Genetic engineering allows scientists to directly manipulate cells to produce a desired effect or eliminate an undesired one. They’re doing so by delivering signals into those cells.
At the DRI, scientists are altering cell function in an attempt to:
- Protect insulin-producing islet cells
- Direct stem cells to become islet cells
Scientists are pursuing two strategies to deliver specific molecules into cells:
- Protein therapy
- Gene therapy
Protein therapy
Of the two strategies, protein therapy may offer greater potential benefit to those with type 1 diabetes. It is also seen as safer and more efficient.
With this strategy, scientists insert specific molecules into a cell to temporarily stimulate certain biological signals – or to block those signals.
Example: when islets are retrieved from a pancreas, processed in a lab and then transplanted into a patient, the cells undergo a great deal of stress. That stress can trigger “signals” that lead to cell death, known as apoptosis.
Dr. Ricardo Pastori, head of the DRI’s molecular biology lab, and his team have shown the potential of a new approach to deliver protective signals into the islets to block these harmful signals and prevent islet death.
To achieve this, they are using molecules that are uniquely capable of crossing cell membranes to reach the cells. The molecules are called PTDs (Protein Transduction Domains). At the DRI, scientists are fusing specific proteins to the PTDs, and using the PTDs to deliver the desired protective signals into the islets.
Researchers are testing whether PTDs can protect islets during various stages of the transplant process: before the cells are isolated from the donor pancreas, during isolation and after – while the cells are in culture in the lab.
If successful, this will help researchers to:
- Consistently obtain more high quality islets
- Reduce the number of transplanted islets required to achieve normal metabolic function
- Prolong the period between isolation and transplantation – allowing patients in remote locations adequate time to travel to a transplant center to undergo the procedure.
Use with stem cells
DRI investigators are also using this biological tool in stem cell development. They already have demonstrated that, by using protein therapy, they can guide a stem cell down the path to become an islet cell.
Scientists call this cell differentiation, when a stem cell follows a developmental sequence, transforming into a specific cell type.
By introducing certain molecular “switches,” the DRI is prompting stem cells to move from one stage to the next. They’ve done so by using PTDs engineered with the key proteins involved in pancreas development.
One switch being used is the protein TAT-Ngn3, which is one of the master regulators of pancreatic islet development. The addition of this switch by protein transduction resulted in significant improvement in the efficiency of endocrine cell development.
Two other switches (TAT-Pax4 and TAT-Pdx1) have already been generated. The current strategy is to test them individually and then in combination with the others.
The ultimate goal is to guide these stem cells down the developmental pathway to become functioning islet cells. If successful, stem cells could provide an unlimited supply of insulin-producing cells for transplant.
This technology is also being used to develop strategies to change an existing cell type, such as a liver cell, into one that produces insulin. These cells are of particular interest since the liver and pancreas share the same developmental pathway. The great appeal of this process, known as “transdifferentiation” is the potential use of a patient’s own cells as a supply source.
In addition, researchers are looking to PTDs as a way to prompt islet cells to regenerate or regrow in the native pancreas.
Gene therapy
We know viruses can make us sick. That’s because they efficiently deliver germs into cells. Researchers at the DRI are trying to take advantage of this – using viruses, not to deliver harmful germs, but to deliver protective genes.
Scientists are testing several types of viruses. The challenge is to identify a safe and effective “carrier” that can deliver the gene into the targeted cell.
And, researchers will need to develop a mechanism to “turn off” the gene when its work is done – or turn it on in a regulated fashion when it is needed.