Production Opportunities: Trends in Stem Cell Therapy Research and Development | Corning

Stem cell research took an enormous leap forward in 2007 with the introduction of induced pluripotent stem cells (iPSCs). A decade and a half later, Corning Field Application Scientists Tom Bongiorno and Whitney Wilson sat down to discuss the trends they're seeing in stem cell therapy research and development.

Shifting from Autologous to Allogeneic Therapies

Bongiorno says he's seeing more labs scaling up stem cell culture in anticipation of production opportunities. This coincides with a shift from autologous therapies to allogeneic therapies. "For a while, the field was really pushing for autologous therapies because of the immune benefits, which drastically reduce the chance of rejection," notes Bongiorno. "While the science side of things worked pretty well, the logistics are really complicated. You have to get your cells from the patient, do your processing, and get cells back to the patient in a very short time." With allogeneic therapy, cells from one donor are used to treat many patients.

Wilson explains that allogeneic therapies allow labs to generate more of an off-the-shelf product. "If you consider something like neural stem cell therapy — to treat someone who's suffered a spinal cord injury — you want to administer those cells within the first eight hours of injury," she says. "That's just not feasible with an autologous product."

Exploring Stem Cell Sources

The move toward allogeneic therapies is also impacting the source of stem cells being used.

"Traditionally," Bongiorno explains, "mesenchymal stem cells (MSCs) would commonly come from bone marrow or adipose tissue. These cells can have issues with differentiating properly and potentially some issues with karyotype stability and senescence during extended in vitro expansion. More recently, we've seen a lot of work with MSCs that are coming from placental tissue or umbilical cord tissue to help address these issues."

"In generating cells for stem cell therapy, the biggest concern is safety," adds Wilson. "In general, younger tissues are better for chromosomal stability. So the iPSC field has been working toward creating iPSC line banks from cord blood, which is very young tissue."

Another concern is having a tissue match for any potential cell therapy patient. "In these stem cell banks, a lot of units are haploidentical," Wilson notes, meaning they're homozygous for a particular human leukocyte antigen (HLA) haplotype. These haploidentical units can be a match for any patient who carries at least one copy of that haplotype. Calculations indicate that the majority of a diverse population could be served with fewer than 80 haploidentical lines.

For patients who may not find a match in these stem cell banks, there's CRISPR. "A lot of folks are using CRISPR on iPS cell lines to take out the different genes that would cause tissue incompatibility," according to Wilson. "This is very similar to something MSCs do on their own. Unlike any other cell type that we know of, MSCs are actually immunoprivileged because they do not express Major Histocompatibility Complex," which is called HLA in human cells. "So basically, anyone can get a mesenchymal stem cell line from any donor," she says.

Creating Stem Cells from Stem Cells

Culturing iPSCs is relatively straightforward, which makes them an excellent source of more challenging stem cell types. As Wilson explains, "Neural stem cells are very few and far between in the body. They're also very difficult to isolate because they live within the brain. This is why working with iPSCs is so powerful. You can expand those cells — to our knowledge indefinitely — and get a really large starting population to then differentiate into neural stem cells."

"Hematopoietic stem cells are also very difficult," continues Wilson. "You can isolate them from adults, but you basically can't grow them more than a day or two. They won't expand in vitro. So a lot of folks are using iPSCs and differentiating them into hematopoietic stem cells. This gives you a more robust starting population for downstream differentiation into things like T cells and natural killer cells."

Scaling up Adherent Cell Culture

One of the big challenges for stem cell-based therapies is that stem cells are a lot more sensitive than cell lines. "Adult stem cells or multipotent stem cells have a very limited time that they can remain multipotent in culture," Wilson explains. "Some cell types will senesce; others will begin to differentiate spontaneously." For stem cell manufacturing, these issues are compounded by the huge numbers of cells required. Clinical cell therapies typically require 100 million to 10 billion stem cells per dose.

Bongiorno explains that "in the past, to scale up, a lot of customers were working to transition naturally adherent cells into a suspension space because there weren't many technologies for scaling up adherent cell culture." However, that situation has since changed. "Corning is a leader in this area and has introduced a lot of new technologies — including Corning® CellSTACK® and HYPERStack® vessels, the Ascent® Fixed Bed Reactor (FBR) system, and dissolvable microcarriers — that can help with adherent cell culture scale up and dramatically expand production opportunities." Surface coatings like Corning Matrigel®, Laminin, fibronectin, and Synthemax™ help stem cells stay attached as single cells or as clusters.

Bongiorno also notes that, in his experience, "Trying to move a cell that's naturally adherent — like a mesenchymal cell or an iPS cell — into a suspension environment is extremely challenging. Honestly, I think it's so challenging that it's not even worth it. It's much better to work in an adherent platform."

Accordingly, one of Corning's newest offerings is the Ascent FBR system, which provides enormous amounts of surface area in a relatively small footprint — up to 5 m2 in a closed, semi-automated benchtop system with larger scale systems in development — and the ability to continuously control nutrient delivery and waste removal. When microbeads, such as Corning dissolvable microcarriers, are paired with third-party bioreactors even larger batches are possible.

Both Wilson and Bongiorno consider microcarriers to be adherent platforms, but Bongiorno cautions, "It's kind of a gray area because the cells are attached to something but are in a dynamic environment. The sheer forces can sometimes impact stem cells and cause them to differentiate. So, I think you absolutely can work with stem cells in a bioreactor with microcarriers, but these considerations are important to test."

Using MSC-Derived Extracellular Vesicles for Therapy

An exciting new trend in this space is the use of MSC-derived extracellular vesicles for therapy. As Wilson explains, "Mesenchymal stem cells are so popular because they excrete a lot of proteins that have a lot of therapeutic advantages. For example, they're really good at quieting down an overactive immune system. It turns out that a lot of those proteins are actually secreted in exosomes or extracellular vesicles (EVs). So, if you can harvest the EVs and administer them into patients, you can have many of the therapeutic benefits without the risk of injecting a cell line into someone."

Bongiorno shares this excitement for EVs but cautions that MSCs might still be the best choice in some situations. "MSCs are a bit more established," he notes. "There's more technical knowledge about how to work with these cells, how to expand them, and how to characterize them." MSCs have also been used in more clinical trials to date.

Wilson adds, "The other big advantage to using mesenchymal stem cells over MSC-derived EVs is that theoretically, the MSCs will exist in the body for much longer than a single dose of EVs. A lot of folks are engineering MSCs to overexpress cytokines or growth factors like brain-derived neurotropic factor." The goal is to transplant these cells into patients so that they can provide long-term therapeutic benefits. "If you were to try the same type of therapy with EVs, it would require multiple injections," she concludes.

Undoubtedly, stem cell therapies will continue to expand as researchers continue to push the limits.

Curious to learn more about the direction this research is heading and the contributions Corning is making? Download the Stem Cell Therapies Playbook or read a related case study to access additional insights.