Previously, we explored some of the factors involved in the technical aspects of autologous fat grafting, and this time, we’ll talk about some of the factors in fat grafting that affect the efficacy of the fat itself. In the world of medical aesthetics, 2017 can be described as the year of fat, with a succession of large and small conferences about fat, and foreign, domestic, public and private experts have expressed their opinions and elaborated their views. Even tattooed buddies who have never studied medicine and have no medical common sense have been drilling fat transplantation on the side of the road and in hotels. Back to the main topic, although there are many academic forums and literature, methods and programs have such and such a difference, but we do not do anything fundamentally different, the whole fat grafting, although there is no absolute standard, but there are basic principles. The fat grafting process includes the basic processes of swelling and anesthesia, liposuction, fat washing and centrifugation, and injection, and the precautions for each of these processes are well known. In terms of the final injected component, it can be subdivided into large-particle fat, micro-particle fat, SVF-containing emulsified fat, purified SVF component, and purified dried fat component from SVF. All of these can be used for fat grafting, and their final clinical results will inevitably vary greatly, of course, the further the technology, the more complex. Instead of going into technique here today, we will simply discuss the effect of fat refinement methods on fat viability in relation to an article in PRS, the leading international plastic surgery journal (Plast. Reconstr. Surg. 135: 1618, 2015.). When large amounts of liposuction are needed, mostly with thick tubes and large side holes, the lobulated fat extracted tends to clog the injection needle (1mm or so), and one of the solutions is to treat the fat prior to injection, and one of the mechanical purification methods is what Tonnard calls microfat, microparticulate fat. It is to use a tee to push two syringes back and forth. The tee can refine the fat particles to make it easier to inject when fat grafting What I want to explore now is whether the more times you push, the more damage you do to the fat cells, and the article compares the results of 0 pushes (no pushes), 5 pushes, and 30 pushes. Top: Push 0 times, Middle: Push 5 times, Bottom: Push 30 times As you can see from the top picture, if you don’t push to refine the fat, its adipose tissue is compact, some of it will contain blood (red blood cells are visible to the naked eye), and there is a very thin layer of oil droplets. In the middle is after 5 pushes, with smaller lumps of fat particles, better uniformity, no visible red blood cell component, and increased oily component. Below is after 30 pushes, with even smaller clumps of tissue, no visible erythrocyte component, and a further increase in the oily component. Also, the color of the adipose tissue changed from orange to yellow as the number of pushes increased. The three types of adipose tissue were brought in for immunofluorescence staining and observed under a confocal microscope, with the red color being fat, the green color being vascular endothelial cells, and the blue color being nuclei. Push 0 times Push 5 times Push 30 times Did you find that, after 30 pushes through the syringe, the cell structure and composition were no different from the unpushed samples, that is to say, the sad pushes refined the fat particles, which facilitated the injection, but at the same time did not affect the cell composition and viability in any way. After 0, 5 and 30 pushes, the number of cells per unit volume of each sample is about the same and not significantly different, with an average of 7500 cells/mm3. The adipose tissue we extracted is not only fat cells, but also contains other components. Cells in the adipose tissue can be categorized into three types: adipocytes, vascular-related cells, and other cells. As can be seen from the figure above, the proportions of the three types of cells were stable and did not differ when pushed through the syringe 0, 5, and 30 times. Among them, adipocytes accounted for only 5±0.2%, vascular-related cells accounted for 43±0.6%, and other cells accounted for 52±1.1%. The above adipocytes refer to mature adipocytes, and the other two types of cells (vascular-associated cells and other cells) have nothing to do with fat grafting, don’t you think? On the contrary, these two types of cells are the ones we need to focus on, and their importance is much higher than that of mature adipocytes. Because, these cells have very important stem/progenitor cells, these cells are very dynamic, they are small, high hypoxia tolerance, high viability, and crucially, they can proliferate and differentiate fat cells. When we centrifuge the extracted fat, the bottom little bit in the centrifuge tube is these cells, which are called vascular stromal components (SVF). Since SVF is critical, someone has to analyze it. Number of SVF Cells Extracted by Centrifugation from Each Ml of Extracted Adipose Tissue The graph above is interesting in that you can see that the average number of SVF cells (i.e., the short horizontal line in the graph) is about the same regardless of whether it’s pushed 0, 5, or 30 times, and the average number of SVF cells that can be extracted from each ml of adipose tissue is 1.288±0.693*106 cells/ml. However, regardless of whether it’s the 0-times group, 5 However, whether it is the group of 0 times, 5 times or 30 times, the values within each group are very scattered, which means that there is a big difference in the amount of SVF cells that can be extracted per ml of fat for each individual, that is to say, the amount of SVF cells contained in fat extracted from different people is very different, which, in common language, can be said to mean that the content of stem cells in the fat meat of each person is very different. Comparison of the viability of SVF cells extracted from different groups As can be seen from the above graph, although the number of stem cells per unit volume of fat meat is different in each person, there is no significant difference in the viability of these cells, and all of them can proliferate and differentiate into fat cells. Changes in mature fat cells after fat grafting As can be seen from the above graph and the previously posted graphic, after fat cells are injected into the recipient area of the body, most of the fat cells die very quickly, but the residual viable SVF stromal cells such as progenitor cells undergo regeneration, proliferation, and differentiation into fat cells, and fat grafting survival is often dependent on the content of this fraction of cells. The previously stated concept of fat graft survival, the “cell survival theory”, is inaccurate because it suggests that clinical results are largely dependent on the amount of fat cells that survive. In reality, most of the transplanted fat is dead, and it is the adipose-derived stromal cells with the potential to differentiate that are responsible for the results. This means that the stem/progenitor cells in SVF play a key role. This explains why some patients have good results with a so-called 80% “survival rate”, while others may only have a 30-40% “survival rate”. This is mainly due to the difference in the percentage of SVF cells.