Concise Review: Bioprinting of Stem Cells for Transplantable Tissue Fabrication

Bioprinting is a quickly progressing technology, which holds the potential to generate replacement tissues and organs. Stem cells offer several advantages over differentiated cells for use as starting materials, including the potential for autologous tissue and differentiation into multiple cell lines. The three most commonly used stem cells are embryonic, induced pluripotent, and adult stem cells. Cells are combined with various natural and synthetic materials to form bioinks, which are used to fabricate scaffold‐based or scaffold‐free constructs. Computer aided design technology is combined with various bioprinting modalities including droplet‐, extrusion‐, or laser‐based bioprinting to create tissue constructs. Each bioink and modality has its own advantages and disadvantages. Various materials and techniques are combined to maximize the benefits. Researchers have been successful in bioprinting cartilage, bone, cardiac, nervous, liver, and vascular tissues. However, a major limitation to clinical translation is building large‐scale vascularized constructs. Many challenges must be overcome before this technology is used routinely in a clinical setting. Stem Cells Translational Medicine2017;6:1940–1948

Bioprinting functional tissues

Despite the numerous lives that have been saved since the first successful procedure in 1954, organ transplant has several shortcomings which prevent it from becoming a more comprehensive solution for medical care than it is today. There is a considerable shortage of organ donors, leading to patient death in many cases. In addition, patients require lifelong immunosuppression to prevent graft rejection postoperatively. With such issues in mind, recent research has focused on possible solutions for the lack of access to donor organs and rejections, with the possibility of using the patient's own cells and tissues for treatment showing enormous potential. Three-dimensional (3D) bioprinting is a rapidly emerging technology, which holds great promise for fabrication of functional tissues and organs. Bioprinting offers the means of utilizing a patient's cells to design and fabricate constructs for replacement of diseased tissues and organs. It enables the precise positioning of cells and biologics in an automated and high throughput manner. Several studies have shown the promise of 3D bioprinting. However, many problems must be overcome before the generation of functional tissues with biologically-relevant scale is possible. Specific focus on the functionality of bioprinted tissues is required prior to clinical translation. In this perspective, this paper discusses the challenges of functionalization of bioprinted tissue under eight dimensions: biomimicry, cell density, vascularization, innervation, heterogeneity, engraftment, mechanics, and tissue-specific function, and strives to inform the reader with directions in bioprinting complex and volumetric tissues. STATEMENT OF SIGNIFICANCE: With thousands of patients dying each year waiting for an organ transplant, bioprinted tissues and organs show the potential to eliminate this ever-increasing organ shortage crisis. However, this potential can only be realized by better understanding the functionality of the organ and developing the ability to translate this to the bioprinting methodologies. Considering the rate at which the field is currently expanding, it is reasonable to expect bioprinting to become an integral component of regenerative medicine. For this purpose, this paper discusses several factors that are critical for printing functional tissues including cell density, vascularization, innervation, heterogeneity, engraftment, mechanics, and tissue-specific function, and inform the reader with future directions in bioprinting complex and volumetric tissues.

Intraoperative Bioprinting: Repairing Tissues and Organs in a Surgical Setting

3D bioprinting directly into injured sites in a surgical setting, intraoperative bioprinting (IOB), is an effective process, in which the defect information can be rapidly acquired and then repaired via bioprinting on a live subject. In patients needing tissue resection, debridement, traumatic reconstruction, or fracture repair, the ability to scan and bioprint immediately following surgical preparation of the defect site has great potential to improve the precision and efficiency of these procedures. In this opinion article, we provide the reader with current major limitations of IOB from engineering and clinical points of view, as well as possibilities of future translation of bioprinting technologies from bench to bedside, and expound our perspectives in the context of IOB of composite and vascularized tissues.

Inflammation-induced intussusceptive angiogenesis in murine colitis

Intussusceptive angiogenesis is a morphogenetic process that forms new blood vessels by the division of a single blood vessel into two lumens. Here, we show that this process of intraluminal division participates in the inflammation-induced neovascularization associated with chemically induced murine colitis. In studies of both acute (4-7 days) and chronic (28-31 days) colitis, intravital microscopy of intravascular tracers demonstrated a twofold reduction in blood flow velocity. In the acute colitis model, the decreased velocity was associated with marked dilatation of the mucosal plexus. In contrast, chronic inflammation was associated with normal caliber vessels and duplication (and triplication) of the quasi-polygonal mucosal plexus. Scanning electron microscopy (SEM) of intravascular corrosion casts suggested that pillar formation and septation, previously linked to the morphogenetic process of intussusceptive angiogenesis, were present within days of the onset of inflammation. Four weeks after the onset of inflammation, SEM of vascular corrosion casts demonstrated replication of the mucosal plexus without significant evidence of sprouting angiogenesis. These data suggest that mucosal capillaries have comparable aggregate cross-sectional area in acute and chronic colitis; however, there is a significant increase in functional capillary density in chronic colitis. We conclude that intussusceptive angiogenesis is a fundamental mechanism of microvascular adaptation to prolonged inflammation.

Vessel painting of the microcirculation using fluorescent lipophilic tracers

Flexible approaches to defining microvessel morphometry are useful in the study of both acute and chronic structural changes of the microcirculation. In this report, we examined the utility of the intravascular infusion of lipophilic carbocyanine tracers in the structural assessment of the retina, skin, lung, and colon microcirculation. The microvessel labeling technique, here termed fluorescent vessel painting, involved the intravascular injection of sulfonated lipophilic carbocyanine tracers. The utility of vessel painting in morphometry was assessed using morphometric comparisons with corrosion casting and 2-dimensional and 3-dimensional scanning electron microscopy. The comparisons demonstrated that fluorescent vessel painting modestly overestimated the interbranch angles, interbranch distances, and vessel diameters of the 2D mucosal plexus of the colon. These differences were narrowed with the application of confocal microscopy. The advantages of fluorescence vessel painting included (1) the filling of all tissues including the relatively high resistance microvessels of the mouse skin, (2) the ability to use tissue counterstains such as DAPI, and (3) the prolonged stability of the lipophilic tracer after aldehyde fixation. These studies suggest the utility of fluorescent vessel painting as a complementary technique to corrosion casting in the morphometric study of the microcirculation.

A Comprehensive NGS Data Analysis of Differentially Regulated miRNAs, piRNAs, lncRNAs and sn/snoRNAs in Triple Negative Breast Cancer

Cancer is the second leading cause of death in the United States and is a major public health concern worldwide. Basic, clinical and epidemiological research is leading to improved cancer detection, prevention, and outcomes. Recent technological advances have allowed unbiased and comprehensive screening of genome-wide gene expression. Small non-coding RNAs (sncRNAs) have been shown to play an important role in biological processes and could serve as a diagnostic, prognostic and therapeutic biomarker for specific diseases. Recent findings have begun to reveal and enhance our understanding of the complex architecture of sncRNA expression including miRNAs, piRNAs, lncRNAs, sn/snoRNAs and their relationships with biological systems. We used publicly available small RNA sequencing data that was derived from 24 triple negative breast cancers (TNBC) and 14 adjacent normal tissue samples to remap various types of sncRNAs. We found a total of 55 miRNAs were aberrantly expressed (p<0.005) in TNBC samples (8 miRNAs upregulated; 47 downregulated) compared to adjacent normal tissues whereas the original study reported only 25 novel miRs. In this study, we used pathway analysis of differentially expressed miRNAs which revealed TGF-beta signaling pathways to be profoundly affected in the TNBC samples. Furthermore, our comprehensive re-mapping strategy allowed us to discover a number of other differentially expressed sncRNAs including piRNAs, lncRNAs, sn/snoRNAs, rRNAs, miscRNAs and nonsense-mediated decay RNAs. We believe that our sncRNA analysis workflow is extremely comprehensive and suitable for discovery of novel sncRNAs changes, which may lead to the development of innovative diagnostic and therapeutic tools for TNBC.

Structural adaptations in the murine colon microcirculation associated with hapten-induced inflammation

BACKGROUND

Blood flowing across the vascular endothelium creates wall shear stress, dependent on velocity of flow and vessel geometry, that tends to disrupt lymphocyte-endothelial cell adhesion.

OBJECTIVE

The microcirculation in a murine model of acute colitis was investigated to identify structural adaptations during acute colitis that may facilitate transmigration.

METHODS

In 2,4,6-trinitrobenzenesulphonic acid-induced acute colitis, the infiltrating cells and colonic microcirculation was investigated by cellular topographic mapping, corrosion casting and three-dimensional scanning electron microscopy (SEM). Colonic blood velocimetry was performed using intravital microscopy.

RESULTS

Clinical and histological parameters suggested a peak inflammatory response at 96 h (p<0.001). The infiltrating cells were spatially related to the mucosal capillary plexus by three-dimensional topographic mapping (p<0.001). In normal mice, corrosion casting and three-dimensional SEM showed a polygonal mucosal plexus supplied by ascending arteries and descending veins. After 2,4,6-trinitrobenzenesulphonic acid stimulation, three-dimensional SEM showed preserved branch angles (p = 0.52) and nominal vessel lengths (p = 0.93), but a significantly dilated mucosal capillary plexus (p<0.001). Intravital microscopy of the mucosal plexus showed a greater than twofold decrease in the velocity of flow (p<0.001).

CONCLUSIONS

The demonstrable slowing of the velocity of flow despite an increase in volumetric flow suggests that these microvascular adaptations create conditions suitable for leucocyte adhesion and transmigration.

Exploration of small RNA-seq data for small non-coding RNAs in Human Colorectal Cancer

Background: Improved healthcare and recent breakthroughs in technology have substantially reduced cancer mortality rates worldwide. Recent advancements in next-generation sequencing (NGS) have allowed genomic analysis of the human transcriptome. Now, using NGS we can further look into small non-coding regions of RNAs (sncRNAs) such as microRNAs (miRNAs), Piwi-interacting-RNAs (piRNAs), long non-coding RNAs (lncRNAs), and small nuclear/nucleolar RNAs (sn/snoRNAs) among others. Recent studies looking at sncRNAs indicate their role in important biological processes such as cancer progression and predict their role as biomarkers for disease diagnosis, prognosis, and therapy. Results: In the present study, we data mined publically available small RNA sequencing data from colorectal tissue samples of eight matched patients (benign, tumor, and metastasis) and remapped the data for various small RNA annotations. We identified aberrant expression of 13 miRNAs in tumor and metastasis specimens [tumor vs benign group (19 miRNAs) and metastasis vs benign group (38 miRNAs)] of which five were upregulated, and eight were downregulated, during disease progression. Pathway analysis of aberrantly expressed miRNAs showed that the majority of miRNAs involved in colon cancer were also involved in other cancers. Analysis of piRNAs revealed six to be over-expressed in the tumor vs benign cohort and 24 in the metastasis vs benign group. Only two piRNAs were shared between the two cohorts. Examining other types of small RNAs [sn/snoRNAs, mt_rRNA, miscRNA, nonsense mediated decay (NMD), and rRNAs] identified 15 sncRNAs in the tumor vs benign group and 104 in the metastasis vs benign group, with only four others being commonly expressed. Conclusion: In summary, our comprehensive analysis on publicly available small RNA-seq data identified multiple differentially expressed sncRNAs during colorectal cancer progression at different stages compared to normal colon tissue. We speculate that deciphering and validating the roles of sncRNAs may prove useful in colorectal cancer prognosis, diagnosis, and therapy.

Melittin-induced membrane permeability: A nonosmotic mechanism of cell death

Derived from honeybees, melittin is a 26-amino acid, alpha-helical, membrane-attack protein that efficiently kills mammalian cells. To investigate the contribution of colloid-osmotic effects to the mechanism of cell death, we studied the effect of melittin on lymphocyte membrane permeability and cell volumes. Melittin concentrations of 0.5 to 2.0 microM induced release of membrane permeability markers without total disruption of the cell membrane. At these melittin concentrations, electrical-impedance cytometry demonstrated melittin-induced changes in red blood cell volumes (P<0.01), but no change in lymphocyte cell volumes (P>0.05). Streaming video microscopy, obtaining images of melittin-treated lymphocytes at 80-ms intervals, demonstrated a loss of optical density (P<0.001) suggesting a flattening of the cell but no significant increase in cell perimeter (P>0.05). Real-time multiparameter flow cytometry of melittin-treated lymphocytes confirmed simultaneous loss of the cytoplasmic marker, calcein, and uptake of the DNA dye, ethidium homodimer, but demonstrated no increase in forward light scatter. Transmission-electron microscopy of melittin-treated lymphocytes showed normal cell volumes but discontinuities in the cell membrane suggesting direct membrane toxicity. We conclude that melittin causes lymphocyte death by a "leaky patch" mechanism that is independent of colloid-osmotic effects.

Hybrid Bioprinting of Zonally Stratified Human Articular Cartilage Using Scaffold-Free Tissue Strands as Building Blocks

The heterogeneous and anisotropic articular cartilage is generally studied as a layered structure of "zones" with unique composition and architecture, which is difficult to recapitulate using current approaches. A novel hybrid bioprinting strategy is presented here to generate zonally stratified cartilage. Scaffold-free tissue strands (TSs) are made of human adipose-derived stem cells (ADSCs) or predifferentiated ADSCs. Cartilage TSs with predifferentiated ADSCs exhibit improved mechanical properties and upregulated expression of cartilage-specific markers at both transcription and protein levels as compared to TSs with ADSCs being differentiated in the form of strands and TSs of nontransfected ADSCs. Using the novel hybrid approach integrating new aspiration-assisted and extrusion-based bioprinting techniques, the bioprinting of zonally stratified cartilage with vertically aligned TSs at the bottom zone and horizontally aligned TSs at the superficial zone is demonstrated, in which collagen fibers are aligned with designated orientation in each zone imitating the anatomical regions and matrix orientation of native articular cartilage. In addition, mechanical testing study reveals a compression modulus of ≈1.1 MPa, which is similar to that of human articular cartilage. The prominent findings highlight the potential of this novel bioprinting approach for building biologically, mechanically, and histologically relevant cartilage for tissue engineering purposes.

Non-coding RNAs in Various Stages of Liver Disease Leading to Hepatocellular Carcinoma: Differential Expression of miRNAs, piRNAs, lncRNAs, circRNAs, and sno/mt-RNAs

Hepatocellular carcinoma (HCC) was the fifth leading cause of cancer death in men and eighth leading cause of death in women in the United States in 2017. In our study, we sought to identify sncRNAs in various stages of development of HCC. We obtained publicly available small RNA-seq data derived from patients with cirrhosis (n = 14), low-grade dysplastic nodules (LGDN, n = 9), high grade dysplastic nodules (HGDN, n = 6), early hepatocellular carcinoma (eHCC, n = 6), and advanced hepatocellular carcinoma (HCC, n = 20), along with healthy liver tissue samples (n = 9). All samples were analyzed for various types of non-coding RNAs using PartekFlow software. We remapped small RNA-seq to miRBase to obtain differential expressions of miRNAs and found 87 in cirrhosis, 106 in LGDN, 59 in HGDN, 80 in eHCC, and 133 in HCC. Pathway analysis of miRNAs obtained from diseased samples compared to normal samples showed signaling pathways in the microRNA dependent EMT, CD44, and others. Additionally, we analyzed the data sets for piRNAs, lncRNAs, circRNAs, and sno/mt-RNAs. We validated the in silico data using human HCC samples with NanoString miRNA global expression. Our results suggest that publically available data is a valuable resource for sncRNA identification in HCC progression (FDR set to <0.05 for all samples) and that a data mining approach is useful for biomarker development.

Hybrid Synthetic-Biological Hydrogel System for Adipose Tissue Regeneration

Hydrogels are promising scaffolds for adipose tissue regeneration. Currently, the incorporation of bioactive molecules in hydrogel system is used, which can increase the cell proliferation rate or improve adipogenic differentiation performance of stromal stem cells but often suffers from high expense or cytotoxicity because of light/thermal curing used for polymerization. In this study, decellularized adipose tissue is incorporated, at varying concentrations, with a thiol-acrylate fraction that is then polymerized to produce hydrogels via a Michael addition reaction. The results reveal that the major component of isolated adipose-derived extracellular matrix (ECM) is Collagen I. Mechanical properties of ECM polyethylene glycol (PEG) are not negatively affected by the incorporation of ECM. Additionally, human adipose-derived stem cells (hASCs) are encapsulated in ECM PEG hydrogel with ECM concentrations varying from 0% to 1%. The results indicate that hASCs maintained the highest viability and proliferation rate in 1% ECM PEG hydrogel with most lipids formation when cultured in adipogenic conditions. Furthermore, more adipose regeneration is observed in 1% ECM group with in vivo study by Day 14 compared to other ECM PEG hydrogels with lower ECM content. Taken together, these findings suggest the ECM PEG hydrogel is a promising substitute for adipose tissue regeneration applications.

Bridging mucosal vessels associated with rhythmically oscillating blood flow in murine colitis

Oscillatory blood flow in the microcirculation is generally considered to be the result of cardiopulmonary influences or active vasomotion. In this report, we describe rhythmically oscillating blood flow in the bridging vessels of the mouse colon that appeared to be independent of known biological control mechanisms. Corrosion casting and scanning electron microscopy of the mouse colon demonstrated highly branched bridging vessels that connected the submucosal vessels with the mucosal plexus. Because of similar morphometric characteristics (19 +/- 11 microm vs. 28 +/- 16 microm), bridging arterioles and venules were distinguished by tracking fluorescent nanoparticles through the microcirculation using intravital fluorescence videomicroscopy. In control mice, the blood flow through the bridging vessels was typically continuous and unidirectional. In contrast, two models of chemically induced inflammation (trinitrobenzenesulfonic acid and dextran sodium sulfate) were associated with a twofold reduction in flow velocity and the prominence of rhythmically oscillating blood flow. The blood oscillation was characterized by tracking the bidirectional displacement of fluorescent nanoparticles. Space-time plots and particle tracking of the oscillating segments demonstrated an oscillation frequency between 0.2 and 5.1 cycles per second. Discrete Fourier transforms demonstrated a power spectrum composed of several base frequencies. These observations suggest that inflammation-inducible changes in blood flow patterns in the murine colon resulted in both reduced blood flow velocity and rhythmic oscillations within the bridging vessels of the mouse colon.

Multi-image particle tracking velocimetry of the microcirculation using fluorescent nanoparticles

Particle tracking velocimetry provides a Lagrangian description of flow properties in the microcirculation. To determine the utility of fluorescent nanoparticles to provide Lagrangian coordinates, we tracked these particles both in vitro and in vivo. The particles had a neutral charge and fluorescence intensity greater than 1,000 times the PKH26-labeled red blood cells. At image acquisition rates of 60 frames per second, particles were tracked at velocities up to 4,000 microm/s. Morphometric changes reflecting streaking artifact were significant at velocities of 4,000 microm/s (P < 0.05), but not at lower velocities (P > 0.05). Intravital microscopy monitoring after intravenous injection of the particles demonstrated a circulation half-life that was inversely related to particle size: 500 nm nanoparticles demonstrated a smaller change in plasma concentration than larger particles. Regardless of the size of the particles, more than 50% of the recovered fluorescence was located in the liver. These results suggest that fluorescent nanoparticles provide a convenient and practical Lagrangian description of flow velocity in the microcirculation.

Development of Citrate-based Dual-Imaging Enabled Biodegradable Electroactive Polymers

Increasing occurrences of degenerative diseases, defective tissues and severe cancers heighten the importance of advanced biomedical treatments, which in turn enhance the need for improved biomaterials with versatile theranostic functionalities yet using minimal design complexity. Leveraging the advantages of citrate chemistry, we developed a multifunctional citrate-based biomaterial platform with both imaging and therapeutic capabilities utilizing a facile and efficient one-pot synthesis. The resulting aniline tetramer doped biodegradable photoluminescent polymers (BPLPATs) not only possess programmable degradation profiles (<1 to >6 months) and mechanical strengths (~20 MPa to > 400 MPa), but also present a combination of intrinsic fluorescence, photoacoustic (PA) and electrical conductivity properties. BPLPAT nanoparticles are able to label cells for fluorescence imaging and perform deep tissue detection with PA imaging. Coupled with significant photothermal performance, BPLPAT nanoparticles demonstrate great potential for thermal treatment and in vivo real-time detection of cancers. Our results on BPLPAT scaffolds demonstrate three-dimensional (3D) high-spatial-resolution deep tissue PA imaging (23 mm), as well as promote growth and differentiation of PC-12 nerve cells. We envision that the biodegradable dual-imaging-enabled electroactive citrate-based biomaterial platform will expand the currently available theranostic material systems and open new avenues for diversified biomedical and biological applications via the demonstrated multi-functionality.

Porous tissue strands: avascular building blocks for scalable tissue fabrication

The scalability of cell aggregates such as spheroids, strands, and rings has been restricted by diffusion of nutrient and oxygen into their core. In this study, we introduce a novel concept in generating tissue building blocks with micropores, which represents an alternative solution for vascularization. Sodium alginate porogens were mixed with human adipose-derived stem cells, and loaded into tubular alginate capsules, followed by de-crosslinking of the capsules. The resultant cellular structure exhibited a porous morphology and formed cell aggregates in the form of strands, called 'porous tissue strands (pTSs).' Three-dimensional reconstructions show that pTSs were able to maintain ∼25% porosity with a high pore interconnectivity (∼85%) for 3 weeks. Owing to the porous structure, pTSs showed up-regulated cell viability and proliferation rate as compared to solid counterparts throughout the culture period. pTSs also demonstrated self-assembly capability through tissue fusion yielding larger-scale patches. In this paper, chondrogenesis and osteogenesis of pTSs were also demonstrated, where the porous microstructure up-regulated both chondrogenic and osteogenic functionalities indicated by cartilage- and bone-specific immunostaining, quantitative biochemical assessment and gene expression. These findings indicated the functionality of pTSs, which possessed controllable porosity and self-assembly capability, and had great potential to be utilized as tissue building blocks in distinct applications such as cartilage and bone regeneration.

Biological and Optical Properties of Fluorescent Nanoparticles Developed for Intravascular Imaging

Intravascular tracers in the blood circulation can provide a description of the flow field over time and space. To address the limitations of existing intravascular tracers, we have developed fluorescent nanoparticles capable of providing detailed information regarding the intravascular flow field. The nanoparticles were designed to maximize plasma half-life as well as minimize interactions with other blood components. The bioavailability of the particles in the blood circulation required nanoscale size and low surface charge density. Intravital imaging of nanoparticles in the microcirculation demonstrated that the fluorescence intensity of the nanoparticles was a major determinant of both temporal and spatial resolution of the flow field. We conclude that nanoparticles prepared with these physical and optical properties can provide an accurate description of the localized intravascular flow field.

Intra-Operative Bioprinting of Hard, Soft, and Hard/Soft Composite Tissues for Craniomaxillofacial Reconstruction

Reconstruction of complex craniomaxillofacial (CMF) defects is challenging due to the highly organized layering of multiple tissue types. Such compartmentalization necessitates the precise and effective use of cells and other biologics to recapitulate the native tissue anatomy. In this study, intra-operative bioprinting (IOB) of different CMF tissues, including bone, skin, and composite (hard/soft) tissues, is demonstrated directly on rats in a surgical setting. A novel extrudable osteogenic hard tissue ink is introduced, which induced substantial bone regeneration, with ≈80% bone coverage area of calvarial defects in 6 weeks. Using droplet-based bioprinting, the soft tissue ink accelerated the reconstruction of full-thickness skin defects and facilitated up to 60% wound closure in 6 days. Most importantly, the use of a hybrid IOB approach is unveiled to reconstitute hard/soft composite tissues in a stratified arrangement with controlled spatial bioink deposition conforming the shape of a new composite defect model, which resulted in ≈80% skin wound closure in 10 days and 50% bone coverage area at Week 6. The presented approach will be absolutely unique in the clinical realm of CMF defects and will have a significant impact on translating bioprinting technologies into the clinic in the future.

Smooth Versus Textured Tissue Expander Breast Reconstruction: Complications and Efficacy

INTRODUCTION

Ongoing recognition of breast implant-associated anaplastic large cell lymphoma (BIA-ALCL) and its link with textured devices has brought a paradigm shift in prosthetic-based breast reconstruction. Many institutions no longer offer textured expansion devices for staged reconstruction. However, there is a paucity of data regarding the efficacy of smooth tissue expanders (TE). We hypothesized that the time to final reconstruction and complication profile between smooth and textured TEs would be similar in breast reconstruction patients.

METHODS

A retrospective chart review was performed of all patients who underwent TE breast reconstruction during a 6-year period at the Penn State Hershey Medical Center. Rates of complications treated nonoperatively and those requiring reoperation were assessed. Mechanical complications, including expander malposition and rupture, were evaluated. Time to final breast reconstruction was quantified. Mixed-effects logistic regression and linear regression models, as appropriate, were used to compare textured to smooth TEs. Patient characteristics and anatomic plane placement were adjusted for in all analyses of outcomes.

RESULTS

Data were collected on 389 patients, encompassing 140 smooth and 604 textured TEs. Textured devices had an increased incidence of complications treated nonsurgically (16.7% vs 10.7%; P = 0.14). However, smooth TEs had an increased incidence of reoperation (12.1% vs 7.6%; P = 0.06). Most noteworthy was that although smooth TEs had a 40-fold increase in malposition (13.6% vs 0.3%; P < 0.001), no reoperation for this complication was warranted. Further, the time to final reconstruction was comparable between the 2 devices (textured expanders: 221 days and smooth expanders: 234 days; P = 0.15).

CONCLUSIONS

Staged, implant-based reconstruction is the most common surgical approach to recreate the breast mound following mastectomy. Textured TEs were the cornerstone to this approach. Unfortunately, the association between textured devices and BIA-ALCL now mandates an alternative. We postulated that smooth expanders would compare favorably for breast reconstruction. Although our study suggests that smooth TEs suffer more malposition, this has a negligible impact on the reconstructive timeline. Thus, smooth TEs may prove beneficial when considering the risk of BIA-ALCL associated with textured devices.

The murine bronchopulmonary microcirculation in hapten-induced inflammation

OBJECTIVE

The clinical observation of central bronchial artery hypertrophy in chronic lung inflammation suggests the possibility that the bronchial circulation may also participate in adaptive responses in peripheral lung inflammation.

METHODS

To investigate the potential role of the bronchial microcirculation in peripheral lung inflammation, we developed a murine model of lung inflammation using the intratracheal instillation of the peptide-hapten trinitrophenol in presensitized mice.

RESULTS

Clinical parameters indicated a peak inflammatory response at 96 hours. Similarly, gross and microscopic evidence of inflammation was observed 96 hours after antigen instillation. Using a forced oscillation technique to probe peripheral lung mechanics at 96 hours, we detected no change in central airway resistance (P > .05), but a significant increase in peripheral tissue resistance (P < .05). The structure of the bronchial circulation was investigated by microsphere occlusion of the pulmonary circulation and corrosion casting of the bronchial circulation. SEM of the bronchial artery casts demonstrated (1) the presence of the peripheral bronchial circulation in mice, (2) interconnections of the two systems in the distal bronchial arteries and at the level of alveolar capillaries, and (3) functional evidence of increased bronchial perfusion of alveolar capillaries during mononuclear inflammation.

CONCLUSION

These results suggest an important adaptive role of the bronchial circulation in pulmonary inflammation.

Small Non-coding RNA Abundance in Adrenocortical Carcinoma: A Footprint of a Rare Cancer

BACKGROUND: Adrenocortical carcinoma (ACC) is a relatively rare, but aggressive type of cancer, which affects both children and adults. OBJECTIVE: Small non-coding RNAs (sncRNAs) play important roles and may serve as biomarkers for disease diagnosis, prognosis and treatment. METHODS: In our study, we sought to identify sncRNAs associated with malignant adrenal tumors. We obtained publicly available, small RNA sequencing data derived from 45 ACC and 30 benign tumors arising from the cortex of the adrenal gland, adrenocortical adenomas (ACA), and compared their sncRNA expression profiles. RESULTS: First, we remapped small RNA-seq to miRBase version 21 to check expression of miRNAs and found 147 miRNAs were aberrantly expressed (p<0.05) in ACC samples compared to ACA samples. Pathway analysis of differentially expressed miRNAs revealed p53 signaling pathways to be profoundly affected in ACC samples. Further examination for other types of small RNAs revealed 16 piRNAs, 48 lncRNAs and 19 sn/snoRNAs identified in ACC samples. Conclusions: Our data analysis suggests that publically available resources can be mined for biomarker development and improvements in-patient care; however, further research must be performed to correlate tumor grade with gene expression.

Regenerative Engineering: Current Applications and Future Perspectives

Many pathologies, congenital defects, and traumatic injuries are untreatable by conventional pharmacologic or surgical interventions. Regenerative engineering represents an ever-growing interdisciplinary field aimed at creating biological replacements for injured tissues and dysfunctional organs. The need for bioengineered replacement parts is ubiquitous among all surgical disciplines. However, to date, clinical translation has been limited to thin, small, and/or acellular structures. Development of thicker tissues continues to be limited by vascularization and other impediments. Nevertheless, currently available materials, methods, and technologies serve as robust platforms for more complex tissue fabrication in the future. This review article highlights the current methodologies, clinical achievements, tenacious barriers, and future perspectives of regenerative engineering.