.12 ± 7.54 μm, t = 16.02, P < 0.001) ; on day 18, the nanovesicle group showed a significantly higher hair follicle density (19.12 ± 0.90) compared with the control group (11.07 ± 1.51, t = 7.92, P = 0.001) ; on day 21, 46.13% ± 8.64% of hair follicles in the nanovesicle group remained in the anagen phase Ⅵ to the catagen phase Ⅱ, and 46.24% ± 3.29% were in the catagen phases Ⅲ to Ⅳ, while 78.89% ± 18.36% of hair follicles in the control group were in the telogen phases Ⅶ to Ⅷ. Transcriptome sequencing showed that differentially expressed genes in the nanovesicle group were significantly positively enriched in the keratinization process (NES = 2.23, P < 0.001) . Conclusion:Umbilical cord MSC-derived nanovesicles could promote the proliferation of DPCs, advance the entry of hair follicles into the anagen phase, delay their entry into the catagen phase, and induce hair regeneration.

Hair follicles are skin appendages with a complex structure and periodical self-renewal ability. The hair follicle cycle includes the anagen phase, catagen phase and telogen phase, and its orderly renewal is important to maintain hair growth. It is currently believed that Wnt, bone morphogenetic protein, and Notch signaling pathways are involved in regulating the hair follicle cycle. As research progresses, various regulatory mechanisms based on these signaling pathways have been gradually revealed, such as growth factors, non-coding RNAs, immune responses, etc. This review elaborates on the above molecular mechanisms and regulatory modalities, aiming to promote better understandingn of regulatory mechanisms underlying the hair follicle cycle and provide a theoretical reference for expanding treatment options for hair loss.

Objective:To investigate the role of umbilical cord mesenchymal stem cell (MSC) -derived nanovesicles in hair regeneration.Methods:(1) Nanovesicles were prepared by continuously extruding umbilical cord MSCs through polycarbonate membranes, and were identified using transmission electron microscopy and nanoparticle tracking analysis. (2) Six C57BL/6 female mice with full-thickness skin wounds were randomly divided into a nanovesicle group (subcutaneously injected with nanovesicles once at the wound margin) and a control group (subcutaneously injected with an equal volume of phosphate-buffered saline [PBS] at the wound margin) ; skin samples were collected on day 16 for hematoxylin-eosin (HE) staining to assess wound healing and hair follicle regeneration. (3) Human hair follicle dermal papilla cells (DPCs) were isolated using a two-step enzyme method; the uptake of PKH26-pre-labeled nanovesicles by DPCs was observed by fluorescence microscopy; the proliferative activity of DPCs co-cultured with nanovesicles was evaluated using cell counting kit-8 (CCK8) and 5-ethynyl-2'-deoxyuridine (EdU) assays. (4) Six healthy C57BL/6 female mice were randomly divided into two groups after anesthesia, and subcutaneously injected with either fluorescent dye DIR-pre-labeled nanovesicles or PBS; an in vivo imaging system was used to observe the uptake and metabolism of nanovesicles in the mouse skin. (5) Twenty-four C57BL/6 female mice with depilated backs were randomly divided into a nanovesicle group (subcutaneously injected with nanovesicles on days 0, 8, and 15) and a control group (subcutaneously injected with an equal volume of PBS at the same time points) ; skin samples were collected on days 4, 18, and 21 for HE staining to analyze differences in hair follicle cycling; transcriptome sequencing was performed on skin samples collected on day 4. Statistical analyses were conducted using the t test. Results:(1) Transmission electron microscopy showed that nanovesicles exhibited a spherical membranous structure with diameters of 141.3 ± 60.0 nm. (2) In 6 C57BL/6 female mice with full-thickness skin wounds, the wound area on day 12 was significantly smaller in the nanovesicle group (1.27 ± 0.50 mm 2) than in the control group (4.13 ± 1.03 mm 2, t = 4.34, P = 0.012). (3) Fluorescence microscopy revealed that nanovesicles were taken up by DPCs within 20 hours; the absorbance of DPCs was significantly higher in the nanovesicle group than in the control group ( t = 20.23, P < 0.001), and the percentage of EdU-positive cells was also significantly higher in the nanovesicle group (49.62% ± 6.45%) than in the control group (37.58% ± 3.42%, t = 3.69, P = 0.006). (4) In vivo imaging of the 6 C57BL/6 female mice showed strong fluorescence in the back of mice in the nanovesicle group on day 0, which markedly decreased by day 8, while no fluorescence was observed in the control group throughout the experiment. (5) Hair follicle cycle experiments on the 24 C57BL/6 female mice with depilated backs showed that the hair follicle length on day 4 after depilation was significantly longer in the nanovesicle group (368.00 ± 63.17 μm) than in the control group (266.90 ± 34.41 μm, t = 9.87, P < 0.001), and the hair bulb diameter was also significantly longer in the nanovesicle group (54.83 ± 10.32 μm) than in the control group (39.12 ± 7.54 μm, t = 16.02, P < 0.001) ; on day 18, the nanovesicle group showed a significantly higher hair follicle density (19.12 ± 0.90) compared with the control group (11.07 ± 1.51, t = 7.92, P = 0.001) ; on day 21, 46.13% ± 8.64% of hair follicles in the nanovesicle group remained in the anagen phase Ⅵ to the catagen phase Ⅱ, and 46.24% ± 3.29% were in the catagen phases Ⅲ to Ⅳ, while 78.89% ± 18.36% of hair follicles in the control group were in the telogen phases Ⅶ to Ⅷ. Transcriptome sequencing showed that differentially expressed genes in the nanovesicle group were significantly positively enriched in the keratinization process (NES = 2.23, P < 0.001) . Conclusion:Umbilical cord MSC-derived nanovesicles could promote the proliferation of DPCs, advance the entry of hair follicles into the anagen phase, delay their entry into the catagen phase, and induce hair regeneration.

Objective:To explore the applicability of the distance between facial marks classification in evaluating the severity of androgenic alopecia in men.Methods:From June to December 2019, the male Chinese with diagnosis of androgenic alopecia were evaluated in the specific clinic of alopecia of Hangzhou First People’s Hospital according to the distance between facial marks and BASP(basic and specific) classification. The classification based on the distance between facial marks measures the distance from the facial marks of the anterior hairline to the horizontal line of the eyebrow and the longest radius of hair loss in the hair rotation center, the hair recession of the patient’s forehead (F), temporal (M) and vertex (V) parts. The hair loss in each region is rated as 0-3 grade from light to heavy, and the final hair loss grading is expressed as FnMnVn, such as F1M2V0. The highest grade of hair loss in F, M and V is the overall grade of hair loss. SPSS 25.0 software was used to statistically analyze the general data of patients, and Kappa test was used to evaluate the consistency between the results of the distance classification and BASP classification. The repeatability of the distance classification was tested by the repetition rate of three hair loss specialists. When two or more specialists gave the same evaluation among the three hair loss specialists, the result was regarded as the standard result. The ease of use of the distance between facial marks classification was tested by the consistency rate between the grading results of two temporary trained general doctors and the standard results.Results:A total of 150 male patients, aged (32.8±7.9) years (19-58 years), were included, of which 99 patients were 24-35 years old, accounting for 66.00%. It can be observed that the onset age was earlier. As assessed in this classification, the patients who participated in the study were graded as mild in 65 cases(43.33%), severe in 58 cases(38.67%), and moderate, which was consistency with the results obtained by BASP classification ( κ=0.573, P<0.001). Three experienced alopecia specialists evaluated 150 patients through the distance between facial marks. The results showed that the repetition rates of frontal, temporal and parietal classification results were 98.00%(147/150), 97.33%(146/150) and 96.00%(144/150), respectively. The repetition rate of the final alopecia classification was 92.00%(138/150), and the repetition rate of the overall alopecia classification was 98.00%(147/150). The consistency rate between the overall alopecia classification results of two temporary trained general doctors and the standard results was 95.92%(141/147) and 96.60%(142/147), respectively, and the consistency rate of the other results was higher than 90.00% except for one general doctor who was 89.86%(124/138) in the final classification. Conclusion:The distance between facial marks classification is a comparatively accurate and easy-to-learn grading method designed for Chinese male androgenic hair loss patients based on objective measurement data.

Objective:To explore the applicability of the distance between facial marks classification in evaluating the severity of androgenic alopecia in men.Methods:From June to December 2019, the male Chinese with diagnosis of androgenic alopecia were evaluated in the specific clinic of alopecia of Hangzhou First People’s Hospital according to the distance between facial marks and BASP(basic and specific) classification. The classification based on the distance between facial marks measures the distance from the facial marks of the anterior hairline to the horizontal line of the eyebrow and the longest radius of hair loss in the hair rotation center, the hair recession of the patient’s forehead (F), temporal (M) and vertex (V) parts. The hair loss in each region is rated as 0-3 grade from light to heavy, and the final hair loss grading is expressed as FnMnVn, such as F1M2V0. The highest grade of hair loss in F, M and V is the overall grade of hair loss. SPSS 25.0 software was used to statistically analyze the general data of patients, and Kappa test was used to evaluate the consistency between the results of the distance classification and BASP classification. The repeatability of the distance classification was tested by the repetition rate of three hair loss specialists. When two or more specialists gave the same evaluation among the three hair loss specialists, the result was regarded as the standard result. The ease of use of the distance between facial marks classification was tested by the consistency rate between the grading results of two temporary trained general doctors and the standard results.Results:A total of 150 male patients, aged (32.8±7.9) years (19-58 years), were included, of which 99 patients were 24-35 years old, accounting for 66.00%. It can be observed that the onset age was earlier. As assessed in this classification, the patients who participated in the study were graded as mild in 65 cases(43.33%), severe in 58 cases(38.67%), and moderate, which was consistency with the results obtained by BASP classification ( κ=0.573, P<0.001). Three experienced alopecia specialists evaluated 150 patients through the distance between facial marks. The results showed that the repetition rates of frontal, temporal and parietal classification results were 98.00%(147/150), 97.33%(146/150) and 96.00%(144/150), respectively. The repetition rate of the final alopecia classification was 92.00%(138/150), and the repetition rate of the overall alopecia classification was 98.00%(147/150). The consistency rate between the overall alopecia classification results of two temporary trained general doctors and the standard results was 95.92%(141/147) and 96.60%(142/147), respectively, and the consistency rate of the other results was higher than 90.00% except for one general doctor who was 89.86%(124/138) in the final classification. Conclusion:The distance between facial marks classification is a comparatively accurate and easy-to-learn grading method designed for Chinese male androgenic hair loss patients based on objective measurement data.

It is currently considered that alopecia areata is caused by the impairment of immune privilege in hair follicles. Stem cells have immunoregulatory functions, and can secrete a variety of cytokines to promote immune privilege in hair follicles. Stem cell therapy, especially umbilical cord- and adipose-derived stem cell therapy, has been applied to a variety of preclinical and clinical studies on alopecia, providing a new approach to refractory alopecia areata.

A case of ichthyosis follicularis,alopecia and photophobia syndrome caused by a novel mutation c.1165C＞T in the membrane-bound transcription factor protease site 2 (MBTPS2) gene was firstly reported.The proband presented with dry skin,congenital hairlessness,follicular keratotic papules,photophobia,epilepsy,and mental and motor retardation.Next-generation and Sanger sequencing analysis confirmed that the proband and his mother both had a c.1165C＞T (p.pro389Ser) mutation in exon 9 of the MBTPS2 gene.According to the clinical manifestations of the patient and genetic characteristics of the MBTPS2 gene mutation,the patient was diagnosed with ichthyosis follicularis,alopecia and photophobia syndrome.

A male patient, who was aged 3 months and 12 days, presented with well-circumscribed erythema and scales on the scrotum, perineum, buttocks and perianal region at 1 month after birth. The lesions gradually involved the perioral and axillary regions, flexor aspect of the elbow, popliteal fossa and neck. Shortness of breath, crying, dysphoria and vomiting occurred without fever and cough 3 days before hospitalization. Laboratory examinations at admission showed metabolic acidosis, hyperlactacidemia, hyperammonemia and organic aciduria. Second-generation sequencing and Sanger sequencing of the holocarboxylase synthetase gene revealed a known mutation c.1522C>T in exon 9 and a novel mutation c.1796_1814del in exon 11. According to a guideline from the American College of Medical Genetics and Genomics, this novel mutation was ranked as a pathogenic mutation. The patient was diagnosed as multiple carboxylase deficiency. His clinical symptoms were improved after oral biotin treatment, no neurological symptoms or signs were observed.

Alopecia areata (AA) is a kind of localized scalp hair loss of sudden onset,and patients with severe AA can progress to alopecia totalis (AT) and alopecia universalis (AU).At present,AA is considered as a kind of organ-specific autoimmune disease with a genetic background,and destruction of immune privileged structures of hair follicles is an important pathogenesis of AA.Currently,therapeutic methods for AA include oral or topical glucocorticoids,intramuscular or intralesional injection of glucocorticoids,topical minoxidil tincture,etc.,but some patients still show no response to the treatments.In recent years,various clinical trials have been conducted in abroad using JAK inhibitors for the treatment of AA.Researches have revealed that about half of patients with moderate to severe AA showed almost complete recovery after the treatment with oral JAK inhibitors.Topical ruxolitinib was also reported for the treatment of AA,but patients showed different response.Although some patients suffered from recurrence after drug withdrawal or infections and other adverse reactions during the treatment,JAK inhibitors can be an effective treatment option for moderate to severe AA.