isolation-papillary-reticular-fibroblasts-from-human-skin

Isolation of Papillary and Reticular Fibroblasts from Human Skin by Fluorescence-activated Cell Sorting

Fibroblasts are a highly heterogeneous cell population implicated in the pathogenesis of many human diseases. In human skin dermis, fibroblasts have ...

Medical University of Vienna

Ribosome-associated mRNA quality control mechanisms ensure the fidelity of protein translation. Although these mechanisms have been extensively studied in yeast, little is known about their role in mammalian tissues, despite emerging evidence that stem cell fate is controlled by translational mechanisms. One evolutionarily conserved component of the quality control machinery, Dom34 (in higher eukaryotes known as Pelota (Pelo)), rescues stalled ribosomes  . Here we show that Pelo is required for mammalian epidermal homeostasis. Conditional deletion of Pelo in mouse epidermal stem cells that express Lrig1 results in hyperproliferation and abnormal differentiation of these cells. By contrast, deletion of Pelo in Lgr5-expressing stem cells has no effect and deletion in Lgr6-expressing stem cells induces only a mild phenotype. Loss of Pelo results in accumulation of short ribosome footprints and global upregulation of translation, rather than affecting the expression of specific genes. Translational inhibition by rapamycin-mediated downregulation of mTOR (mechanistic target of rapamycin kinase) rescues the epidermal phenotype. Our study reveals that the ribosome-rescue machinery is important for mammalian tissue homeostasis and that it has specific effects on different stem cell populations.

An evolutionarily conserved ribosome-rescue pathway maintains epidermal homeostasis.

Chemokines mold the tumor microenvironment by recruiting distinct immune cell populations, thereby strongly influencing disease progression. Previously, we showed that CXCL5 expression is upregulated in advanced stages of primary melanomas, which correlates with the presence of neutrophils in the tumor. The analysis of neutrophil populations in various tissues revealed a distinct phenotype of tumor-associated neutrophils. Tumor-associated neutrophils expressed PD-L1, CXCR4, CCR5, Adam17, and Nos2 and were immunosuppressive in a T-cell proliferation assay. To investigate the impact of CXCL5 and neutrophils in vivo, we established a syngeneic mouse tumor transplantation model using CXCL5-overexpressing and control melanoma cell lines. Growth behavior or vascularization of primary tumors was not affected by CXCL5 expression and neutrophils alone. However, in combination with Poly(I:C), tumor-associated neutrophils were able to attenuate induced antitumoral T-cell responses. CXCL5-overexpressing tumors had reduced lung metastasis compared with control tumors. Neutrophil depletion reversed this effect. In vitro, unstimulated lung-derived neutrophils had higher levels of reactive oxygen species compared with tumor-associated neutrophils, and CXCL5 stimulation further increased reactive oxygen species levels. In summary, in melanoma, neutrophils play a context-dependent role that is influenced by local or systemic factors, and interfere with therapies activating the acquired immune system. Actively switching neutrophils into antitumorigenic mode might be a new therapeutic strategy.

CXCL5 as Regulator of Neutrophil Function in Cutaneous Melanoma.

Human skin dermis is composed of the superficial papillary dermis and the reticular dermis in the lower layers, which can easily be distinguished histologically. In vitro analyses of fibroblasts from explant cultures from superficial and lower dermal layers suggest that human skin comprises at least two fibroblast lineages with distinct morphology, expression profiles, and functions. However, while for mouse skin cell surface markers have been identified, allowing the isolation of pure populations of one lineage or the other via FACS, this has not been achieved for human skin fibroblasts. We have now discovered two cell surface markers that discriminate between papillary and reticular fibroblasts. While FAPCD90 cells display increased proliferative potential, express PDPN and NTN1, and cannot be differentiated into adipocytes, FAPCD90 fibroblasts express high levels of ACTA2, MGP, PPARγ, and CD36 and readily undergo adipogenic differentiation, a hallmark of reticular fibroblasts. Flow cytometric analysis of fibroblasts isolated from superficial and lower layers of human dermis showed that FAPCD90 cells are enriched in the papillary dermis. Altogether, functional analysis and expression profiling confirms that FAPCD90 cells represent papillary fibroblasts, whereas FAPCD90 fibroblasts derive from the reticular lineage. Although papillary and reticular fibroblasts are enriched in the upper or lower dermis, respectively, they are not spatially restricted, and the microenvironment seems to affect their function.

Article	Year
An evolutionarily conserved ribosome-rescue pathway maintains epidermal homeostasis. Nature\| PubMed ID: 29643507	2018
CXCL5 as Regulator of Neutrophil Function in Cutaneous Melanoma. The Journal of investigative dermatology\| PubMed ID: 30009831	2019
Lineage Identity and Location within the Dermis Determine the Function of Papillary and Reticular Fibroblasts in Human Skin. The Journal of investigative dermatology\| PubMed ID: 30179601	2019

Beate M. Lichtenberger

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