Biological and phenotypical characterization of human Adipose Stem Cells and their effect in acute myocardial infarction.

Stem cells are present in almost all tissues and can differentiate into specialized cells. Stem cells are devided into embryonic stem cells (ES) and postnatal stem cells. The ES are omnipotent (differentiate into almost all cell types). Adult stem cells consist of the haematological stem cell, present in bone marrow (differentiate into haematopoietic cell-line), and mesenchymal stem cells reciding in fat, skin, muscle, gut, liver, lungs and brain (MSC; differentiate in mesenchymal cell lines). MSCs the adipose derived stem cells in subcutaneous fat (ASCs), are attractive source for cell therapy because it is easily harvested, available in large quantities and have a higher yield compared to bone marrow. Initially, stem cells were used to replace cells in damaged tissue. More recently however it is thought that paracrine properties are the main working mechanisms. They produce mediators with a direct or indirect effect on the local tissue or the inflammatory response. In an acute myocardial infarction (AMI), besides cell destruction there is an extensive inflammatory response. This inflammatory response clears the infarcted heart of necrotic debris and restore the heart muscle but also increases tissue damage, potentially resulting in heart failure. Besides adipocytes, subcutaneous fat also contains vessels and stroma known as the stromal vascular fraction (SVF) which contains ASCs. Adipose tissue can be harvested by resection, liposuction or ultra-sound assisted liposuction. These procedures can influence ASC function, vitality and clinical applicability. We found that all the above methods did not affect the phenotype or osteogenic differentiation. However ultrasound assisted liposuction decreased the yield and growth rate of ASCs. For cell based therapy resection and conventional liposuction are preferred. ASCs are cultured to increase the quantity of ASCs but this is time consuming and can also affect MSC properties. By using the SVF and thus the uncultured ASCs, this is avoided. For therapy it is important that these SVF isolates contain sufficient ASCs and we investigated to optimal anatomic location for harvesting. The yield of ASCs per volume is higher in the abdomen compared to the hip. Growth kinetics and bone/cartilage differentiation where not affected. In chapter 4 the phenotypic and functional characteristics of ASCs from the SVF were compared with cultured ASCs. We found that uncultured ASCs showed strong expression of CD34, CD117 and HLA-DR which was lost during cultivation. There were no effects on osteogenic differentiation. Therefore, the uncultured ASCs can be used for cell therapy. Cellular therapies for AMI patients are getting more attention. StemBells (SB) were developed to improve homing of ASCs in the heart after AMI. SB are ASCs coupled to gas bubbles, containing antibodies against ICAM-1 on endothelium. These intravascular SB can be guided using ultrasound. We previously found that SB improved cardiac function in a animalmodel, without effecting the number of stem cells entering the heart. The SBs were administered 7 days after AMI when the strong inflammatory response recides. For a clinical application, earlier administration after AMI would be beneficial. We found that injecting SB on day 1 post-infarction resulted in a faster recovery of cardiac function. It however had no significant impact on AMI recovery in the chronic phase.. AMI induces a pro-inflammatory status of the intra-myocardial vasculature in which saccharified-end-product NE-(carboxymethyl)lysine (CML) and NOX2, a source of reactive oxygen species, play an role. This pro-inflammatory status is related to the development of heart failure after AMI. CML and NOX2 are therefore attractive therapeutic targets. CML and NOX2 is increased in the intra-myocardial vessels post AMI. We found that StemBells reduces CML and NOX2 in intra-myocardial vessels after AMI and consequent partially inhibit the pro-inflammatory status and could limit heart failure.