The role of pericyte-endothelial crosstalk in microvascular homeostasis and disease

Abstract Background Cardiovascular diseases are often associated with microvascular dysfunction and rarefaction driven by pericyte (PC) loss or detachment, which disrupts barrier function and leads to vessel instability and organ dysfunction. Purpose To assess how endothelial cells (EC) communicate with PC to preserve vascular stability and how its interruption drives vessel and organ dysfunction. Methods We used an EC-PC co-culture system and transgenic mouse models and multi-omics. PC-EC communication was altered in a model of diphtheria toxin (DTx) -induced PC-depletion and mice with EC-specific deletion of the lactate transporter SLC16A3. Results In Rosa26iDTR×Pdgfrb-CreERT2 mice DTx induced PC depletion that was significant after 3 days. By 7 days PC loss was associated with loss of vascular integrity and diastolic dysfunction with preserved ejection fraction, indicating that loss of EC-PC crosstalk is sufficient to initiate cardiac dysfunction. To examine EC-PC crosstalk in more detail we used a filter co-culture system. RNA-sequencing of ECs and PCs in monoculture versus coculture revealed little impact of ECs on PCs but a clear impact of PCs on ECs. This fit with our previous observation that mitochondria could be transferred from PCs to ECs but not in the other direction. Indeed, numerous EC metabolic process genes were altered by PCs. Proteomics analysis of EC-PC junctions in the filter pores revealed enrichment of several proteins including the lactate transporter SLC16A3. Metabolomics and 13C Glucose flux analysis revealed that ECs cocultured with PC contained more lactate than EC in monoculture, an effect that was abrogated in the presence of a SLC16A1/3 inhibitor. As lactate can post-translationally modify proteins, we determined wether this lactate shuttling could alter protein lactylation. We identified over 60 lactylated proteins in ECs, some that were down regulated and some upregulated by coculture with PC. To determine to the relevance of SLC16A3-dependent lactate exchange in vivo, we generated mice with a tamoxifen inducible deletion of the transporter in ECs (Slc16a3ⁱDEC mice). In the neonatal retina the deletion of SLC16A3 did not affect EC proliferation but had a clear impact on network density and PC coverage resulting in a less complex capillary network. Conclusions Our data indicates that metabolic communication, in particular lactate shuttling, between EC and PC is essential for vascular homeostasis and cardiac function as well as vascular maturation in the retina.