Fibroblasts Studies: The Mitochondria and the Cytoskeleton, and Treating Yeast Biofilms

Fibroblasts are the main cell type in stromal tissue, the supporting tissue of an organ that contains structural and connective components. They are a multifunctional cell type whose main function is to secrete extracellular matrix, which forms the connective tissue of an organ. Fibroblasts play important roles in tissue homeostasis, and fibroblast dysregulation can play a role in disease. For example, cancer-associated fibroblasts accelerate tumor progression by promoting tumor growth and support through secretion of growth factors and increased stroma production. Fibroblasts are a versatile cell type used in many types of research applications and can be used to study cell biology, wound healing, drug efficacy, and much more.

The Lifeline® catalog of fibroblasts includes:

• Cardiac fibroblasts
• Gingival fibroblasts
• Bladder fibroblasts
• Dermal fibroblasts (neonatal and adult)
• Lung fibroblasts
• Uterine fibroblasts
• Vas deferens fibroblasts

Lifeline® fibroblasts are optimized for growth in FibroLife® medium. Below are summaries of two studies that used Lifeline® fibroblasts to investigate the relationship between mitochondria and the cytoskeleton, and identify new compounds to target difficult to treat yeast biofilms.

Recent Studies Using Lifeline® Fibroblasts

Mitochondria are critical components of a cell’s metabolic machinery. They are responsible for cellular respiration, the conversion of nutrients and oxygen into energy in the form of ATP through oxidative phosphorylation. Importantly, within a cell, mitochondria are mobile; they may be directed by cytoskeletal components to areas within the cell that require more energy.

In particular, conditions such as cancer may disrupt mitochondrial dynamics, which can alter cellular metabolism. To dissect how the cytoskeleton regulates mitochondrial movement and whether this affects mitochondrial function, Jang et al. compared the responses of Lifeline® human dermal fibroblasts and human fibrosarcoma cells to nocodazole (a microtubule disruptor), A23 (a calcium ionophore that disrupts microtubules), and cytochalasin D (an actin depolymerizer that disrupts actin microfilaments).

The authors first measured how the net distance traveled by mitochondria changed in response to each individual treatment, as well as a combination treatment of A23 and cytochalasin D. They found that treatment of fibroblasts with A23, cytochalasin D, and the A23/cytochalasin D combination increased net movement, while nocodazole decreased net movement. Interestingly, mitochondria in fibrosarcoma cells exhibited increased movement at baseline compared to that in fibroblasts at baseline. Additionally, while individual treatment with A23 or cytochalasin D did not affect mitochondrial movement, the combination decreased the net distance traveled. Similar to in fibroblasts, nocodazole also decreased mitochondrial movement in fibrosarcoma cells.

Mitochondrial fission (division) and fusion are adaptation responses to environmental changes and stress. The authors found that fibrosarcoma cells had higher rates of fission and fusion than fibroblasts, and while fission and fusion increased in both cell types in response to cytochalasin D, A23, and the combination, nocodazole decreased the occurrence of these events below baseline in fibrosarcoma cells.

Next, the authors determined whether these cytoskeletal disruptions affected mitochondrial function. They demonstrated that at baseline, fibrosarcoma cells exhibited reduced respiration and elevated production of damaging reactive oxygen species (ROS). In contrast, fibroblasts displayed a higher respiration rate that was unaffected by A23 treatment, but significantly increased by A23 and cytochalasin D combination treatment. This combination treatment induced an increase in ROS production, but not to the to level of untreated fibrosarcoma cells.

Together, the results of this study illustrate the dynamic interactions between mitochondria and the cytoskeletal network. Importantly, the authors also reveal interesting differences between normal fibroblasts and cancer cells, which require high energy levels (increased mitochondrial movement), but do not utilize oxidative phosphorylation for the bulk of their energy generation, instead relying on glycolysis (decreased respiratory rate).

Candida albicans is an opportunistic pathogen that is part of the normal human flora. However, as an opportunistic pathogen, it can cause infections such as oral thrush and vaginitis in individuals who may be immunocompromised. Although anti-fungals successfully treat most of these infections, resistance to these agents is a growing problem. In particular, anti-fungal resistance is often driven by growth of the yeast in biofilms, aggregates of the organism that are covered with an extracellular polymeric substance matrix, made up largely of polysaccharides.

To overcome C. albicans resistance to anti-fungals, LaFleur et al. developed a high-throughput screen to identify agents that synergize with clotrimazole (an anti-fungal agent) against C. albicans biofilms. The authors first established that C. albicans biofilms could be used in a high-throughput assay format. In this way, they were able to culture C. albicans biofilms and test the ability of over 120,000 compounds to inhibit biofilm metabolic activity. From this analysis, they identified only 19 promising candidates, of which 14 were available for further analysis. Of these 14, 5 showed significant inhibition of biofilm metabolic activity in combination with clotrimazole.

To determine whether the concentration of each candidate required to inhibit biofilm metabolic activity was cytotoxic to mammalian cells, the authors treated Lifeline® human fibroblasts with increasing doses of each of the 14 test compounds and measured cell metabolic activity. From this assay, they identified 4 compounds that displayed synergistic activity with clotrimazole and were not cytotoxic to fibroblasts. Therefore, this study demonstrates the feasibility of using biofilms in a high-throughput assay format. Importantly, the authors also identified 4 potential therapeutic agents that work in concert with clotrimazole to combat C. albicans biofilms.

Every other week we feature one of our cell types and review the ways researchers are using these cells to answer their scientific questions. Do you use Lifeline® cells in your research? Share your work with us and it could be featured here on a future blog!