RANKL leads to periodic changes in the numbers of osteoclasts. It is of interest to note that in many experiments with RAW 264.7 cells, and especially in primary cultures, we have noticed that the size of osteoclasts tend to increase in subsequent waves of osteoclastogenesis, compared to the first wave. Characterization of long-term dynamics in osteoclast cultures We next varied initial monocyte plating density and concentration of RANKL in long-term cultures of RAW 264.7 cells. We found that the long-term dynamics of changes in osteoclast numbers differed from experiment to experiment. Whereas in some experiments only single peak of osteoclast formation was observed, in other experiments 11904527 clear oscillatory changes in osteoclast numbers were evident. To analyze the patterns of osteoclast dynamics, we pooled together 46 experiments that lasted from 15 to 26 days and were performed with different plating densities or different RANKL treatment. Since the amplitude of osteoclast formation was quite variable, for each 19380825 single experiment we normalized the osteoclast numbers at different times by a maximum MedChemExpress SB-705498 observed in that experiment, and limited the time Results Long term dynamics in monocyte-osteoclast cultures To assess long-term dynamics in osteoclast cultures, we treated RAW 264.7 with RANKL for 1526 days, which is significantly longer than the standard protocol of 57 day osteoclast culture. We observed that treatment with RANKL leads to formation of multinucleated osteoclast-like cells that stain positive for an osteoclast marker, tartrate-resistant acid phosphatase. First osteoclasts appeared in 
culture on day 45 after plating. Osteoclast numbers remained high for 23 days and then started to decline. The decrease in osteoclast numbers was accompanied by the appearance of multinucleated cells with distorted morphology, absent nuclei, and unclear cell periphery, indicating osteoclast death. Osteoclast death, likely by apoptosis, was confirmed by an increase in the percentage of osteoclasts Osteoclast Oscillations duration to 17 days since this was the time frame for the majority of experiments. We next divided 46 single experiments into 3 groups depending on the dynamics observed in each experiment. In group 1, we combined 19 experiments that exhibited only one peak of osteoclast formation. In group 2, we combined 14 experiments that exhibited 2 peaks divided by at least 2 points, which had an osteoclast count of less than 20% of either peak. In group 3, we combined 13 experiments that exhibited 2 peaks divided by just one point, which had an osteoclast count of less than 20% of either peak. In groups 2 and 3 the peaks in different experiments often did not coincide in time, resulting in significant smoothing when average osteoclast count in these groups was assessed. However, when we aligned the time of the first maximum in all the experiments in groups 2 and 3, we have found that the average osteoclast count captures the oscillatory changes observed in individual experiments, suggesting that in contrast to the initial dynamics of osteoclast formation, which may depend on specific experimental conditions, later dynamics of osteoclast changes are likely governed by the same intrinsic mechanism. For further analysis we combined experiments in group 2 and 3 as a single oscillating group. From 27 experiments in oscillating group, in 10 the amplitude of the second peak was less than 50% of the first peak, in 9 experiments the amplitude of the s
