Klf4 has an unexpected protective role in perivascular cells within the microvasculature

Abstract

Recent smooth muscle cell (SMC) lineage-tracing studies have revealed that SMCs undergo remarkable changes in phenotype during development of atherosclerosis. Of major interest, we demonstrated that Kruppel-like factor 4 (KLF4) in SMCs is detrimental for overall lesion pathogenesis, in that SMC-specific conditional knockout of the KLF4 gene ( Klf4) resulted in smaller, more-stable lesions that exhibited marked reductions in the numbers of SMC-derived macrophage- and mesenchymal stem cell-like cells. However, since the clinical consequences of atherosclerosis typically occur well after our reproductive years, we sought to identify beneficial KLF4-dependent SMC functions that were likely to be evolutionarily conserved. We tested the hypothesis that KLF4-dependent SMC transitions play an important role in the tissue injury-repair process. Using SMC-specific lineage-tracing mice positive and negative for simultaneous SMC-specific conditional knockout of Klf4, we demonstrate that SMCs in the remodeling heart after ischemia-reperfusion injury (IRI) express KLF4 and transition to a KLF4-dependent macrophage-like state and a KLF4-independent myofibroblast-like state. Moreover, heart failure after IRI was exacerbated in SMC Klf4 knockout mice. Surprisingly, we observed a significant cardiac dilation in SMC Klf4 knockout mice before IRI as well as a reduction in peripheral resistance. KLF4 chromatin immunoprecipitation-sequencing analysis on mesenteric vascular beds identified potential baseline SMC KLF4 target genes in numerous pathways, including PDGF and FGF. Moreover, microvascular tissue beds in SMC Klf4 knockout mice had gaps in lineage-traced SMC coverage along the resistance arteries and exhibited increased permeability. Together, these results provide novel evidence that Klf4 has a critical maintenance role within microvascular SMCs: it is required for normal SMC function and coverage of resistance arteries. NEW & NOTEWORTHY We report novel evidence that the Kruppel-like factor 4 gene ( Klf4) has a critical maintenance role within microvascular smooth muscle cells (SMCs). SMC-specific Klf4 knockout at baseline resulted in a loss of lineage-traced SMC coverage of resistance arteries, dilation of resistance arteries, increased blood flow, and cardiac dilation.

Perivascular cell-specific knockout of the stem cell pluripotency gene Oct4 inhibits angiogenesis

“…Of interest, recent studies from our lab demonstrated that Klf4, another stem cell reprogramming factor 33 , is also active in SMC-P in a number of processes, including atherosclerosis development, maintenance of resistance arteriole diameter, and arteriole SMC-P coverage 24,34 . Oct4 and Klf4 interact to promote reprogramming to induced pluripotent stem cells (iPSCs) 35 .…”

“…Interestingly, following SMC-P loss of Klf4 in young, healthy non-hyperlipidemic mice, multiple microvascular beds developed gaps in eYFP+ perivascular cell coverage that were filled by Acta2+Myh11+eYFP− cells 34 . Based on bone marrow transfer experiments, we showed that these eYFP− perivascular cells were not of myeloid origin, suggesting an alternative source including: (1) EC underdoing endothelial-to-mesenchymal transition 40 , (2) Sca1+ adventitial progenitor cells 41 , (3) other SMC-P progenitor populations not labeled by the Myh11− CreER T2 system, (4) Myh11− SMC-P populations, and/or (5) Myh11+ SMC-P that failed to undergo recombination.…”

Immune checkpoint inhibitor induces cardiac injury through polarizing macrophages via modulating microRNA-34a/Kruppel-like factor 4 signaling

“…Noticeably, it has an important role in cardiac protection, such as inhibiting KLF4 leading to cardiac hypertrophy 22 . Smooth muscle cell-specific KLF4 knockout at baseline resulted in cardiac dilation 23 . Moreover, KLF4-deficient macrophages demonstrated increased proinflammatory gene expression, indicating that KLF4 is essential for polarization 24 .…”

Pericyte Bridges in Homeostasis and Hyperglycemia

“…Previously, the myosin heavy chain 11 (Myh11) promotor has been used in an inducible lineage-tracing reporter mouse model to track the lineage of smooth muscle cells (33). Myh11 lineage cells also colabeled with the majority of NG2-or PDGFRb-expressing pericytes (16) and have been used to study them.…”