Hypoxia-inducible Factor-1α directs renal regeneration induced by decellularized scaffolds

Heterogeneous porous hypoxia-mimicking scaffolds propel urethral reconstruction by promoting angiogenesis and regulating inflammation

The nasty urine microenvironment (UME) impedes neourethral regeneration by inhibiting angiogenesis and inducing an excessive inflammatory response. Cellular adaptation to hypoxia improves regeneration in numerous tissues. In this study, heterogeneous porous hypoxia-mimicking scaffolds were fabricated for urethral reconstruction via promoting angiogenesis and modulating the inflammatory response based on sustained release of dimethyloxalylglycine (DMOG) to promote HIF-1α stabilization. Such scaffolds exhibit a two-layered structure: a dense layer composed of electrospun poly (l-lactic acid) (PLLA) nanofibrous mats and a loose layer composed of a porous gelatin matrix incorporated with DMOG-loaded mesoporous silica nanoparticles (DMSNs) and coated with poly(glycerol sebacate) (PGS). The modification of PGS could significantly increase rupture elongation, making the composite scaffolds more suitable for urethral tissue regeneration. Additionally, sustained release of DMOG from the scaffold facilitates proliferation, migration, tube formation, and angiogenetic gene expression in human umbilical vein endothelial cells (HUVECs), as well as stimulates M2 macrophage polarization and its regulation of HUVECs migration and smooth muscle cell (SMCs) contractile phenotype. These effects were downstream of the stabilization of HIF-1α in HUVECs and macrophages under hypoxia-mimicking conditions. Furthermore, the scaffold achieved better urethral reconstruction in a rabbit urethral stricture model, including an unobstructed urethra with a larger urethral diameter, increased regeneration of urothelial cells, SMCs, and neovascularization. Our results indicate that heterogeneous porous hypoxia-mimicking scaffolds could promote urethral reconstruction via facilitating angiogenesis and modulating inflammatory response.

Metal-Organic Framework-Based Nanomaterials for Regulation of the Osteogenic Microenvironment

As the global population ages, bone diseases have become increasingly prevalent in clinical settings. These conditions often involve detrimental factors such as infection, inflammation, and oxidative stress that disrupt bone homeostasis. Addressing these disorders requires exogenous strategies to regulate the osteogenic microenvironment (OME). The exogenous regulation of OME can be divided into four processes: induction, modulation, protection, and support, each serving a specific purpose. To this end, metal-organic frameworks (MOFs) are an emerging focus in nanomedicine, which show tremendous potential due to their superior delivery capability. MOFs play numerous roles in OME regulation such as metal ion donors, drug carriers, nanozymes, and photosensitizers, which have been extensively explored in recent studies. This review presents a comprehensive introduction to the exogenous regulation of OME by MOF-based nanomaterials. By discussing various functional MOF composites, this work aims to inspire and guide the creation of sophisticated and efficient nanomaterials for bone disease management.

Decellularized diseased tissues: current state-of-the-art and future directions

Decellularized matrices derived from diseased tissues/organs have evolved in the most recent years, providing novel research perspectives for understanding disease occurrence and progression and providing accurate pseudo models for developing new disease treatments. Although decellularized matrix maintaining the native composition, ultrastructure, and biomechanical characteristics of extracellular matrix (ECM), alongside intact and perfusable vascular compartments, facilitates the construction of bioengineered organ explants in vitro and promotes angiogenesis and tissue/organ regeneration in vivo, the availability of healthy tissues and organs for the preparation of decellularized ECM materials is limited. In this paper, we review the research advancements in decellularized diseased matrices. Considering that current research focuses on the matrices derived from cancers and fibrotic organs (mainly fibrotic kidney, lungs, and liver), the pathological characterizations and the applications of these diseased matrices are mainly discussed. Additionally, a contrastive analysis between the decellularized diseased matrices and decellularized healthy matrices, along with the development in vitro 3D models, is discussed in this paper. And last, we have provided the challenges and future directions in this review. Deep and comprehensive research on decellularized diseased tissues and organs will promote in-depth exploration of source materials in tissue engineering field, thus providing new ideas for clinical transformation.

A comprehensive review on the composition, biogenesis, purification, and multifunctional role of exosome as delivery vehicles for cancer therapy

All forms of life produce nanosized extracellular vesicles called exosomes, which are enclosed in lipid bilayer membranes. Exosomes engage in cell-to-cell communication and participate in a variety of physiological and pathological processes. Exosomes function via their bioactive components, which are delivered to target cells in the form of proteins, nucleic acids, and lipids. Exosomes function as drug delivery vehicles due to their unique properties of innate stability, low immunogenicity, biocompatibility, biodistribution, accumulation in desired tissues, low toxicity in normal tissues, and the stimulation of anti-cancer immune responses, and penetration capacity into distance organs. Exosomes mediate cellular communications by delivering various bioactive molecules including oncogenes, oncomiRs, proteins, specific DNA, messenger RNA (mRNA), microRNA (miRNA), small interfering RNA (siRNA), and circular RNA (circRNA). These bioactive substances can be transferred to change the transcriptome of target cells and influence tumor-related signaling pathways. After considering all of the available literature, in this review we discuss the biogenesis, composition, production, and purification of exosomes. We briefly review exosome isolation and purification techniques. We explore great-length exosomes as a mechanism for delivering a variety of substances, including proteins, nucleic acids, small chemicals, and chemotherapeutic drugs. We also talk about the benefits and drawbacks of exosomes. This review concludes with a discussion future perspective and challenges. We hope that this review will provide us a better understanding of the current state of nanomedicine and exosome applications in biomedicine.

Biomimetic hydrogel derived from decellularized dermal matrix facilitates skin wounds healing

Cutaneous wound healing affecting millions of people worldwide represents an unsolvable clinical issue that is frequently challenged by scar formation with dramatical pain, impaired mobility and disfigurement. Herein, we prepared a kind of light-sensitive decellularized dermal extracellular matrix-derived hydrogel with fast gelling performance, biomimetic porous microstructure and abundant bioactive functions. On account of its excellent cell biocompatibility, this ECM-derived hydrogel could induce a marked cellular infiltration and enhance the tube formation of HUVECs. In vivo experiments based upon excisional wound splinting model showed that the hydrogel prominently imparted skin wound healing, as evidenced by notably increased skin appendages and well-organized collagen expression, coupled with significantly enhanced angiogenesis. Moreover, the skin regeneration mediated by this bioactive hydrogel was promoted by an accelerated M1-to-M2 macrophage phenotype transition. Consequently, the decellularized dermal matrix-derived bioactive hydrogel orchestrates the entire skin healing microenvironment to promote wound healing and will be of high value in treatment of cutaneous wound healing. As such, this biomimetic ddECMMA hydrogel provides a promising versatile opinion for the clinical translation.

3D hypoxia-mimicking and anti-synechia hydrogel enabling promoted neovascularization for renal injury repair and regeneration

In-situ renal tissue engineering is promising yet challenging for renal injury repair and regeneration due to the highly vascularized structure of renal tissue and complex high-oxidative stress and ischemic microenvironment. Herein, a novel biocompatible 3D porous hydrogel (DFO-gel) with sustained release capacity of hypoxia mimicking micromolecule drug deferoxamine (DFO) was developed for in-situ renal injury repair. In vitro and in vivo experimental results demonstrated that the developed DFO-gels can exert the synchronous benefit of scavenging excess reactive oxygen species (ROS) regulating inflammatory microenvironment and promoting angiogenesis for effective renal injury repair by up-regulating hypoxia-inducible factor-1 alpha (HIF-1α) and vascular endothelial growth factor (VEGF). The in-situ neogenesis of neonatal glomerular- and tubular-like structures in the implanted areas in the partially nephrectomized rats also suggested the potential for promoting renal injury repair and regeneration. This multifunctional hydrogel can not only exhibit the sustained release and promoted bio-uptake capacity for DFO, but also improve the renal injured microenvironment by alleviating oxidative and inflammatory stress, accelerating neovascularization, and promoting efficient anti-synechia. We believe this work offers a promising strategy for renal injury repair and regeneration.

Biodegradable Microneedle Array-Mediated Transdermal Delivery of Dimethyloxalylglycine-Functionalized Zeolitic Imidazolate Framework-8 Nanoparticles for Bacteria-Infected Wound Treatment

Bacteria-infected skin wounds caused by external injuries remain a serious challenge to the whole society. Wound healing dressings, with excellent antibacterial activities and potent regeneration capability, are increasingly needed clinically. Here, we reported a novel functional microneedle (MN) array comprising methacrylated hyaluronic acid (MeHA) embedded with pH-responsive functionalized zeolitic imidazolate framework-8 (ZIF-8) nanoparticles to treat bacteria-infected cutaneous wounds. Antibacterial activity was introduced into Zn-ZIF-8 to achieve sterilization through releasing Zn ions, as well as increased angiogenesis by dimethyloxalylglycine (DMOG) molecules that were distributed within its framework. Furthermore, biodegradable MeHA was chosen as a substrate material carrier to fabricate DMOG@ZIF-8 MN arrays. By such design, DMOG@ZIF-8 MN arrays would not only exhibit excellent antibacterial activity against pathogenic bacteria but also enhance angiogenesis within wound bed by upregulating the expression of HIF-1α, leading to a significant therapeutic efficiency on bacteria-infected cutaneous wound healing. Based on these results, we conclude that this new treatment strategy can provide a promising alternative for accelerating infected wound healing via effective antibacterial activity and ameliorative angiogenesis.

The application of 3D bioprinting in urological diseases

Urologic diseases are commonly diagnosed health problems affecting people around the world. More than 26 million people suffer from urologic diseases and the annual expenditure was more than 11 billion US dollars. The urologic cancers, like bladder cancer, prostate cancer and kidney cancer are always the leading causes of death worldwide, which account for approximately 22% and 10% of the new cancer cases and death, respectively. Organ transplantation is one of the major clinical treatments for urological diseases like end-stage renal disease and urethral stricture, albeit strongly limited by the availability of matching donor organs. Tissue engineering has been recognized as a highly promising strategy to solve the problems of organ donor shortage by the fabrication of artificial organs/tissue. This includes the prospective technology of three-dimensional (3D) bioprinting, which has been adapted to various cell types and biomaterials to replicate the heterogeneity of urological organs for the investigation of organ transplantation and disease progression. This review discusses various types of 3D bioprinting methodologies and commonly used biomaterials for urological diseases. The literature shows that advances in this field toward the development of functional urological organs or disease models have progressively increased. Although numerous challenges still need to be tackled, like the technical difficulties of replicating the heterogeneity of urologic organs and the limited biomaterial choices to recapitulate the complicated extracellular matrix components, it has been proved by numerous studies that 3D bioprinting has the potential to fabricate functional urological organs for clinical transplantation and in vitro disease models.

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Outline the advantages and characteristics of 3D printing compared with traditional methods for urological diseases.

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Guide the selection of 3D bioprinting technology and material in urological tissue engineering.

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Discuss the challenges and future perspectives of 3D bioprinting in urological diseases and clinical translation.

Perfusion decellularization for vascularized composite allotransplantation

Vascularized composite allotransplantation is becoming the emerging standard for reconstructive surgery treatment for patients with limb trauma and facial injuries involving soft tissue loss. Due to the complex immunogenicity of composite grafts, patients who undergo vascularized composite allotransplantation are reliant on lifelong immunosuppressive therapy. Decellularization of donor grafts to create an extracellular matrix bio-scaffold provides an immunomodulatory graft that preserves the structural and bioactive function of the extracellular matrix. Retention of extracellular matrix proteins, growth factors, and signaling cascades allow for cell adhesion, migration, proliferation, and tissue regeneration. Perfusion decellularization of detergents through the graft vasculature allows for increased regent access to all tissue layers, and removal of cellular debris through the venous system. Grafts can subsequently be repopulated with appropriate cells through the vasculature to facilitate tissue regeneration. The present work reviews methods of decellularization, process parameters, evaluation of adequate cellular and nuclear removal, successful applications of perfusion decellularization for use in vascularized composite allotransplantation, and current limitations.

Hypoxia: molecular pathophysiological mechanisms in human diseases

Hypoxia, a low O2 tension, is a fundamental feature that occurs in physiological events as well as pathophysiological conditions, especially mentioned for its role in the mechanism of angiogenesis, glucose metabolism, and cell proliferation/survival. The hypoxic state through the activation of specific mechanisms is an aggravating circumstance commonly noticed in multiple sclerosis, cancer, heart disease, kidney disease, liver disease, lung disease, and in inflammatory bowel disease. On the other hand, hypoxia could play a key role in tissue regeneration and repair of damaged tissues, especially by acting on specific tissue stem cells, but their features may result as a disadvantage when it is concerned for neoplastic stem cells. Furthermore, hypoxia could also have a potential role in tissue engineering and regenerative medicine due to its capacity to improve the performance of biomaterials. The current review aims to highlight the hypoxic molecular mechanisms reported in different pathological conditions to provide an overview of hypoxia as a therapeutic agent in regenerative and molecular therapy.

Graphical abstract

Effect of heparinization on promoting angiogenesis of decellularized kidney scaffolds

Native decellularized extracellular matrix provides an adequate platform for tissues and organs and promotes the development of organogenesis and tissue remodeling. However, thrombosis poses a great challenge that hinders the transplantation for a substantial organ in vivo. Therefore, anticoagulation and re-reendothelialization of organ biological scaffolds are the primary concerns to be addressed before orthotopic transplantation. Herein, a heparinized decellularized kidney scaffold (HEP-DKSs) was prepared using end-point attachment technology, followed by binding the vascular endothelial growth factor (VEGF) to greatly improve the hemocompatibility and angiogenesis of DKSs. Based on the anticoagulant, co-culture of human umbilical vein endothelial cells, and subcapsular transplantation of kidney experiments, HEP-VEGF-DKSs are shown to reduce platelet adhesion, which is crucial for subsequent vascularization and slow release of heparin and VEGF, suggesting its ability of improve neovascularization. Taken together, these data indicated an optimal anticoagulation function of HEP-VEGF-DKSs and the potential of vascularization for regeneration of whole decellularized kidney.

A functional map of genomic HIF1α-DNA complexes in the eye lens revealed through multiomics analysis

BACKGROUND

During eye lens development the embryonic vasculature regresses leaving the lens without a direct oxygen source. Both embryonically and throughout adult life, the lens contains a decreasing oxygen gradient from the surface to the core that parallels the natural differentiation of immature surface epithelial cells into mature core transparent fiber cells. These properties of the lens suggest a potential role for hypoxia and the master regulator of the hypoxic response, hypoxia-inducible transcription factor 1 (HIF1), in the regulation of genes required for lens fiber cell differentiation, structure and transparency. Here, we employed a multiomics approach combining CUT&RUN, RNA-seq and ATACseq analysis to establish the genomic complement of lens HIF1α binding sites, genes activated or repressed by HIF1α and the chromatin states of HIF1α-regulated genes.

RESULTS

CUT&RUN analysis revealed 8375 HIF1α-DNA binding complexes in the chick lens genome. One thousand one hundred ninety HIF1α-DNA binding complexes were significantly clustered within chromatin accessible regions (χ2 test p < 1 × 10- 55) identified by ATACseq. Formation of the identified HIF1α-DNA complexes paralleled the activation or repression of 526 genes, 116 of which contained HIF1α binding sites within 10kB of the transcription start sites. Some of the identified HIF1α genes have previously established lens functions while others have novel functions never before examined in the lens. GO and pathway analysis of these genes implicate HIF1α in the control of a wide-variety of cellular pathways potentially critical for lens fiber cell formation, structure and function including glycolysis, cell cycle regulation, chromatin remodeling, Notch and Wnt signaling, differentiation, development, and transparency.

CONCLUSIONS

These data establish the first functional map of genomic HIF1α-DNA complexes in the eye lens. They identify HIF1α as an important regulator of a wide-variety of genes previously shown to be critical for lens formation and function and they reveal a requirement for HIF1α in the regulation of a wide-variety of genes not yet examined for lens function. They support a requirement for HIF1α in lens fiber cell formation, structure and function and they provide a basis for understanding the potential roles and requirements for HIF1α in the development, structure and function of more complex tissues.

Enhancing Kidney Vasculature in Tissue Engineering-Current Trends and Approaches: A Review

Chronic kidney diseases are a leading cause of fatalities around the world. As the most sought-after organ for transplantation, the kidney is of immense importance in the field of tissue engineering. The primary obstacle to the development of clinically relevant tissue engineered kidneys is precise vascularization due to the organ's large size and complexity. Current attempts at whole-kidney tissue engineering include the repopulation of decellularized kidney extracellular matrices or vascular corrosion casts, but these approaches do not eliminate the need for a donor organ. Stem cell-based approaches, such as kidney organoids vascularized in microphysiological systems, aim to construct a kidney without the need for organ donation. These organ-on-a-chip models show complex, functioning kidney structures, albeit at a small scale. Novel methodologies for developing engineered scaffolds will allow for improved differentiation of kidney stem cells and organoids into larger kidney grafts with clinical applications. While currently, kidney tissue engineering remains mostly limited to individual renal structures or small organoids, further developments in vascularization techniques, with technologies such as organoids in microfluidic systems, could potentially open doors for a large-scale growth of whole engineered kidneys for transplantation.

Decellularized kidney scaffold alters the healing response in chronic renal failure

Decellularized (DC) kidney scaffold shows great potential for renal recovering. Our study explored the effect of the DC kidney scaffolds treating on chronic renal failure (CRF) through grafting them on 5/6 nephrectomized (5/6 Nx) rat kidneys compared with gelatin sponges covered the incision edges. Blood urea nitrogen and angiotensin II were significantly lower in most time in scaffold-grafted groups. Remnant kidney tumor necrosis factor-α and fibroblast growth factor in scaffold-grafted groups significantly reduced in majority of time points compared with controls. But platelet-derived growth factor-BB showed a different varied tendency, first higher in scaffold groups on week 2, 4, 6, but lower on week 8, finally no difference on week 12 compared with gelatin-sponge groups. In addition, the index of glomerular sclerosis was significantly lesser in scaffold-grafted groups, and, the accumulation of collagen III and collagen IV decreased in scaffold-grafted groups on week 6, 8, 12 compared with gelatin-sponge groups. Moreover, DC scaffolds enhanced the expression of CD133 on week 2, 6, 8, 12. In conclusion, DC kidney scaffold altered the healing response after 5/6 nephrectomy and ameliorated renal injury to some degree. Therefore, DC kidney scaffold could be a promising therapeutic method on CRF.

Rabbit thyroid extracellular matrix as a 3D bioscaffold for thyroid bioengineering: a preliminary in vitro study

BACKGROUND

Advances in regenerative medicine technologies have been strongly proposed in the management of thyroid diseases. Mechanistically, the adoption of thyroid bioengineering requires a scaffold that shares a similar three-dimensional (3D) space structure, biomechanical properties, protein component, and cytokines to the native extracellular matrix (ECM).

METHODS

24 male New Zealand white rabbits were used in this experimental study. The rabbit thyroid glands were decellularized by immersion/agitation decellularization protocol. The 3D thyroid decellularization scaffolds were tested with histological and immunostaining analyses, scanning electron microscopy, DNA quantification, mechanical properties test, cytokine assay and cytotoxicity assays. Meanwhile, the decellularization scaffold were seeded with human thyroid follicular cells, cell proliferation and thyroid peroxidase were determined to explore the biocompatibility in vitro.

RESULTS

Notably, through the imaging studies, it was distinctly evident that our protocol intervention minimized cellular materials and maintained the 3D spatial structure, biomechanical properties, ECM composition, and biologic cytokine. Consequently, the decellularization scaffold was seeded with human thyroid follicular cells, thus strongly revealing its potential in reinforcing cell adhesion, proliferation, and preserve important protein expression.

CONCLUSIONS

The adoption of our protocol to generate a decellularized thyroid scaffold can potentially be utilized in transplantation to manage thyroid diseases through thyroid bioengineering.

Analysis of structural components of decellularized scaffolds in renal fibrosis

Chronic kidney disease has been recognized as a major public health problem worldwide and renal fibrosis is a common pathological process occurring in chronic renal failure. It is very promising to find the strategies to slow or even prevent the progression of fibrosis. This study focused on whether renal fibrosis decellularized scaffolds has the potential to be a model of cellular mechanisms of tissue fibrosis or donors for tissue engineering. In order to evaluate the feasibility of decellularized scaffolds derived from pathological kidneys, histology, proteomics and ELISA will be used to analysis the changes in the structure and main components of fibrotic tissue. The fibrosis model in this paper was induced by adenine-fed and the results showed that the structure of fibrotic scaffold was changed and some protein were up-regulated or down-regulated, but the cytokines associated with renal regeneration after injury were remained. In cell experiments, endothelial progenitor cells proliferated well, which proved that the fibrotic scaffolds have non-cytotoxic. All these conclusions indicate that the renal fibrosis decellularized scaffolds model has the ability to study fibrosis mechanism and the potential to be engineering donors as well as normal scaffolds.

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A study model of the mechanism of renal fibrosis from natural sources.

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Adenine-induced renal fibrosis with a cytopathic scaffold preserves important cytokines.

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There was no significant difference in cytokine content with natural scaffolds.

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Heat maps of differentially expressed proteins from subcellular localization.

Hypoxia regulates the degradation of non-nuclear organelles during lens differentiation through activation of HIF1a

Formation of the eye lens depends on the continuous differentiation of lens epithelial cells into lens fiber cells. To attain their mature structure and transparent function, nascent lens fiber cells must complete a precise cellular remodeling program hallmarked by the complete elimination of organelles to form the core lens organelle-free zone (OFZ). Lacking a blood supply, the lens resides in a hypoxic environment that results in a decreasing oxygen concentration from the lens surface to the lens core. This oxygen gradient results in a hypoxic microenvironment in the region of the lens where immature lens fiber cells initiate loss of organelles to form the core OFZ. These features of the lens suggest a potential role for low lens oxygen levels in the regulation of organelle degradation and other events critical for mature lens fiber cell formation. Hypoxia activates the master regulator of the hypoxic response, hypoxia-inducible factor 1a (HIF1a) that regulates hypoxia-responsive genes. To identify a potential role for hypoxia and HIF1a in the elimination of organelles during lens fiber cell maturation, we tested the requirement for hypoxia in the degradation of non-nuclear organelles in ex vivo cultured embryonic chick lenses by monitoring the degradation of mitochondria (MT), Golgi apparatus (GA) and endoplasmic reticulum (ER) under conditions of low (1% O₂) and high (21% O₂) oxygen. We also examined the requirement for HIF1a activation for elimination of these organelles under the same conditions using a specific HIF1a activator (DMOG) and a specific HIF1a inhibitor (chetomin) and examined the requirements for hypoxia and HIF1a for regulating transcription of BNIP3L that we previously showed to be required for elimination of non-nuclear lens organelles. We used ChIP-qPCR to confirm direct binding of HIF1a to the 5' untranslated region of the BNIP3L gene. Finally, we examined the effects of expressing an oxygen insensitive mutant form of HIF1a (P402A/P565A) and BNIP3L on non-nuclear organelle degradation. Our data demonstrate that hypoxia and HIF1a are required for the degradation of non-nuclear organelles during lens fiber cell formation and that they regulate this process by governing BNIP3L transcription. Our results also provide evidence that hypoxia and HIF1a are essential for achieving mature lens structure.

The Role of Hypoxia-Inducible Factor 1α in the Regulation of Human Meibomian Gland Epithelial Cells

Purpose

We recently discovered that a hypoxic environment is beneficial for meibomian gland (MG) function. The mechanisms underlying this effect are unknown, but we hypothesize that it is due to an increase in the levels of hypoxia-inducible factor 1α (HIF1α). In other tissues, HIF1α is the primary regulator of cellular responses to hypoxia, and HIF1α expression can be induced by multiple stimuli, including hypoxia and hypoxia-mimetic agents. The objective of this study was to test our hypothesis.

Methods

Human eyelid tissues were stained for HIF1α. Immortalized human MG epithelial cells (IHMGECs) were cultured for varying time periods under normoxic (21% O2) or hypoxic (1% O2) conditions, in the presence or absence of the hypoxia-mimetic agent roxadustat (Roxa). IHMGECs were then processed for the analysis of cell number, HIF1α expression, lipid-containing vesicles, neutral and polar lipid content, DNase II activity, and intracellular pH.

Results

Our results show that HIF1α protein is present in human MG acinar epithelial cells in vivo. Our findings also demonstrate that exposure to 1% O2 or to Roxa increases the expression of HIF1α, the number of lipid-containing vesicles, the content of neutral lipids, and the activity of DNase II and decreases the pH in IHMGECs in vitro.

Conclusions

Our data support our hypothesis that the beneficial effect of hypoxia on the MG is mediated through an increased expression of HIF1α.

Human nail bed extracellular matrix facilitates bone regeneration via macrophage polarization mediated by the JAK2/STAT3 pathway

Critical-sized bone defects caused by trauma, tumor resection or serious infection represent one of the most challenging problems faced by orthopedic surgeons. However, the construction of bone grafts with good osteointegration and osteoinductivity is a clinical challenge. It has been elaborated that the nail bed tissue is an essential element for digit tip regeneration, suggesting that the nail bed may serve as a new material to manipulate bone regeneration. Herein, it was found that human nail bed extracellular matrix derived from amputated patients stimulates macrophage polarization toward a pro-healing phenotype and the expression of BMP2, to facilitate the osteogenic differentiation of bone marrow stromal cells (BMSCs) in vitro. The in vivo osteogenic capacity of decellularized nail bed scaffolds was then confirmed using a rat model of critical-sized calvarial defects. The in-depth analysis of immune responses to implanted scaffolds revealed that macrophage polarization toward the pro-regenerative M2 phenotype directs osteogenesis, as confirmed by macrophage depletion. A combination of proteomics analysis and RNA interference verified that the JAK2/STAT3 pathway is the positive regulator of macrophage polarization initiated by the decellularized nail bed during the promoted osteogenesis process. Thus, the decellularized human nail bed scaffold developed in this work is a promising biomaterial for bone regeneration.

Proximal Tubular Development Is Impaired with Downregulation of MAPK/ERK Signaling, HIF-1α, and Catalase by Hyperoxia Exposure in Neonatal Rats

Supplemental oxygen therapy (hyperoxia) is a widely used treatment for alveolar hypoxia in preterm infants. Despite being closely monitored, hyperoxia exposure is believed to undermine neonatal nephrogenesis and renal function caused by elevated oxidative stress. Previous studies have mostly focused on the hyperoxia-induced impairment of glomerular development, while the long-term impact of neonatal hyperoxia on tubular development and the regulatory component involved in this process remain to be clarified. Here, we examined tubular histology and apoptosis, along with the expression profile of mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase (ERK) signaling, hypoxia-inducible factor 1α (HIF-1α), and catalase, following hyperoxia exposure in neonatal rats. Hematoxylin and eosin (H&E) staining revealed the early disappearance of the nephrogenic zone, as well as dilated lumens and reduced epithelial cells, of mature proximal tubules following neonatal hyperoxia. A robust increase in tubular cell apoptosis caused by neonatal hyperoxia was found using a TUNEL assay. Moreover, neonatal hyperoxia altered renal MAPK/ERK signaling activity and downregulated the expression of HIF-1α and catalase in the proximal tubules throughout nephrogenesis from S-shaped bodies to mature proximal tubules. Cell apoptosis in the proximal tubules was positively correlated with HIF-1α expression on the 14th postnatal day. Our data indicates that proximal tubular development is impaired by neonatal hyperoxia, which is accompanied by altered MAPK/ERK signaling as well as downregulated HIF-1α and catalase. Therapeutic management that targets MAPK/ERK signaling, HIF-1α, or catalase may serve as a protective agent against hyperoxia-induced oxidative damage to neonatal proximal tubules.

Decellularized matrices in regenerative medicine

Of all biologic matrices, decellularized extracellular matrix (dECM) has emerged as a promising tool used either alone or when combined with other biologics in the fields of tissue engineering or regenerative medicine - both preclinically and clinically. dECM provides a native cellular environment that combines its unique composition and architecture. It can be widely obtained from native organs of different species after being decellularized and is entitled to provide necessary cues to cells homing. In this review, the superiority of the macro- and micro-architecture of dECM is described as are methods by which these unique characteristics are being harnessed to aid in the repair and regeneration of organs and tissues. Finally, an overview of the state of research regarding the clinical use of different matrices and the common challenges faced in using dECM are provided, with possible solutions to help translate naturally derived dECM matrices into more robust clinical use.

STATEMENT OF SIGNIFICANCE

Ideal scaffolds mimic nature and provide an environment recognized by cells as proper. Biologically derived matrices can provide biological cues, such as sites for cell adhesion, in addition to the mechanical support provided by synthetic matrices. Decellularized extracellular matrix is the closest scaffold to nature, combining unique micro- and macro-architectural characteristics with an equally unique complex composition. The decellularization process preserves structural integrity, ensuring an intact vasculature. As this multifunctional structure can also induce cell differentiation and maturation, it could become the gold standard for scaffolds.