Abstract
Rationale Pericytes (PCs) and vascular smooth muscle cells (vSMCs), collectively known as mural cells (MCs), are recruited through PDGFB-PDGFRB signaling. MCs are essential for vascular integrity, and their loss has been associated with numerous diseases. Most of this knowledge is based on studies in which MCs are insufficiently recruited or fully absent upon inducible ablation. In contrast, little is known about the physiological consequences that result from impairment of specific MC functions.
Objective Here, we characterize the role of the transcription factor serum response factor (SRF) in MCs and study its function in developmental and pathological contexts.
Methods and Results We generated a mouse model of MC-specific inducible Srf gene deletion and studied its consequences during retinal angiogenesis. By postnatal day (P)6, PCs lacking SRF were morphologically abnormal and failed to properly co-migrate with angiogenic sprouts. As a consequence, PC-deficient vessels at the retinal sprouting front became dilated and leaky. By P12, also the vSMCs had lost SRF, which coincided with the formation of pathological arteriovenous (AV) shunts. Mechanistically, we show that PDGFB-dependent SRF activation is mediated via MRTF co-factors. We further show that MRTF-SRF signaling promotes pathological PC activation during ischemic retinopathy. RNA-sequencing, immunohistology, in vivo live imaging and in vitro experiments demonstrated that SRF regulates expression of contractile SMC proteins essential to maintain the vascular tone.
Conclusions SRF is crucial for distinct functions in PCs and vSMCs. SRF directs PC migration downstream of PDGFRB signaling and mediates pathological PC activation during ischemic retinopathy. In vSMCs, SRF is essential for expression of the contractile machinery, and its deletion triggers formation of AV shunts. These essential roles in physiological and pathological contexts provide a rational for novel therapeutic approaches through targeting SRF activity in MCs.
Competing Interest Statement
The authors have declared no competing interest.
Non-standard Abbreviations and Acronyms
- Actb
- Beta actin
- AV
- arteriovenous
- AVMs
- arteriovenous malformations
- CNS
- Central nervous system
- DEG
- Differential expressed genes
- ECs
- Endothelial cells
- EdU
- 5-ethynyl-2’-deoxyuridine
- ERG
- Electroretinography
- FACS
- Fluorescence-activated cell sorting
- fc
- Fold change
- FDR
- False discovery rate
- flex1
- Floxed exon 1
- GO
- Gene ontology
- GSEA
- Gene set enrichment analysis
- ICG
- Indocyanine green
- iMCKO
- Induced mural cell knockout
- kbp
- Kilo base pair
- KEGG
- Kyoto Encyclopedia of Genes and Genomes
- MCs
- Mural cells
- MRTF
- Myocardin related transcription factor
- NG2
- Neural/glial antigen 2
- NVTs
- Neovascular tufts
- OIR
- Oxygen induced retinopathy
- P
- Postnatal day
- pBPCs
- Primary brain pericytes
- PCA
- Principal Component analysis
- PCs
- Pericytes
- PDGFB
- Platelet derived growth factor b
- PDGFRB
- Platelet derived growth factor receptor beta
- RBCs
- Red blood cells
- SLO
- Scanning laser ophthalmoscopy
- SMCs
- Smooth muscle cells
- SMG
- Smooth muscle gene
- SRF
- Serum response factor
- TCFs
- Ternary complex factors
- vSMC
- vascular smooth muscle cell
- αSMA
- Alpha-smooth muscle actin