Muzaffar, S. | bioRxiv Science

bioRxiv2026

Human skin fibrosis with iPSC-derived organoids reveals RUNX2-mediated fibroblast reprogramming

Fibrotic skin diseases are characterized by persistent fibroblast activation and extracellular matrix remodeling, yet the mechanisms governing fibroblast state transitions remain incompletely understood. Here, we established a human iPSC-derived skin organoid model of fibrosis through chronic TGF-{beta} stimulation. Single-cell RNA sequencing combined with immunofluorescence-based spatial analysis revealed dynamic fibroblast state transitions, spatial reorganization, and expansion of activated fibroblast populations during fibrotic remodeling. Integration with human scleroderma single-cell datasets demonstrated conserved fibroblast states and transcriptional programs between organoids and patient tissues. We further identified broad induction of RUNX2 in the dermal compartment during fibrosis, and RUNX2 depletion attenuated fibrotic marker expression. CUT&RUN profiling revealed RUNX2 occupancy at fibrosis-associated loci, including RUNX1 and LOXL2. Using a machine learning-guided screening approach, we identified F0565-0303, a small molecule that suppressed RUNX2-dependent fibrotic programs in vitro and reduced fibrosis in a bleomycin-induced mouse model. Together, these findings establish human skin organoids as a platform for modeling fibrosis and nominate RUNX2 as a potential therapeutic target.

bioengineering↗

bioRxiv2024

The conserved biochemical activity and function of an early metazoan phosphatidylinositol 5 phosphate 4-kinase regulates growth and development.

The ability to co-ordinate function between multiple cells is a critical requirement for multi-cellularity. This co-ordination is mediated by hormones or growth factors, molecules secreted by one cell type that can convey information to the other cells and influence their behaviour. Hormone-dependent signalling is mediated by second messenger systems;phosphoinositides (PIs) generated by lipid kinase activity are one such key second messenger system. Phosphatidylinositol 5 phosphate 4-kinase (PIP4K) is a lipid kinase that phosphorylates phosphatidylinositol 5-phosphate (PI5P) to generate phosphatidylinositol 4,5 bisphosphate [PI(4,5)P2]. Following a comprehensive bioinformatics analysis of ca. 23296 proteomes covering the tree of life, we find that PIP4K is a metazoan-specific enzyme, although its homologs are also found in choanoflagellate genomes. To understand their function in early metazoans, we experimentally analysed the biochemical activity and physiological function of PIP4K from several early metazoans. We find that the PIP4K enzyme from an early branching metazoan sponge Amphimedon queenslandica (AqPIP4K), regarded as the earliest evolved metazoan, shows a biochemical activity highly conserved with human PIP4K; AqPIP4K is able to selectively phosphorylate PI5P to generate PI(4,5)P2 just as effectively as the human enzyme. Further, AqPIP4K was able to rescue the reduced cell size, growth and development phenotype in larvae of a null mutant in Drosophila PIP4K. These phenotypes are regulated through activity of the hormone insulin, acting via the cell surface insulin receptor, a member of the receptor tyrosine kinase family, that is unique to metazoans. Together, our findings indicate that in early metazoans, AqPIP4K is likely to function in a signal transduction pathway that is required for receptor tyrosine kinase signalling. Overall, our work defines PIP4K as a signal transduction motif required to regulate receptor tyrosine kinase signalling for intercellular communication in the earliest forms of metazoa.

biochemistry↗