Pax proteins mediate segment-specific functions in proximal tubule survival and response to ischemic injury.

Acute kidney injury (AKI) is a common clinical syndrome with few effective treatments. Though the kidney can regenerate after injury, the molecular mechanisms regulating this process remain poorly understood. Pax2 and Pax8 are DNA-binding transcription factors that are upregulated after kidney injury.

Sustained alterations in proximal tubule gene expression in primary culture associate with HNF4A loss.

Primary cultures of proximal tubule cells are widely used to model the behavior of kidney epithelial cells in vitro. However, de-differentiation of primary cells upon culture has been observed and appreciated for decades, yet the mechanisms driving this phenomenon remain poorly understood. This confounds the interpretation of experiments using primary kidney epithelial cells and prevents their use to engineer functional kidney tissue ex vivo.

Gene regulation in regeneration after acute kidney injury.

Acute kidney injury (AKI) is a common condition associated with significant morbidity, mortality, and cost. Injured kidney tissue can regenerate after many forms of AKI. However, there are no treatments in routine clinical practice to encourage recovery.

Renal-specific loss of ferroportin disrupts iron homeostasis and attenuates recovery from acute kidney injury.

Chronic kidney disease is increasing at an alarming rate and correlates with the increase in diabetes, obesity, and hypertension that disproportionately impact socioeconomically disadvantaged communities. Iron plays essential roles in many biological processes including oxygen transport, mitochondrial function, cell proliferation, and regeneration. However, excess iron induces the generation and propagation of reactive oxygen species, which lead to oxidative stress, cellular damage, and ferroptosis.

Pax protein depletion in proximal tubules triggers conserved mechanisms of resistance to acute ischemic kidney injury preventing transition to chronic kidney disease.

Acute kidney injury (AKI) is a common condition that lacks effective treatments. In part, this shortcoming is due to an incomplete understanding of the genetic mechanisms that control pathogenesis and recovery. Identifying the molecular and genetic regulators unique to nephron segments that dictate vulnerability to injury and regenerative potential could lead to new therapeutic targets to treat ischemic kidney injury.

Pax Protein Depletion in Proximal Tubules Triggers Conserved Mechanisms of Resistance to Acute Ischemic Kidney Injury and Prevents Transition to Chronic Kidney Disease.

Unlabelled: Acute kidney injury (AKI) is a common condition that lacks effective treatments. In part this shortcoming is due to an incomplete understanding of the genetic mechanisms that control pathogenesis and recovery. Pax2 and Pax8 are homologous transcription factors with overlapping functions that are critical for kidney development and are re-activated in AKI.

Pre-cultured, cell-encapsulating fibrin microbeads for the vascularization of ischemic tissues.

There is a significant clinical need to develop effective vascularization strategies for tissue engineering and the treatment of ischemic pathologies. In patients afflicted with critical limb ischemia, comorbidities may limit common revascularization strategies. Cell-encapsulating modular microbeads possess a variety of advantageous properties, including the ability to support prevascularization in vitro while retaining the ability to be injected in a minimally invasive manner in vivo.

High-throughput image analysis with deep learning captures heterogeneity and spatial relationships after kidney injury.

Recovery from acute kidney injury can vary widely in patients and in animal models. Immunofluorescence staining can provide spatial information about heterogeneous injury responses, but often only a fraction of stained tissue is analyzed. Deep learning can expand analysis to larger areas and sample numbers by substituting for time-intensive manual or semi-automated quantification techniques.

Stromal cell identity modulates vascular morphogenesis in a microvasculature-on-a-chip platform.

Supportive stromal cells of mesenchymal origins regulate vascular morphogenesis in developmental, pathological, and regenerative contexts, contributing to vessel formation, maturation, and long-term stability, in part via the secretion of bioactive molecules. In this work, we adapted a microfluidic lab-on-a-chip system that enables the formation and perfusion of microvascular capillary beds with connections to arteriole-scale endothelialized channels to explore how stromal cell (SC) identity influences endothelial cell (EC) morphogenesis. We compared and contrasted lung fibroblasts (LFs), dermal fibroblasts (DFs), and bone marrow-derived mesenchymal stem cells (MSCs) for their abilities to support endothelial morphogenesis and subsequent perfusion of microvascular networks formed in fibrin hydrogels within the microfluidic device.

Injectable pre-cultured tissue modules catalyze the formation of extensive functional microvasculature in vivo.

Revascularization of ischemic tissues is a major barrier to restoring tissue function in many pathologies. Delivery of pro-angiogenic factors has shown some benefit, but it is difficult to recapitulate the complex set of factors required to form stable vasculature. Cell-based therapies and pre-vascularized tissues have shown promise, but the former require time for vascular assembly in situ while the latter require invasive surgery to implant vascularized scaffolds.

Cell-mediated matrix stiffening accompanies capillary morphogenesis in ultra-soft amorphous hydrogels.

There is a critical need for biomaterials that support robust neovascularization for a wide-range of clinical applications. Here we report how cells alter tissue-level mechanical properties during capillary morphogenesis using a model of endothelial-stromal cell co-culture within poly(ethylene glycol) (PEG) based hydrogels. After a week of culture, we observed substantial stiffening in hydrogels with very soft initial properties.

Deciphering the relative roles of matrix metalloproteinase- and plasmin-mediated matrix degradation during capillary morphogenesis using engineered hydrogels.

Extracellular matrix (ECM) remodeling is essential for the process of capillary morphogenesis. Here we employed synthetic poly(ethylene glycol) (PEG) hydrogels engineered with proteolytic specificity to either matrix metalloproteinases (MMPs), plasmin, or both to investigate the relative contributions of MMP- and plasmin-mediated ECM remodeling to vessel formation in a 3D-model of capillary self-assembly analogous to vasculogenesis. We first demonstrated a role for both MMP- and plasmin-mediated mechanisms of ECM remodeling in an endothelial-fibroblast co-culture model of vasculogenesis in fibrin hydrogels using inhibitors of MMPs and plasmin.

Engineered extracellular matrices with controlled mechanics modulate renal proximal tubular cell epithelialization.

Acute kidney injury (AKI) is common and associated with significant morbidity and mortality. Recovery from many forms of AKI involves the proliferation of renal proximal tubular epithelial cells (RPTECs), but the influence of the microenvironment in which this recovery occurs remains poorly understood. Here we report the development of a poly(ethylene glycol) (PEG) hydrogel platform to study the influence of substrate mechanical properties on the proliferation of human RPTECs as a model for recovery from AKI.

Molecular regulation of contractile smooth muscle cell phenotype: implications for vascular tissue engineering.

The molecular regulation of smooth muscle cell (SMC) behavior is reviewed, with particular emphasis on stimuli that promote the contractile phenotype. SMCs can shift reversibly along a continuum from a quiescent, contractile phenotype to a synthetic phenotype, which is characterized by proliferation and extracellular matrix (ECM) synthesis. This phenotypic plasticity can be harnessed for tissue engineering.

The effects of heparin releasing hydrogels on vascular smooth muscle cell phenotype.

Poly(ethylene glycol) diacrylate (PEGDA) hydrogel scaffolds were engineered to promote contractile smooth muscle cell (SMC) phenotype via controlled release of heparin. The scaffold design was evaluated by quantifying the effects of free heparin on SMC phenotype, engineering hydrogels to provide controlled release of heparin, and synthesizing cell-adhesive, heparin releasing hydrogels to promote contractile SMC phenotype. Heparin inhibited SMC proliferation and up-regulated expression of contractile SMC phenotype markers, including smooth muscle alpha-actin, calponin, and SM-22alpha, in a dose-dependent fashion (6 microg/ml to 3.

The influence of RGD-bearing hydrogels on the re-expression of contractile vascular smooth muscle cell phenotype.

This study reports on the ability of poly(ethylene glycol) diacrylate (PEGDA) hydrogel scaffolds with pendant integrin-binding GRGDSP peptides (RGD-gels) to support the re-differentiation of cultured vascular smooth muscle cells (SMCs) toward a contractile phenotype. Human coronary artery SMCs were seeded on RGD-gels, hydrogels with other extracellular matrix derived peptides, fibronectin (FN) and laminin (LN). Differentiation was induced on RGD-gels with low serum medium containing soluble heparin, and the differentiation status was monitored by mRNA expression, protein expression, and intracellular protein organization of the contractile smooth muscle markers, smooth muscle alpha-actin, calponin, and SM-22alpha.

The effects of monoacrylated poly(ethylene glycol) on the properties of poly(ethylene glycol) diacrylate hydrogels used for tissue engineering.

This study investigated the effects of poly(ethylene glycol) monoacrylate (PEGMA) on the properties of poly(ethylene glycol) diacrylate (PEGDA)-co-PEGMA hydrogel networks. The PEGMA materials utilized were similar to ligand-linked materials typically copolymerized with PEGDA for use as tissue engineering scaffolds. PEGDA (5-20% wt/wt, 6 kDa) and PEGMA (0-20% wt/wt, 0-43 mM, 5 kDa) were copolymerized by photo-initiated free radical polymerization and the mass swelling ratio and shear modulus of the resulting hydrogels were determined.

DNA array-based transcriptional analysis of asporogenous, nonsolventogenic Clostridium acetobutylicum strains SKO1 and M5.

The large-scale transcriptional program of two Clostridium acetobutylicum strains (SKO1 and M5) relative to that of the parent strain (wild type [WT]) was examined by using DNA microarrays. Glass DNA arrays containing a selected set of 1,019 genes (including all 178 pSOL1 genes) covering more than 25% of the whole genome were designed, constructed, and validated for data reliability. Strain SKO1, with an inactivated spo0A gene, displays an asporogenous, filamentous, and largely deficient solventogenic phenotype.