Hair Papilla Cells Research Articles

CircCSPP1 Competitively Binds miR-10a to Regulate BMP7 Expression and Affects the Proliferation of Dermal Papilla Cells

A series of differentially expressed circular RNAs (circRNAs), microRNAs (miRNAs), and messenger RNAs (mRNAs) were identified through sequencing in the hair follicle tissues of Hu sheep with small-waved and straight wool patterns. Based on these findings, the circCSPP1-miR-10a-BMP7 (Bone Morphogenetic Protein 7) regulatory network was constructed. The preliminary study highlighted that miR-10a and the BMP7 gene exhibited not only significant differential expression across hair follicle tissues with different patterns in Hu sheep but also had an impact on the proliferation of hair papilla cells. The proliferation of hair papilla cells is intricately linked to hair follicle development and growth. Consequently, we selected the circCSPP1-miR-10a-BMP7 regulatory network to validate its role in promoting hair papilla cell proliferation in Hu sheep. Firstly, the authenticity of circCSPP1 was successfully confirmed through RNase R digestion and reverse primer amplification. Additionally, nucleoplasmic localization analysis determined that circCSPP1 was predominantly distributed in the cytoplasm. Using the dual-luciferase gene reporter system, we verified the targeting relationship between circCSPP1 and miR-10a, building upon our previous validation of the miR-10a-BMP7 interaction. This clarified the competing endogenous RNA (ceRNA) mechanism within the circCSPP1-miR-10a-BMP7. Furthermore, rescue experiments confirmed that circCSPP1 competitively binds to miR-10a, thereby regulating BMP7 expression and influencing the proliferation of hair papilla cells in Hu sheep. This discovery provides a solid foundation for future investigations into the mechanisms underlying wool curvature and the formation of lambskin patterns, offering insights into the complex regulatory networks that govern these phenotypic traits in Hu sheep.

Shh Gene Regulates the Proliferation and Apoptosis of Dermal Papilla Cells to Affect Its Differential Expression in Secondary Hair Follicle Growth Cycle of Cashmere Goats.

Sonic hedgehog (Shh) is a component of the Hedgehog signaling pathway, playing an important role in regulating cell proliferation, differentiation, apoptosis, and the repair of damaged organisms. To further clarify the expression pattern of Shh gene in the secondary hair follicle growth cycle of cashmere goats and its mechanism of action on secondary hair follicle papilla cells, and improve cashmere quality, in this study, we took Inner Mongolia Albas white cashmere goats as the research objects and collected skin samples at different growth stages to obtain secondary hair follicles, detected Shh and its gene expression by RT-qPCR, Western blot, immunohistochemistry, and other techniques, while we also cultured DPCs in vitro. Shh gene overexpression and interference vectors were constructed, and the effects of Shh gene on the proliferation and apoptosis of DPCs were studied through cell transfection technology. The results showed that there are significant differences in Shh and its gene expression in the secondary hair follicle growth cycle skins of cashmere goats, with the highest expression level in anagen, followed by catagen, and the lowest expression level in telogen. Shh was mainly expressed in the inner root sheath, outer root sheath, and secondary hair follicle papilla. After the overexpression of Shh gene, the proliferation and vitality of the hair papilla cells were enhanced compared to the interference group. After Shh gene interference, the apoptosis rate of the cells increased, indicating that Shh gene can regulate downstream Ptch, Smo, and Gli2 gene expression to promote the proliferation of DPCs, and thus form its expression pattern in the secondary hair follicle growth cycle of cashmere goats.

Treatment of androgenetic alopecia by exosomes secreted from hair papilla cells and the intervention effect of LTF.

Androgenetic alopecia (AGA) is the most common cause of chronic progressive hair loss in men, and AGA has a severe negative impact on the quality of life and physical and mental health of patients. Four female C57BL/6 mice were isolated from DP cells in culture (≤4 generations) after stimulation of DPC proliferation by herbal concentrations obtained by the CCK-8 method, and exosomes were isolated by differential centrifugation at low temperature. Testosterone propionate and topical hair removal treatments were used together to establish the C57BL/6 mouse AGA model, which was treated with LTF, 5% minoxidil, and LTF-DPC-EXO, respectively. ELISA was used to detect serum hormone levels, in vivo tracing was used to observe dynamic changes in exosomes, H&E staining showed changes in mouse hair follicle tissue, and (q) RT-PCR and WB were used to detect dorsal skin VEGF, AKT1, and CASP3 expression in dorsal skin tissues. Hair regeneration was significant in the LTF group, minoxidil group, and LTF-DPC-EXO group mice, and the hair growth was only seen in the local skin in the model group. The hormone T in all treatment groups was lower than that in the model group, and e2 was higher than that in the model group. (q) RT-PCR and western blot showed that VEGF and AKT1 expressions were upregulated and Caspase3 expression was downregulated in the skin sections of mice in the treatment groups. DPC-EXO obtained through LTF may activate AKT1 and VEGF in the PI3K/AKT signaling pathway to inhibit CASP3, thereby protecting DPC to restore the hair growth.

Experiment on the effect of Artemisia sieversiana extract on hair loss prevention and cell growth

Objectives: This study aimed to examine the safety, effects on proliferation of hair papilla cells, and anti-inflammatory and antioxidant mechanisms of Artemisia sieversiana Ehrh. ex Willd. (AS) extract.Methods: Safety tests through purity testing, acute toxicity tests, and repeated toxicity tests were performed using AS extract (ASE) which had been dried for over two years. Cell culture and proliferation tests were conducted; VEGF (vascular endothelial growth factor), bFGF (basic fibroblast growth factor), and EGF (epidermal growth factor) and protein expression analyses were performed for mechanistic evaluation; and inhibitory effects of ASE on the RNA expression of testosterone, 5α-reductase, and aromatase was assessed. The anti-inflammatory and antioxidant efficacy of ASE was confirmed by measuring the levels of nitric oxide, inflammatory mediators (TNF-α and PGE2), inflammatory cytokines (IL-1β, IL-6, and IL-8), and chemokine MCP-1.Results: The safety of ASE was confirmed. The mechanism of cell proliferation in human hair follicle dermal papilla cells involved the promotion of VEGF, bFGF, and EGF expression. ASE decreased mRNA expression of testosterone, 5α-reductase, and aromatase-1 in a concentration-dependent manner. PGE2 and TNF-α production by inflammatory mediators was also significantly decreased in a concentration-dependent manner, and inflammatory cytokine and chemokine expression was inhibited.Conclusions: ASE is suggested to promote papillary cell growth at the cellular level, to suppress expression of various enzymes involved in hair cycle and cell death, and to inhibit hair loss through anti-androgen, anti-inflammatory, and antioxidant effects.

Oxidative stress and its impact on skin, scalp and hair.

Oxidative stress is an unbalanced condition in which the tissues of the body are not sufficiently able to counteract either exogenous or endogenous sources of reactive oxygen species. Oxidative stress is strongly associated with ageing, both local and systemic, as well as a wide range of local health conditions. This review focuses on the oxidative stress data known for skin, scalp and hair. This oxidative stress may be the 'currency' by which an unhealthy scalp leads to deleterious consequences to the hair. The ramifications of this scalp oxidative stress to normal hair elongation, retention and replacement are discussed.

Evaluation of the Effect of Plant Mixture Ethanol Extracts Containing Biota orientalis L. Extract on Suppression of Sebum in Cultured Sebocytes and on Stimulation of Growth of Keratinocytes Co-cultured with Hair Papilla Cells

Biota orientalis L. leaf extract (BOLE) is used medically to improve strength and arrest hemorrhage. In China, BOLE has been used in traditional medicine for its antibacterial properties and for hair restoration. In this study, we investigated the mechanism of hair restoration by BOLE from the point of view of the sebum suppressant effect and hair loss prevention. BOLE at 25 or 50 μg/mL final concentrations, a hair growth plant ethanol extract (HGPEE), and a hair growth plant water extract (HGPWE) (the latter two each containing BOLE and other plant compounds), were used to study: (1) the sebum suppressant effect in sebocytes from normal golden hamster ear pinna origin; (2) the effect on the growth of human fetal epidermal keratinocytes; and (3) the effect on gene expression related to hair growth stimulation, with (2) and (3) studied in human fetal epidermal keratinocytes and hair papilla cells. BOLE had a sebum depletion effect in cultured sebocytes; moreover, the amounts of mRNA of the hair growth factors, KGF, VEGF, and G3PDH analyzed by real-time polymerase chain reaction in human hair papilla cells were increased by HGPEE. The amount of mRNA of Wnt10b in cultured epidermal keratinocytes was increased by the addition of BOLE, and the growth of the cultured epidermal keratinocytes was promoted by HGPEE in a two-layer culture system of hair papilla cells and epidermal keratinocytes. HGPEE had a hair growth promotion/hair restoration effect and a sebum suppression effect. Hair restorers containing HGPEE may be useful for stimulating hair growth and suppressing excess scalp sebum in males and females.

Transcriptome Analysis of Skin from SMP30/GNL Knockout Mice Reveals the Effect of Ascorbic Acid Deficiency on Skin and Hair.

Senescence marker protein-30/gluconolactonase knockout mice (SMP-30/GNL-KO) are a very useful model for clarifying the involvement of vitamin C (VC) in aging-related diseases. In this study, the effects of VC deficiency on skin and hair growth were investigated using SMP-30/GNL-KO mice by RNA sequencing. SMP-30/GNL-KO mice were given water containing 1.5 g/l VC until up to 8 weeks after birth to maintain a VC concentration in their organs and plasma equivalent to that in wild-type mice. The mice were then divided into two groups: a VC(+) group, where VC was administered, and a VC(-) group, where VC was not administered. Skin samples were collected at 4 and 8 weeks after the treatment. RNA was extracted from each skin sample, followed by cDNA synthesis and RNA-seq. In addition, hair growth was compared between the VC(-) and VC(+) groups after shaving. Skin samples were collected from the shaved area for histological examination by hematoxylin & eosin (HE) staining. RNA-seq revealed that there were 1,736 (FDR<0.001) differentially expressed genes in the VC(-) and VC(+) groups. From the functional analysis of the differentially expressed genes in the VC(-) and VC(+) groups, predicted functionalities including cell death and cytotoxicity increased in the VC(+) group. Furthermore, it was predicted that the difference in hair growth between the VC(-) and VC(+) groups was caused by the expression of genes including keratin-related genes and the Sonic hedgehog gene. It was confirmed that hair growth was significantly promoted; hair growth from hair papilla cells was also confirmed by HE staining of the shaved backs of SMP-30/GNL-KO mice in the VC(+) group. RNA-seq of the skin from VC-deficient mice showed the effects of VC deficiency on the expression of genes involved in cell growth and the hair cycle. Visual inspection suggested that changes in the expression of the genes are involved in delaying hair growth in the VC(-) group. Further research on the relationship among VC deficiency, the hair cycle, and skin cell growth may contribute to research on hair restoration and skin aging.

Identification of Wnt/β‐catenin signaling pathway in dermal papilla cells of human scalp hair follicles: TCF4 regulates the proliferation and secretory activity of dermal papilla cell

It is clear that the dermal papilla cell (DPC), which is located at the bottom of the hair follicle, is a special mesenchymal component, and it plays a leading role in regulating hair follicle development and periodic regeneration. Recent studies showed that the Wnt signaling pathway through β-catenin (canonical Wnt signaling pathway) is an essential component in maintaining the hair-inducing activity of the dermal papilla and growth of hair papilla cells. However, the intrinsic pathways and regulating mechanism are largely unknown. In the previous work, we constructed a cDNA subtractive library of DPC and first found that the TCF4 gene, as a key factor of Wnt signaling pathway, was expressed as the upregulated gene of the hair follicle in low-passage DPC. This study was to explore the role of TCF4 in regulating the proliferation and secretory activity of DPC. We constructed a pcDNA3.0-TCF4 expression vector and transfected it into DPC to achieve stable expression by bangosome 2000. Furthermore, we used the method of chemosynthesis to synthesize three pairs of TCF4 siRNA and transfected them into DPC. Meanwhile, we compared the transfection group and non-transfection group. We first proposed that there was expression difference in TCF4 in DPC under different biological condition. This study may have a high impact on the molecular mechanism of follicular lesions and provide a new vision for the treatment of clinic diseases.

Clonal multipotency and effect of long-term in vitro expansion on differentiation potential of human hair follicle derived mesenchymal stem cells

Hair follicle harbors a rich stem cell pool with mesenchymal lineage differentiation potential. Although previous studies with rodent cells demonstrated that hair follicle sheath and papilla cells possess multi-lineage differentiation potential, human hair follicle derived mesenchymal stem cells (hHF-MSCs) have not been characterized in detail in terms of their multipotency. In addition, it is not clear whether these cells are true stem cells that can differentiate along multiple lineages or whether they represent a collection of progenitor cells with restricted differentiation potential. Here we report that hHF-MSCs are highly proliferative cells that can be maintained in culture for ~ 45 population doublings before they start to show signs of cellular senescence. Under appropriate culture conditions, hHF-MSCs differentiated along the myogenic, osteogenic, adipogenic and chondrogenic lineages, as demonstrated by kinetic gene expression profiling and functional assays. Interestingly, the differentiation potential decreased with time in culture in a lineage-specific manner. Specifically, myogenesis and chondrogenesis showed a moderate decrease over time; osteogenesis was maximum at intermediate passages and adipogenesis was highly sensitive to long-term culture and was diminished at late passages. Finally, hHF-MSCs were clonally multipotent as the majority of hHF-MSCs clones (73%) demonstrated bi- or tri-lineage differentiation potential. These results suggest that hHF-MSCs may present as an alternative source of easily accessible, autologous stem cells for tissue engineering and regenerative medicine.

A Human Folliculoid Microsphere Assay for Exploring Epithelial– Mesenchymal Interactions in the Human Hair Follicle

The search for more effective drugs for the management of common hair growth disorders remains a top priority, both for clinical dermatology and industry. In this pilot study, we report a pragmatic organotypic assay for basic and applied hair research. The patented technique produces microdroplets, which generate human folliculoid microspheres (HFMs), consisting of human dermal papilla fibroblasts and outer root sheath keratinocytes within an extracellular matrix that simulates elements of the hair follicle mesenchyme. Studying a number of different markers (for example, proliferation, apoptosis, cytokeratin-6, versican), we show that these HFMs, cultured under well-defined conditions, retain several essential epithelial-mesenchymal interactions characteristic for human scalp hair follicle. Selected, recognized hair growth-modulatory agents modulate these parameters in a manner that suggests that HFMs allow the standardized preclinical assessment of test agents on relevant human hair growth markers under substantially simplified in vitro conditions that approximate the in vivo situation. Furthermore, we show by immunohistochemistry, reverse transcriptase-PCR, and DNA microarray techniques that HFMs also offer a useful discovery tool for the identification of target genes and their products for candidate hair drugs. HFM thus represent an instructive modern experimental and screening tool for basic and applied hair research in the human system.

The superhydrophilic and superoleophilic leaf surface of Ruellia devosiana (Acanthaceae): a biological model for spreading of water and oil on surfaces.

Most leaves of plants are hydrophobic or even superhydrophobic. Surprisingly the leaves of the tropical herb of Ruellia devosiana Makoy ex E. Morr. Hort. (Acanthaceae) are superamphiphilic. Water droplets (10 µL) spread to a film with a contact angle of zero degree within less than 0.3 s. Such surfaces with a high affinity to water are termed superhydrophilic. Droplets of oil applied on R. devosiana leaves and replicas showed a similar spreading behaviour as water. These surfaces are superoleophilic, and in combination with their superhydrophilicity they are called superamphiphilic. Independent of the growing conditions, a reversibility of the superhydrophilicity in R. devosiana leaves was found. Additionally, on 90° tilted leaves a pressure free capillary transport of water occurs against the force of gravity. By using a low pressure environmental scanning electron microscope (ESEM), the water condensation and evaporation process on the leaves has been observed. The leaf surfaces are composed of five different cell types: conical cells, glands, multicellular hairs, hair-papilla cells and longitudinal expanded, flat epidermis cells, which, in combination with the surrounding papilla cells, form channel like structures. Replication of the leaf surface structure and coating of the replicas with hydrophilic Tween 20 and a water soluble extract gained from the leaf surfaces resulted in artificial surfaces with the same fast water spreading properties as described for the leaves.

Trans-3,4'-Dimethyl-3-hydroxyflavanone, a Hair Growth Enhancing Active Component, Decreases Active Transforming Growth Factor .BETA.2 (TGF-.BETA.2) through Control of Urokinase-Type Plasminogen Activator (uPA) on the Surface of Keratinocytes

trans-3,4'-Dimethyl-3-hydroxyflavanone (t-flavanone) is a synthetic compound with hair growth enhancing activity that is effective against male pattern alopecia. t-Flavanone was designed as a derivative of astilbin, the active hair growth enhancing component of Hypericum perforatum extracts. This study was designed to elucidate the mechanism of hair growth enhancement by t-flavanone. We investigated the effects of t-flavanone on transforming growth factor beta (TGF-beta), a known catagen-inducing factor induced in hair papilla cells by male hormone. When t-flavanone was added to cocultures of human hair papilla cells and human keratinocytes, there was no change in the total level of TGF-beta2. However, levels of active TGF-beta2 were reduced, suggesting the involvement of t-flavanone in the activation pathway of TGF-beta2. In order to investigate the effects of t-flavanone on TGF-beta2 activation by human keratinocytes, we evaluated the level of active TGF-beta2 converted from the inactive form in t-flavanone-treated human keratinocytes. The amount of active TGF-beta2 was reduced compared with controls suggesting that t-flavanone suppresses the TGF-beta2 activation cascade in human keratinocytes. We then examined the activity of urokinase-type plasminogen activator (uPA), the rate-limiting enzyme in the TGF-beta2 activation cascade, in t-flavanone-treated human keratinocytes. We found that t-flavanone reduces uPA activity on the keratinocyte surface. t-Flavanone is a hair growth enhancing component that has a novel mechanism of action which suppresses TGF-beta2 activation, and thereby is expected to have therapeutic effects on other types of alopecia in addition to male pattern alopecia.

Hair follicle regeneration after implantation of hair follicle cells into subcutis of nude mice

To observe the hair follicle regeneration after implantation of hair follicle cells into the subcutis of nude mice. The cultured hair papilla cells,dermal sheath cells and fibroblast of human scalp were mixed with the cells of hair follicle epithelium in different ratio, and then implanted into the subcutis of nude mice. The regeneration of hair follicle was observed. The hair follicle-like structure was formed in cluster where the cultured hair follicle epithelium cells were mixed with hair papilla cells. But no hair follicles were formed where the hair follicle epithelium was implanted with dermal sheath cells or fibroblasts. The hair follicle-like structure is generated in vivo when the mixed cells of early passages cultured hair papilla cells with hair follicle epithelium are implanted into the subcutis of nude mice.

Role of hair papilla cells on induction and regeneration processes of hair follicles.

Hair dermal papilla cells are specialized mesenchymal cells that exist in the dermal papilla located at the bottom of hair follicles. These cells play pivotal roles in hair formation, growth, and cycling. Hair follicle formation is usually directed by an aggregation of dermal mesenchymal cells, the origin of dermal papilla cells, in the embryonic skin. We noticed that cultured dermal papilla cells also have hair-forming activity and do not lose the activity even after long-term cultivation, if they are cultured with conditioned medium from keratinocytes obtained from the sole or with a medium containing fibroblast growth factor. The secreted factors from keratinocytes and fibroblast growth factor are, therefore, important for maintaining the cellular properties of dermal papilla cells. Even if the hair bulb, including the hair matrix and the dermal papilla, has been removed from vibrissal follicles in vivo, the new hair matrix and papilla can regenerate from the rest of the follicle, and eventually a hair shaft regrows. It has been reported that hair bulb regeneration does not occur when the lower half of a hair follicle is removed. However, new hair bulbs were formed in the remaining upper halves of vibrissal follicles if the amputated follicles had been implanted under the kidney capsule. The formed bulbs were small and pelage-type, not large vibrissa-type. Histological studies showed that the new dermal papillae were derived from dermal sheath cells surrounding upper follicular epidermis, and the new hair matrices were produced from the follicular epidermis. Moreover, the upper halves of vibrissal follicles reformed large vibrissa-type bulbs when they were associated with dermal papillae or cultured papilla cells and implanted in the kidney. Thus, dermal papilla cells and probably dermal sheath cells have the ability to induce and form hair bulbs under preferred environmental conditions. Attempts to identify the genes and proteins associated with hair-forming activity of dermal papilla cells have been carried out. We and other groups successfully isolated the molecules that were specifically expressed in dermal papilla cells. The nature of the hair-producing factors could be understood through the studies of these molecules.

Organotypic cocultures as models to study cell-cell and cell-matrix interactions of human hair follicle cells.

In the hair follicle complex interactions of specialized epithelial and mesenchymal cells as well as extracellular components are crucial for regulation of proliferation and differentiation. In order to mimic this situation in vitro, techniques to cultivate follicular cells such as outer root sheath (ORS) cells, hair matrix cells (HMC) and hair papilla cells (HPC) were developed. Human dermal fibroblasts (HDF) and HPC markedly enhanced proliferation of ORS cells when cocultured spatially separated in a two-chamber system, which was more pronounced with postmitotic than with mitotic mesenchymal cells. In organotypic cocultures of ORS cells on HDF- or HPC-populated collagen gels lifted at the air-medium interface, stratified epithelia developed largely reminiscent of the epidermis. The morphology was well structured and differentiation markers were expressed (e.g. suprabasal keratins, filaggrin, involucrin, basement membrane components). Both proliferation and differentiation were dependent on the presence of HDF or HPC. When grown embedded in extracellular matrix (Matrigel) without HDF, ORS cells formed large spheroids with inward directed differentiation. Also herein HDF or HPC sustained both cell growth and balanced, epidermistype differentiation. While in organotypic cocultures with HDF, HMC also organized into stratified epithelia, epidermis-type stratification was prevented by HPC. Similarly, in the presence of HDF, HMC in Matrigel formed keratinizing spheroids, whereas this was largely suppressed in the presence of HPC. However, hair-type differentiation was not observed, suggesting a crucial role of other yet unknown components or of the surrounding matrix.

Effect of minoxidil-sulfate on cultured human hair papilla cells (PCs) and root sheath fibroblasts(RSFs)

Effect of minoxidil-sulfate on cultured human hair papilla cells (PCs) and root sheath fibroblasts(RSFs)

Glycosaminoglycans in the Extracellular Matrix and Medium of Cultured Human Hair Papilla Cells

Glycosaminoglycans in the Extracellular Matrix and Medium of Cultured Human Hair Papilla Cells

Effects of testosterone, dihydrotestosterone and estradiol on growth of human hair outer root sheath keratinocytes in vitro

Human hair follicles are targets of sex hormones, but they do not behave identically, their response varying depending on the body site [5]. Androgens and estrogens transform vellus to terminal hair in genital skin during puberty, whereas, as well as genetic effects, androgens induce regression of terminal hair during the development of male-pattern baldness. Hair growth depends on interaction of mesenchymal and epithelial compartments, i.e. between dermal papilla and hair matrix. After shedding ofa telogen hair, outer root sheath keratinocytes (ORSK) are involved in new hair follicle formation [8, 14] and there is some evidence that matrix cells of a new anagen hair are reconstituted from cells of the outer root sheath [8, 14, 151. Different methods exist for the cultivation of hair follicle cells. Besides the known model for culturing dermal hair papilla cells [10], a new technique has been described for culturing ORSK of plucked anagen scalp hairs [12, 13]. This method is suitable for studying the influence of hormones and drugs on growth behavior of these cells in vitro. The aim of the present study was to investigate the effects of testosterone (T), dihydrotestosterone (DHT) and estradiol (E2) on the growth behaviour of subcultured ORSK compared with interfollicular keratinocytes (IK) of the same male subjects. Anagen hairs (approximately 50-100) were plucked from the frontal scalp region of four healthy male volunteers aged 26 to 36 years, neither suffering from male pattern baldness nor from other diseases affecting hair or skin. The hair shafts were cut off. Anagen hairs with an intact outer root sheath (ORS) were carefully selected

Growth and cell kinetics of human hair papilla cells in vitro. An autoradiographic and flow cytometric study

Hair papilla, a distinct specialized dermal compartment, plays a fundamental role in the biology of hair growth. Recently some attention has been focused on hair papilla cells (HPC) as possible targets for drugs influencing the hair growth. Isolation and cultivation of the HPC facilitates screening for such drugs. In the present work, growth and cell kinetics of human occipital scalp follicle HPC have been studied in vitro. HPC grow according to a Gompertz function, i.e. with considerable growth delay long before becoming confluent cultures, due probably to elongation of the potential doubling time (Tpot) and to a parallel increasing cell loss rate. The [3H]dT labelling index of the HPC strongly depends on the age of the subculture; the cycle time being about 4 days. A potential doubling time of about 93 h, indicative of growth fraction (GF) = 1, and a duration of S phase and G2 + M phase of about 8 h each were found by the combined application of continuous labelling with [3H]dT and DNA flow cytometry.

Dermal cell populations show variable competence in epidermal cell support: stimulatory effects of hair papilla cells

A study was made of the comparative abilities of adult rat vibrissa dermal papilla cells, skin fibroblasts and 3T3 cells to support the initial attachment and subsequent growth and division of directly associated newborn rat skin basal epidermal cells. These associations were made under sub-optimal conditions; that is, in the absence of specific epidermal growth-promoting supplements, in order to assess more accurately the epidermal sustaining capacities of each dermal support. Analysis of epidermal cell counts and close photographic scrutiny revealed that low-passage dermal papilla cells, closely followed by transformed dermal papilla cells, were conducive to the successful attachment and subsequent proliferation of epidermal cell populations under three different experimental protocols. In contrast, skin fibroblasts did not support epidermal cell growth under any circumstances. These findings are particularly interesting in that they constitute a rare in vitro example of epidermal cells that are not only supported, but also encouraged to proliferate, by an actively dividing adult skin-derived dermal cell population.