The morphology of hair follicle afferent fibre collaterals in the spinal cord of the cat

1. The enzyme horseradish peroxidase (HRP) was injected into single axons that innervated hair follicle receptors to study the morphology of their collaterals in the dorsal horn of the cord. The axons were impaled near the dorsal root entrance zone in the lumbosacral spinal cord of anaesthetized cats and HRP injected by passing current through the intra-axonal micro-electrode. The morphology was revealed by subsequent histochemistry.2. Thirteen hair-follicle afferent fibres were stained including six that innervated tylotrichs (type T hair follicle afferent units) and one that innervated guard hairs (type G unit). The remaining six axons were not classified according to hair type, but, on the basis of their axonal conduction velocities, would have been either type G or T.3. Eleven axons could be traced back into the dorsal roots. Eight of these, upon entering the cord, turned and ran towards the brain. They did not divide into rostral and caudal branches. Three of the eleven did divide and gave rise to both rostral and caudal branches.4. Sixty-three collaterals were given off the thirteen stained axons. All well-filled collaterals had a strikingly similar morphology. They descended through laminae I-III of the dorsal horn into the deeper parts of lamina IV or into lamina V, before turning and ascending back into superficial lamina IV and lamina III where they branched profusely to give rise to their terminal arborizations. Terminal boutons, most commonly of the ;en passant' type, were numerous in lamina III, but were also seen in the dorsal part of lamina IV and in ventral lamina II. None were observed in dorsal lamina II or near the junction of the grey and white matter (lamina I) or in lamina V.5. The terminal arborizations of collaterals from a single hair follicle afferent fibre were in line with one another in the longitudinal axis of the cord. In the better-stained preparations the terminal arborizations of adjacent collaterals from a single axon formed a continuous longitudinal column through the dorsal horn. There was a gradual shift of the column of arborizations from lateral to medial as the more rostral collaterals were given off.6. The hair-follicle afferent fibre collaterals are now identified as the ;collaterales grosses et profondes de la substance de Rolando' of Ramón y Cajal (1909) which give rise to the ;flame-shaped arbors' of Scheibel & Scheibel (1968).7. The importance of the longitudinal organization of the terminal arborizations for an understanding of the topographical properties of dorsal horn neurones is discussed.     

Hair cycle induction by hair plucking in Mini rats

Jcl:WistarTGN(ARGHGEN)1Nts rat (Mini rat) is a transgenic rat in which the growth hormone (GH) expression is suppressed by the presence of an antisense transgene for the rat GH gene, and the hair cycle of male Mini rats enters a long-lasting telogen phase after 8 weeks old. In the present study, effects of hair plucking on the hair cycle in the dorsal skin of 11-week-old male Mini rats were examined up to 54 days after the hair plucking. As a result, hair plucking brought about an anagen phase, and hair cycle arrest in telogen phase occurred again. Male Mini rats, having follicles in anagen-inducible long-lasting telogen phase, will offer a powerful tool for investigating the molecular nature and organization of the so-called hair cycle clock.     

Functional characteristics of mechanoreceptors in sinus hair follicles of the cat

1. The discharge of impulses in afferent fibres dissected from the infraorbital and ulnar nerves of anaesthetized cats was recorded during controlled movements of the maxillary and carpal sinus hairs.2. Four main types of afferent units were identified. Two had slowly adapting responses characteristic of the epidermal type I, and dermal type II mechanoreceptors of the hairy skin. Two rapidly adapting responses to movement of the sinus hairs were found, one with a high velocity threshold and another with a low velocity threshold.3. The slowly adapting units showed a power relationship between the degree of displacement of the hair and the mean interspike interval of the response. Slowly adapting units also exhibited a power relationship between the velocity of displacement of a hair and the mean interspike interval of the response.4. The conduction velocities of all types of afferent units were measured and fell in the range of the Aalpha, fast myelinated fibres.5. Movements of the carpal sinus hairs yielded both types of slowly adapting response recorded in fibres of the ulnar nerve directly innervating the carpal sinus hair follicles, and rapidly adapting responses from Pacinian corpuscles, found in close association with, but external to, these follicles.6. On the basis of the findings in this study and the results of anatomical investigations of the receptor structures in the sinus hair follicle a correlation between the distinguishable afferent responses and the morphologically identifiable nerve endings has been proposed.     

Ultrastructure of hair follicle afferent fibre terminations in the spinal cord of the cat

Summary In acute electrophysiological experiments on anaesthetized cats, single identified hair follicle afferent fibres were injected with horseradish peroxidase (HRP). The HRP was injected from an intra-axonal microelectrode in the lumbosacral spinal cord. One to six hours after injection the animals were perfused and the tissue prepared for light and electron microscopy (EM). Axon collateral arborizations containing HRP reaction product were identified in thick sections under the light microscope and the same tissue then cut on the ultramicrotome for EM study. The terminal branches of the collaterals kept their myelin sheaths until they were 0.45–l.0 m in diameter, just before they formed synaptic boutons. Synaptic boutons (1.0–4.0 m in diameter) were usually of theen passant variety and made contact with dendrites. The contacts were asymmetrical (Type I) and contained round, clear synaptic vesicles of 35–60 nm diameter. Both the non-myelinated portion of the terminal axon and the synaptic boutons received axo-axonic contacts. These axo-axonic boutons contained clear (agranular) vesicles irregular in profile.MRC research student.     

Receptors and transporter for serotonin in Merkel cell-nerve endings in the rat sinus hair follicle. An immunohistochemical study

Serotonin (5-HT) has been a candidate for neurotransmitters in cutaneous type I mechanoreceptors (i.e., Merkel cell-nerve endings). Although recent electrophysiological studies have suggested the presence of the 5-HT2 and 3 receptors in the Merkel cell-nerve endings, the histological localization of these receptors are obscure. We thus immunohistochemically examined the presence of 5-HT1, 2, 3 receptors in Merkel cell-nerve endings in sinus hair follicles of the rat whisker pad. We also studied the immunohistochemical localization of the 5-HT transporter to confirm the site of 5-HT secretion. For this purpose, we used antibodies for the 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2C and 5-HT3 receptors, and for the 5-HT transporter, as well as antibodies for cytokeratin 20 (as a marker of Merkel cells) and neurofilament H (a marker of type I sensory nerve terminals). The immuno-stained sections were analyzed under a laser-scanning microscope. It was found that the sensory nerve terminals in the Merkel cell-nerve endings showed strong positive immunoreactions of 5-HT1A and 1B receptors but not 5-HT2A, 2C, and 3 receptors. Furthermore, both the Merkel cells and related axon terminals showed strong immunoreactions of the 5-HT transporter. These findings support the idea that 5-HT molecules are released from the Merkel cells during mechanical reception and indirectly regulate neural actions of sensory neurons via 5-HT1 receptors. The localization of the 5-HT transporter found in this study also suggests a possibility that axon terminals in the Merkel cell-nerve endings also release 5-HT.     

血管内皮生长因子在毛囊生物学中的研究现状

血管内皮生长因子(vascular endothelial growth factor,VEGF)又名血管通透性因子(vascular permeability factor,VPF),是重要的血管生成正性调节因子。作为毛乳头细胞的一种自分泌生长因子,其对毛囊的生长亦有重要作用。血管内皮生长因子不仅能促进毛囊的生长,还参与毛囊生长周期的调控。在内皮细胞中,血管内皮生长因子发挥作用主要是通过与其受体的结合,诱导受体二聚体化和自身磷酸化,从而激活胞内信号转导通路,但在毛囊细胞中是否如此,仍需进一步研究。     

毛囊真皮鞘细胞中过表达Noggin对皮肤及毛囊生长的作用

背景:Noggin蛋白是一个抑制BMP信号通路的重要分子,可以与BMP2/4结合形成复合物,从而阻断BMP信号,影响生物有机体的正常发育过程。研究认为真皮鞘细胞是一类能够长期自我更新的真皮干细胞,参与毛囊再生过程中真皮毛乳头和真皮鞘的形成。在毛囊发育过程中,真皮毛乳头中Noggin参与毛囊的起始,Noggin的缺失会导致毛囊数量的减少和毛囊生长缓慢,但人们对于Noggin蛋白在毛囊真皮鞘中的作用所知甚少。目的:研究Noggin蛋白在毛囊真皮鞘中的生物学功能。方法:利用真皮鞘特异的αSMA-Cre ERT2工具鼠在真皮鞘中特异过表达Noggin蛋白,分别在出生后8,9 d对实验组αSMA-CreER;pMES-Noggin小鼠和对照组αSMA-CreER小鼠注射4-羟基他莫昔芬,在出生后21,23,28 d获取皮肤组织,苏木精-伊红染色观察毛囊生长情况和皮下脂肪层厚度,免疫组化染色分析表型。结果与结论:通过苏木精-伊红染色结果发现毛囊生长并没有受到影响,但毛囊皮下脂肪组织生长发育受到严重影响,小鼠皮下脂肪层变薄。免疫组化结果说明BMP信号降低可能是导致毛囊脂肪层变薄的原因。这一发现拓展了人们对于真皮鞘细胞和Noggin蛋白的认识,也为人们更加准确理解毛囊再生和组织生长机制提供了重要依据。     

角质细胞无血清培养基促进大鼠毛囊干细胞的增殖

背景：以往研究培养毛囊干细胞多使用DMEM/F12+体积分数10%胎牛血清培养基,而进年来开发出的角质细胞无血清培养基也可应用于毛囊干细胞的培养。 目的：观察3种不同培养基对大鼠毛囊干细胞增殖情况及干细胞纯度的影响。 方法：取大鼠触须部皮肤组织,体式显微镜下分离出毛囊组织,中性蛋白酶Ⅱ与胰蛋白酶和乙二胺四乙酸混合液“两步酶法”消化。所得细胞悬液按细胞数平均分为3份,分别使用角质细胞无血清培养基、DMEM/F12+体积分数10%胎牛血清及角质细胞无血清培养基+体积分数10%胎牛血清共3种培养基培养,Ⅳ型胶原差速贴壁法筛选毛囊干细胞,进行传代培养。 结果与结论：培养毛囊干细胞传至第3代,锥虫蓝染色计数法检测结果显示,此3组间细胞活率差异无显著性意义(P > 0.05)。CCK8比色法检测细胞生长曲线显示,培养前2 d,此3组细胞生长均较缓慢;培养4 d,细胞生长进入对数生长期,3种培养基培养的细胞增殖活性：角质细胞无血清培养基+10%胎牛血清组>DMEM/F12+10%胎牛血清>角质细胞无血清培养基(P < 0.05)。流式细胞仪检测显示,角质细胞无血清培养基组CD34的表达高于角质细胞无血清培养基+10%胎牛血清组(P < 0.05)。DMEM/F12+10%胎牛血清组中CD34、β1-整合素(CD29)及CK15标记物的表达低于其他2组(P < 0.05)。结果表明,角质细胞无血清培养基较DMEM/F12+体积分数10%胎牛血清能培养出纯度更高的毛囊干细胞,并且在此培养基培养的基础上加入血清,能够促进毛囊干细胞的增殖。     

Lectin histochemistry of glycoconjugates in the feline hair follicle and hair

The distribution of glycoconjugate in the feline hair follicle and hair was studied by light and electron microscopic histochemical methods. The hair apparatus was found to contain considerable amounts of complex carbohydrates with different saccharide residues (alpha-D-mannose, beta-D-glucose, alpha-L-fucose, beta-N-acetyl-D-glucosamine). Variations of those were detected in the plasma membrane of the hair follicle cells during the course of their differentiation and keratinization, namely, alph-D-glucose, alpha-L-fucose and beta-N-acetyl-D-glucosamine in the suprabulbar and bulbar regions. The reaction level of sialic acid residues in the plasma membrane decreased in some cell layers during the course of differentiation. The results obtained from the present study indicated that interaction between saccharide residues of neutral carbohydrates and sialyl groups during the anagen phase might contribute to cell keratinization in hair follicles and hairs. It is discussed whether the existence of glycogen in outer root sheath cells might enable these cells to provide other hair apparatus cells with energy when necessary. Moreover, it became obvious from variations in sialyl residue distribution that cell differentiation processes terminate first of all in Huxley's and Henle's layers within the suprabulbar region of the hair follicle, as followed by the hair cortex.     

毛囊干细胞研究新进展

毛囊干细胞（hair follicle stem cell）定位于毛囊上部,由外根鞘形成的明显突起,即隆突（Bulge）区域,表现为未分化的原始细胞及标记滞留细胞,有多种明确的分子标记物（CD34／β1／K15／α6等）,并具有多向分化的潜能。下行迁移可分化为毛囊和毛干的各种上皮类群的细胞,形成新毛,促成毛囊周期的形成;而向上迁移则分化为皮脂腺及表皮细胞。近年来,     

Genetically null mice reveal a central role for epidermal growth factor receptor in the differentiation of the hair follicle and normal hair development.

Mice harboring a targeted disruption of the epidermal growth factor receptor (EGFR) allele exhibit a severely disorganized hair follicle phenotype, fuzzy coat, and systemic disease resulting in death before 3 weeks. This skin phenotype was reproduced in whole skin grafts and in grafts of EGFR null hair follicle buds onto nude mice, providing a model to evaluate the natural evolution of skin lacking the EGFR. Hair follicles in grafts of null skin did not progress from anagen to telogen and scanning electron micrografts revealed wavy, flattened hair fibers with cuticular abnormalities. Many of the EGFR null hair follicles in the grafted skin were consumed by an inflammatory reaction resulting in complete hair loss in 67% of the grafts by 10 weeks. Localization of follicular differentiation markers including keratin 6, transglutaminase, and the hair keratins mHa2 and hacl-1 revealed a pattern of premature differentiation within the null hair follicles. In intact EGFR null mice, proliferation in the interfollicular epidermis, but not hair follicles, was greatly decreased in the absence of EGFR. In contrast, grafting of EGFR null skin resulted in a hyperplastic response in the epidermis that did not resolve even after 10 weeks, although the wound-induced hyperplasia in EGFR wild-type grafts had resolved within 3 to 4 weeks. Thus, epithelial expression of the EGFR has complex functions in the skin. It is important in delaying follicular differentiation, may serve to protect the hair follicle from immunological reactions, and modifies both normal and wound-induced epidermal proliferation but seems dispensable for follicular proliferation.     

Controls of hair follicle cycling

Nearly 50 years ago, Chase published a review of hair cycling in which he detailed hair growth in the mouse and integrated hair biology with the biology of his day. In this review we have used Chase as our model and tried to put the adult hair follicle growth cycle in perspective. We have tried to sketch the adult hair follicle cycle, as we know it today and what needs to be known. Above all, we hope that this work will serve as an introduction to basic biologists who are looking for a defined biological system that illustrates many of the challenges of modern biology: cell differentiation, epithelial-mesenchymal interactions, stem cell biology, pattern formation, apoptosis, cell and organ growth cycles, and pigmentation. The most important theme in studying the cycling hair follicle is that the follicle is a regenerating system. By traversing the phases of the cycle (growth, regression, resting, shedding, then growth again), the follicle demonstrates the unusual ability to completely regenerate itself. The basis for this regeneration rests in the unique follicular epithelial and mesenchymal components and their interactions. Recently, some of the molecular signals making up these interactions have been defined. They involve gene families also found in other regenerating systems such as fibroblast growth factor, transforming growth factor-beta, Wnt pathway, Sonic hedgehog, neurotrophins, and homeobox. For the immediate future, our challenge is to define the molecular basis for hair follicle growth control, to regenerate a mature hair follicle in vitro from defined populations, and to offer real solutions to our patients' problems.     

A comparison of primary afferent and cortical neurone activity coding sinus hair movements in the cat

Summary Responses in the somatosensory cortical area S I to stimulation of facial sinus hairs were recorded in the anaesthetized cat and compared with activity in primary afferent fibres innervating vibrissae follicles. The specific cortical vibrissa area is somatotopically organized; 39% of the cortical units in that area responded to stimulation of only a single sinus hair but in some cases all maxillary vibrissae activated a single cortical neurone. The responses consisted of three major groups; either a phasic discharge in response to the movement part of a stimulus, or an additional tonic discharge related to the steady period of vibrissa deflection, or a tonic discharge. On the basis of a comparison of response and excitability characteristics of primary afferent and cortical neurones it is concluded that all four kinds of peripheral units innervating sinus hair follicles project to the somatosensory cortical area S I. It appears from these findings that some cortical neurones receive a specific input related to a particular component of the complex primary afferent response in fibres innervating sinus hair follicles. The results are discussed with respect to previous reports on the central representation of facial sinus hairs in different species.     

The sinus nerve and baroreceptor input to the medulla of the cat.

Electrical stimulation within the medulla of cats revealed that myelinated primary afferent fibres of the sinus nerve terminated within the immediate vicinity of the tractus solitarius and its nucleus. 2. The activity of neurones within this area was also evoked on sinus nerve stimulation, although few (17%) were activated within a latency compatible with monosynaptic excitation. Additional projections over polysynaptic pathways have been shown to the parahypoglossal area and to the area of the nucleus ambiguus. 3. These three areas were shown to contain neurones whose activity was enhanced by stimulation of the baroreceptor endings of the ipsilateral carotid sinus. 4. No evidence for a projection of sinus nerve afferents to the medial reticular formation (an area extending medially from the hypoglossal nucleus and nerve tract and including the paramedian reticular nucleus) was obtained in either antidromic or orthodromic studies. 5. The organization of the central pathway of the carotid sinus baroreceptor reflex is discussed in the light of these results.