Does someone know about non-viral syncytia and what could cause that?

Yes.
C. elegans has Syncytia as a normal part of its development, e.g. in the hypodermis.
see here in the C. elegans server.
Also look for articles by e.g. Benjamin Podbilewicz

Thanks for the article
but now lets say i have transient syncytia (5days) on vero cells (10-15 nuclei /per cell appearing by 8hrs and desappearing after 3-6 days).


(the vero cells have been inoculated with a product=CHO cell culture fluid, and neg control did not present any syncytia)


any idea about the root cause is welcome
thanks (i'll set up experiment to test the hypothesises)

You could try either heat-treating the CHO cell culture medium or filtering it through 0.22 or 0.45 filters to get a better idea as to whether you have a living pathogen or some toxic protein (virulence factor?). I'd also use media that had been taken from CHO cell cultures after different lengths of conditioning to find out whether what ever it is that causes the syncytia is being actively produced by the CHOs or is just a contaminant.

Great idea
the sequential sampling would really help
i tought also about the heat treatment but i had a concern a t that time: was the denaturation of toxic protein that would wrongly lead to viral root cause.

i looked for publication about protein or chemical inducing syncytia , i found onlypublication on fusion protein. these fusion protein need to be expressed on the surface of the cells they can not induce syncytia when spiked into cell culture


what do you think of diluting the cho cell fluid and do something like a dilution limit titration (syncytia forming unit)
if the root cause if infectious , we might have a high concentration of contaminant since the abnormal cell morphology appears just after 8hrs

I guess it depends on whether you want to study the syncytia formation or prevent it from happening in your cultures. If you want to prevent it happening then I'd probably thaw out new CHO cells - preferably from a different batch to exclude the possibility that the cells were frozen down with a low-level contaminant. If it still keeps happeneing with the new CHOs then it becomes more interesting.

In addition to heat treatment (which will indeed also denature some proteins) and filtration, you could try UV inactivating whatever is in the CHO cell medium. If I were testing this in say a 6cm petri, I'd UV inactivate (or not) 1mL of CHO cell medium and add this to your VERO cells together with 4 mL of normal VERO medium. (This is to ensure that the medium on the VEROs is still nice and heathy).

Also, I think your idea of a limiting dilution is good since the syncytia formation seems to be faster than you'd expect if it had been due to something being expressed from inside the VEROs.

I would also test new batchs of media components (e.g. Serum, glutamine, medium etc...) to make sure the casue is coming from the cells, and not from the media.
And instead of UV inactivation, I'd do gamma irradiation.

Thanks Guys for all these excellent ideas
will keep you posted of the outcome of the different experiments

You said that in your negative control there was no syncytia formation so that means that the media and components are OK

CORRECT
means that the syncytia inducing factor is present in the CHO cell culture fluid.
now question is : is that factor infectious or not, is it a virus or not, is it a protein ?

There are tubular syncytia in 5-7 weeks human embryonic gut.
They contain bell-shaped nuclei dividing without mitosis. There is no evidence that this kind of syncytium originates by cells fusion.
Need information on syncytium in early development of Protozoans and Metazoans.
Paper published in "Cancer Genetics and Cytogenetics", January 2006.
Gostjeva et al.
e-mail: gostjeva@mit.edu
Apply for additional images of the syncytia in human embryos