Human stem cell exposure to developmental stage zebrafish extracts: a novel strategy for tuning stemness and senescence patterning

Background: Zebrafishexhibits extraordinary ability for tissue regeneration. Despite growing investigations dissecting the molecular underpinning of such regenerative potential, little is known about the possibility to use the chemical inventory of thezebrafishembryo to modulate human stem cell dynamics.

Methods: Extracts fromzebrafishembryo were collected at different developmental stages, referred to as ZF1, ZF2, ZF3 (early stages), and ZF4, ZF5 (late stages). Human adipose-derived stem cells (hASCs), isolated from microfractured fat tissue obtained with a novel non-enzymatic method (Lipogems), were cultured in absence or presence of each developmental stage extract. Cell viability was assessed by MTT assay. Nuclear morphology was investigated by cell-permeable dye 4’,6-DAPI. Caspase-3 activity was assessed by ELISA. Gene transcription was monitored by real-time PCR.

Results: Late developmental stage extracts decreased cell viability and elicited caspase-3 mediated apoptosis. This effect did not involveBaxorBcl-2transcription. Conversely, early developmental stage ZF1 did not affect cell viability or apoptosis, albeit increasingBax/Bcl-2mRNA ratio. ZF1 enhanced transcription of the stemness/pluripotency genesOct-4, Sox-2andc-Myc. ZF1 also induced the transcription ofTERT, encoding the catalytic subunit of telomerase, as well as the gene expression ofBmi-1, a chromatin remodeler acting as a major telomerase-independent repressor of senescence. These transcriptional responses were restricted to the action of early stage factors, since they were not elicited by late developmental stage ZF5.

Conclusions: Exposure to early developmental stagezebrafishembryo extracts may enhance stem cell expression of multipotency and activate both telomerase-dependent and -independent antagonists of cell senescence. These outcomes may prove rewarding during prolonged expansion in culture, as it occurs in most cell therapy protocols.

Margherita Maioli, Federica Facchin, and Eva Bianconi equally contributed to the study.