Sturgeons, once resilient enough to outlive dinosaurs, are now critically endangered. All 26 species of Acipenseriformes face extinction due to anthropogenic causes. Despite their ecological and economic significance, sturgeon research lacks essential tools such as larval cell lines; the Cellosaurus database lists only one larval cell line (AOXlar7y from Atlantic sturgeon). Larval stages are key to understand fish development, representing a transitional phase between embryonic and adult life that is highly sensitive to temperature shifts, oxygen depletion and pollution. Larval cell lines therefore provide potential in vitro models for studying development and stress responses in endangered species. This study focused on establishing and initially characterizing five novel larval cell lines from siblings of the Siberian sturgeon (Acipenser baerii). The lines proved viable for long-term culture, bio-banking and transfer, displaying different morphologies ranging from epithelial-like to fibroblast-like. Functional assays showed variable mitochondrial activity and extracellular acidification rates. A preliminary targeted gene expression analysis revealed similarity to whole larvae within early passages and in vitro adaptations for certain genes (gapdh, vim, col1a1, pcna). These sibling-derived cell lines hold potential as in vitro tools to deeper explore the biology of Siberian sturgeon larvae and support conservation-focused research.

Caviar extract is widely used in luxury cosmetics and is generally defined as a homogeneous ingredient derived exclusively from sturgeon eggs. However, its molecular composition remains inadequately characterised. In this study, proteomic analyses were performed on 14 commercial caviar samples from different sturgeon species and geographical origins, examined independently in two laboratories. Across three single-origin samples (Germany, Poland, China), 1437 protein groups and 3452 unique peptides were identified, with consistent overlaps with sturgeon ovarian fluid (≥25–38 proteins). Extending this analysis across multiple species confirmed the presence of ovarian fluid-associated proteins in all examined groups, including 69 in Acipenser baerii, 61 in A. gueldenstaedtii, 55 in A. schrenckii, and 49 in H. huso. The results showed that ovarian fluid is consistently co-extracted during standard roe harvesting processes due to its strong egg surface adhesion, making this co-extraction intrinsic rather than incidental. Proteomic profiling revealed a complex mixture of egg- and ovarian fluid-derived proteins, including zona pellucida glycoproteins, immunoglobulins, complement components, proteases, coagulation factors, and antioxidant enzymes. Many of these proteins influence skin biology, suggesting that the functional effects attributed to caviar extract may partially originate from ovarian fluid constituents rather than yolk-derived nutrients alone. At the same time, the presence of immune-active and enzymatic proteins raises important questions regarding safety assessment and regulatory oversight. Species-specific proteomic clustering also indicates considerable composition heterogeneity, challenging assumptions of ingredient standardisation. Together, these results highlight a discrepancy between current definitions and the molecular reality and underscore the need for improved molecular characterisation, updated regulatory definitions, and the consideration of alternative, cell-based production strategies for cosmetic applications.