Application of Bioprinting to Cancer Research

Three-dimensional (3D) printing is an additive manufacturing process by which precursor materials are deposited layer by layer to form complex 3D geometries from computer-aided designs, and bioprinting offers the ability to create 3D architecture living cells. Bioprinting methods have been developed rapidly pattern living cells, biological macromolecules, and biomaterials, and an advantage of the 3D microenviroment over traditional 2-dimensional cell culture is the ability to obtain more accurate and reliable data from model about tumor formation, progression, and response to anticancer therapies. This review focuses on recent advances in the use of biopriniting technologies for cancer research, bioprinting physiologically relevant testing platforms for anticancer drug development, and computational modeling for improvement bioprinting technique.

Vascularization Methods for Tissue Engineers

Tissue engineering is limited by our inability to adequately vascularize tissues post implantation because all tissue-engineered substitutes (with the exception of cornea and cartilage) require a vascular network to provide the nutrient and oxygen supply needed for their survival. This review gives a brief overview of the processes and factors involved in the vascularization and angiogenesis and summarizes the different strategies to overcome the issue of slow vascularization and angiogenesis in a range of tissue-engineered substitutes. Moreover, we will announce some potential future plans.

Manipulating the Angiogenesis by Inflammation

There exists a need to develop strategies that promote neovascularization in virtually all tissue engineering and regenerative medicine efforts. While research typically focuses on understanding and exploiting the role of angiogenic factors and vascular cells on new blood vessel formation, the activity of the immune system is being recognized to impact vascular formation and adaptation. This review will provide both an overview of the relationship of angiogenesis and the immune system, and how biomaterials may be designed to promote favorable angiogenesis by interaction between these 2 systems to promote effective vascularization.

The Present and Future of the Cancer Microenvironment Bioprinting

Cancer is the tissue complex consisted with heterogeneous cellular compositions, and microenvironmental cues. During the various stages of cancer initiation, development, and metastasis, cell–cell interactions as well as cell-extracellular matrix play major roles. Conventional cancer models both 2-dimensional and 3-dimensional (3D) present numerous limitations, which restrict their use as biomimetic models for drug screening and fundamental cancer biology studies. Recently, bioprinting biofabrication platform enables the creation of high-resolution 3D structures. Moreover this platform has been extensively used to model multiple organs and diseases, and this versatile technique has further found its creation of accurate models that figure out the complexity of the cancer microenvironment. In this review we will focus on cancer biology and limitations with current cancer models and we discuss vascular structures bioprinting that are critical to the construction of complex 3D cancer organoids. We finally conclude with current literature on bioprinting cancer models and propose future perspectives.

Poloxamer 407 Hydrogels for Intravesical Instillation to Mouse Bladder: Gel-Forming Capacity and Retention Performance

PURPOSE: Poloxamer 407 (P407) thermo-sensitive hydrogel formulations were developed to enhance the retention time in the urinary bladder after intravesical instillation. MATERIALS AND METHODS: P407 hydrogels (P407Gels) containing 0.2 w/w% fluorescein isothiocyanate dextran (FD, MW 4 kDa) as a fluorescent probe were prepared by the cold method with different concentrations of the polymer (20, 25, and 30 w/w%). The gel-forming capacities were characterized in terms of gelation temperature (G-Temp), gelation time (G-Time), and gel duration (G-Dur). Homogenous dispersion of the probe throughout the hydrogel was observed by using fluorescence microscopy. The in vitro bladder simulation model was established to evaluate the retention and drug release properties. P407Gels in the solution state were administered to nude mice via urinary instillation, and the in vivo retention behavior of P407Gels was visualized by using an in vivo imaging system (IVIS). RESULTS: P407Gels showed a thermo-reversible phase transition at 4℃ (refrigerated; sol) and 37℃ (body temperature; gel). The G-Temp, G-Time, and G-Dur of FD-free P407Gels were approximately 10℃–20℃, 12–30 seconds, and 12–35 hours, respectively, and were not altered by the addition of FD. Fluorescence imaging showed that FD was spread homogenously in the gelled P407 solution. In a bladder simulation model, even after repeated periodic filling-emptying cycles, the hydrogel formulation displayed excellent retention with continuous release of the probe over 8 hours. The FD release from P407Gels and the erosion of the gel, both of which followed zero-order kinetics, had a linear relationship (r²=0.988). IVIS demonstrated that the intravesical retention time of P407Gels was over 4 hours, which was longer than that of the FD solution ( < 1 hour), even though periodic urination occurred in the mice. CONCLUSIONS: FD release from P407Gels was erosion-controlled. P407Gels represent a promising system to enhance intravesical retention with extended drug delivery.

Optimal Condition of Microporous Membrane for Bone Marrow Stromal Cell Allotransplantation to Stimulate Wound Healing in Vitro

PURPOSE: Major drawbacks of conventional bone marrow stromal cells (BSCs) transplantation method are mainly caused by direct transplanted cell to host cell interactions. We hypothesized that separation of the transplanted cells by a microporous membrane might inhibit most of the potential adverse effects and induce superior effect. The purpose of the study is to determine the optimal condition of the microporous membrane. METHODS: First, BSCs were placed in polyethylene terephthalate (PET) transwell inserts with 3, 8, or 12 micrometer pore size, and cultured in 24 well culture plates. After 5 days, bottoms of the plates were observed for presence of attached BSCs in monolayer and cell numbers were evaluated. Second, BSCs were placed PET, polycarbonate (PCT), and mixed cellulose esters (MCE) transwell inserts with 3 and 8 micrometer pore size, and cultured in 24 well culture plates. After 3 days, the supernatants of the media left in culture plate were analyzed for collagen, vascular endothelial growth factor (VEGF), platelet derived growth factor BB (PDGF-BB), and basic fibroblast growth factor (bFGF). Third, BSCs were placed in 15% and 70% of the PET membrane with 3 micrometer pore size. All the experimental conditions and methods were same as the second study. RESULTS: The optimal pore sizes to prevent BSC leakage were 3 micrometer and 8 micrometer. The amounts of type I collagen and three growth factors tested did not show significant differences among PET, PCT, and MCE groups. However, the collagen, VEGF, and bFGF levels were much higher in the high (70%) density group than in the low (15%) density group. CONCLUSION: This study revealed that the optimal pore size of membrane to prevent direct BSC to recipient cell contact is in between 3 micrometer and 8 micrometer. Membrane materials and pore sizes do not influence the collagen and growth factor passage through the membrane. The most striking factor for collagen and growth factor transport is pore density of the membrane.

Central Vagal Involvement in Ovarian Innervation of the Rat / 체질인류학회지

The mammalian ovary has been known as receiving its innervation by sympathetic and sensory neurons of the peripheral nervous system from the brain. Recently, there were several functional reports that the vagus nerves were also regulating the ovarian function, but the vagus nerve had not been identified by clear morphological evidence. A viral transneuronal tracing technique has been used to demonstrate the morphological evidence for the central vagal involvement in ovarian innervation in brain areas. Bartha strain of pseudorabies virus injection was made into the ovary of Sprague Dawley rats. In experimental group, the vagus nerve of the same injection side was removed right after ovarian injection. At five days after initial injection, all the rats were sacrificed and brains were processed for immunohistochemistry. Several central nuclei including hypothalamic paraventricular nucleus showed strong bilateral positive labelings after unilateral injection in control rats, but the positive labelings were disappeared or decreased in several hypothalamic nuclei and nuclei of the vagus nerve. In conclusion, these results provide the morphological evidence that vagus nerve has neural connection to ovary and by which the central nervous system may maintains the state of ovulation and reproduction as a possible parasympathetic routes in mammals.