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Decrease of Laminin-511 in the Basement Membrane Due To

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Decrease of Laminin-511 in the Basement Membrane Due To www.nature.com/scientificreports OPEN Decrease of laminin‑511 in the basement membrane due to photoaging reduces epidermal stem/progenitor cells Shunsuke Iriyama 1*, Masahito Yasuda 2, Saori Nishikawa 1, Eisuke Takai 1, Junichi Hosoi 1 & Satoshi Amano 1 Daily sunlight exposure damages the epidermal basement membrane (BM) and disrupts epidermal homeostasis. Inter-follicular epidermal stem cells (IFE-SCs) regulate epidermal proliferation and diferentiation, which supports epidermal homeostasis. Here, we examine how photoaging afects the function of IFE-SCs and we identify key components in their cellular environment (niche). We found that sun‑exposed skin showed a decrease of MCSP‑positive and β1‑integrin‑positive cells concomitantly with a decrease of laminin‑511 at the dermal–epidermal junction (DEJ), as compared with sun‑protected skin. Higher levels of laminin‑511 were associated with not only increased efciency of colony formation, but also higher expression levels of MCSP as well as other stem cell markers such as Lrig1, ITGB1, CD44, CD46, DLL1, and K15 in keratinocytes from skin of 12‑ to 62‑year‑ old subjects. UVB exposure to cultured human skin impaired laminin‑511 integrity at the dermal– epidermal junction and reduced MCSP‑positive basal epidermal cells as well as K15‑positive cells. Combined treatment with matrix metalloproteinase and heparanase inhibitors protected the integrity of laminin‑511 and inhibited the reduction of MCSP‑positive cells and K15‑positive cells. These results suggest that photoaging may reduce the levels of MCSP‑positive and K15‑positive epidermal stem/ progenitor cells in the epidermis via loss of laminin‑511 at the dermal–epidermal junction. Abbreviations TEWL Transepidermal water loss MMP(s) Matrix metalloproteinase(s) UVB Ultraviolet B HS Heparan sulfate MCSP Melanoma-associated chondroitin sulphate proteoglycan DEJ Dermal–epidermal junction IFE-SCs Interfollicular epidermal stem cells BM Basement membrane SE Skin equivalent Te skin is a multilayered organ that protects the organism against environmental stressors. Te outermost layer of the skin is the epidermis, which has a high turnover rate owing to the continuous shedding (desquamation) of the uppermost cornifed cells. Tis is a part of the process of forming the water-impermeable barrier, the stratum corneum. In human skin tissue, both the epidermal cell turnover rate and barrier function are impaired with aging. In skin tissue, which has a high cell turnover, the role of resident stem cells is crucial for ensuring equilib- rium between cell loss and cell division, i.e., for maintaining homeostasis. Stem cells are instrumental in epider- mal renewal, regeneration, and repair, and the integrity of a mammalian epidermis requires the proliferation of stem cells and the diferentiation of their progeny 1. Multiple pools of stem cells are located in diferent epidermal 1Shiseido Global Innovation Center, 1-2-11 Takashima, Nishi-ku, Yokohama 220-0011, Japan. 2Department of Dermatology, Gunma University Graduate School of Medicine, 3-39-22 Showa-Machi, Maebashi, Gunma 371-8511, Japan. *email: [email protected] SCIENTIFIC REPORTS | (2020) 10:12592 | https://doi.org/10.1038/s41598-020-69558-y 1 Vol.:(0123456789) www.nature.com/scientificreports/ regions, including the permanent portion of the hair follicle (the bulge), the interfollicular epidermis, and the sebaceous glands2. Interfollicular epidermal stem cells (IFE-SCs) play an especially important role in epidermal homeostasis under normal conditions3. Tese cells express high levels of α6 and β1 integrins4,5, but lower levels of transferrin receptor CD71 6. Tey also express Delta 1 7, MCSP (melanoma-associated chondroitin sulphate proteoglycan)8, LRIG1 (Leu-rich repeats and immunoglobulin-like domains 1)9, p75 NGF receptor CD27110, and keratin-1511. It has been reported that MCSP- and CD271-expressing cells decrease in number as a person ages12,13. However, it is not known whether or not photoaging also causes alterations of the IFE-SCs population. Stem cell functions, such as self-renewal, migration, and diferentiation, are regulated by the cellular envi- ronment or niche, which is comprised of surrounding cells, the extracellular matrix (ECM), and soluble factors (growth factors, cytokines and chemokines)14. In the epidermis, the basement membrane (BM) has an important role in infuencing the behavior of stem cells15. Te epidermal BM at the dermal–epidermal junction (DEJ) is a ubiquitous sheet-like polymeric structure that binds the dermis and the epidermis of the skin together. It is mainly composed of type IV and type VII collagens, several laminins (such as 332, 521 and 511), nidogen, and perlecan16. Te epidermal BM is damaged in skin that is regularly exposed to sunlight 17, since several injuri- ous enzymes in the epidermis are activated by UV irradiation18,19. IFE-SCs are regulated by laminin-332 and laminin-51115,20, and the levels of these molecules are reduced with aging 20,21. However, it is not clear whether sunlight exposure infuences the age-dependent change of laminins in the skin. Laminins have been implicated in the control of stem cell maintenance and progenitor cell diferentiation in various adult tissues. Laminin-332 and laminin-511 are present at the BM in the hair follicle, and the precise ratio of laminin-332/laminin-511 is critical for maintaining stem cell homeostasis15. Te subventricular zone of the lateral ventricle is a stem cell niche in the adult brain, containing a population of neural stem cells that are able to self-renew and diferentiate22. Our previous study using a LAMA5-defcient mouse model showed that laminin α5 plays an important role in maintaining neural stem cells as a part of the stem cell niche in the subventricular zone23. In mammary glands, laminin-integrin interactions play an essential role in controlling the proliferative potential of mammary basal stem/progenitor cells 24. Laminins also regulate stem cell maintenance and muscle development25. Laminin α5 in the stem cell niche afects stem cell proliferation and self-renewal, leading to muscle regeneration26. We have shown that matrix metalloproteinases (MMPs) and heparanase are activated in UVB-irradiated human skin27,28, and also that UV-damaged BM structure is reconstituted in the presence of inhibitors of MMPs and heparanase, concomitantly with the induction of epidermal diferentiation markers such as flaggrin, loricrin, and bleomycin hydrolase in the granular layer of the epidermis28. Tis leads to improved barrier function29,30. However, it is not known whether MMP and heparanase inhibitors promote the deposition of laminins at the DEJ in UVB-irradiated human skin. Although the interaction between IFE-SCs and their environmental niche is critical for the maintenance of epidermal homeostasis, the roles of the IFE-SC niche components are not fully understood. Terefore, the aim of this work is to examine how photoaging afects the function of the IFE-SCs and to identify key components in the cellular environment (niche) by comparing sun-exposed skin and sun-protected skin of subjects at various ages. We also examined the role of niche components using organotypic human skin exposed to UV irradiation. Results MCSP‑positive inter-follicular epidermal stem/progenitor cells were reduced with aging in sun-exposed human skin, compared with sun-protected skin. In human skin IFE-SCs are known to highly express MCSP8, β1 integrin4,5 and keratin-15 and to be reduced with aging12. To investigate the age- dependent changes of MCSP-positive cells, we performed immunofuorescence staining of MCSP in sun-exposed and sun-protected skin samples. Age-dependent reduction of MCSP-positive cells was more pronounced in sun-exposed skin than in sun-protected skin (Fig. 1A–E). In addition, the gene expression level of MCSP in cul- tured keratinocytes from sun-protected skin of various ages decreased with aging (Fig. 1F). Similarly, the signal intensity of β1 integrin decreased earlier in sun-exposed skin than in sun-protected skin as compared with β4 integrin’s intensity (Fig. 2A–J). Te gene expression level of Itgb1 decreased with aging whereas Itgb4 showed no change with aging (Fig. 2K, L). Furthermore, keratin-15-positive cells also decreased in number in sun-exposed skin (Fig.S1A–E), and the gene expression level of K15 was reduced with aging (Fig.S1F), although the location of K15-positive cells might be diferent from that of MCSP-positive cells. Tus, our fndings indicate that the aging-related decrease of IFE-SCs occurs earlier in sun-exposed skin than in sun-protected skin. Laminin‑511 was reduced age‑dependently in sun‑exposed skin. In the epidermis, undiferen- tiated stem/progenitor cells residing at the basal layer bind to the basement membrane via integrin-laminin interaction. We next investigated the integrin-laminin interaction of IFE-SCs by immunofuorescence staining of laminin α5 and laminin α3. We found that laminin α5 was clearly reduced in sun-exposed skin (Fig. 3A–E), whereas laminin α3 was not (Fig. 3F–J). We examined the gene expression levels of LAMA5, LAMA3, LAMB3 and LAMB1 in cultured keratinocytes from sun-protected skin in subjects of various ages and compared them with the histological data. Consistent with the age-dependent reduction of laminin α5, we found that the expres- sion levels of LAMA5 and LAMB1 were signifcantly reduced with aging (Fig. 3K–L). However, the expres- sion levels of LAMA3 and LAMB3 did not change with aging (Fig. 3M, N). Tus, our fndings indicate that laminin-511 was decreased more in sun-exposed skin compared to laminin-332. In addition, the gene expres- sion levels of LAMA5 and LAMB1 were unchanged whereas the gene expression of MMP-9 was increased in UVB-irradiated cultured keratinocytes (Supplementary Fig. S2), suggesting that UVB irradiation might lead to the degradation of laminin-511. SCIENTIFIC REPORTS | (2020) 10:12592 | https://doi.org/10.1038/s41598-020-69558-y 2 Vol:.(1234567890) www.nature.com/scientificreports/ Figure 1. Age-dependent change of MCSP-positive cells in sun-protected and sun-exposed skin.
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