Small chemical molecule CPP promotes angiogenesis in surgically created severe lower limb ischemia and diabetes-induced limb vascular reduction models

Abstract

Patients with peripheral artery disease (PAD) commonly experience chronic limb-threatening ischemia (CLTI) in the end stage, leading to severe functional impairment of the limbs, amputation, and even death. Among the various disease factors contributing to PAD, diabetes is significantly associated with PAD risk, leading to more severe symptoms and a poorer prognosis. Promoting angiogenesis at ischemic sites and improving blood flow are key to the recovery of limbs from ischemic injury. Angiogenic therapies based on cells and small-molecule drugs are considered important and promising strategies. Cell-based therapies can be classified based on cell source into allogeneic therapies and autologous therapies. Autologous cells offer the advantage of not requiring immunosuppression but may be limited by factors such as cell unavailability and scarcity due to autologous factors. Allogeneic cells, while offering a more abundant cell source, present drawbacks, including immune incompatibility and ethical concerns, which restrict their application. Small chemical molecules offer advantages such as convenience, low cost, ease of synthesis and storage, and rapid action without the need for introducing exogenous genes. They circumvent the high costs associated with cell therapies and potential side effects from allogeneic cell transplantation, holding significant promise and potential in both biomedical research and clinical applications. Fibroblasts are a cell type with functional and transcriptional heterogeneity and cellular fate plasticity, making them a promising source of seed cells for clinical tissue and organ repair and regeneration. Small molecules have become recognized as crucial tools for the induction of cellular reprogramming. In our laboratory’s previous research, a novel small chemical molecule probe, CPP ((E)-4-(4-(4-(7-(diethylamino)-2-oxo-2H-chromene-3-carbonyl)piperazin-1-yl)styryl)-1-methylpyridin-1-ium iodide), was identified as an inhibitor of prolyl-4-hydroxylase 2 (PHD2). CPP induces the differentiation of cultured human dermal fibroblasts into vascular endothelial cells (VECs) via the PHD2/hypoxia-inducible factor-1α/hairy-related transcription factor 1 (PHD2/HIF1α/HEY1) signaling pathway. The differentiated VECs exhibited therapeutic efficacy in treating lower limb ischemia in mice, indicating that CPP holds promise as a therapeutic candidate for limb ischemia. In this study, we aimed to investigate the capability of CPP to directly induce angiogenesis in vivo under conditions of vascular injury. Critical limb ischemia (CLI) occurs at the end stage of PAD. To evaluate the in situ therapeutic effects of CPP on CLI, a CLI model was established using C57BL/6 mice (Hubei Research Center of Laboratory Animals, Wuhan, China). CPP was synthesized and provided by the laboratory of Professor Baoxiang Zhao at Shandong University (Jinan, China). Following surgery, continuous subcutaneous multipoint injections of CPP were administered for 14 d to mimic localized drug treatment (Figure 1A). Laser speckle blood flow imaging was used to assess lower limb perfusion on days 0, 7, and 14 (Figure 1B, upper panel). The results showed that by day 7 post-surgery, both CPP concentrations significantly enhanced perfusion in the ischemic limb compared to the control group. From days 7 to 14, perfusion changes in both CPP-treated groups plateaued. Meanwhile, the control group showed increased perfusion. Throughout the treatment period, no significant differences were observed between the 1 and 10 mg/kg/day CPP treatment groups (Figure 1C,D). On day 14, the capillary density in the skin and muscle was significantly higher in the 1 mg/kg/day CPP group than in the control group. Although the 10 mg/kg/day group had a slightly higher density than the control, the difference was not statistically significant (Figure 1E–G). In addition, the organ toxicity

1. Introduction

Patients with peripheral artery disease (PAD) commonly experience chronic limb-threatening ischemia (CLTI) in the end stage, leading to severe functional impairment of the limbs, amputation, and even death. Among the various disease factors contributing to PAD, diabetes is significantly associated with PAD risk, leading to more severe symptoms and a poorer prognosis. Promoting angiogenesis at ischemic sites and improving blood flow are key to the recovery of limbs from ischemic injury. Angiogenic therapies based on cells and small-molecule drugs are considered important and promising strategies.

Cell-based therapies can be classified based on cell source into allogeneic therapies and autologous therapies. Autologous cells offer the advantage of not requiring immunosuppression but may be limited by factors such as cell unavailability and scarcity due to autologous factors. Allogeneic cells, while offering a more abundant cell source, present drawbacks, including immune incompatibility and ethical concerns, which restrict their application. Small chemical molecules offer advantages such as convenience, low cost, ease of synthesis and storage, and rapid action without the need for introducing exogenous genes. They circumvent the high costs associated with cell therapies and potential side effects from allogeneic cell transplantation, holding significant promise and potential in both biomedical research and clinical applications.

Fibroblasts are a cell type with functional and transcriptional heterogeneity and cellular fate plasticity, making them a promising source of seed cells for clinical tissue and organ repair and regeneration. Small molecules have become recognized as crucial tools for the induction of cellular reprogramming. In our laboratory’s previous research, a novel small chemical molecule probe, CPP ((E)-4-(4-(4-(7-(diethylamino)-2-oxo-2H-chromene-3-carbonyl)piperazin-1-yl)styryl)-1-methylpyridin-1-ium iodide), was identified as an inhibitor of prolyl-4-hydroxylase 2 (PHD2). CPP induces the differentiation of cultured human dermal fibroblasts into vascular endothelial cells (VECs) via the PHD2/hypoxia-inducible factor-1α/hairy-related transcription factor 1 (PHD2/HIF1α/HEY1) signaling pathway. The differentiated VECs exhibited therapeutic efficacy in treating lower limb ischemia in mice, indicating that CPP holds promise as a therapeutic candidate for limb ischemia. In this study, we aimed to investigate the capability of CPP to directly induce angiogenesis in vivo under conditions of vascular injury.