Hand-held electron spin resonance scanner for subcutaneous oximetry using OxyChip.

PURPOSE: Electron spin resonance (ESR) is used to measure oxygen partial pressure (pO2) in biological media with many clinical applications. Traditional clinical ESR involves large magnets that encompass the subject of measurement. However, certain applications might benefit from a scanner operating within local static magnetic fields. Our group recently developed such a compact scanner for transcutaneous (surface) pO2 measurements of skin tissue. Here we extend this capability to subsurface (subcutaneous) pO2 measurements and verify it using an artificial tissue emulating (ATE) phantom. METHODS: We introduce a new scanner, tailored for subcutaneous measurements up to 2 mm beneath the skin's surface. This scanner captures pulsed ESR signals from embedded approximate 1-mm oxygen-sensing solid paramagnetic implant, OxyChip. The scanner features a static magnetic field source, producing a uniform region outside its surface, and a compact microwave resonator, for exciting and receiving ESR signals. RESULTS: ESR readings derived from an OxyChip, positioned approximately 1.5 mm from the scanner's surface, embedded in ATE phantom, exhibited a linear relation of 1/T2 versus pO2 for pO2 levels at 0, 7.6, 30, and 160 mmHg, with relative reading accuracy of about 10%. CONCLUSION: The compact ESR scanner can report pO2 data in ATE phantom from an external position relative to the scanner. Implementing this scanner in preclinical and clinical applications for subcutaneous pO2 measurements is a feasible next phase for this development. This innovative design also has the potential to operate in conjunction with artificial skin graft for wound healing, combining therapeutic and pO2 diagnostic features.

ECM-based bioactive microencapsulation significantly improves islet function and graft performance.

Microencapsulation is a promising strategy to prolong the survival and function of transplanted pancreatic islets for diabetes therapy, albeit its translation has been impeded by incoherent graft performance. The use of decellularized ECM has lately gained substantial research momentum due to its innate capacity to augment the function of cells originating from the same tissue type. In the present study, the advantages of both these approaches are leveraged in a porcine pancreatic ECM (pECM)-based microencapsulation platform, thus significantly enhancing murine pancreatic islet performance. pECM-encapsulated islets sustain high insulin secretion levels in vitro, surpassing those of islets encapsulated in conventional alginate microcapsules. Moreover, pECM-encapsulated islet cells proliferate and produce an enriched intra-islet ECM framework, displaying a distinctive structural rearrangement. The beneficial effect of pECM encapsulation is further reinforced by the temporary protection against cytokine-induced cytotoxicity. In-vivo, this platform significantly improves glucose tolerance and achieves glycemic correction in 100% of immunocompetent diabetic mice without any immunosuppression, compared to only 50% mice achieved glycemic correction by alginate encapsulation. Altogether, the results presented herein reveal that pECM-based microencapsulation offers a natural pancreatic niche that can restore the function of isolated pancreatic islets and deliver them safely, avoiding the need for immunosuppression. STATEMENT OF SIGNIFICANCE: Aiming to improve pancreatic islet transplantation outcomes in diabetic patients, we developed a microencapsulation platform based on pancreatic extracellular matrix (pECM). In these microcapsules the islets are entrapped within a pECM hydrogel that mimics the natural pancreatic microenvironment. We show that pECM encapsulation supports the islets' viability and function in culture, and provides temporal protection against cytokine-induced stress. In a diabetic mouse model, pECM encapsulation significantly improved glucose tolerance and achieved glycemic correction without any immunosuppression. These results reveal the potential of pECM encapsulation as a viable treatment for diabetes, providing a solid scientific basis for more advanced preclinical studies.

Cultured meat platform developed through the structuring of edible microcarrier-derived microtissues with oleogel-based fat substitute.

With the increasing global demand for meat, cultured meat technologies are emerging, offering more sustainable solutions that aim to evade a future shortage of meat. Here, we demonstrate a cultured meat platform composed of edible microcarriers and an oleogel-based fat substitute. Scalable expansion of bovine mesenchymal stem cells on edible chitosan-collagen microcarriers is optimized to generate cellularized microtissues. In parallel, an oleogel system incorporated with plant protein is developed as a fat substitute, which is comparable to beef fat in appearance and texture. Combining the cellularized microtissues with the developed fat substitute, two types of cultured meat prototypes are introduced: layered cultured meat and burger-like cultured meat. While the layered prototype benefits enhanced stiffness, the burger-like prototype has a marbling meat-like appearance and a softer texture. Overall, this platform and the established technological basis may contribute to the development of different cultured meat products and promote their commercial production.

Extracellular Matrix Hydrogels Originated from Different Organs Mediate Tissue-Specific Properties and Function.

Porcine extracellular matrix (pECM)-derived hydrogels were introduced, in recent years, aiming to benefit the pECM's microstructure and bioactivity, while controlling the biomaterial's physical and mechanical properties. The use of pECM from different tissues, however, offers tissue-specific features that can better serve different applications. In this study, pECM hydrogels derived from cardiac, artery, pancreas, and adipose tissues were compared in terms of composition, structure, and mechanical properties. While major similarities were demonstrated between all the pECM hydrogels, their distinctive attributes were also identified, and their substantial effects on cell-ECM interactions were revealed. Furthermore, through comprehensive protein and gene expression analyses, we show, for the first time, that each pECM hydrogel supports the spontaneous differentiation of induced pluripotent stem cells towards the resident cells of its origin tissue. These findings imply that the origin of ECM should be carefully considered when designing a biomedical platform, to achieve a maximal bioactive impact.

Porcine arterial ECM hydrogel: Designing an in vitro angiogenesis model for long-term high-throughput research.

The field of angiogenesis research provides deep understanding regarding this important process, which plays fundamental roles in tissue development and different abnormalities. In vitro models offer the advantages of low-cost high-throughput research of angiogenesis while sparing animal lives, and enabling the use of human cells. Nevertheless, prevailing in vitro models lack stability and are limited to a few days' assays. This study, therefore, examines the hypothesis that closely mimicking the vascular microenvironment can more reliably support longer angiogenesis processes in vitro. To this end, porcine arterial extracellular matrix (paECM)- a key component of blood vessels-was isolated and processed into a thermally induced hydrogel and characterized in terms of composition, structure, and mechanical properties, thus confirming the preservation of important characteristics of arterial extracellular matrix. This unique hydrogel was further tailored into a three-dimensional model of angiogenesis using endothelial cells and supporting cells, in a configuration that allows high-throughput quantitative analysis of cell viability and proliferation, cell migration, and apoptosis, thus revealing the advantages of paECM over frequently used biomaterials. Markedly, when applied with well-known effectors of angiogenesis, the model measures reflected the expected response, hence validating its efficacy and establishing its potential as a promising tool for the research of angiogenesis.

Robust Fabrication of Composite 3D Scaffolds with Tissue-Specific Bioactivity: A Proof-of-Concept Study.

The basic requirement of any engineered scaffold is to mimic the native tissue extracellular matrix (ECM). Despite substantial strides in understanding the ECM, scaffold fabrication processes of sufficient product robustness and bioactivity require further investigation, owing to the complexity of the natural ECM. A promising bioacive platform for cardiac tissue engineering is that of decellularized porcine cardiac ECM (pcECM, used here as a soft tissue representative model). However, this platform's complexity and batch-to-batch variability serve as processing limitations in attaining a robust and tunable cardiac tissue-specific bioactive scaffold. To address these issues, we fabricated 3D composite scaffolds (3DCSs) that demonstrate comparable physical and biochemical properties to the natural pcECM using wet electrospinning and functionalization with a pcECM hydrogel. The fabricated 3DCSs are non-immunogenic in vitro and support human mesenchymal stem cells' proliferation. Most importantly, the 3DCSs demonstrate tissue-specific bioactivity in inducing spontaneous cardiac lineage differentiation in human induced pluripotent stem cells (hiPSC) and further support the viability, functionality, and maturation of hiPSC-derived cardiomyocytes. Overall, this work illustrates the technology to fabricate robust yet tunable 3D scaffolds of tissue-specific bioactivity (with a proof of concept provided for cardiac tissues) as a platform for basic materials science studies and possible future R&D application in regenerative medicine.

3D Structure and Processing Methods Direct the Biological Attributes of ECM-Based Cardiac Scaffolds.

High hopes are held for cardiac regenerative therapy, driving a vast research effort towards the development of various cardiac scaffolds using diverse technologies and materials. Nevertheless, the role of factors such as fabrication process and structure in determining scaffold's characteristics is yet to be discovered. In the present study, the effects of 3D structure and processing method on cardiac scaffolds are addressed using three distinct scaffolds made through different production technologies from the same biomaterial: decellularized porcine cardiac extracellular matrix (pcECM). pcECM patch, injectable pcECM hydrogel, and electrospun pcECM scaffolds were all proven as viable prospective therapies for MI, thus generally preserving pcECM beneficial properties. Yet, as we demonstrate, minor differences in scaffolds composition and micro-morphology as well as substantial differences in their mechanical properties, which arise from their production process, highly affect the interactions of the scaffold with both proliferating cells and functional cells. Hence, the rates of cell attachment, survival, and proliferation significantly vary between the different scaffolds. Moreover, major differences in cell morphology and alignment as well as in matrix remodeling are obtained. Overall, the effects revealed herein can guide a more rational scaffold design for the improved cellular or acellular treatment of different cardiac disease scenarios.

Restoring the biophysical properties of decellularized patches through recellularization.

Various extracellular matrix (ECM) scaffolds, isolated through decellularization, were suggested as ideal biomimetic materials for 'Functional tissue engineering' (FTE). The decellularization process comprises a compromise between damaging and preserving the ultrastructure and composition of ECM-previously shown to affect cell survival, proliferation, migration, organization, differentiation and maturation. Inversely, the effects of cells on the ECM constructs' biophysical properties, under physiological-like conditions, remain still largely unknown. We hypothesized that by re-cellularizing porcine cardiac ECM (pcECM, as a model scaffold) some of the original biophysical properties of the myocardial tissue can be restored, which are related to the scaffold's surface and the bulk modifications consequent to cellularization. We performed a systematic biophysical assessment of pcECM scaffolds seeded with human mesenchymal stem cells (MSCs), a common multipotent cell source in cardiac regenerative medicine. We report a new type of FTE study in which cell interactions with a composite-scaffold were evaluated from the perspective of their contribution to the biophysical properties of the construct surface (FTIR, WETSEM™) and bulk (DSC, TGA, and mechanical testing). The results obtained were compared with acellular pcECM and native ventricular tissue serving as negative and positive controls, respectively. MSC recellularization resulted in an inter-fiber plasticization effect, increased protein density, masking of acylated glycosaminoglycans (GAGs) and active pcECM remodelling which further stabilized the reseeded construct and increased its denaturation resistance. The systematic approach presented herein, therefore, identifies cells as "biological plasticizers" and yields important methodologies, understanding, and data serving both as a reference as well as possible 'design criteria' for future studies in FTE.

Ultrasound-Mediated Mesenchymal Stem Cells Transfection as a Targeted Cancer Therapy Platform.

Mesenchymal stem cells (MSCs) hold tremendous potential as a targeted cell-based delivery platform for inflammatory and cancer therapy. Genetic manipulation of MSCs, however, is challenging, and therefore, most studies using MSCs as therapeutic cell carriers have utilized viral vectors to transduce the cells. Here, we demonstrate, for the first time, an alternative approach for the efficient transfection of MSCs; therapeutic ultrasound (TUS). Using TUS with low intensities and moderate frequencies, MSCs were transfected with a pDNA encoding for PEX, a protein that inhibits tumor angiogenesis, and studied as a cell vehicle for in vivo tumor therapy. TUS application did not alter the MSCs' stemness or their homing capabilities, and the transfected MSCs transcribed biologically active PEX. Additionally, in a mouse model, 70% inhibition of prostate tumor growth was achieved following a single I.V. administration of MSCs that were TUS-transfected with pPEX. Further, the repeated I.V. administration of TUS-pPEX transfected-MSCs enhanced tumor inhibition up to 84%. Altogether, these results provide a proof of concept that TUS-transfected MSCs can be effectively used as a cell-based delivery approach for the prospective treatment of cancer.

Dynamic Autologous Reendothelialization of Small-Caliber Arterial Extracellular Matrix: A Preclinical Large Animal Study.

Effective cellularization is a key approach to prevent small-caliber (<4 mm) tissue-engineered vascular graft (TEVG) failure and maintain patency and contractility following implantation. To achieve this goal, however, improved biomimicking designs and/or relatively long production times (typically several months) are required. We previously reported on porcine carotid artery decellularization yielding biomechanically stable and cell supportive small-caliber (3-4 mm diameter, 5 cm long) arterial extracellular matrix (scaECM) vascular grafts. In this study, we aimed to study the scaECM graft patency in vivo and possibly improve that patency by graft pre-endothelialization with the recipient porcine autologous cells using our previously reported custom-designed dynamic perfusion bioreactor system. Decellularized scaECM vascular grafts were histologically characterized, their immunoreactivity studied in vitro, and their biocompatibility profile evaluated as a xenograft subcutaneous implantation in a mouse model. To study the scaECM cell support and remodeling ability, pig autologous endothelial and smooth muscle cells (SMCs) were seeded and dynamically cultivated within the scaECM lumen and externa/media, respectively. Finally, endothelialized-only scaECMs-hypothesized as a prerequisite for maintaining graft patency and controlling intimal hyperplasia-were transplanted as an interposition carotid artery graft in a porcine model. Graft patency was evaluated through angiography online and endpoint pathological assessment for up to 6 weeks. Our results demonstrate the scaECM-TEVG biocompatibility preserving a structurally and mechanically stable vascular wall not just following decellularization and recellularization but also after implantation. Using our dynamic perfusion bioreactor, we successfully demonstrated the ability of this TEVG to support in vitro recellularization and remodeling by primary autologous endothelial and SMCs, which were seeded on the lumen and the externa/media layers, respectively. Following transplantation, dynamically endothelialized scaECM-TEVGs remained patent for 6 weeks in a pig carotid interposition bypass model. When compared with nonrevitalized control grafts, reendothelialized grafts provided excellent antithrombogenic activity, inhibited intimal hyperplasia formation, and encouraged media wall infiltration and reorganization with recruited host SMCs. We thus demonstrate that readily available decellularized scaECM can be promptly revitalized with autologous cells in a 3-week period before implantation, indicating applicability as a future platform for vascular reconstructive procedures.

Biohybrid cardiac ECM-based hydrogels improve long term cardiac function post myocardial infarction.

Injectable scaffolds for cardiac tissue regeneration are a promising therapeutic approach for progressive heart failure following myocardial infarction (MI). Their major advantage lies in their delivery modality that is considered minimally invasive due to their direct injection into the myocardium. Biomaterials comprising such scaffolds should mimic the cardiac tissue in terms of composition, structure, mechanical support, and most importantly, bioactivity. Nonetheless, natural biomaterial-based gels may suffer from limited mechanical strength, which often fail to provide the long-term support required by the heart for contraction and relaxation. Here we present newly-developed injectable scaffolds, which are based on solubilized decellularized porcine cardiac extracellular matrix (pcECM) cross-linked with genipin alone or engineered with different amounts of chitosan to better control the gel's mechanical properties while still leveraging the ECM biological activity. We demonstrate that these new biohybrid materials are naturally remodeled by mesenchymal stem cells, while supporting high viabilities and affecting cell morphology and organization. They exhibit neither in vitro nor in vivo immunogenicity. Most importantly, their application in treating acute and long term chronic MI in rat models clearly demonstrates the significant therapeutic potential of these gels in the long-term (12weeks post MI). The pcECM-based gels enable not only preservation, but also improvement in cardiac function eight weeks post treatment, as measured using echocardiography as well as hemodynamics. Infiltration of progenitor cells into the gels highlights the possible biological remodeling properties of the ECM-based platform. STATEMENT OF SIGNIFICANCE: This work describes the development of new injectable scaffolds for cardiac tissue regeneration that are based on solubilized porcine cardiac extracellular matrix (ECM), combined with natural biomaterials: genipin, and chitosan. The design of such scaffolds aims at leveraging the natural bioactivity and unique structure of cardiac ECM, while overcoming its limited mechanical strength, which may fail to provide the long-term support required for heart contraction and relaxation. Here, we present a biocompatible gel-platform with custom-tailored mechanical properties that significantly improve cardiac function when injected into rat hearts following acute and chronic myocardial infarction. We clearly demonstrate the substantial therapeutic potential of these scaffolds, which not only preserved heart functions but also alleviated MI damage, even after the formation of a mature scar tissue.

PLGA-Listeriolysin O microspheres: Opening the gate for cytosolic delivery of cancer antigens.

Strategies for cancer protein vaccination largely aim to activate the cellular arm of the immune system against cancer cells. This approach, however, is limited since protein vaccines mostly activate the system's humoral arm instead. One way to overcome this problem is to enhance the cross-presentation of such proteins by antigen-presenting cells, which may consequently lead to intense cellular response. Here we examined the ability of listeriolysin O (LLO) incorporated into poly-lactic-co-glycolic acid (PLGA) microspheres to modify the cytosolic delivery of low molecular weight peptides and enhance their cross-presentation. PLGA microspheres were produced in a size suitable for uptake by phagocytic cells. The peptide encapsulation and release kinetics were improved by adding NaCl to the preparation. PLGA microspheres loaded with the antigenic peptide and incorporated with LLO were readily up-taken by phagocytic cells, which exhibited an increase in the expression of peptide-MHC-CI complexes on the cell surface. Furthermore, this system enhanced the activation of a specific T hybridoma cell line, thus simulating cytotoxic T cells. These results establish, for the first time, a proof of concept for the use of PLGA microspheres incorporated with a pore-forming agent and the antigen peptide of choice as a unique cancer protein vaccination delivery platform.

Reconstructed stem cell nanoghosts: a natural tumor targeting platform.

The ultimate goal in cancer therapy is achieving selective targeting of cancer cells. We report a novel delivery platform, based on nanoghosts (NGs) produced from the membranes of mesenchymal stem cells (MSCs). Encompassing MSC surface molecules, the MSC-NGs retained MSC-specific in vitro and in vivo tumor targeting capabilities and were cleared from blood-filtering organs. MSC-NGs were found to be biocompatible. Systemic administration of drug loaded MSC-NGs demonstrated 80% inhibition of human prostate cancer.

Encapsulated human mesenchymal stem cells: a unique hypoimmunogenic platform for long-term cellular therapy.

Cell encapsulation is a promising approach for long-term delivery of therapeutic agents. Nonetheless, this system has failed to reach clinical settings, as the entrapped cells provoke a host immune reaction. Mesenchymal stem cells (MSCs), however, potentially may overcome this impediment and serve as a promising platform for cell-based microencapsulation. They are known to be hypoimmunogenic and can be genetically modified to express a variety of therapeutic factors. We have designed alginate-PLL microcapsules that can encapsulate human MSCs (hMSCs) for extended periods, as demonstrated by fluorescence and H(3)-thymidine assays. The encapsulated hMSCs maintained their mesenchymal surface markers and differentiated to all the typical mesoderm lineages. In vitro and in vivo immunogenicity studies revealed that encapsulated hMSCs were significantly hypoimmunogenic, leading to a 3-fold decrease in cytokine expression compared to entrapped cell lines. The efficacy of such systems was demonstrated by genetically modifying the cells to express the hemopexin-like protein (PEX), an inhibitor of angiogenesis. Live imaging and tumor measurements showed that encapsulated hMSC-PEX injected adjacent to glioblastoma tumors in nude mice led to a significant reduction in tumor volume (87%) and weight (83%). We clearly demonstrate that hMSCs are the cell of choice for microencapsulation cell based-therapy, thus bringing this technology closer to clinical application.

Alginate-PLL cell encapsulation system Co-entrapping PLGA-microspheres for the continuous release of anti-inflammatory drugs.

In spite of advances in cell microencapsulation technology in the past three decades, this approach still suffers from obstacles associated with its biocompatibility. We hypothesized that encapsulation system, which incorporates polymeric particles releasing anti-inflammatory drug in addition to the encapsulated cells, will result in improved biocompatibility, thus improving therapeutic efficacy. We have developed, optimized and studied a combined microencapsulation system in which Ibuprofen loaded PLGA microspheres (MS) are co-entrapped with cells. The combined system was developed and optimized in terms of Ibuprofen release profile, and the survival and proliferation of the co-encapsulated cells. The biocompatibility of the system was evaluated in vitro and in vivo. The developed system was shown to release Ibuprofen within two weeks, and support long-term cell viability. The combined system had improved the biocompatibility within the release period of Ibuprofen. All together, the co-encapsulation of anti-inflammatory loaded MS along with cells offers a clear advantage in the development of effective, long lasting cell based drug delivery systems. The choice of the anti-inflammatory agent, or combination of several anti-inflammatory agents needs to be carefully optimized, as well as their release profile to achieve long- term biocompatibility.

Alginate-chitosan complex coacervation for cell encapsulation: effect on mechanical properties and on long-term viability.

The use of chitosan in complexation with alginate appears to be a promising strategy for cell microencapsulation, due to the biocompatibility of both polymers and the high mechanical properties attributed by the use of chitosan. The present work focuses on the optimization and characterization of the alginate-chitosan system to achieve long-term cell encapsulation. Microcapsules were prepared from four types of chitosan using one- and two-stage encapsulation procedures. The effect of reaction time and pH on long-term cell viability and mechanical properties of the microcapsules was evaluated. Using the single-stage encapsulation procedure led to increase of at least fourfold in viability compared with the two-stage procedure. Among the four types of chitosan, the use of high molecular weight (MW) chitosan glutamate and low MW chitosan chloride provided high viability levels as well as good mechanical properties, i.e., more than 93% intact capsules. The high viability levels were found to be independent of the reaction conditions when using high MW chitosan. However, when using low MW chitosan, better viability levels (195%) were obtained when using a pH of 6 and a reaction time of 30 min. An alginate-chitosan cell encapsulation system was devised to achieve high cell viability levels as well as to improve mechanical properties, thus holding great potential for future clinical application.

Semaphorin-3F is an inhibitor of tumor angiogenesis.

The neuropilin-1 (np1) and neuropilin-2 (np2) receptors form complexes with type-A plexins. These complexes serve as signaling receptors for specific class-3 semaphorins. Np1 and np2 function in addition as receptors for heparin-binding forms of vascular endothelial growth factor (VEGF), such as VEGF(165). Human umbilical vein endothelial cells (HUVEC) express tyrosine-kinase receptors for VEGF and basic fibroblast growth factor (bFGF), as well as np1, np2, and several type-A plexins. We have found that semaphorin-3F (s3f), a semaphorin which signals through the np2 receptor, was able to inhibit VEGF(165), as well as bFGF-induced proliferation of HUVECs. Furthermore, s3f inhibited VEGF as well as bFGF-induced phosphorylation of extracellular signal-regulated kinase-1/2. Our experiments indicate that bFGF does not bind to neuropilins, nor does s3f inhibit the binding of bFGF to FGF receptors. It is therefore possible that s3f inhibits the activity of bFGF by a mechanism that requires active s3f signal transduction rather than by inhibition of bFGF binding to FGF receptors. s3f also inhibited VEGF(165), as well as bFGF-induced in vivo angiogenesis as determined by the alginate micro-encapsulation and Matrigel plug assays. Overexpression of s3f in tumorigenic human HEK293 cells inhibited their tumor-forming ability but not their proliferation in cell culture. The tumors that did develop from s3f-expressing HEK293 cells developed at a much slower rate and had a significantly lower concentration of tumor-associated blood vessels, indicating that s3f is an inhibitor of tumor angiogenesis.

VEGF162, a new heparin-binding vascular endothelial growth factor splice form that is expressed in transformed human cells.

The splice forms of vascular endothelial growth factor (VEGF) differ in biological properties such as the receptor types that they recognize and their interaction with heparan sulfate proteoglycans. We have identified a new VEGF mRNA splice form encoding a VEGF species containing 162 amino acids (VEGF(162)) in human A431 ovarian carcinoma cells. This novel mRNA contains the peptides encoded by exons 1-5, 6A, 6B, and 8 of the VEGF gene. Recombinant VEGF(162) is biologically active. It induces proliferation of endothelial cells in vitro and angiogenesis in vivo as determined by the alginate bead assay. VEGF(162) binds less efficiently than VEGF(145) but more efficiently than VEGF(165) to a natural basement membrane produced by corneal endothelial cells. VEGF(138), an artificial VEGF form that contains exon 6B but lacks exons 6A and 7, did not bind to this basement membrane at all, indicating that exon 6B probably interferes with the interaction of exon 6A with heparin and heparan sulfate proteoglycans.