A brief pulse of synthetic mRNAs, which provide instructions for protein production, nearly doubled the number of rat beta-cells; a third mRNA was required for cell division in a human cell model
A brief pulse of synthetic mRNAs, which provide instructions for protein production, nearly doubled the number of rat beta-cells; a third mRNA was required for cell division in a human cell model
On August 24, bioRxiv published a preprint describing synthetic mRNAs that briefly activate the cell division program in beta-cells. Over four days, the number of sorted rat cells in culture increased from 24 654 to 48 407. The two mRNAs were insufficient in the human laboratory model, so the authors added a third mRNA encoding the regulator MYC.
Pancreatic beta-cells produce insulin and rarely divide in adults. In the full preprint, the authors introduced synthetic modified mRNAs into rat cells. These short-lived instructions direct the cells to produce specific proteins. Protein production stops once the mRNA is degraded.
The researchers tested 12 combinations of cyclin D and CDK proteins, which initiate the cell's preparation for division. For the rat cells, they selected mRNAs encoding modified cyclin D1 and CDK4. After sorting, the authors plated 30 thousand beta-cells per culture. Four days later, cultures treated with these two mRNAs contained an average of 48 407 cells, compared with 24 654 in the control cultures.
A label incorporated into newly copied DNA, together with measurements of DNA content, showed how the cells progressed through the cell cycle. A CDK1 inhibitor temporarily arrested the cells before mitosis. After the inhibitor was removed, the cells resumed mitosis and divided. This allowed the authors to confirm that the treatment increased the number of cells, rather than merely increasing the proportion of cells that had begun copying their DNA.
The human experiments used EndoC-βH5, a laboratory beta-cell line derived from human fetal pancreatic tissue. Two mRNAs encoding cyclin D1 and CDK4 initiated the early stages of the cell cycle in these cells. An additional mRNA encoding MYC was required for the cells to complete division.
In this cell line, 14,2% of the cells had divided after 48 hours, rising to 23,6% after 96 hours. The two regulators were sufficient for division in rat cells, whereas MYC enabled the cells in the human model to complete the cycle.
In 2016, Tomáš Koblas and colleagues delivered synthetic mRNAs encoding three developmental factors into a rat pancreatic exocrine cell line and generated insulin-producing cells. The current study uses the same technique for a different purpose: increasing the number of existing beta-cells.
During the mRNA pulse, cell cycle genes became active in the rat cultures, while markers of mature beta-cell identity temporarily declined. By 120 hours, these measures had returned to the levels observed in the control cultures. The authors propose testing whether this method can increase the number of beta-cells in donor pancreatic islets before transplantation.