Anti-angiogenic properties of microRNA-29a in preclinical ocular models.

Abnormal neovascularization is an important cause of blindness in many ocular diseases, for which the etiology and pathogenic mechanisms remain incompletely understood. Recent studies have revealed the diverse roles of noncoding RNAs in various biological processes and facilitated the research and development of the clinical application of numerous RNA drugs, including microRNAs. Here, we report the antiangiogenic activity of microRNA-29a (miR-29a) in three animal models of ocular neovascularization. The miR-29a knockout (KO) mice displayed enhanced vessel pruning, resulting in a decreased vascularized area during retinal development. In contrast, miR-29a deletion in adult mice accelerated angiogenesis in preclinical disease models, including corneal neovascularization, oxygen-induced retinopathy, and choroidal neovascularization, while the administration of agomir-29a ameliorated pathological neovascularization. Furthermore, miR-29a exerted inhibitory effects on endothelial cell proliferation, migration, and tube formation capacities. RNA sequencing analysis of retinas from miR-29a KO mice and RNA interference experiments identified platelet-derived growth factor C and several extracellular matrix genes as downstream targets of miR-29a involved in regulating ocular angiogenesis. Our data suggest that miR-29a may be a promising clinical candidate for the treatment of neovascular diseases.

Identification of Basp1 as a novel angiogenesis-regulating gene by multi-model system studies.

We have previously used the genetic diversity available in common inbred mouse strains to identify quantitative trait loci (QTLs) responsible for the differences in angiogenic response using the corneal micropocket neovascularization (CoNV) assay. Employing a mouse genome-wide association study (GWAS) approach, the region on chromosome 15 containing Basp1 was identified as being significantly associated with angiogenesis in inbred strains. Here, we developed a unique strategy to determine and verify the role of BASP1 in angiogenic pathways. Basp1 expression in cornea had a strong correlation with a haplotype shared by mouse strains with varied angiogenic phenotypes. In addition, inhibition of BASP1 demonstrated a dosage-dependent effect in both primary mouse brain endothelial and human microvascular endothelial cell (HMVEC) migration. To investigate its role in vivo, we knocked out basp1 in transgenic kdrl:zsGreen zebrafish embryos using a widely adopted CRISPR-Cas9 system. These embryos had severely disrupted vessel formation compared to control siblings. We further show that basp1 promotes angiogenesis by upregulating ß-catenin gene and the Dll4/Notch1 signaling pathway. These results, to the best of our knowledge, provide the first in vivo evidence to indicate the role of Basp1 as an angiogenesis-regulating gene and opens the potential therapeutic avenues for a wide variety of systemic angiogenesis-dependent diseases.

Angiogenic responses in a 3D micro-engineered environment of primary endothelial cells and pericytes.

Angiogenesis plays a key role in the pathology of diseases such as cancer, diabetic retinopathy, and age-related macular degeneration. Understanding the driving forces of endothelial cell migration and organization, as well as the time frame of these processes, can elucidate mechanisms of action of important pathological pathways. Herein, we have developed an organ-specific microfluidic platform recapitulating the in vivo angiogenic microenvironment by co-culturing mouse primary brain endothelial cells with brain pericytes in a three-dimensional (3D) collagen scaffold. As a proof of concept, we show that this model can be used for studying the angiogenic process and further comparing the angiogenic properties between two different common inbred mouse strains, C57BL/6J and 129S1/SvlmJ. We further show that the newly discovered angiogenesis-regulating gene Padi2 promotes angiogenesis through Dll4/Notch1 signaling by an on-chip mechanistic study. Analysis of the interplay between primary endothelial cells and pericytes in a 3D microfluidic environment assists in the elucidation of the angiogenic response.

The Prominin-1-Derived Peptide Improves Cardiac Function Following Ischemia.

Myocardial infarction (MI) remains the leading cause of death in the western world. Despite advancements in interventional revascularization technologies, many patients are not candidates for them due to comorbidities or lack of local resources. Non-invasive approaches to accelerate revascularization within ischemic tissues through angiogenesis by providing Vascular Endothelial Growth Factor (VEGF) in protein or gene form has been effective in animal models but not in humans likely due to its short half-life and systemic toxicity. Here, we tested the hypothesis that PR1P, a small VEGF binding peptide that we developed, which stabilizes and upregulates endogenous VEGF, could be used to improve outcome from MI in rodents. To test this hypothesis, we induced MI in mice and rats via left coronary artery ligation and then treated animals with every other day intraperitoneal PR1P or scrambled peptide for 14 days. Hemodynamic monitoring and echocardiography in mice and echocardiography in rats at 14 days showed PR1P significantly improved multiple functional markers of heart function, including stroke volume and cardiac output. Furthermore, molecular biology and histological analyses of tissue samples showed that systemic PR1P targeted, stabilized and upregulated endogenous VEGF within ischemic myocardium. We conclude that PR1P is a potential non-invasive candidate therapeutic for MI.

Identification of Padi2 as a novel angiogenesis-regulating gene by genome association studies in mice.

Recent findings indicate that growth factor-driven angiogenesis is markedly influenced by genetic variation. This variation in angiogenic responsiveness may alter the susceptibility to a number of angiogenesis-dependent diseases. Here, we utilized the genetic diversity available in common inbred mouse strains to identify the loci and candidate genes responsible for differences in angiogenic response. The corneal micropocket neovascularization assay was performed on 42 different inbred mouse strains using basic fibroblast growth factor (bFGF) pellets. We performed a genome-wide association study utilizing efficient mixed-model association (EMMA) mapping using the induced vessel area from all strains. Our analysis yielded five loci with genome-wide significance on chromosomes 4, 8, 11, 15 and 16. We further refined the mapping on chromosome 4 within a haplotype block containing multiple candidate genes. These genes were evaluated by expression analysis in corneas of various inbred strains and in vitro functional assays in human microvascular endothelial cells (HMVECs). Of these, we found the expression of peptidyl arginine deiminase type II (Padi2), known to be involved in metabolic pathways, to have a strong correlation with a haplotype shared by multiple high angiogenic strains. In addition, inhibition of Padi2 demonstrated a dosage-dependent effect in HMVECs. To investigate its role in vivo, we knocked down Padi2 in transgenic kdrl:zsGreen zebrafish embryos using morpholinos. These embryos had disrupted vessel formation compared to control siblings. The impaired vascular pattern was partially rescued by human PADI2 mRNA, providing evidence for the specificity of the morphant phenotype. Taken together, our study is the first to indicate the potential role of Padi2 as an angiogenesis-regulating gene. The characterization of Padi2 and other genes in associated pathways may provide new understanding of angiogenesis regulation and novel targets for diagnosis and treatment of a wide variety of angiogenesis-dependent diseases.

A novel strategy to enhance angiogenesis in vivo using the small VEGF-binding peptide PR1P.

Therapeutic angiogenesis is an experimental frontier in vascular biology that seeks to deliver angiogenic growth factors to ischemic or injured tissues to promote targeted formation of new blood vessels as an alternative approach to surgical revascularization procedures. Vascular endothelial growth factor (VEGF) is a potent angiogenic signal protein that is locally upregulated at sites of tissue injury. However, therapies aimed at increasing VEGF levels experimentally by injecting VEGF gene or protein failed to improve outcomes in human trials in part due to its short half-life and systemic toxicity. We recently designed a novel 12-amino acid peptide (PR1P) whose sequence was derived from an extracellular VEGF-binding domain of the pro-angiogenic glycoprotein prominin-1. In this study, we characterized the molecular binding properties of this novel potential therapeutic for targeted angiogenesis and provided the foundation for its use as an angiogenic molecule that can potentiate endogenous VEGF. We showed that PR1P bound VEGF directly and enhanced VEGF binding to endothelial cells and to VEGF receptors VEGFR2 and neuropilin-1. PR1P increased angiogenesis in the murine corneal micropocket assay when combined with VEGF, but had no activity without added VEGF. In addition, PR1P also enhanced angiogenesis in murine choroidal neovascularization and wound-healing models and augmented reperfusion in a murine hind-limb ischemia model. Together our data suggest that PR1P enhanced angiogenesis by potentiating the activity of endogenous VEGF. In so doing, this novel therapy takes advantage of endogenous VEGF gradients generated in injured tissues and may improve the efficacy of and avoid systemic toxicity seen with previous VEGF therapies.

Melanocyte pigmentation inversely correlates with MCP-1 production and angiogenesis-inducing potential.

The incidence of certain angiogenesis-dependent diseases is higher in Caucasians than in African Americans. Angiogenesis is amplified in wound healing and cornea models in albino C57 mice compared with black C57 mice. Moreover, mouse and human melanocytes with low pigmentation stimulate endothelial cell (EC) proliferation and migration in vitro more than melanocytes with high pigmentation. This effect is due, in part, to the secretion of an angiogenic protein called fibromodulin (FMOD) from lowly pigmented melanocytes. Herein, we expand upon the mechanism contributing to increased angiogenesis in lighter skin and report that monocyte chemotactic protein-1 (MCP-1) is secreted by nonpigmented mouse melanocytes by 5- to 10-fold more than pigmented melanocytes. MCP-1 protein stimulates EC proliferation and migration in vitro and angiogenesis in vivo. Mechanistic studies determine that FMOD is upstream of MCP-1 and promotes its secretion from both melanocytes and activated ECs via stimulation of NF-κB activity. Mice injected with FMOD-neutralizing antibodies show 2.3-fold decreased levels of circulating MCP-1. Human studies confirmed that, on average, Caucasians have 2-fold higher serum levels of MCP-1 than African Americans. Taken together, this study implicates the FMOD/MCP-1 pathway in the regulation of angiogenesis by local melanocytes and suggests that melanogenic activity may protect against aberrant angiogenic diseases.

Cellular mechanism of oral absorption of solidified polymer micelles.

Oral delivery of poorly soluble and permeable drugs represents a significant challenge in drug development. The oral delivery of drugs remains to be the ultimate route of any drugs. However, in many cases, drugs are not absorbed well in the gastrointestinal tract, or they lose their activity. Polymer micelles were recognized as an effective carrier system for drug encapsulation, and are now studied as a vehicle for oral delivery of insoluble compounds. We characterized the properties of monomethoxy polyethylene glycol-poly lactic acid (mPEG-PLA) micelles, and visualized their internalization in mouse small intestine. Using Caco-2 cells as a cellular model, we studied the kinetics of particle uptake, their transport, and the molecular mechanism of their intestinal absorption. Moreover, by inhibiting specific endocytosis pathways, pharmacologically and genetically, we found that mPEG-PLA nanoparticle endocytosis is mediated by clathrin in an energy-dependent manner, and that the low-density lipoprotein receptor is involved. FROM THE CLINICAL EDITOR: Many current drugs used are non-water soluble and indeed, the ability to deliver these drugs via the gastrointestinal tract remains the holy grail for many researchers. The authors in this paper developed monomethoxy polyethylene glycol-poly lactic acid (mPEG-PLA) micelles as a drug nanocarrier, and studied the mechanism of uptake across intestinal cells. The findings should improve our current understanding and point to the development of more nanocarriers.

The albino mutation of tyrosinase alters ocular angiogenic responsiveness.

We have observed substantial differences in angiogenic responsiveness in mice and have mapped the genetic loci responsible for these differences. We have found that the albino mutation is one of the loci responsible for such differences. Using B6.A consomic strains, we determined that chromosome 7 bears a locus that inhibits VEGF-induced corneal neovascularization. F2 crosses between B6.A consomic mice and C57BL/6J parents along with AXB and BXA recombinant inbred strains demonstrated highest linkage near the tyrosinase gene. This region was named AngVq4. Congenic animals confirmed this locus, but could not demonstrate that the classical tyrosinase albino (c) mutation was causative because of the existence of additional linked loci in the congenic region. However, in 1970, a second tyrosinase albino mutation (c-2J) arose in the C57BL/6J background at Jackson Labs. Testing this strain (C57BL/6J) demonstrated that the albino mutation is sufficient to completely explain the alteration in angiogenic response that we observed in congenic animals. Thus, we conclude that the classical tyrosinase mutation is responsible for AngVq4. In contrast to the cornea, where pigmented animals exhibit increased angiogenic responsiveness, iris neovascularization was inhibited in pigmented animals. These results may partially explain increased aggressiveness in amelanotic melanoma, as well as ethnic differences in diabetic retinopathy and macular degeneration.

The stem cell marker prominin-1/CD133 interacts with vascular endothelial growth factor and potentiates its action.

Prominin-1, a pentaspan transmembrane protein, is a unique cell surface marker commonly used to identify stem cells, including endothelial progenitor cells and cancer stem cells. However, recent studies have shown that prominin-1 expression is not restricted to stem cells but also occurs in modified forms in many mature adult human cells. Although prominin-1 has been studied extensively as a stem cell marker, its physiological function of the protein has not been elucidated. We investigated prominin-1 function in two cell lines, primary human endothelial cells and B16-F10 melanoma cells, both of which express high levels of prominin-1. We found that prominin-1 directly interacts with the angiogenic and tumor survival factor vascular endothelial growth factor (VEGF) in both the primary endothelial cells and the melanoma cells. Knocking down prominin-1 in the endothelial cells disrupted capillary formation in vitro and decreased angiogenesis in vivo. Similarly, tumors derived from prominin-1 knockdown melanoma cells had a reduced growth rate in vivo. Further, melanoma cells with knocked down prominin-1 had diminished ability to interact with VEGF, which was associated with decreased bcl-2 protein levels and increased apoptosis. In vitro studies with soluble prominin-1 showed that it stabilized dimer formation of VEGF164, but not VEGF121. Taken together, our findings support the notion that prominin-1 plays an active role in cell growth through its ability to interact and potentiate the anti-apoptotic and pro-angiogenic activities of VEGF. Additionally, prominin-1 promotes tumor growth by supporting angiogenesis and inhibiting tumor cell apoptosis.

Vascular endothelial growth factor C is increased in endometrium and promotes endothelial functions, vascular permeability and angiogenesis and growth of endometriosis.

Endometriosis is an angiogenesis-dependent disease. Many studies demonstrated inhibition of angiogenesis leads to inhibition of endometriotic growth, however underlying mechanism is still not fully understood. Our previous study suggested vascular endothelial growth factor C (VEGF-C) as a target of anti-angiogenesis therapy for endometriosis. In this study, VEGF-C in endometrium and its role in angiogenesis of endometriosis were studied. Human endometrium were obtained from women with and without endometriosis for molecular studies. VEGF-A, VEGF-B, VEGF-C and VEGF-D mRNA and proteins in eutopic and ectopic endometrium were measured. Human endothelial cells were transfected with VEGF-C siRNA in vitro, effects of VEGF-C on endothelial cell migration, invasion and tube formation were investigated in vitro. Angiogenesis was inhibited in wild type mice, vascular permeability in dermal skin was determined in vivo. Transplanted endometrium were inhibited by VEGF-C siRNA in immunocompromised mice, development, growth and angiogenesis of the experimental endometriosis were compared in vivo. The results showed that VEGF-C mRNA and protein were increased in eutopic and ectopic endometrium of endometriosis patients. VEGF-C siRNA significantly inhibited endothelial cell migration and tube formation. VEGF-C siRNA significantly inhibited development and angiogenesis of the experimental endometriotic lesions in mice. Supplementation and over-expression of VEGF-C significantly reversed the inhibitory effects on the endothelial functions, vascular permeability and endometriotic growth. In conclusion, VEGF-C is increased in endometrium and it promotes endothelial functions, vascular permeability and development of experimental endometriosis. VEGF-C is important for angiogenesis in endometriosis.

Genetic heterogeneity of the vasculogenic phenotype parallels angiogenesis; Implications for cellular surrogate marker analysis of antiangiogenesis.

Development of antiangiogenic therapies would be significantly facilitated by quantitative surrogate pharmacodynamic markers. Circulating peripheral blood endothelial cells (CECs) and/or their putative progenitor subset (CEPs) have been proposed but not yet fully validated for this purpose. Herein, we provide such validation by showing a striking correlation between highly genetically heterogeneous bFGF- or VEGF-induced angiogenesis and intrinsic CEC or CEP levels measured by flow cytometry, among eight different inbred mouse strains. Moreover, studies using genetically altered mice showed that levels of these cells are affected by regulators of angiogenesis, including VEGF, Tie-2, and thrombospondin-1. Finally, treatment with a targeted VEGFR-2 antibody caused a dose-dependent reduction in viable CEPs that precisely paralleled its previously and empirically determined antitumor activity.

VEGF, PF4 and PDGF are elevated in platelets of colorectal cancer patients.

Platelets sequester angiogenesis regulatory proteins which suggests an avenue for developing biomarkers to monitor disease. We describe a comparison of angiogenesis regulatory proteins found in platelets of colorectal cancer patients and normal controls. Platelet and plasma content of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), platelet derived growth factor (PDGF), platelet factor 4 (PF4), thrombospondin-1 (TSP-1) and endostatin in 35 patients with colon cancer were compared with 84 age-matched healthy controls using ELISAs. We standardized the platelet preparation procedure, introduced process controls and normalized the respective protein levels to platelet numbers using an actin ELISA. Statistically significant differences were found in the median levels of VEGF, PF4 and PDGF in platelets of patients with cancer compared to healthy individuals. Platelet concentrations in cancer patients versus controls were: VEGF 1.3 versus 0.6 pg/10(6), PF4 18.5 versus 9.4 ng/10(6), and PDGF 34.1 versus 21.0 pg/10(6). Multivariable logistic regression analysis indicated that PDGF, PF4 and VEGF were independent predictors of colorectal carcinoma and as a set provided statistically significant discrimination (area under the curve = 0.893, P < .0001). No significant differences were detected for bFGF, endostatin, or TSP-1. Reference Change Value analysis determined that the differences seen were not clinically significant. Plasma levels yielded no correlations.

Circulating endothelial progenitor cells are up-regulated in a mouse model of endometriosis.

Endometriosis is a debilitating disease characterized by the growth of ectopic endometrial tissue. It is widely accepted that angiogenesis plays an integral part in the establishment and growth of endometriotic lesions. Recent data from a variety of angiogenesis-dependent diseases suggest a critical role of bone marrow-derived endothelial progenitor cells (EPCs) in neovascularization. In this study we examined the blood levels of EPCs and mature circulating endothelial cells in a mouse model of surgically induced endometriosis. Fluorescence-activated cell sorting analysis revealed elevated levels of EPCs in the blood of mice with endometriosis compared with control subject that underwent a sham operation. EPC concentrations positively correlated with the amount of endometriotic tissue and peaked 1 to 4 days after induction of disease. In a green fluorescent protein bone marrow transplant experiment we found green fluorescent protein-positive endothelial cells incorporated into endometriotic lesions but not eutopic endometrium, as revealed by flow cytometry and immunohistochemistry. Finally, treatment of endometriosis-bearing mice with the angiogenesis inhibitor Lodamin, an oral nontoxic formulation of TNP-470, significantly decreased EPC levels while suppressing lesion growth. Taken together, our data indicate an important role for bone marrow-derived endothelial cells in the pathogenesis of endometriosis and support the potential clinical use of anti-angiogenic therapy as a novel treatment modality for this disease.

Thrombospondin 1 missense alleles induce extracellular matrix protein aggregation and TM dysfunction in congenital glaucoma.

Glaucoma is a highly heritable disease that is a leading cause of blindness worldwide. Here, we identified heterozygous thrombospondin 1 (THBS1) missense alleles altering p.Arg1034, a highly evolutionarily conserved amino acid, in 3 unrelated and ethnically diverse families affected by congenital glaucoma, a severe form of glaucoma affecting children. Thbs1R1034C-mutant mice had elevated intraocular pressure (IOP), reduced ocular fluid outflow, and retinal ganglion cell loss. Histology revealed an abundant, abnormal extracellular accumulation of THBS1 with abnormal morphology of juxtacanalicular trabecular meshwork (TM), an ocular tissue critical for aqueous fluid outflow. Functional characterization showed that the THBS1 missense alleles found in affected individuals destabilized the THBS1 C-terminus, causing protein misfolding and extracellular aggregation. Analysis using a range of amino acid substitutions at position R1034 showed that the extent of aggregation was correlated with the change in protein-folding free energy caused by variations in amino acid structure. Extracellular matrix (ECM) proteins, especially fibronectin, which bind to THBS1, also accumulated within THBS1 deposits. These results show that missense variants altering THBS1 p.Arg1034 can cause elevated IOP through a mechanism involving impaired TM fluid outflow in association with accumulation of aggregated THBS1 in the ECM of juxtacanalicular meshwork with altered morphology.

Angiogenesis in wounds treated by microdeformational wound therapy.

BACKGROUND: Mechanical forces play an important role in tissue neovascularization and are a constituent part of modern wound therapies. The mechanisms by which vacuum assisted closure (VAC) modulates wound angiogenesis are still largely unknown. OBJECTIVE: To investigate how VAC treatment affects wound hypoxia and related profiles of angiogenic factors as well as to identify the anatomical characteristics of the resultant, newly formed vessels. METHODS: Wound neovascularization was evaluated by morphometric analysis of CD31-stained wound cross-sections as well as by corrosion casting analysis. Wound hypoxia and mRNA expression of HIF-1α and associated angiogenic factors were evaluated by pimonidazole hydrochloride staining and quantitative reverse transcription-polymerase chain reaction (RT-PCR), respectively. Vascular endothelial growth factor (VEGF) protein levels were determined by western blot analysis. RESULTS: VAC-treated wounds were characterized by the formation of elongated vessels aligned in parallel and consistent with physiological function, compared to occlusive dressing control wounds that showed formation of tortuous, disoriented vessels. Moreover, VAC-treated wounds displayed a well-oxygenated wound bed, with hypoxia limited to the direct proximity of the VAC-foam interface, where higher VEGF levels were found. By contrast, occlusive dressing control wounds showed generalized hypoxia, with associated accumulation of HIF-1α and related angiogenic factors. CONCLUSIONS: The combination of established gradients of hypoxia and VEGF expression along with mechanical forces exerted by VAC therapy was associated with the formation of more physiological blood vessels compared to occlusive dressing control wounds. These morphological changes are likely a necessary condition for better wound healing.

Genetic loci that control the size of laser-induced choroidal neovascularization.

Angiogenesis is controlled by a balance between stimulators and inhibitors. We propose that the balance, as well as the general sensitivity of the endothelium to these factors, varies from individual to individual. Indeed, we have found that individual mouse strains have dramatically different responses to growth factor-induced neovascularization. Quantitative trait loci (QTLs), which influence the extent of corneal angiogenesis induced by vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (FGF2), were previously identified by our laboratory. To investigate the genetic contribution to choroidal neovascularization (CNV), a leading cause of blindness, we have undertaken a similar mapping approach to identify QTLs that influence laser-induced CNV in the BXD series of recombinant inbred mouse strains. Composite interval mapping identified new angiogenic QTLs on chromosomes 2 and 19, in addition to confirming our previous corneal neovascularization QTLs of AngVq1 and AngFq2. The new QTLs are named AngCNVq1 and AngCNVq2. The newly mapped regions contain several candidate genes involved in the angiogenic process, including thrombospondin 1, delta-like 4, BclII modifying factor, phospholipase C, beta 2, adrenergic receptor, beta 1, actin-binding LIM protein 1 and colony stimulating factor 2 receptor, alpha. Differences in these regions may control individual susceptibility to CNV.

Exogenous control of mammalian gene expression through modulation of RNA self-cleavage.

Recent studies on the control of specific metabolic pathways in bacteria have documented the existence of entirely RNA-based mechanisms for controlling gene expression. These mechanisms involve the modulation of translation, transcription termination or RNA self-cleavage through the direct interaction of specific intracellular metabolites and RNA sequences. Here we show that an analogous RNA-based gene regulation system can effectively be designed for mammalian cells via the incorporation of sequences encoding self-cleaving RNA motifs into the transcriptional unit of a gene or vector. When correctly positioned, the sequences lead to potent inhibition of gene or vector expression, owing to the spontaneous cleavage of the RNA transcript. Administration of either oligonucleotides complementary to regions of the self-cleaving motif or a specific small molecule results in the efficient induction of gene expression, owing to inhibition of self-cleavage of the messenger RNA. Efficient regulation of transgene expression is shown in a variety of mammalian cell lines and live animals. In conjunction with other emerging technologies, this methodology may be particularly applicable to the development of gene regulation systems tailored to any small inducer molecule, and provide a novel means of biological sensing in vivo that may have an important application in the regulated delivery of protein therapeutics.

A Method for Developing Novel 3D Cornea-on-a-Chip Using Primary Murine Corneal Epithelial and Endothelial Cells.

Microfluidic-based organ-on-a-chip assays with simultaneous coculture of multi-cell types have been widely utilized for basic research and drug development. Here we describe a novel method for a primary cell-based corneal microphysiological system which aims to recapitulate the basic functions of the in vivo cornea and to study topically applied ocular drug permeation. In this study, the protocols for isolating and cultivating primary corneal epithelial cells and endothelial cells from mouse inbred strain C57BL/6J were optimized, to allow for the development of a primary-cell based microfluidic 3D micro-engineered cornea. This tissue unit, by overcoming the limitations of 2D conventional cell culture, supports new investigations on cornea function and facilitates drug delivery testing.