Safety and efficacy of sustained release of basic fibroblast growth factor using gelatin hydrogel in patients with critical limb ischemia

Unleashing the potential of natural protein based nanoparticles for the delivery of therapeutic nucleic Acid: A comprehensive review

Nucleic acid-based therapeutics represent a revolutionary approach in treating genetic disorders, offering unprecedented potential for addressing pathologies at their molecular level. However, effective cellular delivery remains a critical challenge hindering their clinical implementation. While existing delivery systems, including viral vectors and lipid nanoparticles, have shown utility, they face limitations in immunogenicity, cargo capacity, and manufacturing complexity. Natural protein-based nanoparticles, derived from proteins such as albumin, ferritin, and elastin, have emerged as promising alternative delivery systems. These carriers offer distinct advantages including reduced immunogenicity, enhanced biocompatibility, and optimal biodegradation profiles. Their engineerable nature enables precise control over particle size, surface charge, and ligand conjugation, facilitating selective cellular targeting and improved pharmacokinetics. Recent technological advances have expanded the application of protein nanoparticles across various nucleic acid modalities, including mRNA, siRNA, and plasmid DNA. Extensive research has characterized these systems through rigorous in vitro and in vivo studies, advancing our understanding of their biological behavior and clinical potential. Advanced engineering methodologies have further enhanced their optimization for specific therapeutic applications. This review examines the development and potential of protein-based nanoparticles in nucleic acid delivery, highlighting their advantages and addressing current challenges. By analyzing recent advances and clinical progress, we underscore their significant potential to enhance the safety, specificity, and efficacy of nucleic acid therapeutics, potentially revolutionizing the treatment of genetic disorders.

Thermosensitive Hydrogels as Targeted and Controlled Drug Delivery Systems: Potential Applications in Transplantation

Drug delivery in transplantation plays a vital role in promoting graft survival, preventing rejection, managing complications, and contributing to positive patient outcomes. Targeted and controlled drug delivery can minimize systemic effects. Thermosensitive hydrogels, due to their unique sol-gel transition properties triggered by thermo-stimuli, have attracted significant research interest as a potential drug delivery system in transplantation. This review describes the current status, characteristics, and recent applications of thermosensitive hydrogels for drug delivery. Studies aimed at improving allotransplantation outcomes using thermosensitive hydrogels are then elaborated on. Finally, the challenges and opportunities associated with their use are discussed. Understanding the progress of research will serve as a guide for future improvements in their application as a means of targeted and controlled drug delivery in translational therapeutic applications for transplantation.

A biomimetic approach to modulating the sustained release of fibroblast growth factor 2 from fibrin microthread scaffolds

Aim

The pleiotropic effect of fibroblast growth factor 2 (FGF2) on promoting myogenesis, angiogenesis, and innervation makes it an ideal growth factor for treating volumetric muscle loss (VML) injuries. While an initial delivery of FGF2 has demonstrated enhanced regenerative potential, the sustained delivery of FGF2 from scaffolds with robust structural properties as well as biophysical and biochemical signaling cues has yet to be explored for treating VML. The goal of this study is to develop an instructive fibrin microthread scaffold with intrinsic topographic alignment cues as well as regenerative signaling cues and a physiologically relevant, sustained release of FGF2 to direct myogenesis and ultimately enhance functional muscle regeneration.

Methods

Heparin was passively adsorbed or carbodiimide-conjugated to microthreads, creating a biomimetic binding strategy, mimicking FGF2 sequestration in the extracellular matrix (ECM). It was also evaluated whether FGF2 incorporated into fibrin microthreads would yield sustained release. It was hypothesized that heparin-conjugated and co-incorporated (co-inc) fibrin microthreads would facilitate sustained release of FGF2 from the scaffold and enhance in vitro myoblast proliferation and outgrowth.

Results

Toluidine blue staining and Fourier transform infrared spectroscopy confirmed that carbodiimide-conjugated heparin bound to fibrin microthreads in a dose-dependent manner. Release kinetics revealed that heparin-conjugated fibrin microthreads exhibited sustained release of FGF2 over a period of one week. An in vitro assay demonstrated that FGF2 released from microthreads remained bioactive, stimulating myoblast proliferation over four days. Finally, a cellular outgrowth assay suggests that FGF2 promotes increased outgrowth onto microthreads.

Conclusions

It was anticipated that the combined effects of fibrin microthread structural properties, topographic alignment cues, and FGF2 release profiles will facilitate the fabrication of a biomimetic scaffold that enhances the regeneration of functional muscle tissue for the treatment of VML injuries.

Hydrogel-based cardiac repair and regeneration function in the treatment of myocardial infarction

A life-threatening illness that poses a serious threat to human health is myocardial infarction. It may result in a significant number of myocardial cells dying, dilated left ventricles, dysfunctional heart function, and ultimately cardiac failure. Based on the development of emerging biomaterials and the lack of clinical treatment methods and cardiac donors for myocardial infarction, hydrogels with good compatibility have been gradually applied to the treatment of myocardial infarction. Specifically, based on the three processes of pathophysiology of myocardial infarction, we summarized various types of hydrogels designed for myocardial tissue engineering in recent years, including natural hydrogels, intelligent hydrogels, growth factors, stem cells, and microRNA-loaded hydrogels. In addition, we also describe the heart patch and preparation techniques that promote the repair of MI heart function. Although most of these hydrogels are still in the preclinical research stage and lack of clinical trials, they have great potential for further application in the future. It is expected that this review will improve our knowledge of and offer fresh approaches to treating myocardial infarction.

Protein-based nanoparticles for therapeutic nucleic acid delivery

To realize the full potential of emerging nucleic acid therapies, there is a need for effective delivery agents to transport cargo to cells of interest. Protein materials exhibit several unique properties, including biodegradability, biocompatibility, ease of functionalization via recombinant and chemical modifications, among other features, which establish a promising basis for therapeutic nucleic acid delivery systems. In this review, we highlight progress made in the use of non-viral protein-based nanoparticles for nucleic acid delivery in vitro and in vivo, while elaborating on key physicochemical properties that have enabled the use of these materials for nanoparticle formulation and drug delivery. To conclude, we comment on the prospects and unresolved challenges associated with the translation of protein-based nucleic acid delivery systems for therapeutic applications.

Recent advances of oxidative stress in thromboangiitis obliterans: biomolecular mechanisms, biomarkers, sources and clinical applications

Oxidative stress (OS) has been identified as a key factor in the development of Thromboangiitis Obliterans (TAO). The detection of OS levels in clinical and scientific research practice is mainly based on the measurement of oxidative stress such as reactive oxygen species (ROS), reactive nitrogen species (RNS) and lipid peroxides. These markers are typically assessed through a combination of physical and chemical methods. Smoking is known to the state of OS in TAO, and OS levels are significantly increased in smokers due to inadequate antioxidant protection, which leads to the expression of apoptotic proteins and subsequent cell injury, thrombosis and limb ischemia. There, understanding the role of OS in the pathogenesis of TAO may provide insights into the etiology of TAO and a basis for its prevention and treatment.

Current Trends in Gelatin-Based Drug Delivery Systems

Gelatin is a highly versatile natural polymer, which is widely used in healthcare-related sectors due to its advantageous properties, such as biocompatibility, biodegradability, low-cost, and the availability of exposed chemical groups. In the biomedical field, gelatin is used also as a biomaterial for the development of drug delivery systems (DDSs) due to its applicability to several synthesis techniques. In this review, after a brief overview of its chemical and physical properties, the focus is placed on the commonly used techniques for the development of gelatin-based micro- or nano-sized DDSs. We highlight the potential of gelatin as a carrier of many types of bioactive compounds and its ability to tune and control select drugs' release kinetics. The desolvation, nanoprecipitation, coacervation, emulsion, electrospray, and spray drying techniques are described from a methodological and mechanistic point of view, with a careful analysis of the effects of the main variable parameters on the DDSs' properties. Lastly, the outcomes of preclinical and clinical studies involving gelatin-based DDSs are thoroughly discussed.

Tissue engineering modalities in skeletal muscles: focus on angiogenesis and immunomodulation properties

Muscular diseases and injuries are challenging issues in human medicine, resulting in physical disability. The advent of tissue engineering approaches has paved the way for the restoration and regeneration of injured muscle tissues along with available conventional therapies. Despite recent advances in the fabrication, synthesis, and application of hydrogels in terms of muscle tissue, there is a long way to find appropriate hydrogel types in patients with congenital and/or acquired musculoskeletal injuries. Regarding specific muscular tissue microenvironments, the applied hydrogels should provide a suitable platform for the activation of endogenous reparative mechanisms and concurrently deliver transplanting cells and therapeutics into the injured sites. Here, we aimed to highlight recent advances in muscle tissue engineering with a focus on recent strategies related to the regulation of vascularization and immune system response at the site of injury.

Therapeutic angiogenesis and tissue revascularization in ischemic vascular disease

Ischemic vascular disease is a major healthcare problem. The keys to treatment lie in vascular regeneration and restoration of perfusion. However, current treatments cannot satisfy the need for vascular regeneration to restore blood circulation. As biomedical research has evolved rapidly, a variety of potential alternative therapeutics has been explored widely, such as growth factor-based therapy, cell-based therapy, and material-based therapy including nanomedicine and biomaterials. This review will comprehensively describe the main pathogenesis of vascular injury in ischemic vascular disease, the therapeutic function of the above three treatment strategies, the corresponding potential challenges, and future research directions.

The diversified hydrogels for biomedical applications and their imperative roles in tissue regeneration

Repair and regeneration of tissues after injury are complex pathophysiological processes. Microbial infection, malnutrition, and an ischemic and hypoxic microenvironment in the injured area can impede the typical healing cascade. Distinguished by biomimicry of the extracellular matrix, high aqueous content, and diverse functions, hydrogels have revolutionized clinical practices in tissue regeneration owing to their outstanding hydrophilicity, biocompatibility, and biodegradability. Various hydrogels such as smart hydrogels, nanocomposite hydrogels, and acellular matrix hydrogels are widely used for applications ranging from bench-scale to an industrial scale. In this review, some emerging hydrogels in the biomedical field are briefly discussed. The protective roles of hydrogels in wound dressings and their diverse biological effects on multiple tissues such as bone, cartilage, nerve, muscle, and adipose tissue are also discussed. The vehicle functions of hydrogels for chemicals and cell payloads are detailed. Additionally, this review emphasizes the particular characteristics of hydrogel products that promote tissue repair and reconstruction such as anti-infection, inflammation regulation, and angiogenesis.

Hydrogels and Hydrogel Nanocomposites: Enhancing Healthcare through Human and Environmental Treatment

Humans are constantly exposed to exogenous chemicals throughout their life, which can lead to a multitude of negative health impacts. Advanced materials can play a key role in preventing or mitigating these impacts through a wide variety of applications. The tunable properties of hydrogels and hydrogel nanocomposites (e.g., swelling behavior, biocompatibility, stimuli responsiveness, functionality, etc.) have deemed them ideal platforms for removal of environmental contaminants, detoxification, and reduction of body burden from exogenous chemical exposures for prevention of disease initiation, and advanced treatment of chronic diseases, including cancer, diabetes, and cardiovascular disease. In this review, three main junctures where the use of hydrogel and hydrogel nanocomposite materials can intervene to positively impact human health are highlighted: 1) preventing exposures to environmental contaminants, 2) prophylactic treatments to prevent chronic disease initiation, and 3) treating chronic diseases after they have developed.

Gene Therapy of Chronic Limb-Threatening Ischemia: Vascular Medical Perspectives

A decade ago, gene therapy seemed to be a promising approach for the treatment of chronic limb-threatening ischemia, providing new perspectives for patients without conventional, open or endovascular therapeutic options by potentially enabling neo-angiogenesis. Yet, until now, the results have been far from a safe and routine clinical application. In general, there are two approaches for inserting exogenous genes in a host genome: transduction and transfection. In case of transduction, viral vectors are used to introduce genes into cells, and depending on the selected strain of the virus, a transient or stable duration of protein production can be achieved. In contrast, the transfection of DNA is transmitted by chemical or physical processes such as lipofection, electro- or sonoporation. Relevant risks of gene therapy may be an increasing neo-vascularization in undesired tissue. The risks of malignant transformation and inflammation are the potential drawbacks. Additionally, atherosclerotic plaques can be destabilized by the increased angiogenesis, leading to arterial thrombosis. Clinical trials from pilot studies to Phase II and III studies on angiogenic gene therapy show mainly a mixed picture of positive and negative final results; thus, the role of gene therapy in vascular occlusive disease remains unclear.

Improved myocardial performance in infarcted rat heart by injection of disulfide-cross-linked chitosan hydrogels loaded with basic fibroblast growth factor

Myocardial infarction (MI) has been considered as the leading cause of cardiovascular-related deaths worldwide. Basic fibroblast growth factor (bFGF) is a member of the fibroblast growth factor family that promotes angiogenesis after MI; however, it has poor clinical efficacy due to proteolytic degradation, low drug accumulation, and severe drug-induced side effects. In this study, an injectable disulfide-cross-linked chitosan hydrogel loaded with bFGF was prepared via a thiol-disulfide exchange reaction for MI treatment. The thiol-disulfide exchange reaction between pyridyl disulfide-modified carboxymethyl chitosan (CMCS-S-S-Py) and reduced BSA (rBSA) was carried out under physiological conditions (37 °C and pH 7.4). The mechanical properties of the disulfide-cross-linked chitosan hydrogel were evaluated based on the molar ratio of the pyridyl disulfide groups of CMCS-S-S-Py and the thiol groups of rBSA. The disulfide-cross-linked chitosan hydrogel showed good swelling performance, rapid glutathione-triggered degradation behavior and well-defined cell proliferation towards NIH 3T3 fibroblast cells. In the process of establishing a rat MI model, the squeezing heart method was used to make the operation more accurate and the mortality of rats was decreased by using a ventilator. The disulfide-cross-linked chitosan hydrogel loaded with bFGF (bFGF-hydrogel) was injected into a peri-infarcted area of cardiac tissue immediately following MI. Echocardiography demonstrated that the left ventricular functions were improved by the bFGF-hydrogel after 28 days of treatment. Histological results revealed that the hydrogel significantly reduced the fibrotic area of MI, and this was further improved by the bFGF-hydrogel treatment. TUNEL and immunohistochemical staining results showed that the bFGF-hydrogel had a more synergistic effect on antiapoptosis and proangiogenesis than using either bFGF or the hydrogel alone.

Overcoming ischemia in the diabetic foot: Minimally invasive treatment options

As the global burden of diabetes is rapidly increasing, the incidence of diabetic foot ulcers is continuously increasing as the mean age of the world population increases and the obesity epidemic advances. A significant percentage of diabetic foot ulcers are caused by mixed micro and macro-vascular dysfunction leading to impaired perfusion of foot tissue. Left untreated, chronic limb-threatening ischemia has a poor prognosis and is correlated with limb loss and increased mortality; prompt treatment is required. In this review, the diagnostic challenges in diabetic foot disease are discussed and available data on minimally invasive treatment options such as endovascular revascularization, stem cells, and gene therapy are examined.

Stabilisation of Recombinant Human Basic Fibroblast Growth Factor (FGF-2) against Stressors Encountered in Medicinal Product Processing and Evaluation

Basic fibroblast growth factor (FGF-2) is a highly labile protein with strong potential for tissue engineering. The aim of this study was to develop FGF-2 formulations that are stable against physical stressors encountered in pharmaceutical processing and evaluation. Pharmaceutical excipients, alone or in combination, were added to aqueous FGF-2 (770 ng/mL) solution and the stability of the resulting solutions on storage at 4–37 °C was evaluated. Stability of the solutions to repeated freeze-thaw cycles and lyophilisation was also evaluated, as well as the stability of the lyophilised stabilised protein to storage at −4, 4 and 18 °C for up to 12 months. In all of these experiments FGF-2 was quantified by ELISA assay. The as-received FGF-2, when dissolved in water, was highly unstable, retaining only 50% of baseline protein content after 30 min at 37 °C or 1 h at 25 °C. By contrast, FGF-2 solutions prepared with 0.5% w/v methylcellulose (MC) and 20 mM alanine (formulation F5) or with 0.5% w/v MC and 1 mg/mL human serum albumin (HSA) (formulation F6) were highly stable, having residual FGF-2 content comparable to baseline levels even after 2 h at 37 °C and 5 h at 25 °C. F5 and F6 were also highly stable to repeated freeze-thaw cycles, with >99% of FGF-2 load remaining after the third cycle. In addition, F5 and F6 were stable to lyophilisation, and the lyophilised products could be stored at −4, 4 or 18 °C for at least 12 months, with less than 1% loss in mean FGF-2 content. Thus, FGF-2 solution is effectively stabilised against both thermal and processing stressors in the presence of MC and alanine (F5), or MC and HSA (F6). The resultant FGF-2 solutions may be applied as medicinal products or further processed into more advanced medicinal products, e.g., scaffolds, for wound healing and tissue regeneration.

Development of injectable graphene oxide/laponite/gelatin hydrogel containing Wharton's jelly mesenchymal stem cells for treatment of oxidative stress-damaged cardiomyocytes

In the initial stage of myocardial infarction (MI), cardiomyocyte necrosis activates aninflammatory response and increases the reactive oxygen species (ROS) content. Graphene oxide (GO) possesses potential antioxidant properties and can provide the adequate mechanical support for cell growth. The clinical studies showed that direct injection of Wharton's jelly mesenchymal stem cells (WJ-MSCs) into infarcted areas of myocardium can reduce apoptosis and fibrosis. Gelatin is a natural polymer and can promote cell attachment. Nanoclay laponite with shear-thinning properties can be injected and gelled in-situ without chemical triggers. In the study, injectable GO/laponite/gelatin (GO-LG) hydrogel was developed and characterized. The results of cell viability showed that the optimal concentration of GO flasks (200 to 300 nm) to treat cells was 100 μg/ml. Addition of nanosized GO to the laponite/gelatin (LG) hydrogel could increase the mechanical strength and have both hemocompatibility and cytocompatibility. The release of GO from LG hydrogel could inhibit the H2O2-induced oxidative stress. The GO-LG hydrogel containing WJ-MSCs could decrease inflammation and apoptosis level and increase the cell viability of cardiomyocytes under oxidative stress. We believe that utilizing this newly developed GO-LG hydrogel containing WJ-MSCs may have potential applications in the future for treatment of MI.

Covalently Crosslinked Hydrogels via Step-Growth Reactions: Crosslinking Chemistries, Polymers, and Clinical Impact

Hydrogels are an important class of biomaterials with the unique property of high-water content in a crosslinked polymer network. In particular, chemically crosslinked hydrogels have made a great clinical impact in past years because of their desirable mechanical properties and tunability of structural and chemical properties. Various polymers and step-growth crosslinking chemistries are harnessed for fabricating such covalently crosslinked hydrogels for translational research. However, selecting appropriate crosslinking chemistries and polymers for the intended clinical application is time-consuming and challenging. It requires the integration of polymer chemistry knowledge with thoughtful crosslinking reaction design. This task becomes even more challenging when other factors such as the biological mechanisms of the pathology, practical administration routes, and regulatory requirements add additional constraints. In this review, key features of crosslinking chemistries and polymers commonly used for preparing translatable hydrogels are outlined and their performance in biological systems is summarized. The examples of effective polymer/crosslinking chemistry combinations that have yielded clinically approved hydrogel products are specifically highlighted. These hydrogel design parameters in the context of the regulatory process and clinical translation barriers, providing a guideline for the rational selection of polymer/crosslinking chemistry combinations to construct hydrogels with high translational potential are further considered.

Therapeutic Biomaterial Approaches to Alleviate Chronic Limb Threatening Ischemia

Chronic limb threatening ischemia (CLTI) is a severe condition defined by the blockage of arteries in the lower extremities that leads to the degeneration of blood vessels and is characterized by the formation of non-healing ulcers and necrosis. The gold standard therapies such as bypass and endovascular surgery aim at the removal of the blockage. These therapies are not suitable for the so-called "no option patients" which present multiple artery occlusions with a likelihood of significant limb amputation. Therefore, CLTI represents a significant clinical challenge, and the efforts of developing new treatments have been focused on stimulating angiogenesis in the ischemic muscle. The delivery of pro-angiogenic nucleic acid, protein, and stem cell-based interventions have limited efficacy due to their short survival. Engineered biomaterials have emerged as a promising method to improve the effectiveness of these latter strategies. Several synthetic and natural biomaterials are tested in different formulations aiming to incorporate nucleic acid, proteins, stem cells, macrophages, or endothelial cells in supportive matrices. In this review, an overview of the biomaterials used alone and in combination with growth factors, nucleic acid, and cells in preclinical models is provided and their potential to induce revascularization and regeneration for CLTI applications is discussed.

Bioengineering strategies for the treatment of peripheral arterial disease

Peripheral arterial disease (PAD) is a progressive atherosclerotic disorder characterized by narrowing and occlusion of arteries supplying the lower extremities. Approximately 200 million people worldwide are affected by PAD. The current standard of operative care is open or endovascular revascularization in which blood flow restoration is the goal. However, many patients are not appropriate candidates for these treatments and are subject to continuous ischemia of their lower limbs. Current research in the therapy of PAD involves developing modalities that induce angiogenesis, but the results of simple cell transplantation or growth factor delivery have been found to be relatively poor mainly due to difficulties in stem cell retention and survival and rapid diffusion and enzymolysis of growth factors following injection of these agents in the affected tissues. Biomaterials, including hydrogels, have the capability to protect stem cells during injection and to support cell survival. Hydrogels can also provide a sustained release of growth factors at the injection site. This review will focus on biomaterial systems currently being investigated as carriers for cell and growth factor delivery, and will also discuss biomaterials as a potential stand-alone method for the treatment of PAD. Finally, the challenges of development and use of biomaterials systems for PAD treatment will be reviewed.

Risk Factors, Mechanisms and Treatments of Thromboangiitis Obliterans: An Overview of Recent Research

BACKGROUND

Thromboangiitis obliterans (TAO) is a nonatherosclerotic thromboticocclusive vasculitis that affects the vessels of the small and medium-sized extremities. No explicit etiology or pathogenesis of TAO has been proven, and more effective treatments are needed.

OBJECTIVE

The study aimed to summarize and present an overview of recent advances regarding the risk factors, mechanisms and treatments of TAO and to organize the related information in figures to provide a comparatively complete reference.

METHODS

We searched PubMed for English-language literature about TAO without article type limits, including articles about the risk factors, pathological mechanisms and treatments of TAO in the last 10 years with essential supplements (references over ranges and English abstracts of Russian literature).

RESULTS

After screening content of works of literature, 99 references were evaluated. We found that risk factors of TAO include smoking, gene factors and periodontal diseases. The underlying mechanism of TAO involves oxidative stress, immunity, hemodynamic changes, inflammation and so on. Moreover, similarities in genetic factors and cigarette relevance existed between periodontal diseases and TAO, so further study of relationship was required. For TAO treatment, medicine, endovascular intervention and revascularization surgery, autologous cell therapy and novel therapies were also mentioned. Besides, a hypothesis that infection triggers autoimmunity in TAO could be speculated, in which TLR4 plays a key role.

CONCLUSION

1. A hypothesis is put forward that infections can trigger autoimmunity in TAO development, in which TLR4, as a key agent, can activate immune signaling pathways and induce autoimmune cytokines expression. 2. It is suggested to reconsider the association between periodontal diseases and TAO, as they share the same high-risk population. Controlling periodontal disease severity in TAO studies may provide new clues. 3. For TAO treatment, endovascular intervention and autologous cell therapy both showed promising long-term therapeutic effectiveness, in which autologous cell therapy is becoming more popular, although more clinical comparisons are needed.

Injectable thermosensitive chitosan-based hydrogel containing ferulic acid for treating peripheral arterial disease

Peripheral arterial disease (PAD) affects more than 200 million people worldwide. Recent studies suggest that oxidative stress-related inflammation can lead to the initiation and progression of PAD. Ferulic acid (FA) is a natural phenolic compound and has been proven to have antioxidant and angiogenesis effects. In this study, thermosensitive chitosan-gelatin-based hydrogel was used as a delivery vehicle of FA. The effects of hydrogel encapsulating FA (FA-gel) have been demonstrated in vitro and in vivo. The results revealed that the developed hydrogel with porous structure could provide a sustained release of FA. Post-treatment of FA-gel effectively decreased the oxidative stress-induced damage in human umbilical vein endothelial cells via decreasing endogenous reactive oxygen species production, inflammation-related gene expression and apoptosis level. In the mouse hindlimb ischemia model, the results revealed that FA-gel could improve blood flow, muscle regeneration and decreases inflammation in veins. These results suggested that FA-gel may have a therapeutic potential in PAD.

Improved viability of murine skin flaps using a gelatin hydrogel sheet impregnated with bFGF

Basic fibroblast growth factor (bFGF) promotes epithelial cell proliferation and angiogenesis but its clinical applications are limited by its short half-life and low retention. Recently developed gelatin hydrogel sheets able to release physiologically active substances in a controlled manner have the potential to overcome these issues. In this study, the effects of gelatin hydrogel sheets impregnated with bFGF on flap survival and angiogenesis were examined in a murine skin flap model. A flap of 1 × 3 cm was generated on the backs of 60 C57BL/6 mice. The mice were divided into five groups (n = 12/group): Group I, untreated; Group II, treated with a gelatin hydrogel sheet impregnated with saline; Group III, treated with bFGF (50 µg) without sheets; Groups IV and V, treated with gelatin hydrogel sheets impregnated with 50 and 100 µg of bFGF, respectively. On the seventh day after surgery, the flap survival area and vascular network were examined and hematoxylin and eosin and von Willebrand factor staining were used for histological examinations. The flap survival areas were significantly larger in Groups IV and V than in other groups. The area of new vessels was significantly larger in Group IV than in the other groups. In the murine skin flap model, gelatin hydrogel sheets impregnated with bFGF promoted angiogenesis and improved flap survival. These findings support the use of bFGF-impregnated gelatin hydrogel sheets for improving ischemic flap survival in clinical settings.

Stable Fibroblast Growth Factor 2 Dimers with High Pro-Survival and Mitogenic Potential

Fibroblast growth factor 2 (FGF2) is a heparin-binding growth factor with broad mitogenic and cell survival activities. Its effector functions are induced upon the formation of 2:2 FGF2:FGFR1 tetrameric complex. To facilitate receptor activation, and therefore, to improve the FGF2 biological properties, we preorganized dimeric ligand by a covalent linkage of two FGF2 molecules. Mutations of the FGF2 WT protein were designed to obtain variants with a single surface-exposed reactive cysteine for the chemical conjugation via maleimide-thiol reaction with bis-functionalized linear PEG linkers. We developed eight FGF2 dimers of defined topology, differing in mutual orientation of individual FGF2 molecules. The engineered proteins remained functional in terms of FGFR downstream signaling activation and were characterized by the increased stability, mitogenic potential and anti-apoptotic activity, as well as induced greater migration responses in normal fibroblasts, as compared to FGF2 monomer. Importantly, biological activity of the dimers was much less dependent on the external heparin administration. Moreover, some dimeric FGF2 variants internalized more efficiently into FGFR overexpressing cancer cells. In summary, in the current work, we showed that preorganization of dimeric FGF2 ligand increased the stability of the growth factor, and therefore, enhanced its biological activity.

Heparin-hyaluronic acid nanofibers for growth factor sequestration in spinal cord repair

Growth factor (GF) delivery is a common strategy for spinal cord injury repair, however, GF degradation can impede long-term therapies. GF sequestration via heparin is known to protect bioactivity after delivery. We tested two heparin modifications, methacrylated heparin and thiolated heparin, and electrospun these with methacrylated hyaluronic acid (MeHA) to form HepMAHA and HepSHHA nanofibers. For loaded conditions, MeHA, HepMAHA, and HepSHHA fibers were incubated with soluble basic fibroblast growth factor (bFGF) or nerve growth factor (NGF) and rinsed with PBS. Control groups were hydrated in PBS. L929 fibroblast proliferation was analyzed after 24 hr of culture in either growth media or bFGF-supplemented media. Dissociated chick dorsal root ganglia neurites were measured after 3 days of cell culture in serum free media (SFM) or NGF-supplemented SFM (SFM + NGF). In growth media, fibroblast proliferation was significantly increased in loaded HepMAHA (α < .05) compared to other groups. In SFM, loaded HepMAHA had the longest average neurite length compared to all other groups. In SFM + NGF, HepMAHA and HepSHHA had increased neurite lengths compared to MeHA, regardless of loading (α < .01), suggesting active sequestration of soluble NGF. HepMAHA is a promising biomaterial for sequestering released GFs in a spinal cord injury environment and will be combined with GF filled microspheres for future studies.

Applicability of Transcutaneous Oxygen Tension Measurement in the Assessment of Chronic Limb-Threatening Ischemia

Transcutaneous oxygen tension measurement (TcPO2) is widely applied for the evaluation of chronic limb-threatening ischemia (CLTI). Nevertheless, studies that focused on the clinical value of TcPO2 have shown varying results. We identified factors that potentially play a role in TcPO2 measurement variation such as probe placement, probe temperature, and the use of a reference probe. In this review of the current literature, we assessed the application of these factors. A systematic search was conducted. Parameters that were assessed were probe placement, probe temperature, and mentioning and/or use of a reference probe. In total, 36 articles were eligible for analysis. In 24 (67%) studies, probes were placed on specific anatomical locations. Seven (19%) studies placed probes, regardless of the location of the ulcer, adjacent to an ischemic lesion or ulcer (perilesion). Selected temperature setting of the probe differed; in 18 (50%), a default probe temperature of 44°C was selected, and in 13 (36%), a different temperature was selected. In 31 (84%) studies, the use of a reference probe was not reported. Transcutaneous oxygen tension measurement is applied diversely in patients with CLTI. Homogeneity in TcPO2 protocols is warranted for reliable clinical application and to compare future TcPO2 research.

Myocardial-Infarction-Responsive Smart Hydrogels Targeting Matrix Metalloproteinase for On-Demand Growth Factor Delivery

Although in situ restoration of blood supply to the infarction region and attenuating pre-existing extracellular matrix degradation remain potential therapeutic approaches for myocardial infarction (MI), local delivery of therapeutics has been limited by low accumulation (inefficacy) and unnecessary diffusion (toxicity). Here, a dual functional MI-responsive hydrogel is fabricated for on-demand drug delivery to promote angiogenesis and inhibit cardiac remodeling by targeting upregulated matrix metalloproteinase-2/9 (MMP-2/9) after MI. A glutathione (GSH)-modified collagen hydrogel (collagen-GSH) is prepared by conjugating collagen amine groups with GSH sulfhydryl groups and the recombinant protein GST-TIMP-bFGF (bFGF: basic fibroblast growth factor) by fusing bFGF with glutathione-S-transferase (GST) and MMP-2/9 cleavable peptide PLGLAG (TIMP). Specific binding between GST and GSH significantly improves the amount of GST-TIMP-bFGF loaded in collagen-GSH hydrogel. The TIMP peptide enclosed between GST and bFGF responds to MMPs for on-demand release during MI. Additionally, the TIMP peptide is a competitive substrate of MMPs that inhibits the excessive degradation of cardiac matrix by MMPs after MI. GST-TIMP-bFGF/collagen-GSH hydrogels promote the recovery of MI rats by enhancing vascularization and ameliorating myocardium remodeling. The results suggest that on-demand growth factor delivery by synchronously controlling binding and responsive release to promote angiogenesis and attenuate cardiac remodeling might be promising for the treatment of ischemic heart disease.

Controlled delivery of basic fibroblast growth factor (bFGF) using acoustic droplet vaporization stimulates endothelial network formation

The challenge of translating pro-angiogenic growth factors for therapeutic purposes has stimulated a myriad of biomaterials-based, delivery approaches. Many techniques rely on incorporating a growth factor into a hydrogel. The kinetics of release can be tuned based on the physiochemical properties of the growth factor and scaffold. We have developed an acoustically-responsive scaffold (ARS), whereby release of a growth factor is non-invasively and spatiotemporally controlled in an on-demand manner using focused ultrasound. An ARS consists of a fibrin matrix doped with a growth factor-loaded, sonosensitive emulsion. In this study, we used an ARS to investigate the impact of basic fibroblast growth factor (bFGF) release on endothelial tubule formation. The co-culture model of angiogenic sprouting consisted of endothelial cell-coated microbeads and dispersed fibroblasts. bFGF release correlated with the acoustic pressure applied while sprout length correlated with both the volume of bFGF-loaded emulsion in the ARS and acoustic pressure. Minimal bFGF release and sprouting were observed in the absence of ultrasound exposure. Staggering the release of bFGF via multiple ultrasound exposures did not affect sprouting. Additionally, sprouting did not display a dependence on the distance between each microbead and the ARS. Overall, these results highlight the potential of using ultrasound to control regenerative processes via the controlled delivery of a growth factor. STATEMENT OF SIGNIFICANCE: Due to the ineffectiveness of conventional routes of administration, implantable hydrogels are often used as matrices to deliver growth factors (GFs). Spatial control of release is typically realized using anisotropic constructs while temporal control is obtained by modifying matrix properties and GF-scaffold interactions. In this study, we demonstrate how focused ultrasound can be used to non-invasively and spatiotemporally control release of basic fibroblast growth factor (bFGF), in an on-demand manner, from a composite hydrogel. The acoustically-responsive scaffold (ARS) consists of a bFGF-loaded, monodispersed double emulsion embedded within a fibrin matrix. We demonstrate how controlled release of bFGF can stimulate endothelial network formation. These results may be of interest to groups working on controlled release strategies for GFs, especially in the context of stimulating angiogenesis.

Collagen-binding basic fibroblast growth factor improves functional remodeling of scarred endometrium in uterine infertile women: a pilot study

Intrauterine adhesion (IUA) is a common cause of uterine infertility and one of the most severe clinical features is endometrial fibrosis namely endometrial scarring for which there are few cures currently. Blocked angiogenesis is the main pathological change in the scarred endometrium. The fibroblast growth factor 2 (bFGF), a member of FGF family, is usually applied to promote healing of refractory ulcer and contributes to angiogenesis of tissues. In this study, the sustained-release system of bFGF 100 µg was administrated around scarred endometrium guiding by ultrasound every 4 weeks in 18 patients (2-4 times). Results showed that after treatment, the menstrual blood volume, endometrial thickness and the scarred endometrial area were improved. Histological study showed blood vessel density increased obviously. Three patients (3/18) achieved pregnancy over 20 gestational weeks. Therefore, administrating the bFGF surrounding scarred endometrium may provide a new therapeutic approach for the patients with endometrial fibrosis.

Basic fibroblast growth factor attenuates left-ventricular remodeling following surgical ventricular restoration in a rat ischemic cardiomyopathy model

OBJECTIVE

Although surgical ventricular restoration for ischemic cardiomyopathy is expected as an alternative or bridge to heart transplantation, post-operative remodeling of left ventricle (LV) needs to be addressed. This study aimed to examine the effect of basic fibroblast growth factor (bFGF), which induces angiogenesis and tissue regeneration in ischemic myocardium, to prevent remodeling after surgical ventricular restoration (SVR) using a rat ischemic cardiomyopathy model.

METHODS

Four weeks after coronary artery ligation, rats were divided into two groups: rats treated with SVR alone (SVR; n = 21), and rats treated with SVR and local sustained release of bFGF using gelatin hydrogel sheet (SVR + bFGF; n = 22). Cardiac function was assessed by serial echocardiography and cardiac catheterization. Cardiac tissue sections were histologically examined for vascular density and fibrosis.

RESULTS

Higher systolic function and lower LV end-diastolic pressure (LVEDP) were observed in rats treated with SVR + bFGF (SVR vs SVR + bFGF; Ees: 0.22 ± 0.11 vs 0.33 ± 0.22 mmHg/μL, p = 0.0328; LVEDP: 12.7 ± 7.0 vs 8.5 ± 4.3 mmHg, p = 0.0230). LV area tended to be lower in rats treated with SVR + bFGF compared to rats treated with SVR alone (left-ventricular end-diastolic area: 0.66 ± 0.07 vs 0.62 ± 0.07 cm², p = 0.071). Vascular density tended to be higher in rats treated with SVR + bFGF than those without bFGF (23.3 ± 8.1 vs 28.8 ± 9.5/mm², p = 0.0509).

CONCLUSIONS

BFGF induced angiogenesis and attenuated remodeling after SVR which secured the efficacy of SVR in a rat ischemic cardiomyopathy model.

Toward Regeneration of the Heart: Bioengineering Strategies for Immunomodulation

Myocardial Infarction (MI) is the most common cardiovascular disease. An average-sized MI causes the loss of up to 1 billion cardiomyocytes and the adult heart lacks the capacity to replace them. Although post-MI treatment has dramatically improved survival rates over the last few decades, more than 20% of patients affected by MI will subsequently develop heart failure (HF), an incurable condition where the contracting myocardium is transformed into an akinetic, fibrotic scar, unable to meet the body's need for blood supply. Excessive inflammation and persistent immune auto-reactivity have been suggested to contribute to post-MI tissue damage and exacerbate HF development. Two newly emerging fields of biomedical research, immunomodulatory therapies and cardiac bioengineering, provide potential options to target the causative mechanisms underlying HF development. Combining these two fields to develop biomaterials for delivery of immunomodulatory bioactive molecules holds great promise for HF therapy. Specifically, minimally invasive delivery of injectable hydrogels, loaded with bioactive factors with angiogenic, proliferative, anti-apoptotic and immunomodulatory functions, is a promising route for influencing the cascade of immune events post-MI, preventing adverse left ventricular remodeling, and offering protection from early inflammation to fibrosis. Here we provide an updated overview on the main injectable hydrogel systems and bioactive factors that have been tested in animal models with promising results and discuss the challenges to be addressed for accelerating the development of these novel therapeutic strategies.

First-in-Man Clinical Pilot Study Showing the Safety and Efficacy of Intramuscular Injection of Basic Fibroblast Growth Factor With Atelocollagen Solution for Critical Limb Ischemia

BACKGROUND

Therapeutic angiogenesis with basic fibroblast growth factor (bFGF) with atelocollagen was confirmed in a study using a limb ischemia mouse model. Because the number of elderly patients with critical limb ischemia (CLI) is increasing, particularly that caused by arteriosclerosis obliterans (ASO), the development of less invasive angiogenesis therapies desired.

METHODS AND RESULTS

This first-in-man clinical study was designed to assess the safety and efficacy of i.m. injection of bFGF with atelocollagen. Human recombinant bFGF (200 μg), combined with 4.8 mL 3% atelocollagen solution, was prepared and injected into the gastrocnemius muscle of the ischemic leg. The primary endpoint was safety, evaluated on all adverse events over 48 weeks after this treatment. The secondary endpoint was efficacy, evaluated by improvement of ischemic symptoms. No serious procedure-related adverse events were observed during the follow-up period. Visual analogue scale (VAS) score was significantly improved at 4, 24 and 48 weeks compared with baseline (P<0.05), and 7 patients became pain free during the follow-up period. Fontaine classification was improved in 4 of 10 patients at 48 weeks. Cyanotic lesions disappeared in 2 patients at 4 weeks.

CONCLUSIONS

I.m. injection of bFGF with atelocollagen is safe and feasible in patients with CLI. Randomized controlled trials are therefore needed to confirm these results.

The use of hydrogels for cell-based treatment of chronic kidney disease

Chronic kidney disease (CKD) is a major and growing public health concern with increasing incidence and prevalence worldwide. The therapeutic potential of stem cell therapy, including mesenchymal stem cells (MSCs) and endothelial progenitor cells (EPCs) holds great promise for treatment of CKD. However, there are significant bottlenecks in the clinical translation due to the reduced number of transplanted cells and the duration of their presence at the site of tissue damage. Bioengineered hydrogels may provide a route of cell delivery to enhance treatment efficacy and optimise the targeting effectiveness while minimising any loss of cell function. In this review, we highlight the advances in stem cell therapy targeting kidney disease and discuss the emerging role of hydrogel delivery systems to fully realise the potential of adult stem cells as a regenerative therapy for CKD in humans. MSCs and EPCs mediate kidney repair through distinct paracrine effects. As a delivery system, hydrogels can prolong these paracrine effects by improving retention at the site of injury and protecting the transplanted cells from the harsh inflammatory microenvironment. We also discuss the features of a hydrogel, which may be tuned to optimise the therapeutic potential of encapsulated stem cells, including cell-adhesive epitopes, material stiffness, nanotopography, modes of gelation and degradation and the inclusion of bioactive molecules. This review concludes with a discussion of the challenges to be met for the widespread clinical use of hydrogel delivery system of stem cell therapy for CKD.

Future directions for therapeutic strategies in post-ischaemic vascularization: a position paper from European Society of Cardiology Working Group on Atherosclerosis and Vascular Biology

Modulation of vessel growth holds great promise for treatment of cardiovascular disease. Strategies to promote vascularization can potentially restore function in ischaemic tissues. On the other hand, plaque neovascularization has been shown to associate with vulnerable plaque phenotypes and adverse events. The current lack of clinical success in regulating vascularization illustrates the complexity of the vascularization process, which involves a delicate balance between pro- and anti-angiogenic regulators and effectors. This is compounded by limitations in the models used to study vascularization that do not reflect the eventual clinical target population. Nevertheless, there is a large body of evidence that validate the importance of angiogenesis as a therapeutic concept. The overall aim of this Position Paper of the ESC Working Group of Atherosclerosis and Vascular biology is to provide guidance for the next steps to be taken from pre-clinical studies on vascularization towards clinical application. To this end, the current state of knowledge in terms of therapeutic strategies for targeting vascularization in post-ischaemic disease is reviewed and discussed. A consensus statement is provided on how to optimize vascularization studies for the identification of suitable targets, the use of animal models of disease, and the analysis of novel delivery methods.

Effect of sustained release of basic fibroblast growth factor using biodegradable gelatin hydrogels on frozen-thawed human ovarian tissue in a xenograft model

AIM

Ovarian tissue cryopreservation before cancer treatment is the only option to preserve fertility under some circumstances. However, tissue ischemia after transplantation while awaiting angiogenesis induces dysfunctional folliculogenesis and reduces ovarian reserve and is one of the disadvantages of frozen-thawed ovarian tissue transplantation. Basic fibroblast growth factor (bFGF) is a major regulator of angiogenesis. However, bFGF rapidly loses biological activity when its free form is injected in vivo. This study investigated whether administration of active bFGF helps establish a nurturing environment for follicular survival.

METHODS

A sheet form of a sustained release drug delivery system for bFGF was developed using biodegradable acidic gelatin hydrogel (bFGF sheet). The bFGF sheets or phosphate-buffered saline sheets, as a negative control, were transplanted with frozen-thawed human ovarian tissues subcutaneously into the backs of severe combined immunodeficient mice. Neovascularization, cell proliferation, fibrosis and follicular survival of ovarian grafts were analyzed at 6 weeks after xenografting.

RESULTS

The bFGF sheets were optimized to release bFGF for at least 10 days. The transplantation of bFGF sheets with frozen-thawed ovarian tissues significantly increased human and mouse CD31-positive areas and stromal and endothelial cell proliferations. The administration of bFGF also significantly decreased the percentage of the fibrotic area in the graft, resulting in a significant increase in primordial and primary follicular density.

CONCLUSION

Local administration of a sustained release of biologically active bFGF induced neovascularization in frozen-thawed ovarian tissue grafts, which could establish the nurturing environment required for follicular survival in heterotopic xenografts.

Sustained release of basic fibroblast growth factor using gelatin hydrogel improved left ventricular function through the alteration of collagen subtype in a rat chronic myocardial infarction model

OBJECTIVE

Chronic myocardial infarction (CMI) tends to be resistant to treatments possibly due to extensive solid fibrotic scar, hypoxia mediated by poorly vascularized environment, and/or inflammation and apoptosis. Here we aimed to testify the therapeutic effects of sustained release of basic fibroblast growth factor (bFGF) using gelatin hydrogel (GH) in a rat chronic MI model and to elucidate the therapeutic mechanism including the alteration of extracellular matrix component.

METHODS

CMI model rats are prepared by the permanent ligation of proximal left anterior descending coronary artery. After 4 weeks, GH sheets (GHSs) with bFGF (100 µg) (bFGF group) or with phosphate-buffered saline (Vehicle group) were implanted to the CMI models to evaluate the effect of bFGF-GHS on chronic scar tissue. Sham operation group was also prepared (n = 5 for each).

RESULTS

4 weeks after implantation, bFGF-GHS significantly improved cardiac contractile function (fractional shortening: 21.8 ± 1.1 vs 21.5 ± 1.3 vs 29.7 ± 1.8%; P < 0.001/fractional area change: 33.0 ± 1.4 vs 34.1 ± 2.3 vs 40.6 ± 1.8%; P < 0.001) (Sham vs Vehicle vs bFGF) accompanied with neovascularization. Immunohistochemical studies revealed that bFGF-GHS increased collagen III/I ratio indicating the alteration of solid scar tissue. Quantitative RT-PCR results showed a decrease of collagen I mRNA expression within border MI zone.

CONCLUSIONS

The implantation of bFGF-GHS altered the collagen subtype of the fibrotic scar more suitable for tissue repair. The treatment of sustained-release bFGF may be promising for ischemic heart disease through chronic pathology.

Association of FGF-2 Concentrations with Atheroma Progression in Chronic Kidney Disease Patients

BACKGROUND AND OBJECTIVES

Atherosclerosis is highly prevalent in CKD. The rate of progression of atherosclerosis is associated with cardiovascular events. Fibroblast growth factor 2 (FGF-2) is a member of the FGF family with potentially both protective and deleterious effects in the development of atherosclerosis. The role of circulating FGF-2 levels in the progression of atherosclerosis in CKD is unknown.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We used a multicenter, prospective, observational cohorts study of 481 patients with CKD. We determined the presence of atheroma plaque in ten arterial territories by carotid and femoral ultrasounds. Progression of atheromatosis was defined as an increase in the number of territories with plaque after 24 months. Plasma levels of FGF-2 were measured by multiplex analysis. A multivariable logistic regression analysis was performed to determine whether plasma FGF-2 levels were associated with atheromatosis progression.

RESULTS

Average age of the population was 61 years. The percentage of patients in each CKD stage was 51% in stage 3, 41% in stages 4-5, and 8% in dialysis. A total of 335 patients (70%) showed plaque at baseline. Atheromatosis progressed in 289 patients (67%). FGF-2 levels were similar between patients with or without plaque at baseline (79 versus 88 pg/ml), but lower in patients with atheromatosis progression after 2 years (78 versus 98 pg/ml; P<0.01). In adjusted analyses, higher plasma FGF-2 was associated with lower risk of atheromatosis progression (odds ratio [OR], 0.86; 95% confidence interval [95% CI], 0.76 to 0.96; per 50 pg/ml increment). Analysis of FGF-2 in tertiles showed that atheroma progression was observed for 102 participants in the lowest tertile of FGF-2 (reference group), 86 participants in the middle tertile of FGF-2 (adjusted OR, 0.70; 95% CI, 0.40 to 1.20), and 74 participants in the lowest tertile of FGF-2 (adjusted OR, 0.48; 95% CI, 0.28 to 0.82).

CONCLUSIONS

Low FGF-2 levels are independently associated with atheromatosis progression in CKD.

Growth Factor Delivery Systems for Tissue Engineering and Regenerative Medicine

Growth factors (GFs) are often a key component in tissue engineering and regenerative medicine approaches. In order to fully exploit the therapeutic potential of GFs, GF delivery vehicles have to meet a number of key design criteria such as providing localized delivery and mimicking the dynamic native GF expression levels and patterns. The use of biomaterials as delivery systems is the most successful strategy for controlled delivery and has been translated into different commercially available systems. However, the risk of side effects remains an issue, which is mainly attributed to insufficient control over the release profile. This book chapter reviews the current strategies, chemistries, materials and delivery vehicles employed to overcome the current limitations associated with GF therapies.

Scale-up and Current Clinical Trials for Nanogels in Therapeutics

The fundamentals of hydrogels and their advancement to nanogels, their synthesis, potential bio-medical application, and challenges related to specific applications along with solutions and future prospects have been described in previous chapters. The ultimate aim of developing nanogels of desired properties as a potential nano-bio-polymeric system is to promote them at clinical level for therapeutics. In this chapter, an attempt has been made to describe the strategies related with scale-up approach of nanogels for clinical phases in order to justify the therapeutic applications. The state of the art of nanogel market and possible future prospects is covered in this chapter.

Intramyocardial delivery of bFGF with a biodegradable and thermosensitive hydrogel improves angiogenesis and cardio-protection in infarcted myocardium

Basic fibroblast growth factor (bFGF), a known angiogenic factor, may provide a potential strategy for the treatment of myocardial infarction (MI), but it is limited by a relatively short half-life. Dex-PCL-HEMA/PNIPAAm hydrogel provides a reservoir for the controlled release of growth factors. The aim of the current study was to evaluate the effects of bFGF incorporated into a Dex-PCL-HEMA/PNIPAAm hydrogel on angiogenesis and cardiac health in a rat model of acute MI, induced by coronary artery ligation. Phosphate-buffered solution (PBS group), Dex-PCL-HEMA/PNIPAAm hydrogel (Gel group), bFGF in phosphate-buffered solution (bFGF group) or bFGF in hydrogel (Gel + bFGF group) was injected into a peri-infarcted area of cardiac tissue immediately following MI. On day 30 post-surgery, cardiac function was assessed by echocardiography, apoptosis index by terminal deoxynucleotidyl transferase dUTP nick-end labeling assessment and vascular development by immunohistochemical staining. The findings demonstrated that injection of bFGF along with hydrogel induced angiogenesis, reduced collagen content, MI area and cell apoptosis and improved cardiac function compared with the injection of either bFGF or hydrogel alone. bFGF incorporated with Dex-PCL-HEMA/PNIPAAm hydrogel injection induces angiogenesis, attenuates cardiac remodeling and improves cardiac function following MI.

Gene-based therapies in patients with critical limb ischemia

Critical limb ischemia (CLI) constitutes a life-limiting and life-threatening disease. Revascularization, either endovascular or surgical, remains the best treatment option accompanied by medication and risk factor modification. Patients unable to undergo revascularization, referred as 'no-option patients', have been the center of interest the last few years, subjected to treatment therapies based on proteins (mainly growth factors) involved in angiogenesis via gene delivery to the ischemic tissue. Areas covered: This review focuses on these growth factors, gives an update of the studies available, discusses the possible problems that influence outcomes and describes future perspectives including possible new technologies that will improve them. Additionally, the authors attempt to place therapeutic angiogenesis to the bigger frame of tailored therapy in CLI. Expert opinion: Although encouraging in the beginning, growth factor therapy results have been equivocal and inconclusive. And while it would be misleading to approach gene therapy as panacea, its effect on the micro-circulatory level activating angiogenesis and arteriogenesis could act as an important adjunct in personalized treatment.

Biohybrid methacrylated gelatin/polyacrylamide hydrogels for cartilage repair

We prepared a biohybrid hydrogel based on acrylamide and GelMA, having good mechanical properties, thermal stability, and bioactivity for cartilage regeneration.

The Dose of Intravenously Transplanted Bone Marrow Stromal Cells Determines the Therapeutic Effect on Vascular Remodeling in a Rat Model of Ischemic Stroke

The therapeutic benefits of bone marrow-derived mesenchymal stem cell (BM-MSC) transplantation for ischemic stroke have been extensively demonstrated. However, studies on the optimal cell dose for intravenous administration are still limited. This study aimed to determine an appropriate cell dose for BM-MSC intravenous transplantation and to investigate the effect of cell dose on vascular remodeling in a rat model of ischemic stroke. BM-MSCs at doses of 5104 (low-dose group), 5105 (medium-dose group), and 2106 (high-dose group) were intravenously injected into rats at 72 h after ischemia. The therapeutic efficacy of BM-MSCs was evaluated by measuring infarct volume, vascular diameters, capillary area in the peri-infarct zone, level of basic fibroblast growth factor (bFGF) in the peri-infarct zone, and serum vascular endothelial growth factor (VEGF) level at 7 days after ischemia. Compared with the low-dose and control groups, medium-dose and high-dose BM-MSC transplantation significantly reduced the volume of the infarct area, enlarged the diameters of pial vessels and the basilar artery, and increased the capillary area in the peri-infarct zone of the cerebral cortex. Furthermore, transplanted BM-MSCs elevated the expressions of bFGF in the peri-infarct zone and the serum VEGF level. Administration of 5105 BM-MSCs is an appropriate cell dose for ischemic stroke therapy in rats. These findings may be helpful for designing future clinical trials.

The efficacy of a multidisciplinary team approach in critical limb ischemia

The aim of the present study was to clarify the characteristics of Japanese critical limb ischemia (CLI) patients and analyze the rates of real-world mortality and amputation-free survival (AFS) in all patients with Fontaine stage IV CLI who were treated with/without revascularization therapy by an intra-hospital multidisciplinary care team. All consecutive patients who presented with CLI at Showa University Fujigaoka Hospital between April 2008 and March 2014 were prospectively registered. The intra-hospital committee consisted of cardiologists, plastic surgeons, dermatologists, diabetologists, nephrologists, cardiovascular surgeons, and vascular technologists. The primary endpoint of this study was all-cause mortality and AFS during the follow-up period. The present study included 145 patients with Fontaine stage IV CLI. The mean age was 76.5 ± 10.2 years. The all-cause mortality rate during the follow-up period (15.5 ± 16.1 months) was 21.4 %. The AFS rate during the follow-up period (14.1 ± 16.4 months) was 58.6 %. A multivariate Cox proportional hazards regression analysis found that age >75 years and hemodialysis were significantly associated with all-cause mortality; and that age >75 years, Rutherford 6, and wound infection were significantly associated with AFS. A multidisciplinary approach and comprehensive care may improve the outcomes and optimize the collaborative treatment of CLI patients. However, all-cause mortality remained high in patients with Fontaine stage IV CLI and early referral to a hospital that can provide specialized treatment for CLI, before the occurrence of major tissue loss or infection, is necessary to avoid primary amputation.

Fibroblast growth factors as tissue repair and regeneration therapeutics

Cell communication is central to the integration of cell function required for the development and homeostasis of multicellular animals. Proteins are an important currency of cell communication, acting locally (auto-, juxta-, or paracrine) or systemically (endocrine). The fibroblast growth factor (FGF) family contributes to the regulation of virtually all aspects of development and organogenesis, and after birth to tissue maintenance, as well as particular aspects of organism physiology. In the West, oncology has been the focus of translation of FGF research, whereas in China and to an extent Japan a major focus has been to use FGFs in repair and regeneration settings. These differences have their roots in research history and aims. The Chinese drive into biotechnology and the delivery of engineered clinical grade FGFs by a major Chinese research group were important enablers in this respect. The Chinese language clinical literature is not widely accessible. To put this into context, we provide the essential molecular and functional background to the FGF communication system covering FGF ligands, the heparan sulfate and Klotho co-receptors and FGF receptor (FGFR) tyrosine kinases. We then summarise a selection of clinical reports that demonstrate the efficacy of engineered recombinant FGF ligands in treating a wide range of conditions that require tissue repair/regeneration. Alongside, the functional reasons why application of exogenous FGF ligands does not lead to cancers are described. Together, this highlights that the FGF ligands represent a major opportunity for clinical translation that has been largely overlooked in the West.

Efficient long-term survival of cell grafts after myocardial infarction with thick viable cardiac tissue entirely from pluripotent stem cells

Poor engraftment of cells after transplantation to the heart is a common and unresolved problem in the cardiac cell therapies. We previously generated cardiovascular cell sheets entirely from pluripotent stem cells with cardiomyocytes, endothelial cells and vascular mural cells. Though sheet transplantation showed a better engraftment and improved cardiac function after myocardial infarction, stacking limitation (up to 3 sheets) by hypoxia hampered larger structure formation and long-term survival of the grafts. Here we report an efficient method to overcome the stacking limitation. Insertion of gelatin hydrogel microspheres (GHMs) between each cardiovascular cell sheet broke the viable limitation via appropriate spacing and fluid impregnation with GHMs. Fifteen sheets with GHMs (15-GHM construct; >1 mm thickness) were stacked within several hours and viable after 1 week in vitro. Transplantation of 5-GHM constructs (≈2 × 10(6) of total cells) to a rat myocardial infarction model showed rapid and sustained functional improvements. The grafts were efficiently engrafted as multiple layered cardiovascular cells accompanied by functional capillary networks. Large engrafted cardiac tissues (0.8 mm thickness with 40 cell layers) successfully survived 3 months after TX. We developed an efficient method to generate thicker viable tissue structures and achieve long-term survival of the cell graft to the heart.

Proapoptotic effect of control-released basic fibroblast growth factor on skin wound healing in a diabetic mouse model

The ability of basic fibroblast growth factor (bFGF) to improve wound healing is attenuated by its short half-life in free form. This study aimed to enhance skin wound healing in a diabetes mouse model while concomitantly decreasing scar formation using control-released bFGF together with acidic gelatin hydrogel microspheres (AGHMs). Bilateral full-thickness wounds (10 mm in diameter) were made on the backs of db/db mice. Forty-five mice were divided into three groups, and the base of the wound under the panniculus carnosus and the wound periphery were injected with phosphate-buffered saline (300 μL) containing (1) control-released bFGF (50 μg), (2) control-released bFGF (20 μg), or (3) AGHMs alone. The size of the wound area was recorded on each postoperative day (POD). Mice were sacrificed on postoperative day 4, 7, 10, 14, and 28, and skin wound specimens were obtained to assess the endothelium/angiogenesis index via cluster of differentiation 31 immunohistochemistry, the proliferation index via Ki-67 immunohistochemistry, and the myofibroblast and fibroblast apoptosis indices by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling and alpha-smooth muscle actin or vimentin staining, respectively. Epithelialization rates and indices of proliferation and myofibroblast/fibroblast apoptosis were higher in the bFGF groups than in the AGHM group, mainly within 2 weeks of injury. No dose-effect relationship was found for control-released bFGF, although the actions of 50 μg bFGF seemed to last longer than those of 20 μg bFGF. Therefore, control-released bFGF may accelerate diabetic skin wound healing and induce myofibroblast/fibroblast apoptosis, thereby reducing scar formation.

Intramyocardial delivery of VEGF165 via a novel biodegradable hydrogel induces angiogenesis and improves cardiac function after rat myocardial infarction

Vascular endothelial growth factor (VEGF), an independent mitogen, has been reported to induce angiogenesis and thus attenuates the damage induced by myocardial infarction (MI). VEGF165 is the most abundant and predominant isoform of VEGF. This study investigates whether this effect could be strengthened by local intramyocardial injection of VEGF165 along with a novel biodegradable Dex-PCL-HEMA/PNIPAAm hydrogel and ascertains its possible mechanism of action. Rat models of myocardial infarction were induced by coronary artery ligation. Phosphate-buffered saline (PBS group), Dex-PCL-HEMA/PNIPAAm hydrogel (Gel group), phosphate-buffered saline containing VEGF165 (VP group), and hydrogel containing VEGF165 (VPG group) were injected into a peri-infarcted area of cardiac tissue immediately after myocardial infarction, respectively. The sham group was thoracic but without myocardial infarction. The injection of VEGF165 along with a hydrogel induced angiogenesis, reduced collagen content and MI area, inhibited cell apoptosis, increased the level of VEGF165 protein and the expression of flk-1 and flt-1, and improved cardiac function compared with the injection of either alone after MI in rats. The results suggest that injection of VEGF165 along with a hydrogel acquires more cardioprotective effects than either alone in rat with MI by sustained release of VEGF165, then may enhance the feedback between VEGF and its receptors flk-1 and flt-1.