Diverse factors account for the interest in (and success of) the adult stem cell field in recent years.
These factors include breakthroughs in reprogramming, ethical and regulatory issues more tractable than those encountered with embryonic stem cells, and (with a wink to The Graduate) … plastics. Diverse factors will likely contribute to the field’s future as well. At the “Adult Stem Cell Therapy and Regenerative Medicine Conference” factors such as manipulation, transduction, visualization, and homing were considered, as was cell culture.
How the cells are nurtured can be as important as how they are deployed. When it comes to preparing cells for possible (re)introduction into animals, every precaution needs to be taken—from the obvious (keeping them sterile and cross-contamination-free), to the subtle (housing and manipulating them in conditions that mimic their inherent physiology). Mimetic culture can support viability as well as promote the desired differentiation state.
It’s not enough to keep cells in a 37°C, 5% CO2 incubator, passage them in a laminar flow hood, and then view them on a benchtop microscope. According to Kevin Murray, director of sales and marketing for BioSpherix, cells should be maintained in uninterruptable conditions: “Whatever conditions [you use for] culturing your cells…you should also use for processing them. For instance, incubators are set up to mimic body temperature and control for CO2, which is basically how they manage pH in the media. Another aspect we advocate is oxygen control, because cells in the body don’t see room air.”
Researchers generally take great care to match the body’s physiological conditions in their incubators, but the one thing that hardly anybody controls for is oxygen. “And oxygen is tied to the expression of a multitude of genes, to cell signaling—many of the things that researchers ultimately are looking at, whether they know it or not,” Murray said.
While the cells may not venture out of the incubator for very long, many of these genes may be very oxygen-labile—taking hours to upregulate but literally minutes to downregulate. BioSpherix’ Xvivo system is a set of equipment modules—from hypoxic incubators to containment hoods to processing chambers that can house microscopes, centrifuges, and a variety of other equipment, including automation and robotics, all in a controlled environment. The barrier/isolator modules are designed to fit together in a range of configurations to maintain a constant environment in which cultures can be manipulated without being exposed to the room’s atmosphere.
Only a very small percentage of the millions or billions of cells carefully grown and expanded ex vivo and introduced into an animal will survive to engraft and replicate, Murray said. “One of the main reasons they die is that they get very used to room air—about 21% O2—and when you inject them into the body of an animal they’re probably in an environment that’s less than 5% O2.” Mountain climbers need to acclimate to the atmosphere of Mount Everest, Murray pointed out, and something similar is likely true for injected cells.