We’ve discussed a potential risks of carcinogenesis during mesenchymal stromal cells (MSCs) expansion procedures. This discussion also highlighted lack of assays and importance of development “safety criteria” before release of expanded cell product. The recent study published in Blood, investigated chromosomal instability during clinical-grade production of MSCs.
We thus investigated the immunologic and genetic features of MSCs expanded with fetal calf serum and fibroblast growth factor or with platelet lysate in 4 cell-therapy facilities during 2 multicenter clinical trials.
Moreover, some transient and donor-dependent recurring aneuploidy was detected in vitro, independently of the culture process. However, MSCs with or without chromosomal alterations showed progressive growth arrest and entered senescence without evidence of transformation either in vitro or in vivo.
In the follow-up electronic letter, other group shared their data:
While all MSC donors (BM=7; AT=3) were characterized by a normal karyotype, structural abnormalities (deletions), although in a lower number of metaphases (n=2), were scored at first passage in two BM-derived MSC preparations. The abnormal clones were not recorded in the subsequent passages. Considering the normal karyotype scored on the starting sample, we can state that the emergence of chromosomal abnormalities could have been related to the expansion procedure. However, by taking into account the normal karyotype scored thereafter in passages 2 to 5, it could be argued that the genetic alterations detected were not associated with a selective growth advantage in vitro and that the abnormal clone was subsequently spontaneously eliminated from the culture during the subsequent passages.
So, seem like karyotyping is not the best assay for safety control of clinically-grade expanded MSCs. The authors suggest to use genomic assays (such as microarrays) together with karyotyping to confirm the safety of cell products.
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Update!
When I was writing this post I realized that the official position of ISCT on safety of MSCs clinical-grade cell production was just released:
It is our position that the conditions for safe expansion of MSC without generating tumorigenic cells are now well documented. In particular, clinical experience so far shows that if the cells are harvested for therapy well before the cultures reach senescence, there is a very low probability of malignant transformation and tumor formation in patients.
Related posts:
- Minimal criteria for defining human multipotent mesenchymal stromal cells
- Isolation of mesenchymal stem cells from mouse compact bone – video protocol
- Isolation and culture of mesenchymal stem cells from mouse bone marrow
- Preclinical assessment of cord blood hematopoietic stem cell expansion
- Mesenchymal stem cells isolation in one step
