Human Papillary and Reticular Fibroblasts Show Distinct Functions on Tumor Behavior in 3D-Organotypic Cultures Mimicking Melanoma and HNSCC

Identification of Small-Molecule Inhibitors Targeting Different Signaling Pathways in Cancer-Associated Fibroblast Reprogramming under Tumor-Stroma Interaction

Cancer-associated fibroblasts (CAFs) interact reciprocally with tumor cells through various signaling pathways in many cancer types, including cutaneous squamous cell carcinoma. Among normal fibroblast subtypes, papillary fibroblasts (PFs) and reticular fibroblasts (RFs) respond distinctly to tumor cell signaling, eventuating the differentiation of RFs rather than PFs into CAFs. The regulation of subtype differentiation in fibroblasts remains poorly explored. In this study, we assessed the differences between PFs, RFs, and CAFs and examined the effects of small-molecule inhibitors targeting the TGFβ, phosphoinositide 3-kinase/protein kinase B/mTOR, and NOTCH pathways on the tumor-promoting property of CAFs and CAF reprogramming in 2-dimensional and 3-dimensional cultures. Blocking TGFβ and phosphoinositide 3-kinase strongly deactivated and concurrently induced a PF phenotype in RFs and CAFs. Three-dimensional coculturing of a cutaneous squamous cell carcinoma cell line MET2 with RFs or CAFs led to enhanced tumor invasion, RF-CAF transition, and cytokine production, which were further repressed by blocking TGFβ and phosphoinositide 3-kinase/mTOR pathways but not NOTCH pathway. In conclusion, the study identified biomarkers for PFs, RFs, and CAFs and displayed different effects of blocking key signaling pathways in CAFs and tumor cell-CAF interplay. These findings prompted a CAF-to-PF therapeutic strategy and provided perspectives of using included inhibitors in CAF-based cancer therapy.

The development of in vitro organotypic 3D vulvar models to study tumor-stroma interaction and drug efficacy

BACKGROUND

Vulvar squamous cell carcinoma (VSCC) is a rare disease with a poor prognosis. To date, there's no proper in vitro modeling system for VSCC to study its pathogenesis or for drug evaluation.

METHODS

We established healthy vulvar (HV)- and VSCC-like 3D full thickness models (FTMs) to observe the tumor-stroma interaction and their applicability for chemotherapeutic efficacy examination. VSCC-FTMs were developed by seeding VSCC tumor cell lines (A431 and HTB117) onto dermal matrices harboring two NF subtypes namely papillary fibroblasts (PFs) and reticular fibroblasts (RFs), or cancer-associated fibroblasts (CAFs) while HV-FTMs were constructed with primary keratinocytes and fibroblasts isolated from HV tissues.

RESULTS

HV-FTMs highly resembled HV tissues in terms of epidermal morphogenesis, basement membrane formation and collagen deposition. When the dermal compartment shifted from PFs to RFs or CAFs in VSCC-FTMs, tumor cells demonstrated more proliferation, EMT induction and stemness. In contrast to PFs, RFs started to lose their phenotype and express robust CAF-markers α-SMA and COL11A1 under tumor cell signaling induction, indicating a favored 'RF-to-CAF' transition in VSCC tumor microenvironment (TME). Additionally, chemotherapeutic treatment with carboplatin and paclitaxel resulted in a significant reduction in tumor-load and invasion in VSCC-FTMs.

CONCLUSION

We successfully developed in vitro 3D vulvar models mimicking both healthy and tumorous conditions which serve as a promising tool for vulvar drug screening programs. Moreover, healthy fibroblasts demonstrate heterogeneity in terms of CAF-activation in VSCC TME which brings insights in the future development of novel CAF-based therapeutic strategies in VSCC.

Fibroblasts in Diabetic Foot Ulcers

Fibroblasts are stromal cells ubiquitously distributed in the body of nearly every organ tissue. These cells were previously considered to be "passive cells", solely responsible for ensuring the turnover of the extracellular matrix (ECM). However, their versatility, including their ability to switch phenotypes in response to tissue injury and dynamic activity in the maintenance of tissue specific homeostasis and integrity have been recently revealed by the innovation of technological tools such as genetically modified mouse models and single cell analysis. These highly plastic and heterogeneous cells equipped with multifaceted functions including the regulation of angiogenesis, inflammation as well as their innate stemness characteristics, play a central role in the delicately regulated process of wound healing. Fibroblast dysregulation underlies many chronic conditions, including cardiovascular diseases, cancer, inflammatory diseases, and diabetes mellitus (DM), which represent the current major causes of morbidity and mortality worldwide. Diabetic foot ulcer (DFU), one of the most severe complications of DM affects 40 to 60 million people. Chronic non-healing DFU wounds expose patients to substantial sequelae including infections, gangrene, amputation, and death. A complete understanding of the pathophysiology of DFU and targeting pathways involved in the dysregulation of fibroblasts are required for the development of innovative new therapeutic treatments, critically needed for these patients.

Trichothiodystrophy-associated MPLKIP maintains DBR1 levels for proper lariat debranching and ectodermal differentiation

The brittle hair syndrome Trichothiodystrophy (TTD) is characterized by variable clinical features, including photosensitivity, ichthyosis, growth retardation, microcephaly, intellectual disability, hypogonadism, and anaemia. TTD-associated mutations typically cause unstable mutant proteins involved in various steps of gene expression, severely reducing steady-state mutant protein levels. However, to date, no such link to instability of gene-expression factors for TTD-associated mutations in MPLKIP/TTDN1 has been established. Here, we present seven additional TTD individuals with MPLKIP mutations from five consanguineous families, with a newly identified MPLKIP variant in one family. By mass spectrometry-based interaction proteomics, we demonstrate that MPLKIP interacts with core splicing factors and the lariat debranching protein DBR1. MPLKIP-deficient primary fibroblasts have reduced steady-state DBR1 protein levels. Using Human Skin Equivalents (HSEs), we observed impaired keratinocyte differentiation associated with compromised splicing and eventually, an imbalanced proteome affecting skin development and, interestingly, also the immune system. Our data show that MPLKIP, through its DBR1 stabilizing role, is implicated in mRNA splicing, which is of particular importance in highly differentiated tissue.

Requisite instruments for the establishment of three-dimensional epidermal human skin equivalents-A methods review

Human skin equivalents (HSEs) are three-dimensional skin organ culture models raised in vitro. This review gives an overview of common techniques for setting up HSEs. The HSE consists of an artificial dermis and epidermis. 3T3-J2 murine fibroblasts, purchased human fibroblasts or freshly isolated and cultured fibroblasts, together with other components, for example, collagen type I, are used to build the scaffold. Freshly isolated and cultured keratinocytes are seeded on top. It is possible to add other cell types, for example, melanocytes, to the HSE-depending on the research question. After several days and further steps, the 3D skin can be harvested. Additionally, we show possible markers and techniques for evaluation of artificial skin. Furthermore, we provide a comparison of HSEs to human skin organ culture, a model which employs human donor skin. We outline advantages and limitations of both models and discuss future perspectives in using HSEs.