Optimal Initial Cell Density that Yields the Highest Number of Primary Synovial Mesenchymal Stem Cells in a Clinical Setting

Abstract

Background Synovial mesenchymal stem cell (MSC) transplantation improved clinical outcomes in knees with cartilage defects and after repairs of degenerative torn menisci. For these, nucleated cells were cultured with 10% autologous serum for 14 days. Importantly, nucleated cell number and serum volume practically varied by patient, and initial cell density and dish number affected yield/donor. Our purpose was to examine the effect of plating density within range in clinical studies on fold increase and to estimate the MSC yield/donor, which are affected by the nucleated cell number and serum volume.Methods We obtained the data of the autologous serum volume, nucleated cell number, and initial plating cell density from 10 patients who participated in our previous clinical studies. Experimentally, synovial nucleated cells harvested from three patients with osteoarthritis during total knee arthroplasty were cultured with 10% mixed allogenic human serum for 14 days to examine the effect of initial cell density on fold increase. We used both our previous clinical data and our current experimental data to predict the yields of synovial MSCs in nine cases within the range of clinical studies.Results In the clinical studies, collected serum ranged between 87 and 186 ml, harvested nucleated cells ranged between 6.2 and 23 million, and the top five total MSC yields were obtained from donors when the initial plating cell density ranged from 919 to 1905 cells/cm2. Experimentally, fold increase significantly decreased between 700 and 1,900 cells/cm2. In cases where the cell number was low and the serum volume was high, the estimated yield/donor decreased along with the initial density, while in cases where the cell number was high and the serum volume was low, the estimated yield/donor increased along with the initial density. In cases both where some nucleated cells were discarded at low density and no cells were discarded at high density, the maximum yield/donor were obtained when the initial density was the lowest density that does not discard cells.Conclusions There was an optimal initial density that yields the highest number of primary MSCs in a clinical setting when cell numbers and human serum volumes are limited.