During routine microscopic observation of Cancer Associated Fibroblasts (CAFs), my colleague Pedro Barcellos and I came across these odd geometric "dark" structures inside the cells. We haven't been able to determine what this would be. This was not evident in all cells, but in a fair share of them. And also present in different biological replicates.
We would love to know what these structures represent or to have any hints about what they might be.
Hi Murilo,
We found a similar pattern in exostosis chondrocytes, which had cytoskeletal abnormalities including "massive accumulations composed of actin bundled by 1.5-microm repeat cross-bridges of alpha-actinin. Western blot analysis shows that exostosis chondrocytes from two out of three patients aberrantly produce high levels of muscle-specific alpha-actin, whereas beta-actin levels are similar to normal chondrocytes."
It would be very interesting if your cancer associated fibroblasts have the same phenotype, which might help toward identifying the mechanism. Hope this helps.
Best,
Mark
References
1. Bernard et al. (2000) Cytoskeletal abnormalities in chondrocytes with EXT1 and EXT2 mutations. J Bone Miner Res. 15(3):442-50.
2. Bernard et al. (2001) Diminished levels of the putative tumor suppressor proteins EXT1 and EXT2 in exostosis chondrocytes. Cell Motil Cytoskeleton. 48(2):149-62.
Are these cells fixed? Because I have seen a similar pattern in fixed cells. Maybe you can try staining with F-actin, dapi and fibronectic, and then you can zero down the specific part of the cell.
Best,
Adity.
Mark as a matter of fact this observation of yours seems fitting to what we have seen. We may even wonder if the tgfbeta signaling involved in fibroblast activation into CAFs can also activate BMP pathways that could be seem in your cells.
Sebastian, we have done a few immufluorescence experiments with these cells. But, unlike what Adity observed, this pattern gets more hard to find when cells are seeded and fixed.
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