Early pharmacological blockade of the CXCL12-CXCR4 axis attenuates vertebral hypercalcification in a zebrafish model of pseudoxanthoma elasticum

Pseudoxanthoma elasticum (PXE), caused by pathogenic variants in <i>ABCC6</i>, is characterized by pathological ectopic calcification with poorly understood mechanisms and no effective therapies. To address this, we developed the first zebrafish model of human PXE by introducing the pathogenic <i>ABCC6</i> point mutation (<i>abcc6a</i> ^{<i>R1463C/R1463C</i>} , F2 generation) using the highly efficient zhyA3A-CBE5 cytosine base editor. Three mutant types (Type1-Type3, T1-T3) stratified by calcification severity, exhibited reduced levels of the calcification inhibitors vitamin K1 (VK1) and carboxylated matrix Gla protein (cMGP), which were inversely correlated with the severity of calcification. Vertebral transcriptomics revealed dysregulated pathways related to ossification, bone remodeling-associated extracellular matrix (ECM), and immune responses, with the CXCL12-CXCR4 axis identified as a pivotal signaling hub. Early pharmacological blockade of CXCR4 using AMD3100 initiated at 5 days post-fertilization (dpf), significantly attenuated hypercalcification, whereas late intervention (from 1 month post-fertilization, mpf) demonstrated minimal efficacy. Notably, dual-target therapy combining VK1 and AMD3100 synergistically reduced hypercalcification in T3 mutants, surpassing the effects of either monotherapy. This synergy indicates functional crosstalk between vitamin K metabolism and CXCL12-CXCR4 signaling. These findings identify the CXCL12-CXCR4 axis as a therapeutic target for ectopic calcification and propose a novel dual-target strategy for PXE treatment.