Citrullination in hair growth and alopecia

Grantee: Maria Genander, Assistant Professor, Karolinska Institutet

Amount: DKK 4,020,645

Grant category: Research Grants in open competition

Year: 2023

Geography: Sweden

Maria Genander’s project aims to understand the physiological role of the enzymes PADI3 and PADI4, which convert the amino acid arginine to citrulline, in normal hair growth – to ultimately better understand the changes that happen during unwanted hair loss, alopecia.

Hair follicle (HF) growth, leading to the generation of the hair shaft, requires coordinated development of the cells that make up hair. Protein modifications act to fine-tune the action of the signaling that leads to cellular maturation and differentiation and impacts directly on the properties of structural proteins required for hair formation. In this project, Maria Genander and her team investigate the expression of the protein-modifying enzymes PADI3 and PADI4 in the HF to understand the functional impact of PADI-mediated citrullination on cell differentiation and hair growth. Preliminary data indicate that PADI4 restricts proliferation of HF progenitor cells committed to the hair shaft lineage. Using sophisticated methodology, they aim to decipher mechanistically how PADI4 influences HF lineage progression. In addition, they will use in-utero lentiviral injections in mice to probe the function of PADI3a and PADI3b to understand how distinct PADI3 isoforms impacts hair formation and the development of alopecia.

Collectively, Maria Genander’s work will focus on addressing citrullination in hair follicle growth and hair formation. Understanding normal hair follicle development is a prerequisite for development of therapeutic strategies targeting alopecia.

Understanding the role of FOXO4-mediated regulatory network in the biology of Th22 cells

Grantee: Kilian Eyerich, Chief Physician, Karolinska Institutet

Amount: DKK 2,045,000

Grant category: Research Grants in open competition

Year: 2023

Geography: Sweden

Kilian Eyerich’s project aims to investigate the role of the transcription factor FOXO4 in the development of a specific type of T cells – the Th22 cells.

Th22 cells are a distinct subset of CD4+ T helper cells, and their effector cytokine IL-22 plays a protective role in barrier homeostasis by regulating innate immune responses, antimicrobial defense mechanisms, and wound healing. The natural differentiation of naive CD4+ T cells into the Th22 lineage and production of IL-22 by these cells is a multifactorial process that is not yet fully understood. In this project, Kilian Eyerich, along with colleague Kunal Das Mahapatra and team, will investigate the hypothesis that the transcription factor FOXO4 is a novel regulator of IL-22 production in Th22 cells. Pilot data show that FOXO4 is upregulated in human skin derived Th22 clones. It has a pattern of early induction and steady increment during Th22 differentiation, which is governed by the cytokines IL-6 and TNF-a. Moreover, the team has shown that silencing FOXO4 in naive T cells in a

Th22-inducing condition leads to reduced IL-22 secretion and that there is a protective effect of this regulation on epithelial cells, as observed in a scratch assay where keratinocytes, cultured in the supernatant from FOXO4-depleted T cells, migrated less efficiently.

The proposed project therefore aims to perform a deeper characterization of FOXO4 in Th22 cells by systematically identifying FOXO4-regulated genes, downstream pathways, and potential co-factors. In addition, the extrinsic role of FOXO4 on keratinocytes and skin wound healing will be assessed by ex vivo assays and analysis of multi-omics data from human patients.

Taken together, this project may offer novel insights into the regulatory processes in development and function of Th22 T cells.