Publisher Correction: PEG-4MAL hydrogels for human organoid generation, culture, and in vivo delivery.

In the version of this protocol originally published, the caption for Fig. 3 was erroneously placed with Fig. 4, and that for Fig. 4 was placed with Fig. 3. This error has been corrected in the HTML and PDF versions of the paper.

PEG-4MAL hydrogels for human organoid generation, culture, and in vivo delivery.

In vitro differentiation of human pluripotent stem cell (hPSC)-derived organoids (HOs) facilitates the production of multicellular three-dimensional structures analogous to native human tissues. Most current methods for the generation of HOs rely on Matrigel, a poorly defined basement membrane derivative secreted by Engelbreth-Holm-Swarm mouse sarcoma cells, limiting the potential use of HOs for regenerative medicine applications. Here, we describe a protocol for the synthesis of a fully defined, synthetic hydrogel that supports the generation and culture of HOs. Modular, cell-encapsulating hydrogels are formed from a four-armed poly(ethylene glycol) macromer that has maleimide groups at each terminus (PEG-4MAL) and is conjugated to cysteine-containing adhesive peptides and cross-linked via protease-degradable peptides. The protocol also includes guidelines for the localized in vivo delivery of PEG-4MAL hydrogel-encapsulated HOs to injured mouse colon. The PEG-4MAL hydrogel supports the engraftment of the HOs and accelerates colonic wound repair. This culture and delivery strategy can thus be used to develop HO-based therapies to treat injury and disease. Hydrogel and tissue preparation and subsequent encapsulation can be performed within 2.5-3.5 h. Once HOs have been cultured in synthetic hydrogels for at least 14 d, they can be prepared and delivered to the mouse colon in under 5 h.

Serum Amyloid A1 Is an Epithelial Prorestitutive Factor.

Several proteins endogenously produced during the process of intestinal wound healing have demonstrated prorestitutive properties. The presence of serum amyloid A1 (SAA1), an acute-phase reactant, within inflamed tissues, where it exerts chemotaxis of phagocytes, is well recognized; however, a putative role in intestinal wound repair has not been described. Herein, we show that SAA1 induces intestinal epithelial cell migration, spreading, and attachment through a formyl peptide receptor 2-dependent mechanism. Induction of the prorestitutive phenotype is concentration and time dependent and is associated with epithelial reactive oxygen species production and alterations in p130 Crk-associated substrate staining. In addition, using a murine model of wound recovery, we provide evidence that SAA1 is dynamically and temporally regulated, and that the elaboration of SAA1 within the wound microenvironment correlates with the influx of SAA1/CD11b coexpressing immune cells and increases in cytokines known to induce SAA expression. Overall, the present work demonstrates an important role for SAA in epithelial wound recovery and provides evidence for a physiological role in the wound environment.

Synthetic hydrogels for human intestinal organoid generation and colonic wound repair.

In vitro differentiation of human intestinal organoids (HIOs) from pluripotent stem cells is an unparalleled system for creating complex, multicellular three-dimensional structures capable of giving rise to tissue analogous to native human tissue. Current methods for generating HIOs rely on growth in an undefined tumour-derived extracellular matrix (ECM), which severely limits the use of organoid technologies for regenerative and translational medicine. Here, we developed a fully defined, synthetic hydrogel based on a four-armed, maleimide-terminated poly(ethylene glycol) macromer that supports robust and highly reproducible in vitro growth and expansion of HIOs, such that three-dimensional structures are never embedded in tumour-derived ECM. We also demonstrate that the hydrogel serves as an injection vehicle that can be delivered into injured intestinal mucosa resulting in HIO engraftment and improved colonic wound repair. Together, these studies show proof-of-concept that HIOs may be used therapeutically to treat intestinal injury.

Macrophage-derived IL-10 mediates mucosal repair by epithelial WISP-1 signaling.

In response to injury, epithelial cells migrate and proliferate to cover denuded mucosal surfaces and repair the barrier defect. This process is orchestrated by dynamic crosstalk between immune cells and the epithelium; however, the mechanisms involved remain incompletely understood. Here, we report that IL-10 was rapidly induced following intestinal mucosal injury and was required for optimal intestinal mucosal wound closure. Conditional deletion of IL-10 specifically in CD11c-expressing cells in vivo implicated macrophages as a critical innate immune contributor to IL-10-induced wound closure. Consistent with these findings, wound closure in T cell- and B cell-deficient Rag1-/- mice was unimpaired, demonstrating that adaptive immune cells are not absolutely required for this process. Further, following mucosal injury, macrophage-derived IL-10 resulted in epithelial cAMP response element-binding protein (CREB) activation and subsequent synthesis and secretion of the pro-repair WNT1-inducible signaling protein 1 (WISP-1). WISP-1 induced epithelial cell proliferation and wound closure by activating epithelial pro-proliferative pathways. These findings define the involvement of macrophages in regulating an IL-10/CREB/WISP-1 signaling axis, with broad implications in linking innate immune activation to mucosal wound repair.