Hi,

This does not look like any contamination. Upon, osteo differentiation induction, such morphological changes have been seen, which could be a kind of cell clustering phenomenon. After completion of induction, when you will stain with alizarin Red, you will find that these clusters are more stained representing calcium deposition.

Check the close images of these articles, you will figure it out.

Fig. 1c. https://www.ecmjournal.org/papers/vol023/pdf/v023a02.pdf

Fig. 4 & 5. https://www.biorxiv.org/content/10.1101/2020.04.27.063230v1.full.pdf+html

Regards

Saurabh

Hey Santiago,

I think it is not contamination. This clusters are formed by the cells itself and as --Saurabh Mandal mentioned above, can be stained with Alisarin Red for calcium deposition in the mineralized extracellular matrix proteins. These clusters are called "osteogenic nodules" or "bone-like nodules". In a well differntiated sample these nodules will be stained bright red, in a moderate case brownish red. In my experience, these Alisarin Red stained moderate brownish nodules can arise in the normal mouse bone marrow MSC culture of high confluency.

Hi,

This seems not to be the contaminant.

You may trypsinize them not well, and we got the clump for next seeding.

You can filter after trypsinizing with cell strainer 70-80 um or pick them out by precut Tip 1000.

This culture condition will differentiate MSC cells in long term, not for short term like 1 week, unless we culture them in the differentiation medium

Hope it helps

Hello Santiago, Did you solve this problem? I also got the same problem during Umbilical cord MSC culture. this thing appears when cell confluency is high. or when cell seeding cell concentration is high. but I want to maintain high cell confluency with high cell seeding volume. one more thing I observe it appears rapidly when cultured in a glass culture plate even if the cell confluency is less the 50%. If you know how to solve this, please suggest