Noninvasive Measurement of Ear Cartilage Elasticity on the Cellular Level: A New Method to Provide Biomechanical Information for Tissue Engineering

Zinc finger protein 521 attenuates osteoarthritis via the histone deacetylases 4 in the nucleus

To determine whether zinc finger protein 521 (Zfp521) has a chondroprotective effect by maintaining extracellular matrix (ECM) homeostasis to attenuate osteoarthritis (OA). In chondrocytes, Zfp521 was overexpressed or silenced to detect its effects on proliferation, apoptosis, and ECM homeostasis. Adenovirus encoding Zfp521 was injected into the knee joints of anterior cruciate ligament transection rats to test its efficacy against OA. Combined with proteomic analysis, the molecular mechanism of Zfp521 in cartilage degeneration was further explored. An intra-articular injection of adenovirus carrying a Zfp521 sequence showed a chondroprotective effect against OA. The molecular mechanism around Zfp521 was classified at the molecular, cellular, histological, and functional levels. It was reported that Zfp521 could effectively promote cartilage proliferation, inhibit apoptosis, and maintain the balance of anabolism and catabolism of ECM. Moreover, it was confirmed that Zfp521 exerted its effect better by upregulating histone deacetylases 4 (HDAC4) in the nucleus and was significantly weakened in the absence of HDAC4 in the nucleus. Overall, Zfp521 better exerts its efficacy against OA by increasing the HDAC4 content in the nucleus, making it a promising strategy for OA treatment.

Assessment of nanoindentation in stiffness measurement of soft biomaterials: kidney, liver, spleen and uterus

Nanoindentation technology with high spatial resolution and force sensitivity is widely used to measure the mechanical properties of hard biomaterials and tissues. However, its reliability to analyze soft biomaterials and organs has not been tested. Here, we evaluated the utility of nanoindentation to measure the passive mechanical properties of soft biological specimen. Kidney, liver, spleen and uterus samples were harvested from C57BL/6 N mice. We assessed test-retest repeatability in biological specimen and hydrogel controls using Bland-Altman diagrams, intraclass correlation coefficients (ICCs) and the within-subject coefficients of variation (COVs). The results were calculated using Hertzian, JKR and Oliver & Pharr models. Similar to hydrogels, Bland-Altman plots of all biological specimen showed good reliability in stiffness test and retest examinations. In gels, ICCs were larger than 0.8 and COVs were smaller than 15% in all three models. In kidney, liver, spleen and uterus, ICCs were consistently larger than 0.8 only in the Hertzian model but not in the JKR and Oliver & Pharr models. Similarly, COVs were consistently smaller than 15% in kidney, liver, spleen and uterus only in the Hertzian model but not in the other models. We conclude that nanoindentation technology is feasible in detecting the stiffness of kidney, liver, spleen and uterus. The Hertzian model is the preferred method to provide reliable results on ex vivo organ stiffness of the biological specimen under study.

Lab-On-Fiber Technology: A Roadmap toward Multifunctional Plug and Play Platforms

This review presents an overview of the “lab-on-fiber technology” vision and the main milestones set in the technological roadmap to achieve the ultimate objective of developing flexible, multifunctional plug and play fiber-optic platforms designed for specific applications. The main achievements, obtained with nanofabrication strategies for unconventional substrates, such as optical fibers, are discussed here. The perspectives and challenges that lie ahead are highlighted with a special focus on full spatial control at the nanoscale and high-throughput production scenarios. The rapid progress in the fabrication stage has opened new avenues toward the development of multifunctional plug and play platforms, discussed here with particular emphasis on new functionalities and unparalleled figures of merit, to demonstrate the potential of this powerful technology in many strategic application scenarios. The paper also analyses the benefits obtained from merging lab-on-fiber (LOF) technology objectives with the emerging field of optomechanics, especially at the microscale and the nanoscale. We illustrate the main advances at the fabrication level, describe the main achievements in terms of functionalities and performance, and highlight future directions and related milestones. All achievements reviewed and discussed clearly suggest that LOF technology is much more than a simple vision and could play a central role not only in scenarios related to diagnostics and monitoring but also in the Information and Communication Technology (ICT) field, where optical fibers have already yielded remarkable results.

Mapping the mechanical properties of paintings via nanoindentation: a new approach for cultural heritage studies

A comprehensive understanding of the behaviour of the heterogenous layers within the paint stratigraphies in historical paintings is crucial to evaluate their long term stability. We aim to refine nanoindentation as a new tool to investigate the mechanical behaviour of historical oil paints, by adapting the probes and the protocol already used in biomechanical research on soft tissues. The depth-controlled indentation profile performed with a spherical probe provides an evaluation of the non-linear viscoelastic behaviour of the individual layers in paint at local scale. The technique is non-destructive and guarantees the integrity of the surface after indentation. The mapping of elasticity demonstrates the properties' heterogeneity of the composite material within the paint layers, as well as between the individual layers and their interfaces.

A multilayer micromechanical elastic modulus measuring method in ex vivo human aneurysmal abdominal aortas

Abdominal aortic aneurysms (AAA) are common and potentially life-threatening aortic dilatations, due to the effect of hemodynamic changes on the aortic wall. Previous research has shown a potential pathophysiological role for increased macroscopic aneurysmal wall stiffness; however, not investigating micromechanical stiffness. We aimed to compile a new protocol to examine micromechanical live aortic stiffness (elastic moduli), correlated to histological findings with quantitative immunofluorescence (QIF). Live AAA biopsies (n = 7) and non-dilated aortas (controls; n = 3) were sectioned. Local elastic moduli of aortic intima, media and adventitia were analysed in the direction towards the lumen and vice versa with nanoindentation. Smooth muscle cells (SMC), collagen and fibroblasts were examined using QIF. Nanoindentation of AAA vs. controls demonstrated a 4-fold decrease in elastic moduli (p = 0.022) for layers combined and a 26-fold decrease (p = 0.017) for media-to-intima direction. QIF of AAA vs. controls revealed a 4-, 3- and 6-fold decrease of SMC, collagen and fibroblasts, respectively (p = 0.036). Correlations were found between bidirectional intima and media measurements (ρ = 0.661, p = 0.038) and all QIF analyses (ρ = 0.857-0.905, p = 0.002-0.007). We present a novel protocol to analyse microscopic elastic moduli in live aortic tissues using nanoindentation. Hence, our preliminary findings of decreased elastic moduli and altered wall composition warrant further microscopic stiffness investigation to potentially clarify AAA pathophysiology and to explore potential treatment by wall strengthening. STATEMENT OF SIGNIFICANCE: Although extensive research on the pathophysiology of dilated abdominal aortas (aneurysms) has been performed, the exact underlying pathways are still largely unclear. Previously, the macroscopic stiffness of the pathologic and healthy aortic wall has been studied. This study however, for the first time, studied the microscopic stiffness changes in live tissue of dilated and non-dilated abdominal aortas. This new protocol provides a device to analyse the alterations on cellular level within their microenvironment, whereas previous studies studied the aorta as a whole. Outcomes of these measurements might help to better understand the underlying origin of the incidence and progression of aneurysms and other aortic diseases.

Reseeding endothelial cells with fibroblasts to improve the re-endothelialization of pancreatic acellular scaffolds

Pancreatic transplantation remains the only cure for diabetes, but the shortage of donors limits its clinical application. Whole organ decellularized scaffolds offer a new opportunity for pancreatic organ regeneration; however inadequate endothelialization and vascularization can prevent sufficient transport of oxygen and nutrient supplies to the transplanted organ, as well as leading unwanted thrombotic events. In the present study, we explored the re-endothelialization of rat pancreatic acellular scaffolds via circulation perfusion using human skin fibroblasts (FBs) and human umbilical vein endothelial cells (HUVECs). Our results revealed that the cell adhesion rate when these cells were co-cultured was higher than under control conditions, and this increase was associated with increased release of growth factors including VEGF, FGFb, EGF, and IGF-1 as measured by ELISA. When these recellularized organs were implanted in vivo for 28 days in rat dorsal subcutaneous pockets, we found that de novo vasculature formation in the co-culture samples was superior to the control samples. Together these results suggest that endothelial cell and FB co-culture enhances the re-endothelialization and vascularization of pancreatic acellular scaffolds.

3D-printing porosity: A new approach to creating elevated porosity materials and structures

We introduce a new process that enables the ability to 3D-print high porosity materials and structures by combining the newly introduced 3D-Painting process with traditional salt-leaching. The synthesis and resulting properties of three 3D-printable inks comprised of varying volume ratios (25:75, 50:50, 70:30) of CuSO₄ salt and polylactide-co-glycolide (PLGA), as well as their as-printed and salt-leached counterparts, are discussed. The resulting materials are comprised entirely of PLGA (F-PLGA), but exhibit porosities proportional to the original CuSO₄ content. The three distinct F-PLGA materials exhibit average porosities of 66.6-94.4%, elastic moduli of 112.6-2.7 MPa, and absorbency of 195.7-742.2%. Studies with adult human mesenchymal stem cells (hMSCs) demonstrated that elevated porosity substantially promotes cell adhesion, viability, and proliferation. F-PLGA can also act as carriers for weak, naturally or synthetically-derived hydrogels. Finally, we show that this process can be extended to other materials including graphene, metals, and ceramics.

STATEMENT OF SIGNIFICANCE

Porosity plays an essential role in the performance and function of biomaterials, tissue engineering, and clinical medicine. For the same material chemistry, the level of porosity can dictate if it is cell, tissue, or organ friendly; with low porosity materials being far less favorable than high porosity materials. Despite its importance, it has been difficult to create three-dimensionally printed structures that are comprised of materials that have extremely high levels of internal porosity yet are surgically friendly (able to handle and utilize during surgical operations). In this work, we extend a new materials-centric approach to 3D-printing, 3D-Painting, to 3D-printing structures made almost entirely out of water-soluble salt. The structures are then washed in a specific way that not only extracts the salt but causes the structures to increase in size. With the salt removed, the resulting medical polymer structures are almost entirely porous and contain very little solid material, but the maintain their 3D-printed form and are highly compatible with adult human stem cells, are mechanically robust enough to use in surgical manipulations, and can be filled with and act as carriers for biologically active liquids and gels. We can also extend this process to three-dimensionally printing other porous materials, such as graphene, metals, and even ceramics.