Immortalization of mouse primary astrocytes

Development of a Bmi1+ Cardiac Mouse Progenitor Immortalized Model to Unravel the Relationship with Its Protective Vascular Endothelial Niche

The adult mammalian heart has been demonstrated to be endowed with low but real turnover capacity, especially for cardiomyocytes, the key functional cell type. The source, however, of that turnover capacity remains controversial. In this regard, we have defined and characterized a resident multipotent cardiac mouse progenitor population, Bmi1+DR (for Bmi1+ Damage-Responsive cells). Bmi1+DR is one of the cell types with the lowest ROS (Reactive Oxygen Species) levels in the adult heart, being particularly characterized by their close relationship with cardiac vessels, most probably involved in the regulation of proliferation/maintenance of Bmi1+DR. This was proposed to work as their endothelial niche. Due to the scarcity of Bmi1+DR cells in the adult mouse heart, we have generated an immortalization/dis-immortalization model using Simian Vacuolating Virus 40-Large Antigen T (SV40-T) to facilitate their in vitro characterization. We have obtained a heterogeneous population of immortalized Bmi1+DR cells (Bmi1+DRIMM) that was validated attending to different criteria, also showing a comparable sensitivity to strong oxidative damage. Then, we concluded that the Bmi1-DRIMM population is an appropriate model for primary Bmi1+DR in vitro studies. The co-culture of Bmi1+DRIMM cells with endothelial cells protects them against oxidative damage, showing a moderate depletion in non-canonical autophagy and also contributing with a modest metabolic regulation.

Immortalization and Characterization of GFAP-expressing Glial Cells from the Adult Mouse Hypothalamus, Cortex, and Brain Stem

The generation of astrocyte cell lines from the hypothalamus is key to study glial involvement in hypothalamic physiology, including energy homeostasis. As such, we immortalized astrocytes from the hypothalamus of an adult male CD-1 mouse using SV40 T-antigen to generate the mHypoA-Ast1 cell line. A comparative approach was taken with two other murine GFAP-expressing cell lines that were also generated in this study: a mixed glial cell line from the cortex (mCortA-G1) and an oligodendrocyte cell line from the brainstem (mBstA-Olig1), as well as an established microglial cell line (IMG). mHypoA-Ast1 cells express GFAP, alongside other astrocytic markers such as Aldh1l1, Aqp4, Glt1 and S100b, and express low levels of microglial, ependymal and oligodendrocyte markers. 100 ng/mL lipopolysaccharide (LPS) elevated mRNA levels of Il6, Il1b, Tnfα and Cxcl5 in mHypoA-Ast1 cells after 4 h, while 50 μM palmitate increased Il6 and Chop mRNA, demonstrating the ability of these cells to respond to inflammatory and nutrient signals. Interestingly, co-culture of mHypoA-Ast1 cells with mHypoE-N46 hypothalamic neuronal cells prevented the palmitate-mediated increase in orexigenic neuropeptide Agrp mRNA in mHypoE-N46 cells, suggesting that this cell line can alter neuronal responses to nutrients. In conclusion, we report mHypoA-Ast1 cells representing a functional astrocyte cell line from the adult mouse brain that can be used to study the complex interactions of hypothalamic cells, as well as dysregulation that may occur in disease states, providing a key tool for neuroendocrine research.

Generation and application of immortalized sheep fetal fibroblast cell line

BACKGROUND

Primary sheep fetal fibroblasts (SFFCs) have emerged as a valuable resource for investigating the molecular and pathogenic mechanisms of orf viruses (ORFV). However, their utilization is considerably restricted due to the exorbitant expenses associated with their isolation and culture, their abbreviated lifespan, and the laborious procedure.

RESULTS

In our investigation, the primary SFFCs were obtained and immortalized by introducing a lentiviral recombinant plasmid containing the large T antigen from simian virus 40 (SV40). The expression of fibronectin and vimentin proteins, activity of SV40 large T antigen, cell proliferation assays, and analysis of programmed cell death revealed that the immortalized large T antigen SFFCs (TSFFCs) maintained the same physiological characteristics and biological functions as the primary SFFCs. Moreover, TSFFCs demonstrated robust resistance to apoptosis, extended lifespan, and enhanced proliferative activity compared to primary SFFCs. Notably, the primary SFFCs did not undergo in vitro transformation or exhibit any indications of malignancy in nude mice. Furthermore, the immortalized TSFFCs displayed live ORFV vaccine susceptibility.

CONCLUSIONS

Immortalized TSFFCs present valuable in vitro models for exploring the characteristics of ORFV using various techniques. This indicates their potential for secure utilization in future studies involving virus isolation, vaccine development, and drug screening.

Primary Astrocytes Purification and Immortalization

Astrocytes, the most abundant cells in the central nervous system (CNS), are essential for neuronal development, network formation, and overall CNS homeostasis. Primary astrocyte culture has been successfully used as a tool to study astrocyte biology in vitro. In the present protocol, a modified immunopanning method was utilized to obtain and purify primary astrocytes from mouse cortex and spinal cord in a relatively quick and inexpensive way. Purified primary astrocytes were then immortalized through infection of lentivirus expressing the SV40 large T antigens. In addition, we provide protocols to determine the expression levels of astrocyte-specific markers and to perform functional studies measuring the ATP-induced calcium flux in the immortalized astrocytes. Following the described protocols assures that the immortalized astrocytes that one prepares mimic the cell biology of primary astrocytes in culture. Thus, the purification and immortalization protocols for primary astrocytes presented in here provide two models for the studies of astrocyte biology and may be useful for the immortalization of other types of primary cells. © 2023 Wiley Periodicals LLC. Basic Protocol 1: Primary astrocyte purification by a modified immunopanning method Support Protocol: Serum-free primary astrocyte culture Basic Protocol 2: Primary astrocyte immortalization Basic Protocol 3: Calcium transient detection in astrocytes.