Tagging cells of experimental organisms with genetic markers is commonly used in biomedical research. Insertion of artificial gene constructs can be highly beneficial for research as long as this tagging is functionally neutral and does not alter the tissue function. The transgenic UBC-GFP mouse has been recently found to be questionable in this respect, due to a latent stem cell defect compromising its lymphopoiesis and significantly influencing the results of competitive transplantation assays. In this study, we show that the stem cell defect present in UBC-GFP mice negatively affects T-lymphopoiesis significantly more than B-lymphopoiesis. The production of granulocytes is not negatively affected. The defect in T-lymphopoiesis causes a low total number of white blood cells in the peripheral blood of UBC-GFP mice which, together with the lower lymphoid/myeloid ratio in nucleated blood cells, is the only abnormal phenotype in untreated UBCGFP mice to have been found to date. The defective lymphopoiesis in UBC-GFP mice can be repaired by transplantation of congenic wild-type bone marrow cells, which then compensate for the insufficient production of T cells. Interestingly, the wild-type branch of haematopoiesis in chimaeric UBC-GFP/wild-type mice was more active in lymphopoiesis, and particularly towards production of T cells, compared to the lymphopoiesis in normal wild-type donors.
Prediction of the final transferred fat volume is essential for the success of fat grafting, but remains elusive. Between 20 and 80 % of the initial transplanted volume can be creabsorbed. Although graft survival has many determinants, CD34+ progenitor cells from the vascular stroma of adipose tissue play a central role by promoting growth of blood vessels and adipocytes. We aimed to verify the hypothesis that a higher proportion of total CD34+ cells in the transplant is associated with better preservation of the graft volume. Human lipoaspirates from 16 patients were processed by centrifugation and two grafts per donor were subcutaneously injected into 32 nude mice in 1 ml volumes in the right upper flank area. The volume of each graft was measured using a preclinical MRI scanner immediately after grafting and at three months. The percentage of CD34+ cells in the graft before implantation was determined by flow cytometry. The final graft volume at three months after implantation directly correlated with the percentage of CD34+ cells in the grafted material (r = 0.637, P = 0.019). The minimum retention of the fat graft was 28 % and the maximum retention was 81 %, with an average of 54 %. Our study found that fat retention after fat transfer directly correlated with the fraction of CD34+ cells in the graft. The simple and fast determination of the CD34+ cell percentage on site can help predicting outcomes of fat transplantation. and Corresponding authors: Ondřej Měšťák, Luděk Šefc