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August 26, 2020

Patient stem cells for drug screening a rare autoimmune disease

The Megumu Saito laboratory reports a high-throughput drug screening system for neonatal onset multisystem inflammatory disease that uses patient iPS cells.

Drug discovery for autoinflammatory diseases is difficult for two reasons. One is the acquisition of enough immune cells from the patient to conduct the drug screening. The other is variability in the immune cells due to disease. In a new study, CiRA researchers show how iPS cell technology can overcome these problems by designing a high-throughput screening system to find drug compounds for treatment against neonatal onset multisystem inflammatory disease (NOMID).

NOMID is a very rare disease, with only about 100 cases reported in Japan, all caused by mutations in the NLRP3 gene. The disease is characterized by fever, rash, and symptoms in the joints and central nervous systems, caused by hyperactive macrophages and normally begin before the patient's first birthday. Drug treatments exist, but the severity of the symptoms between patients is so great that the drugs are either ineffective at diminishing macrophage activity or too strong, leaving the patient either unimproved or susceptible to infection.

For macrophages to exert their immune effect, they must assemble the NLRP3 inflammasome. Normally, this assembly requires a priming step followed by an activating stimulus. However, in NOMID patients, the assembly occurs with only the priming step, resulting in autoinflammation.

In principle, researchers could collect macrophages from patients to study the NLRP3 inflammasome. However, as CiRA Associate Professor Megumu Saito explains that iPS cell technology has certain advantages for drug discovery in autoimmune diseases.

"The behavior of macrophages can be affected by the condition of the patient, which creates large variability in the experimental results and leads to misleading drug candidates. iPS cell technology can be used to make a homogenous myeloid population for reproducible results," he said.

The macrophages made from iPS cells have never actually been in the body and therefore are not affected by the patient's condition.

To generate a homogeneous population, Saito's team immortalized myeloid cells prepared from the iPS cells of a NOMID patient by forcing the expression of three genes, MYC, BMI1 and MDM2. Macrophages from these immortalized cells were prepared cheaply and quickly for the high-throughput screening.

Nearly 5,000 compounds were tested for their ability to reduce the production of IL-1β, a cytokine whose presence marks activation of the NLRP3 inflammasome, leading to 7 hits, all of which had been identified in previous research by other groups, validating the iPS cell approach.

Saito adds that it should be easy to extend this system to other immunological and hematological diseases.

"Our strategy can be applied to other immunological disorders in which macrophages play a critical role or by immortalizing hematopoietic cells made from iPS cells can be applied to hematopoietic disorders," he said.

Paper Details
  • Journal: PLoS One
  • Title: Induced pluripotent stem cell-derived monocytic cell lines from a NOMID patient serve as a screening platform for modulating NLRP3 inflammasome activity
  • Authors: Ryosuke Seki1,2, Akira Ohta3, Akira Niwa2, Yoshiori Sugimine1,4, Haruna Naito2,
    Tatsutoshi Nakahata3, and Megumu K. Saito1
  • Author Affiliations:
    1. Department of Clinical Application, Center for iPS Cell Research and Application, Kyoto University, Kyoto, Japan
    2. Nippon Shinyaku, Co., Ltd., Kyoto, Japan
    3. Department of Fundamental Cell Technology, Center for iPS Cell Research and Application,
      Kyoto University, Kyoto, Japan
    4. Department of Pediatrics, Japanese Red Cross Wakayama Medical Center, Wakayama, Japan
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