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Advances in 3D and other in vitro tissue model platforms have led to fundamental improvements in research on human disease, development of novel therapies, and safety testing. In addition, histological and cellular investigations of human tissues continue to serve as keystones in understanding disease and health processes. In recognition of the importance of human tissues in research, the Physicians Committee for Responsible Medicine held a workshop. Working closely with key stakeholders from the research community, regulatory agencies, and organ procurement organizations, the goal was to explore, understand, and address the barriers to increased use of human organs, tissues, and cells in research. Workshop participants were tasked with identifying the challenges of accessing and qualifying tissues for research purposes and creating a strategy to help meet the needs of the research communities to increase the availability and quality of human tissues in biomedical and translational research. Break-out groups identified significant challenges in the areas of policy, scientific development, and public engagement with respect to the provision and application of tissues and cells for scientific advancement. Following working group recommendations, stakeholders concluded that there is a need to facilitate the availability and quality of human tissues for the research community, as well as provide a framework for education of the public, medical professionals, and researchers to foster donation and utilization for research in place of animal models. The success of these new initiatives will facilitate greater access to high-quality human tissues for biomedical and translational research and help ensure the transition away from the dependence on animal models.

Summary: The human intestinal mucosa is a critical site for absorption, distribution, metabolism, and excretion (ADME)/Tox studies in drug development and is difficult to recapitulate in vitro. Using bioprinting, we generated three-dimensional (3D) intestinal tissue composed of human primary intestinal epithelial cells and myofibroblasts with architecture and function to model the native intestine. The 3D intestinal tissue demonstrates a polarized epithelium with tight junctions and specialized epithelial cell types and expresses functional and inducible CYP450 enzymes. The 3D intestinal tissues develop physiological barrier function, distinguish between high- and low-permeability compounds, and have functional P-gp and BCRP transporters. Biochemical and histological characterization demonstrate that 3D intestinal tissues can generate an injury response to compound-induced toxicity and inflammation. This model is compatible with existing preclinical assays and may be implemented as an additional bridge to clinical trials by enhancing safety and efficacy prediction in drug development. : In Vitro Toxicology Including 3D Culture; Bioengineering; Tissue Engineering Subject Areas: In Vitro Toxicology Including 3D Culture, Bioengineering, Tissue Engineering

Directed differentiation of human pluripotent stem cells to kidney organoids brings the prospect of drug screening, disease modelling and the generation of tissue for renal replacement. Currently, these applications are hampered by organoid variability, nephron immaturity, low throughput and limited scale. Here, we apply extrusion-based three-dimensional cellular bioprinting to deliver rapid and high-throughput generation of kidney organoids with highly reproducible cell number and viability. We demonstrate that manual organoid generation can be replaced by 6- or 96-well organoid bioprinting and evaluate the relative toxicity of aminoglycosides as a proof of concept for drug testing. In addition, three-dimensional bioprinting enables precise manipulation of biophysical properties, including organoid size, cell number and conformation, with modification of organoid conformation substantially increasing nephron yield per starting cell number. This facilitates the manufacture of uniformly patterned kidney tissue sheets with functional proximal tubular segments. Hence, automated extrusion-based bioprinting for kidney organoid production delivers improvements in throughput, quality control, scale and structure, facilitating in vitro and in vivo applications of stem cell-derived human kidney tissue.

Introduction One challenge in tissue engineering (TE) is designing a construct which ensures adequate oxygen diffusion and removal of waste throughout the implanted tissue. In native tissue, the ma...

Hepatic fibrosis develops from a series of complex interactions among resident and recruited cells making it a challenge to replicate using standard in vitro approaches. While studies have demonstrated the importance of macrophages in fibrogenesis, the role of Kupffer cells (KCs) in modulating the initial response remains elusive. Previous work demonstrated utility of 3D bioprinted liver to recapitulate basic fibrogenic features following treatment with fibrosis-associated agents. In the present study, culture conditions were modified to recapitulate a gradual accumulation of collagen within the tissues over an extended exposure timeframe. Under these conditions, KCs were added to the model to examine their impact on the injury/fibrogenic response following cytokine and drug stimuli. A 28-day exposure to 10 ng/mL TGF-β1 and 0.209 μM methotrexate (MTX) resulted in sustained LDH release which was attenuated when KCs were incorporated in the model. Assessment of miR-122 confirmed early hepatocyte injury in response to TGF-β1 that appeared delayed in the presence of KCs, whereas MTX-induced increases in miR-122 were observed when KCs were incorporated in the model. Although the collagen responses were mild under the conditions tested to mimic early fibrotic injury, a global reduction in cytokines was observed in the KC-modified tissue model following treatment. Furthermore, gene expression profiling suggests KCs have a significant impact on baseline tissue function over time and an important modulatory role dependent on the context of injury. Although the number of differentially expressed genes across treatments was comparable, pathway enrichment suggests distinct, KC- and time-dependent changes in the transcriptome for each agent. As such, the incorporation of KCs and impact on baseline tissue homeostasis may be important in recapitulating temporal dynamics of the fibrogenic response to different agents.

Recent advances in the directed differentiation of human pluripotent stem cells to kidney brings with it the prospect of drug screening and disease modelling using patient-derived stem cell lines. Development of such an approach for high content screening will require substantial quality control and improvements in throughput. Here we demonstrate the use of the NovoGen MMX 3D bioprinter for the generation of highly reproducible kidney organoids from as few as 4,000 cells. Histological and immunohistochemical analyses confirmed the presence of renal epithelium, glomeruli, stroma and endothelium, while single cell RNAseq revealed equivalence to the cell clusters present within previously described organoids. The process is highly reproducible, rapid and transferable between cell lines, including genetically engineered reporter lines. We also demonstrate the capacity to bioprint organoids in a 96-well format and screen for response to doxorubicin toxicity as a proof of concept for high content compound screening.

Compound-induced liver injury leading to fibrosis remains a challenge for the development of an Adverse Outcome Pathway useful for human risk assessment. Latency to detection and lack of early, systematically detectable biomarkers make it difficult to characterize the dynamic and complex intercellular interactions that occur during progressive liver injury. Here, we demonstrate the utility of bioprinted tissue constructs comprising primary hepatocytes, hepatic stellate cells, and endothelial cells to model methotrexate- and thioacetamide-induced liver injury leading to fibrosis. Repeated, low-concentration exposure to these compounds enabled the detection and differentiation of multiple modes of liver injury, including hepatocellular damage, and progressive fibrogenesis characterized by the deposition and accumulation of fibrillar collagens in patterns analogous to those described in clinical samples obtained from patients with fibrotic liver injury. Transient cytokine production and upregulation of fibrosis-associated genes ACTA2 and COL1A1 mimics hallmark features of a classic wound-healing response. A surge in proinflammatory cytokines (eg, IL-8, IL-1β) during the early culture time period is followed by concentration- and treatment-dependent alterations in immunomodulatory and chemotactic cytokines such as IL-13, IL-6, and MCP-1. These combined data provide strong proof-of-concept that 3D bioprinted liver tissues can recapitulate drug-, chemical-, and TGF-β1-induced fibrogenesis at the cellular, molecular, and histological levels and underscore the value of the model for further exploration of compound-specific fibrogenic responses. This novel system will enable a more comprehensive characterization of key attributes unique to fibrogenic agents during the onset and progression of liver injury as well as mechanistic insights, thus improving compound risk assessment.

Due to its exposure to high concentrations of xenobiotics, the kidney proximal tubule is a primary site of nephrotoxicity and resulting attrition in the drug development pipeline. Current pre-clinical methods using 2D cell cultures and animal models are unable to fully recapitulate clinical drug responses due to limited in vitro functional lifespan, or species-specific differences. Using Organovo's proprietary 3D bioprinting platform, we have developed a fully cellular human in vitro model of the proximal tubule interstitial interface comprising renal fibroblasts, endothelial cells, and primary human renal proximal tubule epithelial cells to enable more accurate prediction of tissue-level clinical outcomes. Histological characterization demonstrated formation of extensive microvascular networks supported by endogenous extracellular matrix deposition. The epithelial cells of the 3D proximal tubule tissues demonstrated tight junction formation and expression of renal uptake and efflux transporters; the polarized localization and function of P-gp and SGLT2 were confirmed. Treatment of 3D proximal tubule tissues with the nephrotoxin cisplatin induced loss of tissue viability and epithelial cells in a dose-dependent fashion, and cimetidine rescued these effects, confirming the role of the OCT2 transporter in cisplatin-induced nephrotoxicity. The tissues also demonstrated a fibrotic response to TGFβ as assessed by an increase in gene expression associated with human fibrosis and histological verification of excess extracellular matrix deposition. Together, these results suggest that the bioprinted 3D proximal tubule model can serve as a test bed for the mechanistic assessment of human nephrotoxicity and the development of pathogenic states involving epithelial-interstitial interactions, making them an important adjunct to animal studies.

SUMMARY The tumor microenvironment plays a critical role in tumor growth, progression, and therapeutic resistance, but interrogating the role of specific tumor-stromal interactions on tumorigenic phenotypes is challenging within in vivo tissues. Here, we tested whether three-dimensional (3D) bioprinting could improve in vitro models by incorporating multiple cell types into scaffold-free tumor tissues with defined architecture. We generated tumor tissues from distinct subtypes of breast or pancreatic cancer in relevant microenvironments and demonstrate that this technique can model patient-specific tumors by using primary patient tissue. We assess intrinsic, extrinsic, and spatial tumorigenic phenotypes in bioprinted tissues and find that cellular proliferation, extracellular matrix deposition, and cellular migration are altered in response to extrinsic signals or therapies. Together, this work demonstrates that multi-cell-type bioprinted tissues can recapitulate aspects of in vivo neoplastic tissues and provide a manipulable system for the interrogation of multiple tumorigenic endpoints in the context of distinct tumor microenvironments., In Brief Langer et al. use three-dimensional bioprinting to incorporate multiple cell types, including patient-derived cells, into scaffold-free in vitro tumor tissues. They show that cells within these tissues self-organize, secrete extracellular matrix factors, and respond to extrinsic signals and that multiple tumorigenic phenotypes can be assessed simultaneously., Graphical ABSTRACT

As the fields of engineering and biology continue to merge, the in vitro fabrication of more complex biological structures is becoming a reality. Advancements in additive manufacturing techniques include the development of instrumentation platforms that can handle and dispense living cells with a remarkable degree of spatial control. Although there are inherent challenges and limitations—cell supply, building and supporting larger-scale tissues, and achieving functionally relevant architecture in complex tissues—these exist with any tissue-engineering strategy and are not unique to automated three-dimensional fabrication. The kidney is an exquisitely complex organ with an intricate architecture composed of more than 20 unique and highly specialized cell types, several of which to date have not been propagated outside the adult body. Yet, during development, the kidney arises from relatively few cell types from the intermediate mesoderm. Thus, tissue engineering approaches that combine spatially directed tissue fabrication with multipotent renal stem cells are particularly compelling. This chapter will cover the limited history of bioprinting for tissue engineering and will offer a perspective on the possibilities of engineering the kidney with additive manufacturing approaches.

Chronic kidney disease (CKD) is a global health problem; the growing gap between the number of patients awaiting transplant and organs actually transplanted highlights the need for new treatments to restore renal function. Regenerative medicine is a promising approach from which treatments for organ-level disorders (e.g., neurogenic bladder) have emerged and translated to clinics. Regenerative templates, composed of biodegradable material and autologous cells, isolated and expanded ex vivo, stimulate native-like organ tissue regeneration after implantation. A critical step for extending this strategy from bladder to kidney is the ability to isolate, characterize, and expand functional renal cells with therapeutic potential from diseased tissue. In this study, we developed methods that yield distinct subpopulations of primary kidney cells that are compatible with process development and scale-up. These methods were translated to rodent, large mammal, and human kidneys, and then to rodent and human tissues with advanced CKD. Comparative in vitro studies demonstrated that phenotype and key functional attributes were retained consistently in ex vivo cultures regardless of species or disease state, suggesting that autologous sourcing of cells that contribute to in situ kidney regeneration after injury is feasible, even with biopsies from patients with advanced CKD.

The lack of biological complexity and limited life span of conventional human hepatocyte culture models are major limitations in toxicological research. Recent advances in three-dimensional (3D) mo...

Renal toxicity is a major cause of drug attrition at the clinical trial stage, and the primary site of this toxicity is within the proximal tubule. Conventional renal cell culture models lack the c...

Recently we described a method for estimating the oxygen consumption rate (OCR) of cells in static culture from equilibrium measurements of dissolved oxygen concentration (dO2), using an oxygen-sensing microplate and the steady-state solution to Fick's Law (Guarino et al. 2004). Here we describe a complementary method for estimating OCR from the transient-state rate of change of measured dO2. Although the system is open to the atmosphere and subject to a significant lag in sensor response, the rate of change of the measured dO2 immediately after seeding correlated directly with both cell number and steady-state OCR. This transient-state method is linear with cell number to a much higher density than is possible with the steady-state method because it derives from measurements made before diffusion limitations can be established. For a given sensor thickness, the same correlation line between the transient and non-diffusion-limited steady-state estimates of OCR was found to apply for various preparations of rat hepatocytes. The correlation slope varied predictably with sensor thickness. Thus, despite the non-idealities of this system, the initial rate measurement offers a rapid method to obtain an estimate of absolute OCR. To demonstrate the utility of this method, we purposefully treated rat hepatocytes in ways expected to change OCR. Cells deprived of oxygen by storage under several centimeters of medium showed decreases in both OCR and viability with time. Likewise, the OCR of hepatocytes exposed to the oxidative phosphorylation inhibitor rotenone decreased, whereas those exposed to the uncoupler dinoseb increased.

In recent years the concept of a stem cell has evolved to encompass the hypotheses that stem cells exist within many adult tissues, and that a common 'interchangeable' progenitor cell may exist within the bone marrow capable of regenerating and repairing tissues throughout the body. As more knowledge is gained about stem cells, their potential roles in disease processes, including the development and progression of cancer, have moved to the forefront. The underlying hypothesis of this review is that cell fate is determined by a combination of intrinsic and extrinsic factors; growth and differentiation are regulated through intracellular integration of a multitude of signals initiated by internal and external stimuli. The development of successful stem cell based therapies may depend on experimental approaches that consider both the intrinsic and extrinsic factors that control cell fate.

Normal prostate epithelial cells are difficult to propagate in vitro without experimental immortalization. The goal of this study was to isolate and characterize a propagable epithelial cell line from normal adult rat prostate. Enrichment of proliferation-competent cells was accomplished in vivo by initiating a single cycle of prostatic involution/regeneration. The RPE-F344 cell line was established from an androgen-deprived, involuted prostate four days after the initiation of regeneration by administration of testosterone. The cell line has been cultured in vitro for50 passages, forms a uniform monolayer in culture, exhibits contact inhibition at confluence, and does not form colonies in soft agar. Immunocytochemical and RT-PCR analyses demonstrated that the RPE-F344 cells express anti-apoptotic genes associated with cell survival, and several growth factor receptors important in prostate development and homeostasis. RPE-F344 cells are p27kip1 negative, telomerase positive, and express high molecular weight cytokeratins specific for prostatic basal cells. They also express low levels of androgen receptor (AR) and prostatic acid phosphatase (PAP); features associated with secretory luminal epithelial cells. RPE-F344 cells are maintained in vitro without androgen supplementation, but addition of 15nM dihydrotesterone (DHT) to the culture media results in a significant but transient enhancement of cellular proliferation. Establishment of RPE-F344-like colonies from rat prostate is limited to the ventral and dorsal lobes of the prostate 2-4 days after initiation of regeneration, suggesting that RPE-F344 cells may originate from a stem cell-like compartment that is responsible for regenerative repopulation.

Telomeres, which are specialized structures consisting of T2AG3 repeats and proteins at the ends of chromosomes, may be essential for genomic stability. To test whether telomere length maintenance preserves genomic stability in rats (Rattus rattus and Fischer 344), we assayed telomerase activity and telomere length in the rat hepatic epithelial stem–like cell line WB-F344 during aging in vitro and in tumor-derived lines. Telomerase activity in the parental WB-F344 line was repressed at low and intermediate passage levels in vitro and reexpressed at high passages. Southern blot hybridization and quantitative fluorescence in situ hybridization analyses demonstrated that telomeres were significantly eroded at intermediate passage levels, when telomerase was repressed, and at high passage levels, when telomerase was expressed. Fluorescence in situ hybridization analysis also revealed interstitial telomeric sequences in rat chromosomes. Tumor-derived WB-F344 cell lines that express telomerase had variably shortened telomeres. Cytogenetic analyses performed on WB-F344 cells at low, intermediate, and high passages demonstrated that chromosome instability was most severe in the intermediate passage cells. These data suggest that telomere shortening during aging of rat hepatic epithelial stem–like WB-F344 cells in vitro and during selection of tumorigenic lines in vivo may destabilize chromosomes. Expression of telomerase in high passage cells appeared to partially stabilize chromosomes. Mol. Carcinog. 24:209–217, 1999. © 1999 Wiley-Liss, Inc.

Several studies have shown that cultured rat liver epithelial cells transform spontaneously after chronic maintenance in a confluent state in vitro. In the present study, multiple independent lineages of low-passage WB-F344 rat liver epithelial stem-like cells were initiated and subjected in parallel to selection for spontaneous transformation to determine whether spontaneous acquisition of tumorigenicity was the result of events (genetic or epigenetic) that occurred independently and stochastically, or reflected the expression of a pre-existing alteration within the parental WB-F344 cell line. Temporal analysis of the spontaneous acquisition of tumorigenicity by WB-F344 cells demonstrated lineage-specific differences in the time of first expression of the tumorigenic phenotype, frequencies and latencies of tumor formation, and tumor differentiations. Although spontaneously transformed WB-F344 cells produced diverse tumor types (including hepatocellular carcinomas, cholangiocarcinomas, hepatoblastomas, and osteogenic sarcomas), individual lineages yielded tumors with consistent and specific patterns of differentiation. These results provide substantial evidence that the stochastic accumulation of independent transforming events during the selection regimen in vitro were responsible for spontaneous neoplastic transformation of WB-F344 cells. Furthermore, cell lineage commitment to a specific differentiation program was stable with time in culture and with site of transplantation. This is the first report of a cohort of related, but independent, rat liver epithelial cell lines that collectively produce a spectrum of tumor types but individually reproduce a specific tumor type. These cell lines will provide valuable reagents for investigation of the molecular mechanisms involved in the differentiation of hepatic stem-like cells and for examination of potential causal relationships in spontaneously transformed rat liver epithelial cell lines between molecular/cellular alterations and the ability to produce tumors in syngeneic animals.

The genomic evolution of a cohort of WB-F344 rat liver epithelial cell lineages undergoing spontaneous neoplastic transformation was followed to define the mechanistic relationship between genomic instability and progression to the neoplastic phenotype. Eighteen independent populations of WB-F344 cells (initiated from a single diploid-founding population) were subjected to 12 cycles of selective growth at confluent cell density, and cellular DNA contents were measured after each selection cycle. Flow cytometry demonstrated significant gains in the amount of G1 DNA after selection cycles 3, 6, and 7 in 44% (8 of 18), 89% (16 of 18), and 39% (7 of 18) of the cell populations, respectively. All populations subsequently lost DNA and returned to a diploid or pseudo-diploid DNA content within 1 to 2 selection cycles after the appearance of an increased DNA content. Additionally, appearance and subsequent disappearance of aneuploid or tetraploid subpopulations was observed in 11% (2 of 18) and 83% (15 of 18) of the experimental lineages, respectively. Although perturbations of G1 DNA content were apparent as early as selection cycle 3, at least 8 cycles of selective growth were required for the acquisition of tumorigenicity. While the independent lineages demonstrated significant fluctuations in G1 DNA content between selection cycles 3 and 8, the majority (11 of 13) of the populations contained a diploid or pseudo-diploid DNA content at the time tumorigenicity was expressed. Genomic instability preceded the acquisition of tumorigenic potential in rat liver epithelial cells subjected to selective growth conditions of maintenance at confluence, and may be required for its expression.

The Dunning H rat prostate tumor (R3327H) is a widely used experimental model of human prostatic adenocarcinoma (CaP). The Dunning H tumor has been characterized as androgen-sensitive, androgen-receptor (AR) positive, prostate-specific antigen and prostatic acid phosphatase (PAP) positive. To date, the tumor has been maintained by serial passage in vivo because of the lack of an in vitro cell line that retains the characteristics of the in vivo tumor. The objective of the present study was to establish a propagable cell line from R3327H adenocarcinoma that maintained androgen sensitivity and expression of AR, PSA and PAP. Tissue harvested from an in vivo R3327H tumor was dissociated with collagenase and placed into Richter's improved media (with supplements). A cytokeratin-positive epithelial cell line (HUNC-E) and a vimentin-positive stromal cell line (HUNC-S) were generated from the primary culture, subcultured continuously for >300 days, and passaged >50 times. Survival of the HUNC-E cell line in vitro depended on several media supplements, including nicotinamide, insulin, transferrin, selenium and epidermal growth factor (EGF). HUNC-E cells expressed AR and produced PSA and PAP throughout the culture period, as confirmed by immunocytochemistry and Western blot analyses. Addition of 14 nM testosterone (T) or dihydrotestosterone (DHT) to HUNC-E cells, stimulated DNA synthesis as well as anchorage-independent growth and PSA production, which demonstrated the androgen-sensitive nature of the cells in vitro. When HUNC-E and HUNC-S cells were combined in a 3:1 ratio and introduced subcutaneously into syngeneic male hosts, tumors formed in 2/3 animals with an average latency of 7 months. RT-PCR and immunocytochemical characterization of the HUNC cell lines revealed that the cells expressed several growth factors and their cognate receptors, including HGF, TGF-alpha and the TGF-betas, indicating the establishment of potential autocrine loops in the neoplastic cells. The HUNC-E and HUNC-S CaP cell lines, which retain the characteristics of the epithelial and stromal components of the in vivo R3327H tumor, will allow a more thorough and informative molecular and biological analysis of prostatic adenocarcinoma.

Telomerase is a ribonucleoprotein that synthesizes telomeric DNA repeats onto the ends of chromosomes. More than 85% of human cancers express telomerase activity and a large proportion of human hepatocellular carcinomas are positive. To study the role of telomerase expression in rat hepatocarcinogenesis, telomerase activity was assayed in various rat tissues and in two types of liver epithelial cells: hepatocytes and hepatic epithelial stem-like cells. In the present study, we demonstrate that telomerase activity in rats is tissue-specific and stable with animal aging. Liver and testis were found to be telomerase positive, spleen had low or no activity, and kidney was negative. Telomerase activity did not change significantly in 18 month-old rats compared to 2 month-old rats, but was moderately (twofold) increased during liver regeneration induced by a 2/3's partial hepatectomy. Telomerase activity was detected in isolated rat hepatocytes and low passage hepatic epithelial stem-like cells (WB-F344). Telomerase activity displayed significant variations in a propagable clone of WB-F344 cells. At low passage levels after establishment in vitro (passages 4 – 9) non-tumorigenic WB-F344 cells expressed telomerase activity. During further in vitro passaging these cells lost expression of telomerase. Expression of telomerase in the tumor-derived lines of WB-F344 cells but not in the selectively cycled, parental lineages of these cells suggests that there may be a role for telomerase in hepatocarcinogenesis.

We have previously shown that rat liver epithelial cells (RLEC) transfected with and constitutively expressing transforming growth factor-α (TGF-α) have an enhanced mitogenic response to hepatocyte growth factor (HGF). In the study reported here, we examined tumor clones derived from the TGF-α transfectants with respect to mitogenic response to HGF. Tumor cell lines that expressed TGF-α responded to HGF with a greater increase in DNA synthesis than did the nontransfected parental RLEC (pRLEC). The tumor clones had also acquired a lower threshold for HGF response, which enabled them to undergo significant DNA synthesis at a low concentration of HGF that did not evoke a response in the pRLEC or TGF-α transfectants. We investigated the mechanisms by which TGF-α expression may influence the HGF/c-met pathway. We showed that most TGF-α transfectants and tumor cells displayed increases in c-met mRNA and protein, indicating that the enhanced HGF response may be due in part to an increase in the amount of receptor present. However, in all transfectants and tumor clones that constitutively expressed TGF-α, c-met was tyrosine phosphorylated in the absence of ligand (HGF) or another exogenous growth factors. These data suggest that induction of c-met mRNA and transactivation of c-met may be a sequela of the constitutive expression of TGF-α and that constitutive activation of the epidermal growth factor receptor pathway leads to phosphorylation and activation of c-met. These studies provide evidence for a novel mechanism of communication between epidermal growth factor receptor and c-met pathways that may partially explain the synergistic effects reported between TGF-α and HGF. Mol. Carcinog. 18:244–255, 1997. © 1997 Wiley-Liss, Inc.

New treatment paradigms that slow or reverse progression of chronic kidney disease (CKD) are needed to relieve significant patient and healthcare burdens. We have shown that a population of selected renal cells (SRCs) stabilized disease progression in a mass reduction model of CKD. Here, we further define the cellular composition of SRCs and apply this novel therapeutic approach to the ZSF1 rat, a model of severe progressive nephropathy secondary to diabetes, obesity, dyslipidemia, and hypertension. Injection of syngeneic SRCs into the ZSF1 renal cortex elicited a regenerative response that significantly improved survival and stabilized disease progression to renal structure and function beyond 1 year posttreatment. Functional improvements included normalization of multiple nephron structures and functions including glomerular filtration, tubular protein handling, electrolyte balance, and the ability to concentrate urine. Improvements to blood pressure, including reduced levels of circulating renin, were also observed. These functional improvements following SRC treatment were accompanied by significant reductions in glomerular sclerosis, tubular degeneration, and interstitial inflammation and fibrosis. Collectively, these data support the utility of a novel renal cell-based approach for slowing renal disease progression associated with diabetic nephropathy in the setting of metabolic syndrome, one of the most common causes of end-stage renal disease.

Despite efforts to improve the ability to identify the toxicity of therapeutic compounds, the attrition rate for both experimental and approved drugs remains very high. Cardioand hepatotoxicity remain primary reasons for late stage failures and post-market withdrawals. Therefore more robust human, in vitro models of these organ systems are needed. We have developed a bioprinted th-ree-dimensional (3D) liver system that captures several key features of in vivo tissue, in a multi-well format suitable for drug screening. Using NovoGenTM bioprinting technology we have fabricated 3D liver constructs containing architecturallyand physiologically-relevant features for two hepatic cell lines and primary hepatocytes, within standard multi-well culture plates. Bioprinted, 3D hepatic neotissues were further enhanced in complexity with the addition of endothelial and hepatic stellate cells. Biochemical studies demonstrate that several critical liver functions are present including cytochrome P450 activity. Tight junction protein expression was observed throughout the 3D tissue. Analysis of cell death and proliferation following in vitro maturation revealed the constructs were viable. These results demonstrate a flexible bioprinting method to rapidly fabricate multi-cellular 3D liver constructs in a multi-well format enabling both drug screening and interrogation of liver biology. Program Number: 872.12 Abstract: 7979 Figure 1. NovoGen MMX Bioprinter. Materials and Methods Cell culture. All cells utilized in these experiments were sourced from commercial vendors and cultured according to the manufacturer’s recommended protocols. Cryo-preserved primary hepatocytes were purified by Percoll gradient centrifugation prior to use in bioprinted constructs. iPSC-derived hepatocyte-like cells (iCell Hepatocytes) were generously provided by Cellular Dynamics, Inc. Bio-ink preparation. Bio-ink was prepared based on protocols and techniques described in Norotte et. al., (Biomaterials 30: 5910-5917). For preparation of hydrogels containing cells, NovoGel 2.0 (Organovo, Inc.) was prepared according to manufacturer’s instructions and non-parenchymal cell populations were incorporated prior to bioprinting. Bioprinting. All tissues were fabricated directly into standard tissue culture plates (Corning Transwell) using standard Organovo bioprinting protocols and the NovoGen MMX Bioprinter or modifications thereof. Secreted protein detection. Spent media was analyzed by commercially available ELISA kits for the following liver metabolites: albumin, fibrinogen, and transferrin. Cholesterol biosynthesis was quantified fluorimetrically (Cayman Biochemical). CYP P450 analysis. CYP1A2 and CYP3A4 activity was assessed with the Pro-GloTMCYP P450 Assay system (Promega). Liver tissues were challenged with either verapamil (10μM) or dexamethasone (10μM) to stimulate CYP1A2 or CYP3A4 activity. Fold-induction was calculated as the increase in expression of the treated samples relative to the non-treated control samples. Histological analysis. Tissues were fixed in 10% buffered formalin, paraffin-embedded, and subjected to standard histochemical analysis. In some experiments, tissues were snap frozen upon harvest and cryosectioned prior to histologic or immunohistologic analysis. Results Conclusions Bioprinting enabled highly reproducible fabrication of architectually-and compositionally-defined 3D tissues into standard tissue culture formats. Bioprinted 3D liver tissues exhibited several key features that remained stable over time: 1.) Tissue-like cellular density, with high viability and development of well-organized microarchitecture (microvasculature, tight junctions) indicative of substantial intercellular communication. 2.) Cell type-specific compartmentalization, with establishment and retention of user-defined spatial localization of parenchymal and non-parenchymal components. 3.) Multi-layered architecture, ranging from 250-500 microns in thickness. 3D liver tissues possessed critical liver functions, including albumin production, cholesterol biosynthesis, fibrinogen and transferrin production, and inducible CYP 1A2 and CYP 3A4 activities. Per cell protein production (Albumin) by 3D bioprinted liver tissues was 5.0-8.6X greater than matched 2D controls, suggesting superior functionality in 3D. Acknowledgements This work was funded in part by the National Institute of Digestive Diseases and Kidney (NIDDK;1R43DK095584-01). iPSC-derived hepatocytes (iCell hepatocytes) were generously provided by Cellular Dynamics, Inc. Safe Harbor Statement Any statements contained in this presentation that do not describe historical facts may constitute forward-looking statements as that term is defined in the Private Securities Litigation Reform Act of 1995. Any forward-looking statements contained herein are based on current expectations, but are subject to a number of risks and uncertainties. The factors that could cause actual future results to differ materially from current expectations include, but are not limited to, risks and uncertainties relating to the Company's ability to develop, market and sell products based on its technology; the expected benefits and efficacy of the Company’s products and technology; the availability of substantial additional funding for the Company to continue its operations and to conduct research and development, clinical studies and future product commercialization; and, the Company's business, research, product development, regulatory approval, marketing and distribution plans and strategies. These and other factors are identified and described in more detail in our filings with the SEC, including our annual report for the period ended December 31, 2012 on Form 10-K and our current reports filed on Form 10K . We do not undertake to update these forward-looking statements made by us. Figure 2. 3D tissue geometries with relevant architecture and cellular features fabricated using the NovoGen Bioprinter. Figure 3. Bioprinted 3D human liver tissues constructed with primary hepatocytes and hepatic cell lines are metabolically active with CYP450 induction. T=39hrs T=63hrs T=87hrs T=135hrs H & E 20X 100 μm 100 μm Trichrome 20X Single Unit Geometry 100 μm E-Cadherin: Green DAPI: Blue 20X Multi-hexagonal acini Fused Compartmentalized Tissue 3D Liver tissues containing Primary Hepatocytes are stable and metabolically active over time. T=48hrs 3D Liver tissues containing HepaRG cells are metabolically active over time. Figure 5. 3D tissues bioprinted from iPSC derived hepatocyte-like cells outperform 2D culture. Multi-Unit Geometry Single Unit Geometry Albumin production per cell was significantly enhanced in both multi-unit (p

Modeling clinically relevant tissue responses using cell models poses a significant challenge for drug development, in particular for drug induced liver injury (DILI). This is mainly because existing liver models lack longevity and tissue-level complexity which limits their utility in predictive toxicology. In this study, we established and characterized novel bioprinted human liver tissue mimetics comprised of patient-derived hepatocytes and non-parenchymal cells in a defined architecture. Scaffold-free assembly of different cell types in an in vivo-relevant architecture allowed for histologic analysis that revealed distinct intercellular hepatocyte junctions, CD31+ endothelial networks, and desmin positive, smooth muscle actin negative quiescent stellates. Unlike what was seen in 2D hepatocyte cultures, the tissues maintained levels of ATP, Albumin as well as expression and drug-induced enzyme activity of Cytochrome P450s over 4 weeks in culture. To assess the ability of the 3D liver cultures to model tissue-level DILI, dose responses of Trovafloxacin, a drug whose hepatotoxic potential could not be assessed by standard pre-clinical models, were compared to the structurally related non-toxic drug Levofloxacin. Trovafloxacin induced significant, dose-dependent toxicity at clinically relevant doses (≤ 4uM). Interestingly, Trovafloxacin toxicity was observed without lipopolysaccharide stimulation and in the absence of resident macrophages in contrast to earlier reports. Together, these results demonstrate that 3D bioprinted liver tissues can both effectively model DILI and distinguish between highly related compounds with differential profile. Thus, the combination of patient-derived primary cells with bioprinting technology here for the first time demonstrates superior performance in terms of mimicking human drug response in a known target organ at the tissue level.

Myocardin (MYOCD) is a smooth and cardiac muscle-specific transcriptional coactivator that is required for the proper expression of contraction-related genes. Through its function to transactivate effector genes, MYOCD plays an essential role in mediating the switch between contractile and non-contractile phenotypes, particularly in smooth muscle cells (SMC). There are at least two known transcript variants of MYOCD that are expressed in SMC, differing only by the presence (+) or absence (Δ) of Exon 11. To date, no functional role has been assigned to the domain encoded by Exon 11, nor have any notable differences between the ability of each isoform to activate contraction-related genes been observed. In this study we compared sequences for Exon 11 among several mammalian species and identified a highly conserved, putative target sequence for glycogen synthase kinase 3 (GSK3) phosphorylation, suggesting a regulatory role for Exon 11 that can be modulated by alternative splicing. The function of Exon 11 was investigated by altering MYOCD splice selection in cultured porcine SMC with small interfering RNAs (siRNA) and specific chemical inhibitors, resulting in a relative increase in expression of ΔExon 11 variants in the endogenous pool of MYOCD mRNA. The relative increase in ΔExon 11 mRNAs correlated with a reduction of contractile phenotype in the porcine SMC as evidenced by morphological assessment and molecular analysis of effector genes. Together, these data suggest that MYOCD ΔExon 11 may participate in modulating SMC phenotype, potentially acting as a dominant-negative repressor of contraction-related genes.

Established chronic kidney disease (CKD) may be identified by severely impaired renal filtration that ultimately leads to the need for dialysis or kidney transplant. Dialysis addresses only some of the sequelae of CKD, and a significant gap persists between patients needing transplant and available organs, providing impetus for development of new CKD treatment modalities. Some postulate that CKD develops from a progressive imbalance between tissue damage and the kidney's intrinsic repair and regeneration processes. In this study we evaluated the effect of kidney cells, delivered orthotopically by intraparenchymal injection to rodents 4–7 wk after CKD was established by two-step 5/6 renal mass reduction (NX), on the regeneration of kidney function and architecture as assessed by physiological, tissue, and molecular markers. A proof of concept for the model, cell delivery, and systemic effect was demonstrated with a heterogeneous population of renal cells (UNFX) that contained cells from all major compartments of the kidney. Tubular cells are known contributors to kidney regeneration in situ following acute injury. Initially tested as a control, a tubular cell-enriched subpopulation of UNFX (B2) surprisingly outperformed UNFX. Two independent studies (3 and 6 mo in duration) with B2 confirmed that B2 significantly extended survival and improved renal filtration (serum creatinine and blood urea nitrogen). The specificity of B2 effects was verified by direct comparison to cell-free vehicle controls and an equivalent dose of non-B2 cells. Quantitative histological evaluation of kidneys at 6 mo after treatment confirmed that B2 treatment reduced severity of kidney tissue pathology. Treatment-associated reduction of transforming growth factor (TGF)-β1, plasminogen activator inhibitor (PAI)-1, and fibronectin (FN) provided evidence that B2 cells attenuated canonical pathways of profibrotic extracellular matrix production.

The most common molecular alteration observed in human cancers,1 loss of heterozygosity (LOH), is a significant mecha-nism by which critical genes involved in growth regulation and homeostasis become inactivated, or silenced, during disease evolution. This chapter provides a review of LOH and its implications in various cancers as well as a review of LOH in nonmalignant diseases. Only 0.08% of those base pairs within the entire human genome (3 billion base pairs) vary between any two humans, and only 0.02% of those variations actually result in an expressed protein with a different amino acid as a result of the change.2 Even more remarkable, 90% of those variations are changes that are common in the population and lead to normal variation in traits among individuals; eye color, for example.

Lung cancer remains the leading cause of cancer-related death, accounting for over 1 million deaths per year worldwide.1, 2, 3 Exposure to insult, primarily tobacco smoke, is the indisputable root cause of most lung cancers,4 but it is the consequential epigenetic and genetic changes (promoter methylation, mutations, deletions, and amplifications) that drive tumor formation, progression, and metastasis. Loss of heterozygosity (LOH) is an extremely common genetic feature of lung cancer and is a significant mechanism by which critical genes involved in growth regulation and homeostasis become inactivated, or silenced, during disease evolution. This chapter reviews LOH and its implications in the major classes of lung cancer as well as in nonmalignant lung diseases.

This chapter deals with basic concepts and techniques in nucleic acid blotting. Many of the techniques involved with Southern blotting and Northern blotting are similar. Negatively charged, purified nucleic acids from prokaryotic or eukaryotic cells are separated according to size by electrophoresis through an agarose gel matrix. The RNA or denatured DNA is subse– quently transferred and immobilized onto a membrane com– posed of nitrocellulose or nylon. The nucleic acids on the membrane are then hybridized to a specific labeled “probe,” which consists of homologous single-stranded nucleic acids that carry molecules, allowing detection and visualization of the hybridized probe. Hybridization between the immobilized nucleic acids and labeled probe allows detection of specific DNA or RNA sequences within a complex mixture of DNA or RNA. The specific method of detection and visualization is dependent on the nature of the labeled probe; radioactive probes enable autoradiographic detection, and probes labeled with enzymes facilitate chemiluminescent or colorimetric detection. Nucleic acid blotting yields valuable information pertaining to gene integrity and copy number (Southern blot) and provides a means of analyzing gene expression and mRNA size (Northern blot). These methods can be used to character– ize tissues and cultured cells in the laboratory and often provide valuable information for clinical evaluation of patient samples.

As breast cancer is a disease of multiple cell types in which the growth, invasion, and metastasis of epithelial carcinomas is heavily influenced by the surrounding cell types, screening of anti-cancer compounds using cancer cell lines grown in 2D often overestimates drug potency. Regulatory agencies are currently seeking improved preclinical oncology models to overcome hurdles to efficient drug development, including bridging the gap between the use of 2D cell lines and 3D animal models. One way to more accurately determine the effects of anti-cancer compounds is through the use of cancer tissue models that incorporate stromal cells of the tumor microenvironment. Breast stroma, composed of fibroblasts, endothelial cells, and adipocytes, plays a key role in the process of carcinogenesis and metastasis. These cell types secrete extracellular matrix, growth factors, and hormones that affect how therapeutic agents access and target cancer cells. We have used Organovo's NovoGen BioprintingTM Platform to develop a model of human breast cancer in which a core of breast cancer cells is surrounded by a physiologically-relevant stromal milieu consisting of adipocytes, mammary fibroblasts, and endothelial cells. This system has several advantages over current screening tools, including the ability to simultaneously measure the effects of small molecules on cancer cells as well as different cell types in the breast microenvironment. Histological analyses of bioprinted neotissues demonstrated that they were stable and viable for at least 14 days in culture and characterized by interaction between stroma and carcinoma compartments. Incorporation of endothelial cells into the 3D neotissue led to the formation of robust microvascular networks. Breast cancer neotissues were fabricated directly into multi-well plates and used to establish biological response profiles to the standard chemotherapeutic agents cisplatin, paclitaxel, methotrexate, and tamoxifen. The cytotoxic effects of chemotherapeutic drugs on specific cell types within the neotissues were assessed biochemically and histologically. he response of the 3D breast cancer neotissues to chemotherapeutic gents was compared to the response of 2D breast cancer cell lines to determine he relative efficacy of compounds in 2D versus 3D. This model can be used to screen new anti-cancer therapeutics in the context of the in vivo-like microenvironment, leading to enhanced efficiency and accuracy of the drug development process. Citation Format: Shelby M. King, Sharon C. Presnell, Deborah G. Nguyen. Development of 3D bioprinted human breast cancer for in vitro drug screening. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2034. doi:10.1158/1538-7445.AM2014-2034

Cell cycle checkpoints are barriers to carcinogenesis as they function to maintain genomic integrity. Attenuation or ablation of checkpoint function may enhance tumor formation by permitting outgrowth of unstable cells with damaged DNA. To examine the function of cell cycle checkpoints in rat hepatocarcinogenesis, we analyzed the responses of the G (1), G (2) and mitotic spindle assembly checkpoints in normal rat hepatocytes, hepatic epithelial stem-like cells (WB-F344) and transformed derivatives of both. Normal rat hepatocytes (NRH) displayed a 73% reduction in the fraction of nuclei in early S-phase 6-8 h following 8 Gy of ionizing radiation (IR) as a quantitative measure of G (1) checkpoint function. Chemically and virally transformed hepatocyte lines displayed significant attenuation of G (1) checkpoint function, ranging from partial to complete ablation. WB-F344 rat hepatic epithelial cell lines at low, mid and high passage levels expressed G (1) checkpoint function comparable with NRH. Only one of four malignantly transformed WB-F344 cell lines displayed significant attenuation of G (1) checkpoint function. Attenuation of G (1) checkpoint function in transformed hepatocytes and WB-F344 cells was associated with alterations in p53, ablated/attenuated induction of p21 (Waf1) by IR, as well as aberrant function of the spindle assembly checkpoint. NRH displayed 93% inhibition of mitosis 2 h after 1 Gy IR as a quantitative measure of G (2) checkpoint function. All transformed hepatocyte and WB-F344 cell lines displayed significant attenuation of the G (2) checkpoint. Moreover, the parental WB-F344 line displayed significant age-related attenuation of G (2) checkpoint function. Abnormalities in the function of cell cycle checkpoints were detected in transformed hepatocytes and WB-F344 cells at stages of hepatocarcinogenesis preceding tumorigenicity, sustaining a hypothesis that aberrant checkpoint function contributes to carcinogenesis.

Human tissue xenograft models are currently the only tool for conducting in vivo analyses of intact human tissue. The goal of the present study was to develop reliable methods for successful generation of short-term primary tissue xenografts from benign and tumor-derived human prostate tissue. Primary human prostate xenografts were established in athymic nu/nu mice from eight of eight benign and five of five prostate cancer tissues, collected from a total of 10 patients who underwent radical prostatectomy for the treatment of prostate cancer. An average of 13 xenografts was established per specimen. Two tissue specimens were cryopreserved for >1 month before successful generation of prostate xenografts. After 1 month in vivo, xenograft tissues were harvested and examined regarding: gross evidence of vascularization; tissue morphology; proliferation; apoptosis; and expression of androgen receptor, prostate-specific antigen, and high molecular weight cytokeratins specific for basal cells in the prostate. Direct comparison of the original tissue specimen and the 1-month xenografts revealed similar histology; similar apoptotic and proliferative fractions in most cases; and comparable expression levels and expression patterns of androgen receptor, prostate-specific antigen, and high molecular weight cytokeratins. These data demonstrate that primary human prostate xenografts, benign and malignant, can be established routinely from human prostate tissue surgical specimens, and that the xenografts maintain tissue architecture and expression of key prostatic markers. The development of this methodology, including the technique for cryopreservation of human tissue, will allow multiple (successive) analyses of human prostate tissue to be conducted throughout time using a tissue sample derived from a single patient; and simultaneous analysis of human prostate tissues derived from a cohort of patients.

Chemical-induced liver cancer in animal models, and primary human liver cancers are mainly male diseases. Sex-related differences in metabolism/detoxification of carcinogenic agents and cultural practices may contribute to the striking sensitivity of males to hepatocellular carcinoma development. No physiological mechanisms have been identified to explain the relative insensitivity of females to liver carcinogenesis. We compared the capacity of the male versus female liver tissue microenvironment to support/suppress tumorigenicity of orthotopically transplanted tumor liver cells. GN6TF rat liver epithelial cells, that are 100% tumorigenic at ectopic sites, were transplanted into the liver microenvironment of male and female syngeneic hosts that were fed ad libitum or were maintained on a caloric restricted diet. The liver microenvironment of young adult (3–9 mo.) ad lib-fed male rats suppressed tumor formation completely. Transplanted cells migrated into liver plates where they underwent hepatocytic differentiation. Transplantation of GN6TF cells into the livers of old male hosts (18–24 mo.) resulted in the formation of tumors within 90 days (66–100% of hosts, respectively). Transplantation of GN6TF cells into the livers of old male, caloric restricted animals were followed by rapid formation of tumors (latency = 40 days). In contrast, transplantation of GN6TF cells into female rats resulted in suppression of the tumorigenic phenotype in 85% of old and 100% of young female rats. These data suggest that hormonal- directed epigenetic suppression of tumorigenicity contributes to the sex-specific sensitivity to liver carcinogenesis.

We have previously identified and mapped a locus within human chromosome 11p11.2-p12 that suppresses the tumorigenic potential of some rat liver tumor cell lines. In the present study, possible molecular mechanisms of human 11p11.2-p12-mediated liver tumor suppression were investigated by examining gene expression patterns in suppressed and non-suppressed microcell hybrid (MCH) cell lines. The parental rat liver tumor cell lines (GN6TF and GP7TB) express moderate levels of p53 mRNA and protein, overexpress mRNAs for c-H-ras, c-myc, and TGFá, and do not express detectable levels of WT1 mRNA or protein. Suppression of tumorigenicity by human chromosome 11p11.2-p12 was not accompanied by significant alterations in the levels of expression of p53, c-myc, or TGFá. Expression of c-H-ras was decreased significantly in both suppressed and non-suppressed MCH cell lines, suggesting that down-regulation of c-H-ras is not directly responsible for tumor suppression. In contrast, the level of expression of WT1 correlated precisely with tumor suppression in this model system. All suppressed MCH cell lines expressed WT1 mRNA and protein at levels comparable to that of untransformed rat liver epithelial cells (WB-F344), whereas only trace WT1 mRNA and protein were detected in a non-suppressed MCH cell line. PCR analysis demonstrated that two suppressed MCH cell lines do not carry the human WT1 gene, indicating that WT1 expression in these lines originates from the rat locus. Furthermore, RT-PCR analysis showed that each of the four known splice variants of the WT1 mRNA are expressed in these suppressed MCH cell lines, recapitulating the expression pattern observed in the untransformed rat liver epithelial cells. Re-expression of tumorigenicity by suppressed MCH cell lines was accompanied by the coordinate loss of human chromosome 11p11.2-p12 and of WT1 gene expression, suggesting that one or more human 11p11.2-p12 genes are required for sustained expression of WT1 in these cell lines. Together, these results suggest that the molecular mechanism governing human chromosome 11p11.2-p12-mediated liver tumor suppression may involve induction of rat WT1 gene expression under the direct or indirect transcriptional regulation of a genetic locus (or loci) on human 11p11.2-p12.

A model of spontaneous malignant transformation was used to evaluate the molecular changes that take place in WB-F344 rat liver epithelial cells during neoplastic transformation and tumorigenesis. A comparison of wild-type low-passage WB-F344 cells to spontaneously transformed tumor cell lines revealed that the majority of the tumor cell lines have an increased capacity for autonomous proliferation and motility when maintained in serum-free media. In the current study, we show that c-met is expressed at some level in wild-type WB-F344 cells and in all of the spontaneously transformed tumor cell lines, and that 9/16 of the tumor cell lines have acquired hepatocyte growth factor (HGF) expression. In vitro growth of HGF-expressing tumor cell lines is inhibited as much as 68% by the addition of neutralizing antibodies to HGF or antisense HGF oligonucleotides, indicating that the production of HGF by the tumor cells is partially responsible for driving autonomous proliferation in a subset of tumor cell lines. Furthermore, conditioned media collected from HGF-expressing tumor cell lines stimulates DNA synthesis in wild-type WB-F344 cells, and this effect can be abrogated by pre-incubation of the conditioned media with neutralizing antibodies to HGF. Because HGF is a motility-promoting growth factor, all cell lines were evaluated to determine if expression of HGF stimulated motogenesis. All tumor cell lines (regardless of HGF expression) were highly motile in comparison with wild-type WB-F344 cells, with a 3.5-fold to 20-fold greater number of motile cells. The high basal rate of motility characteristic of the tumor cell lines is not a result of the production of HGF, because it is also a property of the cell lines that do not express HGF messenger RNA. Furthermore, tumor cell motility is not inhibited by antisense oligonucleotides or neutralizing antibodies. Establishment of an autocrine HGF/c-met loop in a subset of spontaneously transformed WB-F344 cell lines may influence development and/or expression of the tumorigenic phenotype by driving cellular proliferation.