Cytocentric Blog

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Cytocentric Visionaries: Donald Phinney

Part 3: The Cell Cycle Is the Redox Cycle, and All Clinical MSC are Stressed

In Part Two, Chief Scientific Officer Alicia Henn talked with Dr. Phinney about MSC, the exosomes that they produce and therapeutics. Today we talk about MSC and oxidative stress in vitro. This conversation was edited for length.

 

You set up MSC and macrophage to interact on a stage to study them. Any good play begins with a stressor and in this case, it was oxidative stress.

DP: This is something that has evolved over a number of years now. It is quite clear that bone marrow is a low oxygen environment. Oxygen saturation varies across the bone marrow and sinusoids, but it is certainly low. For many years, because they had little choice in the early days, people grew cells in atmospheric oxygen.

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Cytocentric Visionaries: Donald Phinney

Part Two: MSC vs Exosomes and Therapies

In Part One, Chief Scientific Officer Alicia Henn talks with Dr. Phinney about his publication in Nature Communications, ”Mesenchymal stem cells use extracellular vesicles to outsource mitophagy and shuttle microRNAs”[Phinney et al., 2015]. Here we continue that conversation (edited for length).

 

What direction are you taking your exosome research?

DP: I’m fascinated that there are so many papers suggesting that exosomes have as many applications as MSCs. The idea for a number of years has been that MSCs are a unique cell therapy product because they can adapt to their microenvironment. Various companies’ websites clearly state that their therapy is advantageous because if the cells are in an ischemic or inflammatory environment they can respond appropriately and produce paracrine factors to mitigate the effects of that environment.

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Cytocentric Visionaries: Donald Phinney, Chair Department of Molecular Therapeutics, The Scripps Research Institute

Part One: Mesenchymal Stem Cells, as Healers, Aren’t So Selfless

Chair of the Molecular Therapeutics Department at Scripps, Dr. Phinney has almost 20 years of experience in the adult stem cell field and has been an editor of prominent stem cell journals. Here, Alicia Henn talks with Dr. Phinney about his latest publication in Nature Communications, ”Mesenchymal stem cells use extracellular vesicles to outsource mitophagy and shuttle microRNAs”[Phinney et al., 2015]. This conversation was edited for length.

Phinney and his co-authors reported that in response to oxidative stress, MSCs export damaged mitochondria to nearby macrophages, which recycle them for their own bioenergetics. The MSCs also export exosomes containing miRNAs that reduce the inflammatory activities of macrophage through TLR-7 signaling pathways. This benefits the nearby MSCs, and is also a mechanism by which MSCs may have their clinical effects on surrounding tissues.

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Dalton in the Incubator: Gas Control in Semi-sealed Chambers

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We are all familiar with how CO2 is infused into cell culture incubators to raise CO2 to physiologic levels and keep carbonic acid based media in the proper pH range for cells. However, managing a system for infusing other gases necessitates understanding how mixed gases work in a semi-sealed chamber.

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Temperature, CO2, and pH in Cell Culture Media -

What Seems Best for Incubation is Not Always Best for Handling

Most, but not all, cell culture media contain carbonate-based buffers which work with elevated gaseous carbon dioxide levels in the incubator to stabilize cell culture pH (see figure).  Carbonate-based buffers are present in vivo and so seem like an obvious choice for physiologically relevant incubation conditions. However, carbonate-based buffers can create non-optimal conditions for cultures during cell culture handling outside of the incubator. The critical cell parameters of temperature and carbon dioxide levels can affect carbonate buffered cell media.

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