Therapeutic Angiogenesis Using Autologous CD34-Positive Cells for Vascular Diseases.

Online October 3, 2022 doi: 10.3400/avd.ra.22-00086 Ann Vasc Dis Vol. 15, No. 4; 2022; pp 241–252 Review Article Therapeutic Angiogenesis Using Autologous CD34-Positive Cells for Vascular Diseases Yasuyuki Fujita, MD, PhD and Atsuhiko Kawamoto, MD, PhD CD34 is a cell surface marker, which is expressed in various somatic stem/progenitor cells such as bone marrow (BM)derived hematopoietic stem cells and endothelial progenitor cells (EPCs), skeletal muscle satellite cells, epithelial hair follicle stem cells, and adipose tissue mesenchymal stem cells. CD34+ cells in BM and peripheral blood are known as a rich source of EPCs. Thus, vascular regeneration therapy using granulocyte colony stimulating factor (G-CSF) mobilized- or BM CD34+ cells has been carried out in patients with various vascular diseases such as chronic severe lower limb ischemia, acute myocardial infarction, refractory angina, ischemic cardiomyopathy, and dilated cardiomyopathy as well as ischemic stroke. Pilot and randomized clinical trials demonstrated the safety, feasibility, and effectiveness of the CD34+ cell therapy in peripheral arterial, cardiovascular, and cerebrovascular diseases. This review provides an overview of the preclinical and clinical reports of CD34+ cell therapy for vascular regeneration. Keywords: CD34+ cell therapy, peripheral arterial disease, cardiovascular disease, cerebrovascular disease Introduction CD34 cell surface antigen is a single transmembrane phosphoglycoprotein whose molecular weight is approximately 115 kDa. CD34 was first identified in 1984 on hematopoietic stem and progenitor cells (HSPCs).1) Although the Translational Research Center for Medical Innovation, Foundation for Biomedical Research and Innovation at Kobe, Kobe, Hyogo, Japan Received: August 8, 2022; Accepted: August 13, 2022 Corresponding author: Atsuhiko Kawamoto, MD, PhD. Translational Research Center for Medical Innovation, Foundation for Biomedical Research and Innovation at Kobe, 1-5-4 MinatojimaMinamimachi, Chuo-ku, Kobe, Hyogo 650-0047, Japan Tel: +81-78-304-5772, Fax: +81-78-304-5263 E-mail: ©2022 The Editorial Committee of Annals of Vascular Diseases. This article is distributed under the terms of the Creative Commons Attribution License, which permits use, distribution, and reproduction in any medium, provided the credit of the original work, a link to the license, and indication of any change are properly given, and the original work is not used for commercial purposes. Remixed or transformed contributions must be distributed under the same license as the original. Annals of Vascular Diseases Vol. 15, No. 4 (2022) CD34 antigen is structurally well investigated and useful in identifying HSPCs, the actual functions of the CD34 antigen have remained relatively elusive. Accumulated studies revealed that CD34 is expressed in various somatic stem/progenitor cells such as endothelial progenitor cells (EPCs), skeletal muscle satellite cells, corneal keratocytes, interstitial dendritic cells, epithelial progenitor cells, and adipose tissue mesenchymal stem cells as well as bone marrow (BM)-derived HSPCs.2) In other words, CD34 is considered to be a marker of various stem cells in vivo. Cells expressing CD34 are referred to as CD34-positive (CD34+) cells. In 1997, EPCs were first identified in adult human peripheral blood (PB) as CD34+ mononuclear cells (MNCs).3) They are phenotypically characterized by the expression of antigens associated with HSPCs including CD133, CD34, c-kit, vascular endothelial growth factor receptor-2, CD144 (vascular endothelial–cadherin), and stem cell antigen-1. The discovery of circulating EPCs changed the traditional paradigm that “vasculogenesis” occurs exclusively in the developing embryo. EPC concentration in the PB is low under normal conditions; however, EPCs residing in the BM are mobilized into PB in response to physiological and pathological stimuli, such as myocardial and peripheral ischemia. Mobilized EPCs recruit to the foci of neovascularization where they form structural components of the growing vasculature. Conversely, Gehling et al.4) reported that cells in PB expressing AC133 (CD133), an undifferentiated hematopoietic stem cell marker, can differentiate into vascular endothelial sequences. As a vascular regeneration mechanism by EPC, besides vascular endothelial development by EPC itself, EPCs were found to produce various cytokines and vascular growth factors involved in angiogenesis, such as vascular endothelial growth factor, basic fibroblast growth factor, angiopoietin-1, hepatocyte growth factor, insulin-like growth factor-1, stromal cell-derived factor-1, and endothelial nitric oxide synthase, promoting the proliferation of the existing vascular endothelium and cellular migration (paracrine effect).5–7) Furthermore, EPCs have been shown to secrete not only angiogenesis-related proteins but also ribonucleic acids and exosomes containing microRNA, which contribute to the paracrine effect via 241 Fujita Y and Kawamoto A Fig. 1 Kinetics of EPCs. EC: endothelial cell; EPC: endothelial progenitor cell; G-CSF: granulocyte colony-stimulating factor; GM-CSF: granulocyte macrophage–colony-stimulating factor; MMP-9: matrix metalloproteinase-9; PlGF: placental growth factor; SDF-1: stromal cell-derived factor; sKit L: soluble kit ligand; VEGF: vascular endothelial growth factor gene control mechanisms (Fig. 1).8,9) The superiority of isolated EPCs over unselected BMor PB-MNCs as a cell source for vascular regeneration therapy has been demonstrated in several preclinical studies. Yoon et al.10) showed that myocardial calcification occurred with high frequency when whole BM cells were transplanted intramyocardially into the rat model of acute myocardial ischemia. Kawamoto et al.11) demonstrated that intramyocardial transplantation of highdose PB-MNCs into the rat model of acute myocardial ischemia led to intramyocardial hemorrhage with infiltration of many inflammatory cells and a less improvement in neovascularization and cardiac function. By contrast, transplantation of purified CD34+ cells was associated with an absence of such adverse reactions, high levels of neovascularization, and sustained recovery of cardiac function. The in vitro EPC colony-forming assay developed by Masuda et al.12) showed that EPC colonies are formed from CD34+ cells at a high frequency, whereas EPC colonies could not be obtained from CD34− MNCs even when using 100 times more cells, demonstrating a marked difference in vascularization potential between the EPC and non-EPC fractions. These results suggest that the transplantation of purified EPCs is superior to BM- or PB-MNC transplantation in terms of therapeutic effect and safety. Moreover, CD34+ or CD133+ cell therapy is feasible because a clinical-grade device for immunomag242 netic cell separation has already been developed and cell culture is not required in the separation process (Fig. 2). In this review, focusing on BM- or PB (...truncated)