Surface Crystal and Degradability of Shape Memory Scaffold Essentialize Osteochondral Regeneration.

The minimally invasive deployment of scaffolds is a key safety factor for the regeneration of cartilage and bone defects. Osteogenesis relies primarily on cell-matrix interactions, whereas chondrogenesis relies on cell-cell aggregation. Bone matrix expansion requires osteoconductive scaffold degradation. However, chondrogenic cell aggregation is promoted on the repellent scaffold surface, and minimal scaffold degradation supports the avascular nature of cartilage regeneration. Here, a material satisfying these requirements for osteochondral regeneration is developed by integrating osteoconductive hydroxyapatite (HAp) with a chondroconductive shape memory polymer (SMP). The shape memory function-derived fixity and recovery of the scaffold enabled minimally invasive deployment and expansion to fill irregular defects. The crystalline phases on the SMP surface inhibited cell aggregation by suppressing water penetration and subsequent protein adsorption. However, HAp conjugation SMP (H-SMP) enhanced surface roughness and consequent cell-matrix interactions by limiting cell aggregation using crystal peaks. After mouse subcutaneous implantation, hydrolytic H-SMP accelerated scaffold degradation compared to that by the minimal degradation observed for SMP alone for two months. H-SMP and SMP are found to promote osteogenesis and chondrogenesis, respectively, in vitro and in vivo, including the regeneration of rat osteochondral defects using the binary scaffold form, suggesting that this material is promising for osteochondral regeneration.

Shape-Configurable Mesh for Hernia Repair by Synchronizing Anisotropic Body Motion.

Continuous progress has been made in elucidating the relationship between material property, device design, and body function to develop surgical meshes. However, an unmet need still exists wherein the surgical mesh can handle the body motion and thereby promote the repair process. Here, the hernia mesh design and the advanced polymer properties are tailored to synchronize with the anisotropic abdominal motion through shape configuration. The thermomechanical property of shape configurable polymer enables molding of mesh shape to fit onto the abdominal structure upon temperature shift, followed by shape fixing with the release of the heat energy. The microstructural design of mesh is produced through finite element modeling to handle the abdominal motion efficiently through the anisotropic longitudinal and transverse directions. The design effects are validated through in vitro, ex vivo, and in vivo mechanical analyses using a self-configurable, body motion responsive (BMR) mesh. The regenerative function of BMR mesh leads to effective repair in a rat hernioplasty model by effectively handling the anisotropic abdomen motion. Subsequently, the device-tissue integration is promoted by promoting healthy collagen synthesis with fibroblast-to-myofibroblast differentiation. This study suggests a potential solution to promote hernia repair by fine-tuning the relationship between material property and mesh design.

Serum glucose excretion after Roux-en-Y gastric bypass: a potential target for diabetes treatment.

OBJECTIVE: The mechanisms underlying type 2 diabetes resolution after Roux-en-Y gastric bypass (RYGB) are unclear. We suspected that glucose excretion may occur in the small bowel based on observations in humans. The aim of this study was to evaluate the mechanisms underlying serum glucose excretion in the small intestine and its contribution to glucose homeostasis after bariatric surgery. DESIGN: 2-Deoxy-2-[18F]-fluoro-D-glucose (FDG) was measured in RYGB-operated or sham-operated obese diabetic rats. Altered glucose metabolism was targeted and RNA sequencing was performed in areas of high or low FDG uptake in the ileum or common limb. Intestinal glucose metabolism and excretion were confirmed using 14C-glucose and FDG. Increased glucose metabolism was evaluated in IEC-18 cells and mouse intestinal organoids. Obese or ob/ob mice were treated with amphiregulin (AREG) to correlate intestinal glycolysis changes with changes in serum glucose homeostasis. RESULTS: The AREG/EGFR/mTOR/AKT/GLUT1 signal transduction pathway was activated in areas of increased glycolysis and intestinal glucose excretion in RYGB-operated rats. Intraluminal GLUT1 inhibitor administration offset improved glucose homeostasis in RYGB-operated rats. AREG-induced signal transduction pathway was confirmed using IEC-18 cells and mouse organoids, resulting in a greater capacity for glucose uptake via GLUT1 overexpression and sequestration in apical and basolateral membranes. Systemic and local AREG administration increased GLUT1 expression and small intestinal membrane translocation and prevented hyperglycaemic exacerbation. CONCLUSION: Bariatric surgery or AREG administration induces apical and basolateral membrane GLUT1 expression in the small intestinal enterocytes, resulting in increased serum glucose excretion in the gut lumen. Our findings suggest a novel, potentially targetable glucose homeostatic mechanism in the small intestine.

Dilation-Responsive Microshape Programing Prevents Vascular Graft Stenosis.

Shape memory materials have been successfully applied to minimally invasive implantation of medical devices. However, organ-movement-specific shape programing at a microscale level has never been demonstrated despite significant unmet needs. As vein-to-artery grafting induces vein dilation and stenosis, a polymeric self-enclosable external support (SES) is designed to wrap the vascular out-wall. Its micropores are programmed to increase sizes and interconnections upon dilation. Vessel dilation promotes venous maturation, but overdilation induces stenosis by disturbed blood flow. Therefore, the unique elastic shape-fixity of SES provides a foundation to enable a stable microscale shape transition by maintaining the vein dilation. The shape transition of micropore architecture upon dilation induces beneficial inflammation, thereby regenerating vasa vasorum and directing smooth muscle cell migration toward adventitia with the consequent muscle reinforcement of veins. This game-changer approach prevents the stenosis of vein-to-artery grafting by rescuing ischemic disorders and promoting arterial properties of veins.

Anti-Atherogenic Effect of Stem Cell Nanovesicles Targeting Disturbed Flow Sites.

Atherosclerosis development leads to irreversible cascades, highlighting the unmet need for improved methods of early diagnosis and prevention. Disturbed flow formation is one of the earliest atherogenic events, resulting in increased endothelial permeability and subsequent monocyte recruitment. Here, a mesenchymal stem cell (MSC)-derived nanovesicle (NV) that can target disturbed flow sites with the peptide GSPREYTSYMPH (PREY) (PMSC-NVs) is presented which is selected through phage display screening of a hundred million peptides. The PMSC-NVs are effectively produced from human MSCs (hMSCs) using plasmid DNA designed to functionalize the cell membrane with PREY. The potent anti-inflammatory and pro-endothelial recovery effects are confirmed, similar to those of hMSCs, employing mouse and porcine partial carotid artery ligation models as well as a microfluidic disturbed flow model with human carotid artery-derived endothelial cells. This nanoscale platform is expected to contribute to the development of new theragnostic strategies for preventing the progression of atherosclerosis.

Spatial Organization of Superparamagnetic Iron Oxide Nanoparticles in/on Nano/Microsized Carriers Modulates the Magnetic Resonance Signal.

Superparamagnetic iron oxide nanoparticles (SPIONs) are often encapsulated into drug-carrying nano/microsized particles for simultaneous magnetic resonance (MR) imaging and treatment of diseased tissues. Unfortunately, encapsulated SPIONs may have a limited ability to modulate the T2-weighted relaxation of water protons, but this insight has not been examined systematically. This study demonstrates that SPIONs immobilized on 200 nm diameter poly(lactic- co-glycolic acid) (PLGA) nanoparticles using Pickering emulsification present 18-fold higher relaxivity than encapsulated SPIONs and 1.5-fold higher relaxivity than free SPIONs. In contrast, the SPIONs immobilized on 10 µm diameter PLGA particles exhibit a minor increase in MR relaxivity. This interesting finding will significantly impact current efforts to synthesize and assemble advanced MR contrast agents.

High-content image informatics of the structural nuclear protein NuMA parses trajectories for stem/progenitor cell lineages and oncogenic transformation.

Stem and progenitor cells that exhibit significant regenerative potential and critical roles in cancer initiation and progression remain difficult to characterize. Cell fates are determined by reciprocal signaling between the cell microenvironment and the nucleus; hence parameters derived from nuclear remodeling are ideal candidates for stem/progenitor cell characterization. Here we applied high-content, single cell analysis of nuclear shape and organization to examine stem and progenitor cells destined to distinct differentiation endpoints, yet undistinguishable by conventional methods. Nuclear descriptors defined through image informatics classified mesenchymal stem cells poised to either adipogenic or osteogenic differentiation, and oligodendrocyte precursors isolated from different regions of the brain and destined to distinct astrocyte subtypes. Nuclear descriptors also revealed early changes in stem cells after chemical oncogenesis, allowing the identification of a class of cancer-mitigating biomaterials. To capture the metrology of nuclear changes, we developed a simple and quantitative "imaging-derived" parsing index, which reflects the dynamic evolution of the high-dimensional space of nuclear organizational features. A comparative analysis of parsing outcomes via either nuclear shape or textural metrics of the nuclear structural protein NuMA indicates the nuclear shape alone is a weak phenotypic predictor. In contrast, variations in the NuMA organization parsed emergent cell phenotypes and discerned emergent stages of stem cell transformation, supporting a prognosticating role for this protein in the outcomes of nuclear functions.

ROS-Responsive Biomaterial Design for Medical Applications.

Stimuli-responsive biomaterials undergo significant alterations in material structure and property in response to changes of local environmental factors (e.g. pH, temperature, enzyme activation, and water absorption). In particular, reactive oxygen species (ROS) is considered as a major stimulus because over-production of ROS involves most types of major pathogenesis. The application of ROS-responsive biomaterials requires suitable material designs to program user-defined changes of their structure and property in response to a sudden change in the local ROS level. This chapter summarizes the progress in designing and applying major types of ROS-responsive biomaterials within the past 10 years.

Aging Donor-Derived Human Mesenchymal Stem Cells Exhibit Reduced Reactive Oxygen Species Loads and Increased Differentiation Potential Following Serial Expansion on a PEG-PCL Copolymer Substrate.

Human mesenchymal stem cells (hMSCs) have been widely studied for therapeutic development in tissue engineering and regenerative medicine. They can be harvested from human donors via tissue biopsies, such as bone marrow aspiration, and cultured to reach clinically relevant cell numbers. However, an unmet issue lies in the fact that the hMSC donors for regenerative therapies are more likely to be of advanced age. Their stem cells are not as potent compared to those of young donors, and continue to lose healthy, stemness-related activities when the hMSCs are serially passaged in tissue culture plates. Here, we have developed a cheap, scalable, and effective copolymer film to culture hMSCs obtained from aged human donors over several passages without loss of reactive oxygen species (ROS) handling or differentiation capacity. Assays of cell morphology, reactive oxygen species load, and differentiation potential demonstrate the effectiveness of copolymer culture on reduction in senescence-related activities of aging donor-derived hMSCs that could hinder the therapeutic potential of autologous stem cell therapies.

In Situ Forming Gelatin Hydrogels-Directed Angiogenic Differentiation and Activity of Patient-Derived Human Mesenchymal Stem Cells.

Directing angiogenic differentiation of mesenchymal stem cells (MSCs) still remains challenging for successful tissue engineering. Without blood vessel formation, stem cell-based approaches are unable to fully regenerate damaged tissues due to limited support for cell viability and desired tissue/organ functionality. Herein, we report in situ cross-linkable gelatin-hydroxyphenyl propionic acid (GH) hydrogels that can induce pro-angiogenic profiles of MSCs via purely material-driven effects. This hydrogel directed endothelial differentiation of mouse and human patient-derived MSCs through integrin-mediated interactions at the cell-material interface, thereby promoting perfusable blood vessel formation in vitro and in vivo. The causative roles of specific integrin types (α1 and αvß3) in directing endothelial differentiation were verified by blocking the integrin functions with chemical inhibitors. In addition, to verify the material-driven effect is not species-specific, we confirmed in vitro endothelial differentiation and in vivo blood vessel formation of patient-derived human MSCs by this hydrogel. These findings provide new insight into how purely material-driven effects can direct endothelial differentiation of MSCs, thereby promoting vascularization of scaffolds towards tissue engineering and regenerative medicine applications in humans.

Biomaterial-Based Approaches to Address Vein Graft and Hemodialysis Access Failures.

Veins used as grafts in heart bypass or as access points in hemodialysis exhibit high failure rates, thereby causing significant morbidity and mortality for patients. Interventional or revisional surgeries required to correct these failures have been met with limited success and exorbitant costs, particularly for the US Centers for Medicare & Medicaid Services. Vein stenosis or occlusion leading to failure is primarily the result of neointimal hyperplasia. Systemic therapies have achieved little long-term success, indicating the need for more localized, sustained, biomaterial-based solutions. Numerous studies have demonstrated the ability of external stents to reduce neointimal hyperplasia. However, successful results from animal models have failed to translate to the clinic thus far, and no external stent is currently approved for use in the US to prevent vein graft or hemodialysis access failures. This review discusses current progress in the field, design considerations, and future perspectives for biomaterial-based external stents. More comparative studies iteratively modulating biomaterial and biomaterial-drug approaches are critical in addressing mechanistic knowledge gaps associated with external stent application to the arteriovenous environment. Addressing these gaps will ultimately lead to more viable solutions that prevent vein graft and hemodialysis access failures.

Combined usage of stem cells in end-stage heart failure therapies.

Remarkable achievements have been made in the clinical application of mechanical circulatory support and cardiac transplantation for patients with end-stage heart failure. Despite the successes, complications associated with these therapies continue to drive cardiac regenerative research utilizing stem cell based therapies. Multiple stem cell lineages hold clinical promise for cardiac regeneration-mostly through cellular differentiation, cellular fusion, and paracrine signaling mechanisms. Bone marrow-derived endothelial progenitor cells are among the most intriguing and controversial cell types currently being investigated. Formidable barriers exist, however, in finding the ideal cardiac regenerative stem cell, such as identifying specific lineage markers, optimizing in vitro cellular expansion and improving methods of stem cell delivery. Hybrid approaches of cardiac regeneration using stem cell therapies in conjunction with immunomodulation after cardiac transplantation or with mechanical circulatory support produce cutting edge stem cell technologies. This review summarizes the current knowledge and therapeutic applications of stem cells in patients with end-stage heart failure, including stem cell therapy after implantation of mechanical circulatory support and cardiac transplantation.

In Situ Crosslinkable Gelatin Hydrogels for Vasculogenic Induction and Delivery of Mesenchymal Stem Cells.

Clinical trials utilizing mesenchymal stem cells (MSCs) for severe vascular diseases have highlighted the need to effectively engraft cells and promote pro-angiogenic activity. A functional material accomplishing these two goals is an ideal solution as spatiotemporal and batch-to-batch variability in classical therapeutic delivery can be minimized, and tissue regeneration would begin rapidly at the implantation site. Gelatin may serve as a promising biomaterial due to its excellent biocompatibility, biodegradability, and non-immuno/antigenicity. However, the dissolution of gelatin at body temperature and quick enzymatic degradation in vivo have limited its use thus far. To overcome these challenges, an injectable, in situ crosslinkable gelatin was developed by conjugating enzymatically-crosslinkable hydroxyphenyl propionic acid (GHPA). When MSCs are cultured in 3D in vitro or injected in vivo in GHPA, spontaneous endothelial differentiation occurs, as evidenced by marked increases in endothlelial cell marker expressions (Flk1, Tie2, ANGPT1, vWF) in addition to forming an extensive perfusable vascular network after 2-week subcutaneous implantation. Additionally, favorable host macrophage response is achieved with GHPA as shown by decreased iNOS and increased MRC1 expression. These results indicate GHPA as a promising soluble factor-free cell delivery template which induces endothelial differentiation of MSCs with robust neovasculature formation and favorable host response.

Passage-dependent cancerous transformation of human mesenchymal stem cells under carcinogenic hypoxia.

Bone marrow-derived human mesenchymal stem cells (hMSCs) either promote or inhibit cancer progression, depending on factors that heretofore have been undefined. Here we have utilized extreme hypoxia (0.5% O2) and concurrent treatment with metal carcinogen (nickel) to evaluate the passage-dependent response of hMSCs toward cancerous transformation. Effects of hypoxia and nickel treatment on hMSC proliferation, apoptosis, gene and protein expression, replicative senescence, reactive oxygen species (ROS), redox mechanisms, and in vivo tumor growth were analyzed. The behavior of late passage hMSCs in a carcinogenic hypoxia environment follows a profile similar to that of transformed cancer cells (i.e., increased expression of oncogenic proteins, decreased expression of tumor suppressor protein, increased proliferation, decreased apoptosis, and aberrant redox mechanisms), but this effect was not observed in earlier passage control cells. These events resulted in accumulated intracellular ROS in vitro and excessive proliferation in vivo. We suggest a mechanism by which carcinogenic hypoxia modulates the activity of three critical transcription factors (c-MYC, p53, and HIF1), resulting in accumulated ROS and causing hMSCs to undergo cancer-like behavioral changes. This is the first study to utilize carcinogenic hypoxia as an environmentally relevant experimental model for studying the age-dependent cancerous transformation of hMSCs.

Femtosecond laser-patterned nanopore arrays for surface-mediated peptide treatment.

The major goal of this study was to create easy-to-use, reusable substrates capable of storing any peptides or bioactive molecules for a desired period of time until cells uptake them without the need for bioactive molecule or peptide-specific techniques. Nanopore arrays of uniform size and distribution were machined into fused silica substrates using femtosecond laser ablation and loaded with peptides by simple adsorption. The nanopore substrates were validated by examining the effect of N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) loaded nanopores on macrophage phagocytosis and intracellular production of reactive oxygen species (ROS) with and without the pro-inflammatory lipopolysaccharide (LPS). Our results demonstrated that nanopores were generated in a uniform array fashion. Ac-SDKP peptides were stably stored in nanopores and internalized by macrophages. Significant reductions in ROS production and phagocytosis in macrophages were observed over control substrates, even in combination with LPS stimulation, indicating that loading Ac-SDKP peptides in pores significantly improved the anti-inflammatory effects. FROM THE CLINICAL EDITOR: This team of scientists intended to create easy-to-use, reusable substrates for storing peptides or bioactive molecules for a desired period of time before cellular uptake occurs, and without the need for bioactive molecule or peptide-specific techniques. They demonstrate the successful generation of nanopores in a uniform array that stably stores Ac-SDKP peptides in the nanopores. When peptides were internalized by macrophages, significant reductions in ROS production and phagocytosis were observed, indicating improved anti-inflammatory effects.

In situ Reprogramming as a Pro-Angiogenic Inducer to Rescue Ischemic Tissues.

Background: Enhanced regenerative therapeutic strategies are required to treat intractable ischemic heart disease. Summary: Since the discovery of putative endothelial progenitor cells (EPCs) in 1997, many studies have focused on their extraction, ex vivo processing, and autotransplantation under ischemic conditions. Nonetheless, numerous randomized clinical trials involving thousands of patients have yielded only marginal treatment effects, highlighting the need for advances regarding insufficient dosage and complex ex vivo processing. The prevailing paradigm of cellular differentiation highlights the potential of direct cellular reprogramming, which paves the way for in situ reprogramming. In situ reprogramming holds the promise of significantly enhancing current therapeutic strategies, yet its success hinges on the precise targeting of candidate cells for reprogramming. In this context, the spleen emerges as a pivotal "in situ reprogramming hub," owing to its dual function as both a principal site for nanoparticle distribution and a significant reservoir of putative EPCs. The in situ reprogramming of splenic EPCs offers a potential solution to overcome critical challenges, including the aforementioned insufficient dosage and complex ex vivo processing. Key Messages: This review explores the latest advancements in EPC therapy and in situ reprogramming, spotlighting a pioneering study that integrates those two strategies with a specific focus on the spleen. Such an innovative approach will potentially herald a new era of regenerative therapy for ischemic heart disease.

Chip collection of hepatocellular carcinoma based on O2 heterogeneity from patient tissue.

Hepatocellular carcinoma frequently recurs after surgery, necessitating personalized clinical approaches based on tumor avatar models. However, location-dependent oxygen concentrations resulting from the dual hepatic vascular supply drive the inherent heterogeneity of the tumor microenvironment, which presents challenges in developing an avatar model. In this study, tissue samples from 12 patients with hepatocellular carcinoma are cultured directly on a chip and separated based on preference of oxygen concentration. Establishing a dual gradient system with drug perfusion perpendicular to the oxygen gradient enables the simultaneous separation of cells and evaluation of drug responsiveness. The results are further cross-validated by implanting the chips into mice at various oxygen levels using a patient-derived xenograft model. Hepatocellular carcinoma cells exposed to hypoxia exhibit invasive and recurrent characteristics that mirror clinical outcomes. This chip provides valuable insights into treatment prognosis by identifying the dominant hepatocellular carcinoma type in each patient, potentially guiding personalized therapeutic interventions.

Vascular Cast to Program Antistenotic Hemodynamics and Remodeling of Vein Graft.

The structural stability of medical devices is established by managing stress distribution in response to organ movement. Veins abruptly dilate upon arterial grafting due to the mismatched tissue property, resulting in flow disturbances and consequently stenosis. Vascular cast is designed to wrap the vein-artery grafts, thereby adjusting the diameter and property mismatches by relying on the elastic fixity. Here, a small bridge connection in the cast structure serves as an essential element to prevent stress concentrations due to the improved elastic fixity. Consequently, the vein dilation is efficiently suppressed, healthy (laminar and helical) flow is induced effectively, and the heathy functions of vein grafting are promoted, as indicated by the flow directional alignment of endothelial cells with arterialization, muscle expansion, and improved contractility. Finally, collaborative effects of the bridge drastically suppress stenosis with patency improvement. As a key technical point, the advantages of the bridge addition are validated via the computational modeling of fluid-structure interaction, followed by a customized ex vivo set-up and analyses. The calculated effects are verified using a series of cell, rat, and canine models towards translation. The bridge acted like "Little Dutch boy" who saved the big mass using one finger by supporting the cast function.

Body-Shaping Membrane to Regenerate Breast Fat by Elastic Structural Holding.

Tissue regeneration requires structural holding and movement support using tissue-type-specific aids such as bone casts, skin bandages, and joint protectors. Currently, an unmet need exists in aiding breast fat regeneration as the breast moves following continuous body motion by exposing the breast fat to dynamic stresses. Here, the concept of elastic structural holding is applied to develop a shape-fitting moldable membrane for breast fat regeneration ("adipoconductive") after surgical defects are made. The membrane has the following key characteristics: (a) It contains a panel of honeycomb structures, thereby efficiently handling motion stress through the entire membrane; (b) a strut is added into each honeycomb in a direction perpendicular to gravity, thereby suppressing the deformation and stress concentration upon lying and standing; and (c) thermo-responsive moldable elastomers are used to support structural holding by suppressing large deviations of movement that occur sporadically. The elastomer became moldable upon a temperature shift above Tm. The structure can then be fixed as the temperature decreases. As a result, the membrane promotes adipogenesis by activating mechanotransduction in a fat miniature model with pre-adipocyte spheroids under continuous shaking in vitro and in a subcutaneous implant placed on the motion-prone back areas of rodents in vivo.

O2 variant chip to simulate site-specific skeletogenesis from hypoxic bone marrow.

The stemness of bone marrow mesenchymal stem cells (BMSCs) is maintained by hypoxia. The oxygen level increases from vessel-free cartilage to hypoxic bone marrow and, furthermore, to vascularized bone, which might direct the chondrogenesis to osteogenesis and regenerate the skeletal system. Hence, oxygen was diffused from relatively low to high levels throughout a three-dimensional chip. When we cultured BMSCs in the chip and implanted them into the rabbit defect models of low-oxygen cartilage and high-oxygen calvaria bone, (i) the low oxygen level (base) promoted stemness and chondrogenesis of BMSCs with robust antioxidative potential; (ii) the middle level (two times ≥ low) pushed BMSCs to quiescence; and (iii) the high level (four times ≥ low) promoted osteogenesis by disturbing the redox balance and stemness. Last, endochondral or intramembranous osteogenesis upon transition from low to high oxygen in vivo suggests a developmental mechanism-driven solution to promote chondrogenesis to osteogenesis in the skeletal system by regulating the oxygen environment.