Biology subjects

Grindel, S. H.

Publications and source records attributed to Grindel, S. H..

4 recordsLinked to original sources

bioRxiv2026

Synthetic budding morphogenesis by optogenetic receptor tyrosine kinase signaling

The mammalian kidney relies on a branched network of collecting ducts for fluid transport and homeostasis. Replicating this network in vitro would parallelize function in synthetic replacement kidneys, yet current organoids have limited branching capacity. Here, we establish a developmentally-informed strategy to control organoid budding through optogenetic control of a receptor tyrosine kinase, RET. We first show pharmacological manipulation of RET signaling controls the extent of branching in mouse embryonic kidneys and human stem cell-derived kidney organoids. Next, we develop an optogenetic RET receptor (optoRET) that signals in a ligand-independent manner via blue light-mediated clustering. Epithelial cells expressing optoRET reproduce stereotyped RET signaling, scattering, and symmetry breaking in response to blue light. Human kidney organoids undergo budding with controllable orientation in response to spatially patterned optoRET stimulation. Our results establish ligand-free optogenetic control of branching and inspire new synthetic biology strategies for epithelial organoid design. HighlightsGDNF-RET controls branching and tip cell state in mouse and human kidney tissues. OptoRET reproduces endogenous RET signaling and morphogenesis in cell lines. OptoRET enables ligand-free budding in human renal epithelial organoids. Spatially patterned optoRET stimulation controls budding orientation.

bioengineering↗

bioRxiv2023

Nephron progenitors rhythmically alternate between renewal and differentiation in synchrony with kidney branching morphogenesis

The developing mammalian kidney exponentially duplicates nephron-forming stem cell niches at the tips of the urinary collecting duct tree to achieve massively parallel function. Nephron formation rate has a clinically meaningful effect on person-to-person variability in nephron endowment1-5, while exerting in vitro control could enable sustained waves of nephrogenesis in organoid-derived synthetic kidney tissues6,7. However, how the kidney arrives at an appropriate number and ratio of nephrons to collecting ducts is unclear. Here we show that nephron formation is rhythmic and synchronized with branching of the ureteric bud tree (the future urinary collecting ducts). We correlate human and mouse spatial transcriptomics data with the branching life-cycle to uncover rhythmically alternating signatures of nephron progenitor differentiation and renewal. The nephron progenitor rhythm parallels rhythmic nuclear elongation and other hallmarks of mechanical tension in surrounding stromal cells that we attribute to branching-induced deformation. Stroma-specific knockdown of actomyosin activity leads to a striking loss of synchronization between nephron formation and ureteric bud branching without blocking either. These results suggest that the stroma acts as a mechanically entrained pacemaker for nephron formation. Together, our findings uncover a feedback mechanism for clock-like coordination of organ composition during exponential growth.

developmental biology↗

bioRxiv2023

Rho/ROCK activity tunes cell compartment segregation and differentiation in nephron-forming niches

Controlling the time and place of nephron formation in vitro would improve nephron density and connectivity in next-generation kidney replacement tissues. Recent developments in kidney organoid technology have paved the way to achieving self-sustaining nephrogenic niches in vitro. The physical and geometric structure of the niche are key control parameters in tissue engineering approaches. However, their relationship to nephron differentiation is unclear. Here we investigate the relationship between niche geometry, cell compartment mixing, and nephron differentiation by targeting the Rho/ROCK pathway, a master regulator of the actin cytoskeleton. We find that the ROCK inhibitor Y-27632 increases mixing between nephron progenitor and stromal compartments in native mouse embryonic kidney niches, and also increases nephrogenesis. Similar increases are also seen in reductionist mouse primary cell and human induced pluripotent stem cell (iPSC)-derived organoids perturbed by Y-27632, dependent on the presence of stromal cells. Our data indicate that niche organization is a determinant of nephron formation rate, bringing renewed focus to the spatial context of cell-cell interactions in kidney tissue engineering efforts.

bioengineering↗

bioRxiv2023

Highly-parallel production of designer organoids by mosaic patterning of progenitors

Human organoids are a promising approach for disease modeling and regenerative medicine. However, organoid variability and limited control over morphological outcomes remain significant challenges. Here we extend a DNA velcro cell patterning approach, precisely controlling the number and ratio of human stem cell-derived progenitors contributing to nephron and mosaic nephron/ureteric bud organoids within arrays of microwells. We demonstrate long-term control over organoid size and morphology, decoupled from geometric constraints.

bioengineering↗