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An introduction to skin and skin disease
Published in Rashmi Sarkar, Anupam Das, Sumit Sethi, Concise Dermatology, 2021
The epidermis mainly contains keratinocytes; but it also contains non-keratinocytes – melanocytes and Langerhans cells, both of which possess dendrites. This cellular structure is some three to five cell-layers thick, on average, 35–50 μm thick in absolute terms. Not unexpectedly, the epidermis is about two to three times thicker on the hands and feet, particularly the palms and soles. The epidermis is indented by finger-like projections from the dermis known as the dermal papillae and rests on a complex junctional zone that consists of a basal lamina and a condensation of dermal connective tissue (Figure 1.3).
Repigmentation in Vitiligo
Published in Vineet Relhan, Vijay Kumar Garg, Sneha Ghunawat, Khushbu Mahajan, Comprehensive Textbook on Vitiligo, 2020
Bharat Bhushan Mahajan, Richa Nagpal
Hair pigmentation is provided by very active follicular melanocytes located above the dermal papilla [9]. Synthesis and transfer of melanin granules are regulated by a group of enzymes, structural and regulatory proteins, transporters, and receptors and their ligands, acting on all development stages and cells of the hair follicle [10]. Follicular melanogenesis is tightly coupled to the anagen stage of the hair cycle, becoming switched off during catagen and remaining absent through telogen. During each hair cycle, at the point from the anagen to catagen, melanocytes in the hair bulb matrix undergo apoptosis, and their reconstitution occurs just when the next anagen phase begins, a sequence that is possible because of stem cells at the bulge that activate and induce melanocyte proliferation and migration; this cycle repeats itself producing melanin granules for hair shaft pigmentation.
Transgenic Mice with Cytokine Mutations Affecting the Skin
Published in John P. Sundberg, Handbook of Mouse Mutations with Skin and Hair Abnormalities, 2020
Manfred Blessing, Erby Wilkinson, Brigid L. M. Hogan
Considering the processes going on in an actively growing hair follicle, this expression domain of BMP-2 coincides with a crucial switch in differentiation. Descendants of the follicular stem cells, which reside in the bulge region (Figure 1),33 form the outer root sheath. They proliferate at a moderate rate, especially in anagen phase, when the distance between the bulb and the bulge is increasing, and they express keratins typical for epidermal differentiation. Among these are keratins 5 and 14, which are also present in the basal cells of interfollicular epidermis, and keratins 6 and 16, which are normally not seen in interfollicular epidermis. At the base of the follicle, the matrix cells divide rapidly in order to produce the trichocytes, which form the hair shaft. As the cells lose contact with the dermal papilla, they immediately cease proliferation and switch on markers typical for trichocytic differentiation, for example, hair keratins.18,19,21,22 This cessation of proliferation and the onset of expression of trichocytic markers coincide with the expression of BMP-2, suggesting that this factor mediates one or both of these processes in an autocrine manner.
Hair growth potential of Salvia plebeia extract and its associated mechanisms
Published in Pharmaceutical Biology, 2020
Guang-Ri Jin, Yi-Lin Zhang, Jonathan Yap, William A. Boisvert, Bog-Hieu Lee
In this study, cytotoxicity assays demonstrated that SP extract induced significant proliferation of cultured hDPCs at concentrations ranging from 3.9 to 62.5 μg/mL compared with the non-treated group (Figure 1). Also, we investigated the effect of SP extract on hDPC migration by using a scratch assay, which is particularly suited to study the stimulation of cell migration by cell interactions with extracellular matrix and cell–cell interactions (Liang et al. 2007; Enshell-Seijffers et al. 2010). It is known that dermal papilla mediates the growth and differentiation of follicular keratinocytes, the main component of hair shaft (Enshell-Seijffers et al. 2010). The number of DPC was observed to increase during the growth phase of the hair cycle and the size of DPC is well correlated with hair growth (Elliott et al. 1999). Chi et al. (2013) also reported that when the number of DPC is below a critical threshold, hair follicles with a normal keratinocyte compartment are unable to form new hairs. The proliferation and migration effects of SP extract on hDPCs might be one of the factors that maintain and elongate the anagen phase of hair cycle.
Needle-free cutaneous delivery of living human cells by Er:YAG fractional laser ablation
Published in Expert Opinion on Drug Delivery, 2018
Jing Yu, Sachin Dubey, Yogeshvar N. Kalia
To date, cell-based therapy has shown promise in the treatment of certain skin diseases [2,5]; for example, the clinical trial of allogeneic whole bone marrow transplantation in seven children with RDEB [6,7] and EB [8]. Moreover, mesenchymal stem cells have been used for the treatment of skin inflammatory disorders, such as graft versus host disease [9,10], systemic sclerosis [11,12], lupus [13], or dermatomyositis [14]，and cell vaccines have been tested for melanoma treatment [15,16]. Recently, adult human cultured dermal papilla and epithelial cells were reported to be able to induce hair growth in nude mice [17]. However, neither systemic administration by intravenous or subcutaneous injection nor microneedle treatment [18–20] can specifically target the epidermis. Minimally invasive intraepidermal delivery of cells is a significant unmet need that if addressed would facilitate the clinical use of cell-based therapies.
Use of autologous platelet-rich plasma in androgenetic alopecia in women: a systematic review and meta-analysis
Published in Journal of Dermatological Treatment, 2023
Antonio Flávio Queiroz de Oliveira, Francisco Plácido Nogueira Arcanjo, Maria Rosineida Paiva Rodrigues, Ana Augusta Rosa e Silva, Peter Richard Hall
Given this scenario, the number of clinical trials evaluating the efficacy of platelet-rich plasma (PRP) in male and female androgenic alopecia has increased exponentially over the last decade and has shown promise (4). It is a centrifuged human blood derivative that contains a high concentration of cytokines, platelet-derived growth factor (PDGF), transforming growth factor (TGF), interleukin-1, VEGF, EGF, and IGF. These growth factors stimulate hair follicle stem cells, promoting neovascularization through interaction with mesenchymal cells of the dermal papilla (7).