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Melissa H. Little (PI)
Murdoch Childrens Research Institute
We have previously shown that human kidney tissue can be generated from human pluripotent stem cells. Our project focuses on characterizing and optimizing this approach to improve tubular maturation and cellular function and generating reporter lines for the isolation of specific cell types. In the long term, human kidney tissue generated in this way may be used for drug screening, tissue regeneration or cell therapy.
Little, Melissa H.; Combes, Alexander N.. Genes & development. 33(19-20):1319–1345. October 2019.
There are now many reports of human kidney organoids generated via the directed differentiation of human pluripotent stem cells (PSCs) based on an existing understanding of mammalian kidney organogenesis. Such kidney organoids potentially represent tractable tools for the study of normal human development and disease with improvements in scale, structure, and functional maturation potentially providing future options for renal regeneration. The utility of such organotypic models, however, will ultimately be determined by their developmental accuracy. While initially inferred from mouse models, recent transcriptional analyses of human fetal kidney have provided greater insight into nephrogenesis. In this review, we discuss how well human kidney organoids model the human fetal kidney and how the remaining differences challenge their utility.
Vanslambrouck, Jessica M.; Wilson, Sean B.; Tan, Ker Sin; Soo, Joanne Y.-C.; Scurr, Michelle; Spijker, H. Siebe; Starks, Lakshi T.; Neilson, Amber; Cui, Xiaoxia; Jain, Sanjay; Little, Melissa Helen; Howden, Sara E.. Journal of the American Society of Nephrology. 30(10):1811–1823. 2019.
Kidney organoids generated from human induced pluripotent stem cells (iPSCs) show great potential for modeling kidney diseases and studying disease pathogenesis. However, the relative accuracy with which kidney organoids model normal morphogenesis, as well as the maturity and identity of the renal cell types they comprise, remain to be fully investigated. The authors describe the generation and validation of ten fluorescent CRISPR/Cas9 gene-edited iPSC reporter lines specifically designed for the visualization, isolation, and characterization of cell types and states within kidney organoids, and demonstrate the use of these lines for cellular isolation, time-lapse imaging, protocol optimization, and lineage-tracing applications. These tools offer promise for better understanding this model system and its congruence with human kidney morphogenesis.Background The generation of reporter lines for cell identity, lineage, and physiologic state has provided a powerful tool in advancing the dissection of mouse kidney morphogenesis at a molecular level. Although use of this approach is not an option for studying human development in vivo, its application in human induced pluripotent stem cells (iPSCs) is now feasible.Methods We used CRISPR/Cas9 gene editing to generate ten fluorescence reporter iPSC lines designed to identify nephron progenitors, podocytes, proximal and distal nephron, and ureteric epithelium. Directed differentiation to kidney organoids was performed according to published protocols. Using immunofluorescence and live confocal microscopy, flow cytometry, and cell sorting techniques, we investigated organoid patterning and reporter expression characteristics.Results Each iPSC reporter line formed well patterned kidney organoids. All reporter lines showed congruence of endogenous gene and protein expression, enabling isolation and characterization of kidney cell types of interest. We also demonstrated successful application of reporter lines for time-lapse imaging and mouse transplantation experiments.Conclusions We generated, validated, and applied a suite of fluorescence iPSC reporter lines for the study of morphogenesis within human kidney organoids. This fluorescent iPSC reporter toolbox enables the visualization and isolation of key populations in forming kidney organoids, facilitating a range of applications, including cellular isolation, time-lapse imaging, protocol optimization, and lineage-tracing approaches. These tools offer promise for enhancing our understanding of this model system and its correspondence with human kidney morphogenesis.
Kumar, Santhosh V.; Er, Pei X.; Lawlor, Kynan T.; Motazedian, Ali; Scurr, Michelle; Ghobrial, Irene; Combes, Alexander N.; Zappia, Luke; Oshlack, Alicia; Stanley, Edouard G.; Little, Melissa H. Development. 146(5):dev172361. March 2019.
Kidney organoids have potential uses in disease modelling, drug screening and regenerative medicine. However, novel cost-effective techniques are needed to enable scaled-up production of kidney cell types in vitro. We describe here a modified suspension culture method for the generation of kidney micro-organoids from human pluripotent stem cells. Optimisation of differentiation conditions allowed the formation of micro-organoids, each containing six to ten nephrons that were surrounded by endothelial and stromal populations. Single cell transcriptional profiling confirmed the presence and transcriptional equivalence of all anticipated renal cell types consistent with a previous organoid culture method. This suspension culture micro-organoid methodology resulted in a three- to fourfold increase in final cell yield compared with static culture, thereby representing an economical approach to the production of kidney cells for various biological applications.
Howden, Sara E; Vanslambrouck, Jessica M; Wilson, Sean B; Tan, Ker Sin; Little, Melissa H. EMBO Rep. March 2019.
Nephron formation continues throughout kidney morphogenesis in both mice and humans. Lineage tracing studies in mice identified a self‐renewing Six2‐expressing nephron progenitor population able to give rise to the full complement of nephrons throughout kidney morphogenesis. To investigate the origin of nephrons within human pluripotent stem cell‐derived kidney organoids, we performed a similar fate‐mapping analysis of the SIX2‐expressing lineage in induced pluripotent stem cell (iPSC)‐derived kidney organoids to explore the feasibility of investigating lineage relationships in differentiating iPSCs in vitro. Using CRISPR/Cas9 gene‐edited lineage reporter lines, we show that SIX2‐expressing cells give rise to nephron epithelial cell types but not to presumptive ureteric epithelium. The use of an inducible (CreERT2) line revealed a declining capacity for SIX2+ cells to contribute to nephron formation over time, but retention of nephron‐forming capacity if provided an exogenous WNT signal. Hence, while human iPSC‐derived kidney tissue appears to maintain lineage relationships previously identified in developing mouse kidney, unlike the developing kidney in vivo, kidney organoids lack a nephron progenitor niche capable of both self‐renewal and ongoing nephrogenesis.EMBO Reports (2019) e47483
Phipson, Belinda; Er, Pei X.; Combes, Alexander N.; Forbes, Thomas A.; Howden, Sara E.; Zappia, Luke; Yen, Hsan-Jan; Lawlor, Kynan T.; Hale, Lorna J.; Sun, Jane; Wolvetang, Ernst; Takasato, Minoru; Oshlack, Alicia; Little, Melissa H. Nature Methods. 16(1):79–87. January 2019.
The utility of human pluripotent stem cell–derived kidney organoids relies implicitly on the robustness and transferability of the protocol. Here we analyze the sources of transcriptional variation in a specific kidney organoid protocol. Although individual organoids within a differentiation batch showed strong transcriptional correlation, we noted significant variation between experimental batches, particularly in genes associated with temporal maturation. Single-cell profiling revealed shifts in nephron patterning and proportions of component cells. Distinct induced pluripotent stem cell clones showed congruent transcriptional programs, with interexperimental and interclonal variation also strongly associated with nephron patterning. Epithelial cells isolated from organoids aligned with total organoids at the same day of differentiation, again implicating relative maturation as a confounder. This understanding of experimental variation facilitated an optimized analysis of organoid-based disease modeling, thereby increasing the utility of kidney organoids for personalized medicine and functional genomics.
Combes, Alexander N.; Zappia, Luke; Er, Pei Xuan; Oshlack, Alicia; Little, Melissa H. Genome Medicine. 11(1):3. January 2019.
Human kidney organoids hold promise for studying development, disease modelling and drug screening. However, the utility of stem cell-derived kidney tissues will depend on how faithfully these replicate normal fetal development at the level of cellular identity and complexity.
Hale, Lorna J.; Howden, Sara E.; Phipson, Belinda; Lonsdale, Andrew; Er, Pei X.; Ghobrial, Irene; Hosawi, Salman; Wilson, Sean; Lawlor, Kynan T.; Khan, Shahnaz; Oshlack, Alicia; Quinlan, Catherine; Lennon, Rachel; Little, Melissa H. Nature Communications. 9(1):5167. December 2018.
The podocytes within the glomeruli of the kidney maintain the filtration barrier by forming interdigitating foot processes with intervening slit diaphragms, disruption in which results in proteinuria. Studies into human podocytopathies to date have employed primary or immortalised podocyte cell lines cultured in 2D. Here we compare 3D human glomeruli sieved from induced pluripotent stem cell-derived kidney organoids with conditionally immortalised human podocyte cell lines, revealing improved podocyte-specific gene expression, maintenance in vitro of polarised protein localisation and an improved glomerular basement membrane matrisome compared to 2D cultures. Organoid-derived glomeruli retain marker expression in culture for 96 h, proving amenable to toxicity screening. In addition, 3D organoid glomeruli from a congenital nephrotic syndrome patient with compound heterozygous NPHS1 mutations reveal reduced protein levels of both NEPHRIN and PODOCIN. Hence, human iPSC-derived organoid glomeruli represent an accessible approach to the in vitro modelling of human podocytopathies and screening for podocyte toxicity.
Howden, SE; Thomson, JA; Little, MH. Nature Protocols. 13(5):875–898. April 2018.
The utility of human induced pluripotent stem cells (iPSCs) is enhanced by an ability to precisely modify a chosen locus with minimal impact on the remaining genome. However, the derivation of gene-edited iPSCs typically involves multiple steps requiring lengthy culture periods and several clonal events. Here, we describe a one-step protocol for reliable generation of clonally derived gene-edited iPSC lines from human fibroblasts in the absence of drug selection or FACS enrichment. Using enhanced episomal-based reprogramming and CRISPR/Cas9 systems, gene-edited and passage-matched unmodified iPSC lines are obtained following a single electroporation of human fibroblasts. To minimize unwanted mutations within the target locus, we use a Cas9 variant that is associated with decreased nonhomologous end-joining (NHEJ) activity. This protocol outlines in detail how this streamlined approach can be used for both monoallelic and biallelic introduction of specific base changes or transgene cassettes in a manner that is efficient, rapid (∼6–8 weeks), and cost-effective.
van den Berg, CW; Ritsma, L; Avramut, MC; Wiersma, LE; van den Berg, BM; Leuning, DG; Lievers, E; Koning, M; Vanslambrouck, JM; Koster, AJ; Howden, SE; Takasato, M; Little, MH; Rabelink, TJ. Stem Cell Reports.. 10(3):751–765. March 2018.
Human pluripotent stem cell (hPSC)-derived kidney organoids may facilitate disease modeling and the generation of tissue for renal replacement. Long-term application, however, will require transferability between hPSC lines and significant improvements in organ maturation. A key question is whether time or a patent vasculature is required for ongoing morphogenesis. Here, we show that hPSC-derived kidney organoids, derived in fully defined medium conditions and in the absence of any exogenous vascular endothelial growth factor, develop host-derived vascularization. In vivo imaging of organoids under the kidney capsule confirms functional glomerular perfusion as well as connection to pre-existing vascular networks in the organoids. Wide-field electron microscopy demonstrates that transplantation results in formation of a glomerular basement membrane, fenestrated endothelial cells, and podocyte foot processes. Furthermore, compared with non-transplanted organoids, polarization and segmental specialization of tubular epithelium are observed. These data demonstrate that functional vascularization is required for progressive morphogenesis of human kidney organoids.
Combes, AN; Phipson, B; Zappia, L; Lawlor, KE; Er, PX; Oshlack, A; Little, MA. bioRxiv. December 2017.
Recent advances in our capacity to differentiate human pluripotent stem cells to human kidney tissue are moving the field closer to novel approaches for renal replacement. Such protocols have relied upon our current understanding of the molecular basis of mammalian kidney morphogenesis. To date this has depended upon population based-profiling of non-homogenous cellular compartments. In order to improve our resolution of individual cell transcriptional profiles during kidney morphogenesis, we have performed 10x Chromium single cell RNA-seq on over 6000 cells from the E18.5 developing mouse kidney, as well as more than 7000 cells from human iPSC-derived kidney organoids. We identified 16 clusters of cells representing all major cell lineages in the E18.5 mouse kidney. The differentially expressed genes from individual murine clusters were then used to guide the classification of 16 cell clusters within human kidney organoids, revealing the presence of distinguishable stromal, endothelial, nephron, podocyte and nephron progenitor populations. Despite the congruence between developing mouse and human organoid, our analysis suggested limited nephron maturation and the presence of off target populations in human kidney organoids, including unidentified stromal populations and evidence of neural clusters. This may reflect unique human kidney populations, mixed cultures or aberrant differentiation in vitro. Analysis of clusters within the mouse data revealed novel insights into progenitor maintenance and cellular maturation in the major renal lineages and will serve as a roadmap to refine directed differentiation approaches in human iPSC-derived kidney organoids.
Phipson, B; Er, PX; Hale, L; Yen, DH; Lawlor, KE; Takasato, M; Sun, J; Wolvetang, E; Oshlack, A; Little, MH. bioRxiv. December 2017.
We have previously reported a protocol for the directed differentiation of human induced pluripotent stem cells to kidney organoids comprised of nephrons, proximal and distal epithelium, vasculature and surrounding interstitial elements. The utility of this protocol for applications such as disease modelling will rely implicitly on the developmental accuracy of the model, technical robustness of the protocol and transferability between iPSC lines. Here we report extensive transcriptional analyses of the sources of variation across the timecourse of differentiation from pluripotency to complete kidney organoid, focussing on repeated differentiations to day 18 organoid. Individual organoids generated within the same differentiation experiment show Spearmans correlation coefficients of \textgreater0.99. The greatest source of variation was seen between experimental batch, with the enrichment for genes that also varied temporally between day 10 and day 25 organoids implicating nephron maturation as contributing to transcriptional variance between individual differentiation experiments. A morphological analysis revealed a transition from renal vesicle to capillary loop stage nephrons across the same time period. Distinct iPSC clones were also shown to display congruent transcriptional programs with inter-experimental and inter-clonal variation most strongly associated with nephron patterning. Even epithelial cells isolated from organoids showed transcriptional alignment with total organoids of the same day of differentiation. This data provides a framework for managing experimental variation, thereby increasing the utility of this approach for personalised medicine and functional genomics.
Oxburgh, L; Carroll, TJ; Cleaver, O; Gossett, DR; Hoshizaki, DK; Hubbell, JA; Humphreys, BD; Jain, S; Jensen, J; Kaplan, DL; Kesselman, C; Ketchum, CJ; Little, MH; McMahon, AP; Shankland, SJ; Spence, JR; Valerius, MT; Wertheim, JA; Wessely, O; Zheng, Y; Drummond, IA. J Am Soc Nephrol. 28(5):1370–1378. May 2017.
(Re)Building a Kidney is a National Institute of Diabetes and Digestive and Kidney Diseases-led consortium to optimize approaches for the isolation, expansion, and differentiation of appropriate kidney cell types and the integration of these cells into complex structures that replicate human kidney function. The ultimate goals of the consortium are two-fold: to develop and implement strategies for in vitro engineering of replacement kidney tissue, and to devise strategies to stimulate regeneration of nephrons in situ to restore failing kidney function. Projects within the consortium will answer fundamental questions regarding human gene expression in the developing kidney, essential signaling crosstalk between distinct cell types of the developing kidney, how to derive the many cell types of the kidney through directed differentiation of human pluripotent stem cells, which bioengineering or scaffolding strategies have the most potential for kidney tissue formation, and basic parameters of the regenerative response to injury. As these projects progress, the consortium will incorporate systematic investigations in physiologic function of in vitro and in vivo differentiated kidney tissue, strategies for engraftment in experimental animals, and development of therapeutic approaches to activate innate reparative responses.
Takasato, M; Little, MH. Dev Biol. 420(2):210–220. December 2016.
Directed differentiation of human pluripotent stem cells (hPSCs) can provide us any required tissue/cell types by recapitulating the development in vitro. The kidney is one of the most challenging organs to generate from hPSCs as the kidney progenitors are composed of at least 4 different cell types, including nephron, collecting duct, endothelial and interstitium progenitors, that are developmentally distinguished populations. Although the actual developmental process of the kidney during human embryogenesis has not been clarified yet, studies using model animals accumulated knowledge about the origins of kidney progenitors. The implications of these findings for the directed differentiation of hPSCs into the kidney include the mechanism of the intermediate mesoderm specification and its patterning along with anteroposterior axis. Using this knowledge, we previously reported successful generation of hPSCs-derived kidney organoids that contained all renal components and modelled human kidney development in vitro. In this review, we explain the developmental basis of the strategy behind this differentiation protocol and compare strategies of studies that also recently reported the induction of kidney cells from hPSCs. We also discuss the characterization of such kidney organoids and limitations and future applications of this technology.
Takasat, M; Er, PX; Chiu, HS; Little, MH. Nat Protoc. 11(9):1681–92. September 2016.
The human kidney develops from four progenitor populations-nephron progenitors, ureteric epithelial progenitors, renal interstitial progenitors and endothelial progenitors-resulting in the formation of maximally 2 million nephrons. Until recently, the reported methods differentiated human pluripotent stem cells (hPSCs) into either nephron progenitor or ureteric epithelial progenitor cells, consequently forming only nephrons or collecting ducts, respectively. Here we detail a protocol that simultaneously induces all four progenitors to generate kidney organoids within which segmented nephrons are connected to collecting ducts and surrounded by renal interstitial cells and an endothelial network. As evidence of functional maturity, proximal tubules within organoids display megalin-mediated and cubilin-mediated endocytosis, and they respond to a nephrotoxicant to undergo apoptosis. This protocol consists of 7 d of monolayer culture for intermediate mesoderm induction, followed by 18 d of 3D culture to facilitate self-organizing renogenic events leading to organoid formation. Personnel experienced in culturing hPSCs are required to conduct this protocol.