Background

Interleukin-22 (IL-22) is an anti-inflammatory cytokine that plays a critical role in promoting wound healing during intestinal inflammation. Its expression is decreased in inflamed ulcerative colitis tissue (De Souza and Fiocchi, 2016). Microinjection of IL-22 cDNA into the colon of colitic mice showed its potential in curing ulcerative colitis. Targeted delivery of IL-22 cDNA ameliorated local intestinal inflammation through induction of mucus production, enhancing STAT3 activation in colonic epithelial cells and promoting restitution of goblet cells. Additionally, inhibition of IL-22 activity suppressed goblet cell restitution during the recovery phase of the mouse model (Sugimoto et al., 2008).

Despite its effectiveness, microinjection is an invasive technique that requires trained personnel and specific medical equipment. Contrarily, oral delivery is noninvasive and more convenient for patient self-administration. Due to their excellent biocompatibility and drug-loading capability, nanostructured lipid carriers, such as solid lipid nanoparticles and liposomes, have become an attractive oral drug delivery platform that is starting to replace conventional drug delivery systems (Ahadian et al., 2020). However, challenges exist when the delivery system passes through the gastrointestinal tract, including high enzymatic activity and variation in pH and absorption efficiency across the intestinal epithelium.

We previously used ginger-derived lipid nanoparticles (GDNPs) for orally delivering CD98 siRNA (Zhang et al., 2017) and 6-shogaol (Yang et al., 2021) to treat ulcerative colitis. These studies suggested that GDNPs could overcome the challenges of oral drug delivery. Further, we found that monogalactosyl-diacylglycerol (MGDG), digalactosyl-diacylglycerol (DGDG), and phosphatidic acid (PA) constitute more than 90% of the total lipids of GDNPs (Zhang et al., 2016; Zhang et al., 2017). In this protocol, we will describe how to use these three lipids at the same ratios found in the GDNPs in the synthesis of new lipid nanoparticles (nLNPs) to encapsulate IL-22 mRNA. The nLNP-encapsulated mRNA showed its therapeutic efficacy in one of our recently published studies (Sung et al., 2022).