Heart and kidney communicate with one another in an interdependent relationship and they influence each other's behavior reciprocally, as pathological changes in one organ can damage the other.... Show moreHeart and kidney communicate with one another in an interdependent relationship and they influence each other's behavior reciprocally, as pathological changes in one organ can damage the other. Although independent human in vitro models for heart and kidney exist, they do not capture their dynamic crosstalk. We have developed a microfluidic system which can be used to study heart and kidney interaction in vitro. Cardiac microtissues (cMTs) and kidney organoids (kOs) derived from human induced pluripotent stem cells (hiPSCs) were generated and loaded into two separated communicating chambers of a perfusion chip. Static culture conditions were compared with dynamic culture under unidirectional flow. Tissue viability was maintained for minimally 72 h under both conditions, as indicated by the presence of sarcomeric structures coupled with beating activity in cMTs and the presence of nephron structures and albumin uptake in kOs. We concluded that this system enables the study of human cardiac and kidney organoid interaction in vitro while controlling parameters like fluidic flow speed and direction. Together, this "cardiorenal-unit" provides a new in vitro model to study the cardiorenal axis and it may be further developed to investigate diseases involving both two organs and their potential treatments. Show less
Wiersma, L.E.; Avramut, M.C.; Lievers, E.; Rabelink, T.J.; Berg, C.W. van den 2022
Background: The generation of human induced pluripotent stem cells (hiPSCs) has opened a world of opportunities for stem cell-based therapies in regenerative medicine. Currently, several human... Show moreBackground: The generation of human induced pluripotent stem cells (hiPSCs) has opened a world of opportunities for stem cell-based therapies in regenerative medicine. Currently, several human kidney organoid protocols are available that generate organoids containing kidney structures. However, these kidney organoids are relatively small ranging up to 0.13 cm(2) and therefore contain a small number of nephrons compared to an adult kidney, thus defying the exploration of future use for therapy. Method: We have developed a scalable, easily accessible, and reproducible protocol to increase the size of the organoid up to a nephron sheet of 2.5 cm(2) up to a maximum of 12.6 cm(2) containing a magnitude of nephrons. Results: Confocal microscopy showed that the subunits of the nephrons remain evenly distributed throughout the entire sheet and that these tissue sheets can attain similar to 30,000-40,000 glomerular structures. Upon transplantation in immunodeficient mice, such nephron sheets became vascularized and matured. They also show reuptake of injected low-molecular mass dextran molecules in the tubular structures, indicative of glomerular filtration. Furthermore, we developed a protocol for the cryopreservation of intermediate mesoderm cells during the differentiation and demonstrate that these cells can be successfully thawed and recovered to create such tissue sheets. Conclusion: The scalability of the procedures, and the ability to cryopreserve the cells during differentiation are important steps forward in the translation of these differentiation protocols to future clinical applications such as transplantable auxiliary kidney tissue. Show less
Differentiated kidney organoids from induced pluripotent stem cells hold promise as a treatment for patients with kidney diseases. Before these organoids can be translated to the clinic,... Show moreDifferentiated kidney organoids from induced pluripotent stem cells hold promise as a treatment for patients with kidney diseases. Before these organoids can be translated to the clinic, shortcomings regarding their cellular and extracellular compositions, and their developmental plateau need to be overcome. We performed a proteomic analysis on kidney organoids cultured for a prolonged culture time and we found a specific change in the extracellular matrix composition with increased expression of types 1a1, 2 and 6a1 collagen. Such an excessive accumulation of specific collagen types is a hallmark of renal fibrosis that causes a life-threatening pathological condition by compromising key functions of the human kidney. Here we hypothesized the need for a threedimensional environment to grow the kidney organoids, which could better mimic the in vivo surroundings of the developing kidney than standard culture on an air-liquid interface. Encapsulating organoids for four days in a soft, thiol-ene cross-linked alginate hydrogel resulted in decreased type 1a1 collagen expression. Furthermore, the encapsulation did not result in any changes of organoid structural morphology. Using a biomaterial to modulate collagen expression allows for a prolonged kidney organoid culture in vitro and a reduction of abnormal type 1a1 collagen expression bringing kidney organoids closer to clinical application. Show less
