This posting is for informational purposes only and in no way intended as medical and other personal advice
Summary. Given the great ability of gastrointestinal (GI) organs to continuously regenerate their epithelial cells, Ariyachet and co-workers (reference 1) set out: (1) to reprogramm cells, located in the antral stomach region of mice, to insulin secreting pancreatic Beta-like cells (here referred to as insulin+ cells) capable of reversing hyperglycemia and sustain normal glucose in mice rendered type 1 diabetic; and (2) to make this technology more relevant to potential testing in humans, these investigators excised stomach tissues from the insulin+ transgenic mice and made “stomach mini-organs” that, upon implant in the omentum of type 1 diabetic mice, restored insulin production and normalized glucose levels in these animals. Moreover, when the insulin+ cells were purposely killed, new insulin+ cells freshly regenerated and kept producing insulin in response to high glucose levels.
Scientists all-over the world are in a hot pursuit of technologies that would enable the replacement of lost or damaged pancreatic Beta-cells in patients with Type 1 Diabetes (T1D) to permanently restore their bodies abilities to keep glucose under control. We have already addressed research’s successes to produce pancreatic Beta-cells/and islets from stem cells and protect them from the host immune system upon their insertion into T1D animal models or patients. In fact, in previous narratives in our post, Type 1 Diabetes: Research Advances to develop a cure, we discussed: (1) islets transplants in the liver and omentum of T1D patients; (2) the development of protocols for the conversion of stem cells into large quantities of Beta-cells for future transplants in humans; (3) efforts in the re-education of the faulty immune system that kills Beta-cells; and (4) advances to clinical trials of technologies related to the encapsulation of insulin producing Beta-cells/and islets into devices that protect them from attack by the host immune system.
Here we describe work by Ariyachet and coworkers (just appeared in the Press, reference 1) related to reprogramming stomach cells to become insulin secreting pancreatic Beta-like cells (insulin+ cells) and their application to normalize glucose levels in mice rendered type 1 diabetic.
Stomach tissue reprogrammed to produce Beta-cells
Ariyachet and coworkers (Reference 1) set out to explore whether they could convert cells of the Gastrointestinal (GI) epithelium into insulin+ cells. The underlying concept for exploring the GI epithelium (especially stomach and intestine) is that the GI is an organ that contain many adult stem/progenitor cells with a great ability to continuously regenerate epithelial cells; therefore, if an effective strategy to coax GI adult stem/progenitor cells to become insulin+ cells is developed, then these new cells could take over the role of lost or damaged natural pancreatic Beta-cells and produce insulin in response to glucose. Moreover, each time the insulin+ cells are killed by T1D autoimmunity, the regenerative power of the engineered GI tissues will be able to crank out fresh insulin+ cells and provide a renewable source of insulin.
Previous studies regarding reprogramming GI tissues to insulin+ cells have employed either deletion of Foxo1 gene (Reference 2 and comments) or the expression of Ngn3, Pdx1, and Mafa genes (abbreviated NPM, see Reference 3 and comments); and by using these two strategies epithelial cells from the intestine were converted to insulin+ cells. However, neither of the two strategies led to insulin expression in the stomach.
To explore whether there are cells in the GI epithelium that would be converted to insulin+ cells more efficiently than those of the intestine, Ariyachet and co-workers engineered mice (transgenic mice, footnote 1 ) able to express the three NPM factors in the GI. In fact, when they treated the transgenic mice with doxycycline (Dox), to induce the expression of the NPM genes, they found a good conversion efficiency of GI cells into insulin+ cells. The highest conversion was observed in the antral stomach which was found to be nearly twice as much that found in the duodenum and almost three times that of the intestine.
When the natural pancreatic Beta-cells of the mice were killed by treatment with streptozotocin (STZ), the insulin+ cells, obtained by reprogramming the GI cells, took over the production of insulin and the animals remained normoglycemic (normal glucose) for the time they were monitored (up to 6 months), while control mice (with no insulin+ cells expression) also treated with SZT (to eliminate their the natural pancreatic Beta-cells) became hyperglycemic and died within 8 weeks.
Next they eliminated the insulin+ cells with a second SZT treatment leaving the mice with hyperglycemia as they had no cells left able to produce insulin. Yet, this situation of hyperglycemia did not last long; the efficient regenerative power of the engineered GI stem/progenitor cells rapidly converted them into new insulin+ cells which were able to normalize blood sugar levels.
Bioengineered insulin producing mini-organs implanted into mice made T1D able to control glucose
The approach described above is an interesting “proof of concept” showing that, in transgenic mice, GI cells can be programmed to become insulin producing cells, but performing this conversion with the idea of future development in humans is not sound as the conversion in the stomach might use up many GI cells and may disrupt important physiological processes normally carried out by GI cells.
To make this technology more relevant to potential testing in humans, these investigators excised stomach tissues from the insulin+ transgenic mice. The tissues were embedded in gels that were loaded into scaffolds and the resulting products were transplanted in the omentum of mice where they formed stomach spheres (“stomach mini-organs”) within a few weeks.
They tested whether the stomach mini-organs harboring the engineered genes capable to convert GI cells into insulin+ cells would support production of insulin. To do that, they killed the natural pancreatic Beta-cells of the mice by treatment with STZ. Indeed, the stomach mini-organs (of 5 out 22 mice, footnote 2) took over the production of insulin and the animals remained normoglycemic for the 6 week time they were monitored, while control mice (with no reprogrammed cells) also treated with SZT became hyperglycemic.
Next, they tested whether the engineered stomach mini-organs would be able to use their reservoir of stem/progenitor cells to continuously renew dead insulin+ cells. To that extent, they eliminated the insulin+ cells present in the stomach mini-organs with a second SZT treatment leaving the mice with hyperglycemia as they had no cells left able to produce insulin; yet, this situation of hyperglycemia did not last long because the highly generative capacity of the genetically engineered GI tissues rapidly cranked out new insulin+ cells which were able to normalize blood sugar levels.
In conclusion, Ariyachet and coworkers reached their objective “to devise improved strategies to derive functional insulin-secreting (insulin+) cells from GI tissues and to harness insulin-secreting (insulin+) cells from GI tissues“. These are interesting findings because they may be relevant to future development of T1D treatment. IF stem cell technology will become safely applicable to humans, one could in principle take stomach tissues from a T1D patient and make, in the laboratory, “stomach mini-organs” capable of converting their reservoir of stem cells to producing insulin+ cells. Upon “stomach mini-organs” implant in the patient, they would maintain normal glucose levels and keep self renewing the insulin+ cells as they are killed by the immune system.
(1). Recombinant DNA technology has made it possible deleting or modifying genes of the genomes of living organisms, or introducing certain genes in the genome. In addition, it allows transferring genes from one species to another. Animals genetically modified are called transgenic animals and are useful in medical research. For example, in the study report discussed here, the introduction of three genes in GI tissues allowed to induce GI cells to convert into insulin+ cells. Indeed, gene modifications make it possible to study the normal function of genes (and the proteins they express) and their involvement in diseases.
(2). Only five out of 22 mice had insulin+ cells; this is because making stem cells organizing into mini-organs in the laboratory is still an inefficient process.
(1). Ariyachet et al., (2016); Reprogrammed Stomach Tissue as a Renewable Source of Functional b Cells for Blood Glucose Regulation, Cell Stem Cell, 18, 1-12 http://dx.doi.org/10.1016/j.stem.2016.01.003
(2). Bouchi et al. (2014); FOXO1 inhibition yields functional insulin-producing cells in human gut organoid cultures. Nat. Commun. 5, 4242 http://www.nature.com/ncomms/2014/140630/ncomms5242/pdf/ncomms5242.pdf
The major discovery of this work is that when the Foxo1 gene is switched off either in the early development of the animal or in its adulthood, progenitor cells of the intestine generate cells that produced insulin. Exciting results, but we have to keep in mind that Foxo1 expresses a protein involved in important metabolic functions and its inhibition might cause undesirable side effects.
(3). Chen et al. (2014). De novo formation of insulin-producing ‘‘neo-Beta cell islets’’ from intestinal crypts. Cell Rep. 6, 1046–1058 http://www.cell.com/cell-reports/pdf/S2211-1247(14)00113-2.pdf
These investigators introduced the three genes Ngn3, Pdx1, and Mafa in mice. They express proteins called transcription factors because they regulate the expression of other genes, and are very important in pancreas’ development. In this paper they found that expression of these genes in the intestine of immune deficient mice, converts specific cells into insulin+ cells. The potential of this work is interesting because, some day, it might allow taking T1D patient’s intestine cells, converting them into insulin+ cells, and re-introducing them into the patients to normalize glucose.
We have also to point out that several studies have shown that cells such as liver cells (and others) have been also reprogrammed to become insulin+ cells and we will comment about them in the future.