As biologic, epidemiologic, and clinical trial data have demonstrated, inflammation is a key driver of coronary artery atherosclerosis, which is associated with pathologic injury and dysregulation of the endothelial cells lining the luminal wall of arteries, accumulation of lipids, macrophages, smooth muscle cells, "foam cells", and aggregated platelets at the arterial luminal wall, resulting in plaque formation. Circulating biomarkers of inflammation, including high-sensitivity C-reactive protein (hsCRP) and interleukin-6 (IL-6), are associated with increased risk of cardiovascular events independent of cholesterol and other traditional risk factors. Recently, a gigantic proof-ofconcept trial CANTOS (Canakinumab Anti-inflammatory Thrombosis Outcomes Study) showed that an antibody that neutralizes IL (interleukin)-1β can reduce recurrent cardiovascular events in secondary prevention, which provides intriguing support for the inflammatory hypothesis of atherosclerosis. Moreover, another agent widely used to treat inflammatory conditions, colchicine,the LoDoCo study (Low-Dose Colchicine) trial has also showed a highly significant reduction in recurrent cardiovascular events over a 3-year follow-up, which also showed promise anti-inflammation in coronary artery disease. Therefore, these studies has demonstrated beyond doubt that inflammation plays a role in the development of atherothrombosis and, more importantly, that it can be effectively modulated.

However, fatal infections encountered and high cost in CANTOS. Colchicine causes gastrointestinal distress sufficient to warrant discontinuation of the medication in over 10% of individuals, the both of which severely limits the wide range of clinical applications. Moreover, more recent clinical evidence from the Cardiovascular Inflammation Reduction Trial (CIRT) has come to challenge the above presented clinical data. low-dose MTX, when compared with placebo, failed to reduce the adverse CV events comprising the original primary end point regarding the cardioprotective effects of MTX. Evidence suggested that the inconsistent cardioprotective effects of different anti-inflammatory agents may be a reflection of the distinct pathways targeted. Atherosclerosis is a chronic inflammatory and immune disease involving multiple cell types, including monocytes, macrophages, T-lymphocytes, endothelial cells, smooth muscle cells and mast cells (MCs). Thus, therapies seek to target the intricate balance between pro- and anti-inflammatory pathways in an attempt to limit inflammation injury.

The latest cell biological studies have demonstrated that mesenchymal stem cells have a unique immunomodulatory function. In low-density lipoproteinreceptor knockout mice atherothrombosis models, MSC-treated mice displayed a signifcant 33% reduction in circulating LY-6C hei monocytes, a 77% reduction of serum CCL2 levels, and signifcantly affected lesion development, which was reduced by 33% in the aortic root. These lesions contained 56% less macrophages and showed a 61% reduction in T cell numbers. MSCs contribute to a critical role in regulating the inflammatory microenvironment and interacting with immune cells, including T cells, B cells, natural killer (NK) cells, and dendritic cells (DCs). MSC induce anti- inflammatory macrophages, inhibit foam cell formation, suppress immune responses of endothelial cells and innate lymphoid cells, and increase phagocytic capacity, which indirectly suppresses T cell proliferation. More recently, the paracrine potency might vary with sources and microenvironment of MSCs. MSCs isolated from fetal tissues such as umbilical cord (UC) and UC-blood (UCB) were shown to have increased secretion of anti-inflammatory factors (TGF-β,IL-10) and growth factors than MSCs obtained from adult adipose tissue or bone marrow. Our previous research found that the expression characteristics of special immunomodulatory genes of human umbilical cord Wharton's jelly-derived MSCs (WJMSCs) .We found WJMSCs transplantation significantly reduced the number of inflammatory macrophages (M1), increased the number of anti-inflammatory macrophages (M2) and prevented the expansion of AMI during early stage of AMI in mouse AMI models. At present, many studies have demonstrated WJMSC possess a robust immunomodulatory potential and anti-inflammatory effects through release of secretome consisting of a diverse range of cytokines, chemokines, and extracellular vesicles (EVs), the cross talk and interplay of WJMSCs and local environment reversely control and regulate the paracrine activity of MSCs. Thus WJMSCs are important regulators of immune responses and may hold great potential to be used as a therapeutic in atherosclerosis. In particular safety and feasibility of WJMSCs transplant have been clearly proved by us and other studies.

Given the current evidence, systemic paracrinemediated anti-inflammatory effects of WJMSCs can drive beneficial in therapy of atherosclerosis. These concepts lead to a potentially transformative strategy that intravenous delivery of WJMSCs, through systemic anti-inflammatory mechanisms.Therefore, the investigators performed a double-blind, placebo- controlled trial, randomly assigning 300 patients with coronary artery disease to receive three times at 30-day intervals for equal doses of 1x106 /kg of WJMSCs or placebo , to investigate the therapeutic efficacy and safety of WJMSCs in patients with coronary artery disease.