Rosenzweig, Anthony

Background: Endothelial progenitor cells (EPCs) may originate from the bone marrow and are capable of contributing to cardiovascular regeneration. However, the identities of these bone marrow cells and the signaling pathways that regulate their differentiation into functional EPCs remain poorly understood. Hematopoiesis consists of a cascade by which hematopoietic stem cells (HSCs) give rise to either a common myeloid progenitor (CMPs) or common lymphoid progenitor (CLPs). The CMP cells can give rise to either granulocyte-monocyte progenitors (GMPs) or megakaryocyte-erythrocyte progenitors (MEPs). Methods and Results: Herein, we identify that CMPs and GMPs preferentially differentiate into CD34+KDR+ EPCs as measured by FACS, uptake of DiIacLDL and U.lex Lectin, matrigel studies, and endothelial markers. Co-culture studies in matrigel demonstrate increased network formation and incorporation when HUVECs were co-incubated with CMPs and GMPs only. Treatment of CMPs or GMPs with IFN-g blocked EPC differentiation, whereas treatment with TGF-b1 potently induced EPC differentiation. Conversely, EPC formation was markedly impaired using blocking antibodies or TGF-b1 deficient CMPs or GMPs, whereas IFN-g deficient mice have increased EPC differentiation. Functionally, EPCs derived from CMPs and GMPs more potently adhered to fibronectin-coated plates, migrated faster in transwell Boyden chambers, and released VEGF nearly ~2 to 2.5-fold higher than EPCs from MEPs and HSCs. Finally, we identified that a TGF-b1-responsive Kruppel-like transcription factor, KLF10, as robustly expressed ~60-fold in EPCs derived from CMPs and GMPs, compared to hematopoietic progenitors lacking EPC markers. Consistently, KLF10−/− mice have marked defects in EPC differentiation (−23.6% vs. WT, P<0.002), TGF-b1 responsiveness (completedly abolished), and impaired blood flow recovery in response to hindlimb ischemia (−23.8% vs. WT, P<0.008), an effect associated with reduced levels of circulating EPCs (−28.2% vs. WT, P<0.05). Conclusion: Among bone marrow progenitors, a hierarchy exists for EPC differentiation. Targeting KLF10 may alter EPC differentiation from bone marrow-derived CMPs and GMPs and influence cardiovascular repair.

Peripartum cardiomyopathy (PPCM) is an idiopathic form of pregnancy-induced heart failure associated with preeclampsia. Circulating factors in late pregnancy are thought to contribute to both diseases, suggesting a common underlying pathophysiological process. However, what drives this process remains unclear. Using serum proteomics, we identified the senescence-associated secretory phenotype (SASP), a marker of cellular senescence associated with biological aging, as the most highly up-regulated pathway in young women with PPCM or preeclampsia. Placentas from women with preeclampsia displayed multiple markers of amplified senescence and tissue aging, as well as overall increased gene expression of 28 circulating proteins that contributed to SASP pathway enrichment in serum samples from patients with preeclampsia or PPCM. The most highly expressed placental SASP factor, activin A, was associated with cardiac dysfunction or heart failure severity in women with preeclampsia or PPCM. In a murine model of PPCM induced by cardiomyocyte-specific deletion of the gene encoding peroxisome proliferator–activated receptor γ coactivator-1α, inhibiting activin A signaling in the early postpartum period with a monoclonal antibody to the activin type II receptor improved heart function. In addition, attenuating placental senescence with the senolytic compound fisetin in late pregnancy improved cardiac function in these animals. These findings link senescence biology to cardiac dysfunction in pregnancy and help to elucidate the pathogenesis underlying cardiovascular diseases of pregnancy.

Abstract Emerging evidence demonstrates that proangiogenic cells (PACs) originate from the BM and are capable of being recruited to sites of ischemic injury where they contribute to neovascularization. We previously determined that among hematopoietic progenitor stem cells, common myeloid progenitors (CMPs) and granulocyte-macrophage progenitor cells (GMPs) differentiate into PACs and possess robust angiogenic activity under ischemic conditions. Herein, we report that a TGF-β1–responsive Krüppel- like factor, KLF10, is strongly expressed in PACs derived from CMPs and GMPs, ∼ 60-fold higher than in progenitors lacking PAC markers. KLF10−/− mice present with marked defects in PAC differentiation, function, TGF-β responsiveness, and impaired blood flow recovery after hindlimb ischemia, an effect rescued by wild-type PACs, but not KLF10−/− PACs. Overexpression studies revealed that KLF10 could rescue PAC formation from TGF-β1+/− CMPs and GMPs. Mechanistically, KLF10 targets the VEGFR2 promoter in PACs which may underlie the observed effects. These findings may be clinically relevant because KLF10 expression was also found to be significantly reduced in PACs from patients with peripheral artery disease. Collectively, these observations identify TGF-β1 signaling and KLF10 as key regulators of functional PACs derived from CMPs and GMPs and may provide a therapeutic target during cardiovascular ischemic states.