Brigitte Gautier

Thyroid hormone receptor β1 is expressed in the human hair follicle: THYROID HORMONE RECEPTOR β1 IN HUMAN HAIR

To understand better the mechanisms by which thyroid hormone can exert its effects on the hair follicle, we looked for the expression of members of the thyroid hormone receptor (TR) family in human hair follicles. Immunoreactive TRs were detected in both dermal and epithelial compartments of the human pilosebaceous unit. Using reverse transcriptase–polymerase chain reaction, we established that TRβ1 was the predominant form of TR expressed in the human hair follicle. In addition, we investigated the effects of 3,3′,5‐triiodo‐ l‐thyronine (T3) on the survival of human hair follicles in vitro, to understand the role of this thyroid hormone on hair follicle homeostasis. A physiological level of free T3 significantly enhanced human hair survival in vitro.

Expression of peroxisome proliferator activated receptors (PPARs) in human hair follicles and PPARα involvement in hair growth

Peroxisome proliferator-activated receptors (PPARs), which belong to the nuclear hormone receptor superfamily, have recently been described as potent key regulators of epidermal development. As 1,25-dihydroxyvitamin D3, retinoic acid and triiodothyronine are known to exert effects on skin and hair follicle growth through similar receptors, we decided to investigate both the expression pattern of the PPAR alpha, -delta and -gamma subtypes and their role in human hair follicles. Using reverse transcriptase-polymerase chain reaction and immunohistochemistry, we established that PPAR alpha, -delta and -gamma were expressed in both dermal and epithelial human hair follicle cells. Additionally, we evaluated the dose effect of clofibrate, a PPAR alpha ligand, on the survival of human hair follicles in culture. A beneficial effect was observed within a narrow range of concentrations.

Ceramide binding to African–American hair fibre correlates with resistance to hair breakage

Repetitive hair‐relaxing treatments often applied to African–American hair weaken the hair structure. Therefore hair breakage is a common feature of African–American hair and an important cause of hair loss. Recently, by analysing the lipids extracted from human hair, a fraction of free‐ceramide was isolated in which sphinganine was predominant. This study shows that this sphinganine‐derived ceramide (i.e. C18‐dhCer) binds to African–American hair and protects it from weakening caused by chemicals. To show this binding, we used two methods: radioactivity detection with a microimagerTM and secondary ion mass spectrometry.

Pro-Inflammatory Cytokine Cascade in Human Plucked Hair

Using reverse transcriptase polymerase chain reaction we showed that freshly plucked human anagen hair expressed both type 1 (80 kD) and type 2 (60 kD) interleukin (IL)-1 receptor mRNAs. The IL-1 rece

Hair keratin pattern in human hair follicles grown in vitro.

Abstract: The keratin family includes epithelial (soft) keratins and hair (hard) keratins, and can be divided into acidic type I and basic to neutral type II subfamilies. Recently, nine type I and six type II hair keratin genes have been characterized through the screening of a human PAC library. The expression of these genes in the hair follicle was determined in vivo and a combined catalog of acidic and basic hair keratins was established. In this study, we investigated the expression and localization of most of the human hair keratin members of both types in human hair grown in vitro. We show that in vitro growth of hair follicles for 10 days in complete Williams E culture medium did not alter the expression pattern of hair keratins. Similarly to the in vivo situation, each hair keratin was localized in precise and discrete compartments of the follicle, ranging from the matrix to the upper cortex and/or the hair cuticle. This study shows that the increase in length of in vitro grown follicles was accompanied by the proper hair shaft keratinization process. It also shows that hair follicle integrity was maintained in vitro, both in terms of gross morphology and molecular organization despite the complexity of the keratin expression pattern.

Protective effects of taurine on human hair follicle grown in vitro

Taurine is a naturally occurring β‐amino acid produced by methionine and cysteine metabolism. It is involved in a variety of physiological functions, including immunomodulatory and antifibrotic. Taking advantage of the ability of human hair follicle grown in vitro to recapitulate most of the characteristic features of normal hair follicle in vivo, we studied (i) taurine uptake by isolated human hair follicles; (ii) its effects on hair growth and survival rate; and (iii) its protective potential against transforming growth factor (TGF)‐β1, an inhibitor of in vitro hair growth and a master switch of fibrotic program. We showed that taurine was taken up by the connective tissue sheath, proximal outer root sheath and hair bulb, promoted hair survival in vitro and prevented TGF‐β1‐induced deleterious effects on hair follicle.

Expression of NAD+ dependent 15-hydroxyprostaglandin dehydrogenase and protection of prostaglandins in human hair follicle

Abstract:  NAD+ dependent 15‐hydroxyprostaglandin dehydrogenate (15‐PGDH) catalyses oxidation of 15(S)‐hydroxyl group of prostaglandins and as a result inactivates their physiological potential. Positive effects of prostaglandins or prostaglandin analogues were reported on terminal hair, vellus hair or eyelash growth and a complex prostaglandin network was recently described in human hair follicle. In the present study, we showed that 15‐PGDH was expressed in human hair follicle mainly in melanocytes and keratinocytes, which brought us to consider this enzyme as a possible target to sustain local prostaglandin production. Using a recombinant enzymatic strategy, specific 15‐PGDH inhibitors were screened. We identified a thiazolidine dione derivative exhibiting efficacy on follicular outer root sheath keratinocytes, since it concomitantly decreased the production of deactivated 13,14 dihydro 15‐ketoprostaglandin F2α and sustained prostaglandin F2αin vitro production. In the context of recent interest in prostaglandins and prostaglandin analogues as hair regrowth agents, we postulated that the use of selected 15‐PGDH inhibitors could reinforce or prolong the effect of these physiological mediators on hair and skin.

Human hair follicle pigmentary unit as a direct target for modulators of melanogenesis, as studied by [14C]‐2‐Thiouracil incorporation

Abstract:  The purpose of this study was to evaluate human hair follicle melanogenic activity using the [14C]‐2‐thiouracil, which was known to incorporate into nascent melanins. Results obtained on pigmented, grey and non‐pigmented hair follicles demonstrated that [14C]‐2‐TU incorporation was restricted to the melanogenic compartment with a strong accumulation located around dermal papilla and within the fibre of pigmented hair follicles. Quantitative analysis of [14C]‐2‐TU incorporation showed a significant increase in pigmented hair follicles upon stimulation with 1 μm forskolin concomitant to an increase in tyrosinase levels. A strong significant decrease in [14C]‐2‐TU incorporation was noted, when hair follicles were incubated with the tyrosinase competitive inhibitor kojic acid (200 μm). Incubation with the MC1‐R agonist α‐MSH (0.2 μm) did not induce a significant stimulation of hair melanogenesis. The present model could thus represent a useful new tool to identify modulators of human hair pigmentation.

6-O glucose linoleate supports in vitro human hair growth and lipid synthesis

The hair follicle is a very active organ with a complex structure, which produces a hair fibre at a rate of 0.3 mm a day. Accordingly, the hair follicle is highly demanding in energy source, as the hair bulb matrix cells are endowed with one of the highest rates of proliferation in the human body. Moreover, recent data have shown the involvement of lipids in hair follicle function. As in vitro‐grown hair follicle keeps producing a hair fibre that closely resembles the natural hair fibre, we decided to use this model to investigate the role of a new of glucose linoleate derivative (6‐O‐linoleyl‐d‐glucose: 6‐O‐GL) as a lipid precursor and energy provider. Our results demonstrated that 6‐O‐GL was (i) quite stable and surprisingly resistant to oxidative degradation, and (ii) readily taken up and metabolized by the hair follicle into various lipids, namely neutral lipids, ceramides and polar lipids. Moreover, it supported hair follicle growth and survival in a glucose‐ and linoleic‐acid free medium. 6‐O‐GL thus appeared to be a bi‐functional nutrient, ensuring both proper fibre quality and production by the hair follicle.

Seasonally-induced alterations of some facial signs in Caucasian women and their changes induced by a daily application of a photo-protective product

These were two‐fold: (i) to assess the possible changes in some facial signs induced in a 6‐month period by the periodical shift from winter to summer in Caucasian women and (ii) to appraise the preventive effects of a strong photo‐protective product.