SummaryHuman intestinal organoids (HIOs) represent a powerful system to study human development and are promising candidates for clinical translation as drug-screening tools or engineered tissue. Experimental control and clinical use of HIOs is limited by growth in expensive and poorly defined tumor-cell-derived extracellular matrices, prompting investigation of synthetic ECM-mimetics for HIO culture. Since HIOs possess an inner epithelium and outer mesenchyme, we hypothesized that adhesive cues provided by the matrix may be dispensable for HIO culture. Here, we demonstrate that alginate, a minimally supportive hydrogel with no inherent cell instructive properties, supports HIO growth in vitro and leads to HIO epithelial differentiation that is virtually indistinguishable from Matrigel-grown HIOs. In addition, alginate-grown HIOs mature to a similar degree as Matrigel-grown HIOs when transplanted in vivo, both resembling human fetal intestine. This work demonstrates that purely mechanical support from a simple-to-use and inexpensive hydrogel is sufficient to promote HIO survival and development.

Human pluripotent stem cell (hPSC)-derived intestinal organoids (HIOs) generated using directed differentiation lack some cellular populations found in the native organ, including vasculature. Using single cell RNA sequencing (scRNAseq), we have identified a transient population of endothelial cells (ECs) present early in HIO differentiation that are lost over time in culture. Here, we have developed a method to enhance co-differentiation and maintenance of ECs within HIOs (vHIOs). Given that ECs are known to possess organ specific gene expression, morphology and function, we used bulk RNAseq and scRNAseq to interrogate the developing human intestine, lung, and kidney in order to identify organ-enriched EC-gene signatures in these organ systems. By comparing organ-specific gene signatures along with markers validated by fluorescent in situ hybridization to HIO ECs, we find that HIO ECs grown in vitro share the highest similarity with native intestinal ECs relative to kidney and lung. Together, these data show that HIOs can co-differentiate a native EC population that are properly patterned with an intestine-specific EC transcriptional signature in vitro..

Highlights d Cell atlas of multiple developing human endoderm-derived organs d Identified organ-specific epithelial stem cell and mesenchymal cell signatures d Benchmarked intestinal organoid fidelity and maturation using the multi-organ atlas d Interrogated genetic and culture perturbations of epithelium and mesenchyme development

Organoids are complex three-dimensional in vitro organ-like model systems. Human organoids, which are derived from human pluripotent stem cells or primary human donor tissue, have been used to address fundamental questions about human development, stem cell biology and organ regeneration. Focus has now shifted towards implementation of organoids for biological discovery and advancing existing systems to more faithfully recapitulate the native organ. This work has highlighted significant unknowns in human biology and has invigorated new exploration into the cellular makeup of human organs during development and in the adultwork that is crucial for providing appropriate benchmarks for organoid systems. In this Review, we discuss efforts to characterize human organ cellular complexity and attempts to make organoid models more realistic through co-culture, transplantation and bioengineering approaches.

A fully biodegradable zwitterionic polymer and the corresponding conjugate with paclitaxel (PTX) were synthesized as promising biomaterials. Allyl-functionalized polylactide (PLA) was employed as the precursor of polymer backbones. UV-induced thiol-ene reaction was conducted to conjugate thiol-functionalized sulfobetaine (SB) with the PLA-based backbone. The resulting zwitterionic polymer did not exhibit considerable cytotoxicity. A polymer-drug conjugate was also obtained by thiol-ene reaction of both thiol-functionalized SB and PTX with allyl-functionalized PLA. The conjugate could readily form narrowly-dispersed nanoparticles in aqueous solutions with a volume-average hydrodynamic diameter (Dh,V) of 19.3 ± 0.2 nm. Such a polymer-drug conjugate-based drug delivery system showed full degradability, well-suppressed non-specific interaction with biomolecules, and sustained drug release. In vitro assessments also confirmed the significant anti-cancer efficacy of the conjugate. After 72 h incubation with PLA-SB/PTX containing 10 μg/mL of PTX, the cell viabilities of A549, MCF7, and PaCa-2 cells were as low as 20.0 ± 2.5 %, 1.7 ± 1.7 %, and 14.8 ± 0.9 %, respectively. Both flow cytometry and confocal microscopy suggested that the conjugates could be easily uptaken by A549 cells before the major release of PTX moieties. Overall, this work elucidates promising potentials of biodegradable zwitterionic polymer-based materials in biomedical applications.