# The Establishment of Asian Black Bear (Ursus thibetanus) Fibroblast Cell Line

## TL;DR

Researchers created an immortalized cell line from Asian black bear skin to study their skin health and diseases without harming wild animals.

## Contribution

The first immortalized fibroblast cell line for the Asian black bear (Ursus thibetanus) was established using hTERT gene transduction.

## Key findings

- The hTERT gene enabled indefinite division of Asian black bear skin fibroblasts while maintaining genetic and functional integrity.
- The cell line effectively models wound healing processes under inflammatory conditions.
- The immortalized cell line provides a sustainable model for studying skin physiology and diseases in this protected species.

## Abstract

The Asian bear (Ursus thibetanus, UT) is a a protected species, and research into its skin physiology and diseases is severely limited by the scarcity of tissue samples and the difficulty of maintaining cells in the laboratory. To overcome these challenges, this study established a permanent (immortalized) line of skin fibroblast cells from the Asian black bear. By introducing the human hTERT gene into primary skin cells, we enabled them to divide indefinitely while retaining their normal genetic structure and biological functions. We further validated that these cells can effectively simulate wound healing processes, such as cell migration, under inflammatory conditions. This newly established cell line provides a sustainable and valuable tool for studying skin health and diseases in Asian black bears, supporting conservation efforts without the need for repeated sampling from wild animals.

The Asian black bear (Ursus thibetanus, UT), a Class II protected species in China, presents significant challenges for dermatological research due to limited availability of skin specimens and technical difficulties in fibroblast isolation. To address this, this study developed an immortalized fibroblast cell line through lentiviral-mediated introduction of human telomerase reverse transcriptase (hTERT). The hTERT gene fragment was amplified via PCR and cloned into a eukaryotic expression plasmid using homologous recombination. The recombinant plasmid was packaged into lentiviral particles using a three-plasmid system (psPAX2, pMD2.G) for stable transduction of primary Ursus thibetanus skin fibroblasts (UTSF). Puromycin selection enabled isolation of positive clones, which were subsequently expanded to establish an immortalized cell line. Comprehensive validation through Western blotting, PCR and immunofluorescence confirmed successful genomic integration and sustained expression of hTERT. This study successfully immortalized the skin fibroblasts of black bears and established a fibroblast cell line of Asian black bears. This immortalized UTSF cell line provides a critical in vitro model system for investigating cutaneous physiology and pathogen interactions in this protected species.