Kinetics of blood flow after topical application of benzyl nicotinate on different anatomic sites

Cutaneous characteristics, e.g., thickness of the SC and density of follicles, affect the penetration of topically applied substances. In the present study, the penetration of benzyl nicotinate, causing a vasodilation, was studied on three anatomic sites (forearm, forehead and calf) differing in their skin characteristics. Therefore, the blood flow of the superficial dermal plexus and that of the larger capillaries in the deeper skin layers was simultaneously measured using a laser Doppler flowmeter. In addition, the cutaneous temperature and redness were determined as a function of time. These four biological reactions were measured in turn on a skin area treated with a gel containing benzyl nicotinate and on an untreated control area. The highest basal levels were observed on the forehead. Topical application of benzyl nicotinate resulted in an increase in each biological response. Compared to the other sites, the maximal values were reached earliest on the forehead, which also showed the fastest decrease. No significant differences were obtained comparing the kinetic data of the calf with that of the forearm. The results indicate an additional contribution by the numerous vellus hair follicles of the forehead to the penetration and exposure of the drug.     

Follicular penetration and targeting

In the past, intercellular penetration was assumed to be the most important penetration pathway of topically applied substances. First hints that follicular penetration needs to be taken into consideration were confirmed by recent investigations, presented during the workshop "Follicular Penetration and Targeting" at the 4th Intercontinental Meeting of Hair Research Societies", in Berlin 2004. Hair follicles represent an efficient reservoir for the penetration of topically applied substances with subsequent targeting of distinct cell populations, e.g., nestin-expressing follicular bulge cells. The volume of this reservoir can be determined by differential stripping technology. The follicular penetration processes are significantly influenced by the state of the follicular infundibulum; recent experimental investigations could demonstrate that it is essential to distinguish between open and closed hair follicles. Topically applied substances can only penetrate into open hair follicle. Knowledge of follicular penetration is of high clinical relevance for functional targeting of distinct follicular regions. Human hair follicles show a hair-cycle-dependent variation of the dense neuronal and vascular network. Moreover, during hair follicle cycling with initiation of anagen, newly formed vessels occur. Thus, the potential of nestin-expressing hair follicle stem cells to form neurons and blood vessels was investigated.     

Human hair follicle: reservoir function and selective targeting

Penetration of topically applied compounds may occur via the stratum corneum, skin appendages and hair follicles. The follicular infundibulum increases the surface area, disrupts the epidermal barrier towards the lower parts of the follicle, and serves as a reservoir. Topical delivery of active compounds to specific targets within the skin, especially to distinct hair follicle compartments or cell populations, may help to treat local inflammatory reactions selectively, with reduced systemic side-effects. Various in vitro and in vivo methods exist for studying the hair follicle structure and follicular penetration pathways. These include cyanoacrylate skin surface stripping, confocal microscopy and cyanoacrylate scalp follicle biopsy. The complex anatomical structure as well as the cyclical activity of the hair follicle must be taken into consideration when designing delivery systems. In addition, delivery into and retention inside the infundibular reservoir are controlled by, for example, molecule or particle size, their polarity and the type of preparation. Preferred penetration depth and storage time must also be considered. Particles with release mechanisms should be preferred; however, the release of drugs from nanoparticles still requires further investigations.     

Histochemical applications of skin surface biopsy

SUMMARY.— The method of skin surface biopsy in which a cyanoacrylate adhesive is used to remove a coherent strip of stratum corneum, has been used to investigate aspects of epidermal function. The Sudan dyes were employed to demonstrate sebum in the hair follicle openings. Although increased quantities of Sudanophilic material were detected with increasing time intervals before sampling, it proved impractical to measure sebum secretion quantitatively by this method. Hydrolase activity in and around hair follicle orifices of the back, forehead and forearm were demonstrated, using enzyme histochemical methods for non-specific esterase, acid phosphatase, leucine aminopeptidase and β-glucuronidase activities. Specimens from the forehead and back were found to have stronger activities than those from the forearm. Apart from the vicinity of the follicular openings, non-specific esterase activity was not normally found in the superficial stratum corneum, although scattered areas of activity were present in the deeper parts of the horny layer. Strong, non-specific esterase activity was detected in skin surface biopsies from lesions of pityriasis lichenoides and, to a lesser extent, those of psoriasis. Mitochondrial enzyme activities were retained in parakeratotic scale from patients with psoriasis, pityriasis rubra pilaris and areas made parakeratotic after repeated removal of the stratum corneum, although not from the lesions of pityriasis lichenoides. The method also proved suitable for the demonstration of melanin granules, blood pigment and sweat gland activity.     

Investigation of follicular penetration of topically applied substances

The influence of specific follicle properties, sebum production and hair growth on the follicular penetration of topically applied substances was investigated. The behavior of follicles identified in selected skin areas of volunteers was analyzed by various tape stripping and staining methods in combination with laser scanning microscopy. Furthermore hair growth in the selected skin areas was determined. A correlation between sebum production, hair growth activity and follicular penetration was observed.     

毛囊混合细胞在胶原/壳聚糖多孔支架上重建毛囊样结构

目的探讨利用毛囊混合细胞植入胶原／壳聚糖多孔支架内体外重建毛囊的可行性。方法用滴加法或注射法将体外培养的C57BL／6J近交系乳鼠背部皮肤毛囊混合细胞以不同传代数、不同细胞密度接种至胶原／壳聚糖多孔支架，倒置显微镜下观察支架表面或浅层的细胞生长或毛囊形成情况。将支架经10％甲醛固定后行组织学观察（H-E染色）。另用共聚焦激光扫描显微镜观察支架内活细胞的生长以及毛囊样结构的形成。结果在一定传代次数和细胞密度下，在支架内可形成具有毛干的毛囊样结构。激光共聚焦扫描显微镜发现团块内细胞排列呈同心圆状，整个三维结构似一长颈花瓶，且该结构仅见于注射法接种细胞的支架内。结论毛囊混合细胞植入胶原／壳聚糖多孔支架内体外可形成具有毛干的毛囊样结构。     

Innovative liposomes as a transfollicular drug delivery system: penetration into porcine hair follicles

Liposomes had been widely used for drug delivery in the past. In this study, five different liposomes were used as a follicular delivery system in pig ear skin. The liposomes mainly differed in their sphere diameter, lipid composition, and surface charge. A novel class of liposomes being amphoteric in their charge behavior are compared to established anionic and cationic liposomes. Two different fluorescent dyes, hydrophilic carboxyfluoresceine or lipophilic curcumin, were enclosed in the liposomes and used as model drugs. The fluorescent dyes were also applied in a standard formulation for reference. The penetration depth of the dyes was measured by laser scanning microscopy in histological sections. One hour, 3, 5, and 7 days after application, biopsies were taken and the penetration depth into the hair follicle was measured in longitudinal sections. The liposomes showed a higher penetration depth compared to the standard formulation. The relative penetration depth of the dyes, applied in the standard formulation, averaged 30% of the full follicle length during the whole observation period, whereas the liposomal formulations penetrated considerably deeper into the hair follicles. Amphoteric and cationic liposomes reached an average relative penetration depth of approximately 70% of the full hair follicle length.     

Follicular targeting--a promising tool in selective dermatotherapy

The penetration of topically applied compounds varies considerably in the different regions of the human body. The presence of hair follicles significantly contributes to this effect by an increase in surface area and a disruption of the epidermal barrier towards the lower parts of the hair follicle. The human hair follicle, hereby, serves not only as a reservoir, but also as a major entry point for topically applied compounds. Topical delivery of active compounds to specific targets within the skin may help reduce side-effects caused by unspecific reactions, and may help develop new strategies in the prevention and treatment of skin diseases. Various drug carrier and drug delivery systems are currently being investigated. The aim of these investigational efforts is to direct topically applied compounds to the different types of hair follicles and, ideally, to specific compartments and cell populations within the hair follicles. Follicular targeting offers opportunities for new developments, not only in hair therapy and in the treatment of hair follicle associated diseases but also in gene therapy and immunotherapy.     

雄秃样纤维性秃发一例

【摘要】 报道1例雄秃样纤维性秃发（FAPD）及其临床病理、皮肤镜和TrichoScan特征,以提高对FAPD的认识。患者男,23岁,前额及头顶部进行性脱发10年,伴局部头发变细、软,偶有头皮瘙痒。皮肤科检查：前额至头顶部头发弥漫性稀疏,前额发际线后移,局部发质细软,脱发区可见部分毛囊角化性丘疹、毛囊周围红斑,未见明显鳞屑。TrichoScan检查：毛发密度明显降低,毳毛比例增加。皮肤镜检查：部分毛囊开口消失,融合性白点征。头皮组织病理检查：毛囊漏斗部、峡部淋巴细胞苔藓样浸润,毛囊周围同心层状纤维化,毛囊结构破坏,毛囊性微瘢痕形成,残留毛囊直径变异度明显增加,可见部分毳毛。诊断：FAPD。FAPD临床易误诊为雄激素性秃发,需及早诊断并治疗。     

Penetration of titanium dioxide microparticles in a sunscreen formulation into the horny layer and the follicular orifice.

Coated titanium dioxide (TiO2) microparticles are commonly used as UV filter substances in commercial sunscreen products. The penetration of these microparticles into the horny layer and the orifice of the hair follicle was investigated. The distribution of the microparticles in the horny layer was analyzed using the method of tape stripping in combination with spectroscopic measurements. Deeper layers of the stratum corneum were devoid of TiO(2) even after repetitive application of sunscreen preparation when analyzing interfollicular areas. Only in the areas of the pilosebaceous orifices could microparticles be identified. The penetration of TiO(2) was investigated in histological skin sections. A biopsy was taken from a skin area from which the horny layer had been removed by tape stripping. In isolated areas, a penetration of coated TiO2 into the open part of the follicle was observed. The amount of TiO2 found in a given follicle was less than 1% of the applied total amount of sunscreens. A penetration of microparticles into viable skin tissue could not be detected.     

中波紫外线诱导小鼠皮肤光损伤中miRNA141表达的研究

【摘要】 目的 探讨小室移植法重建小鼠毛囊,观察细胞成分对毛囊再生的影响。 方法 取0 ～ 2 d的C57BL/6乳鼠背部皮肤,胰酶消化后分离表真皮,再分离出毛囊上皮细胞。实验分表皮细胞混合毛囊胚芽组、真皮细胞组、表皮细胞混合毛囊胚芽 + 真皮细胞组、毛囊上皮细胞 + 真皮细胞组。用小室移植法接种于裸鼠背部,并于移植后1、2、4、8周观察变化,HE染色观察毛囊组织学形态。 结果 小鼠毛囊细胞移植1周时,背部小室开始脱落,伤口结痂;2周时除表皮细胞组外,另3组均长出了短小的毛发,镜下可见毛囊样结构;4周及8周时除表皮细胞组外,均长出了正常的毛发,表皮细胞与真皮细胞混合组及毛囊上皮细胞与真皮细胞混合组毛发生长情况良好,优于单独的真皮细胞组。 结论 毛囊细胞小室移植后可形成新的毛囊,上皮细胞及真皮细胞在毛囊重建中具有重要的作用。 【关键词】 毛囊; 毛囊重建; 鼠科     

Porcine ear skin: an in vitro model for human skin

BACKGROUND/PURPOSE: Porcine ear skin is used in studies of percutaneous penetration as a substitute for human skin. The structure of this tissue, including hair follicles, was studied qualitatively and quantitatively in comparison with human skin. METHODS: Sections of shock-frozen biopsies, biopsies embedded in paraffin and cyanoacrylate skin surface biopsies were investigated using microscopy. The thickness of the different skin layers and the follicular characteristics were determined. RESULTS: The thickness of the stratum corneum was 17-28 microm, whereas the viable epidermis was 60-85 microm thick. On 1 cm(2), 11-25 hairs were detected, showing a diameter of 58-97 microm and a maximal extension depth of 0.96-1.38 mm into the skin. The orifices of the porcine infundibula showed a diameter of approximately 200 microm. CONCLUSIONS: The results obtained are similar to those of human skin, indicating the suitability of this porcine tissue as a model for human skin.     

Single follicular unit transplantation reconstructs arrector pili muscle and nerve connections and restores functional hair follicle piloerection

The autologous transplantation of hair follicles that have been separated into single follicular units is an accepted treatment for androgenetic alopecia. Recent studies demonstrate that the multiple stem cell populations and surrounding cutaneous tissues coordinately regulate the hair follicle functions and skin homeostasis. Therefore, the critical issues for consideration regarding functional hair restoration therapy are reproduction the correct connectivity and cooperation with host cutaneous tissues, including the arrector pili muscle (APM) and nerve system. We report successful establishment of mouse single follicular transplantation model and autonomous restoration of transplanted hair follicle piloerection in mouse skin. Transplanted hair follicles were responsive to the neurotransmitter acetylcholine and formed proper connections with surrounding host tissues such as APM and nerve fibers, which in turn connect with not only the hair follicle bulge region but also the APM. These results demonstrate that the piloerection ability of transplanted hair follicles can be estimated quantitatively. This study makes a substantial contribution towards the development of transplantation therapy that will facilitate future functional regeneration therapy for skin and skin appendages.     

A comparative study of refatting kinetics on the scalp and forehead

A modified photometric technique has shown considerable differences between the refatting kinetics of the scalp and forehead. The refatting on the forehead occurs rapidly, probably due to the large follicular reservoir. The follicular reservoir of the scalp, which bears a large terminal hair, is much smaller and so the refatting time is longer. Thus, sebum excretion and sebum production rates probably correlate better on the scalp than on the forehead, and we suggest that the scalp may be a better site than the forehead for investigating sebaceous gland physiology.     

毛囊黑素生成及其调节

毛干中黑素成分[正常和(或)褐色素]是毛囊色素单位长期精确相互作用的结果,毛囊黑素生成涉及一系列过程:毛囊黑素的生成活性,黑素颗粒向皮质和髓质角质形成细胞的转运以及有色毛干的形成.在色素形成的不同阶段,受到许多酶、结构和调节蛋白、转运蛋白、受体及其配体所调节.毛囊黑素生成与毛囊周期的生长期紧密相联,毛囊上部的黑素细胞为表皮复色和下一轮生长期毛球的周期性形成提供一个储存库.     

Differences in hair follicle dermal papilla volume are due to extracellular matrix volume and cell number: implications for the control of hair follicle size and androgen responses

The size of a hair follicle is thought to be determined by the volume of its dermal papilla. The volume of the dermal papilla depends on the number of cells it contains and on the volume of the extracellular matrix. To establish which of these two variables is related to differences in hair follicle size we performed a stereologic study on 235 hair follicles from different sites, including male facial skin (beard), female facial skin, and scalp. In facial follicles there was a strong correlation between the area of the hair cortex and the volume of the dermal papilla. The area of the hair cortex also correlated with the number of cells in the dermal papilla and with the volume of dermal papilla per cell. In scalp hair follicles, where there was a smaller range of sizes, the correlations between these variables were weaker. In large male facial follicles the mean total dermal papilla volume was almost 40-fold higher than in vellus follicles from female facial skin. This difference was associated with a mean 17-fold greater number of cells in the dermal papilla and a 2.4-fold greater volume associated with each cell. Intermediate results were obtained in scalp follicles. In many regions of the skin hair follicles enlarge in response to androgens during adult life hair. Our results imply that the increase in the volume of the dermal papilla in these follicles is due to an increase in the number of cells, either through proliferation or through the migration of cells from the follicular dermal sheath, and to an increase in the amount of extracellular matrix per cell. As androgens are thought to act primarily on the dermal papilla, these changes may have a direct bearing on the mechanism of androgen-mediated alterations in hair follicle size.     

Pemphigus and the terminal hair follicle

The scalp is frequently involved in the autoimmune skin disease pemphigus. This study demonstrates the distribution of pemphigus antigen in the scalp terminal hair follicle; as well as being found in the epidermis, it is distributed throughout the whole hair follicle outer root sheath and in the dermal bulb matrix cells. The increase in volume of target antigen offered by the follicular epithelium could be a factor determining scalp involvement in pemphigus.     

Hair cycle-dependent changes in adrenergic skin innervation, and hair growth modulation by adrenergic drugs

Skin nerves may exert "trophic" functions during hair follicle development, growth, and/or cycling. Here, we demonstrate hair cycle-related plasticity in the sympathetic innervation of skin and hair follicle in C57BL/6 mice. Compared with telogen skin, the number of nerve fibers containing norepinephrine or immunoreactive for tyrosine hydroxylase increased during the early growth phase of the hair cycle (anagen) in dermis and subcutis. The number of these fibers declined again during late anagen. beta2-adrenoreceptor-positive keratinocytes were transiently detectable in the noncycling hair follicle epithelium, especially in the isthmus and bulge region, but only during early anagen. In early anagen skin organ culture, the beta2-adrenoreceptor agonist isoproterenol promoted hair cycle progression from anagen III to anagen IV. The observed hair cycle-dependent changes in adrenergic skin innervation on the one hand, and hair growth modulation by isoproterenol, accompanied by changes in beta2-adrenoreceptor expression of selected regions of the hair follicle epithelium on the other, further support the concept that bi-directional interactions between the hair follicle and its innervation play a part in hair growth control. This invites one to systematically explore the neuropharmacologic manipulation of follicular neuroepithelial interactions as a novel therapeutic strategy for managing hair growth disorders.     

Fibrosing alopecia in a pattern distribution: patterned lichen planopilaris or androgenetic alopecia with a lichenoid tissue reaction pattern?

BACKGROUND: Androgenetic alopecia is characterized by a defined area of progressive nonscarring alopecia. The clinical and histological findings in 15 women and 4 men with progressive scarring alopecia in a pattern distribution were studied. The results were evaluated and compared with clinicopathologic entities that feature scarring of the central scalp area, specifically, lichen planopilaris, pseudopelade, and follicular degeneration syndrome. OBSERVATIONS: Patients developed progressive fibrosing alopecia of the central scalp, without the multifocal areas of involvement typical of lichen planopilaris and pseudopelade. Perifollicular erythema, follicular keratosis, and loss of follicular orifices were limited to a patterned area of involvement. Biopsy specimens of early lesions demonstrated hair follicle miniaturization and a lichenoid inflammatory infiltrate targeting the upper follicle region. Advanced lesions showed perifollicular lamellar fibrosis and completely fibrosed follicular tracts indistinguishable from end-stage lichen planopilaris, pseudopelade, or follicular degeneration syndrome. CONCLUSIONS: Some patients with androgenetic alopecia might have additional clinical and histological features of inflammation and fibrosis limited to the area of androgenetic hair loss. In these patients, the histological findings of early lesions are identical to those seen in lichen planopilaris. The lichenoid tissue reaction leading to follicular destruction in these patients might be pathogenetically related to the events underlying androgenetic alopecia.