PHDs inhibitor DMOG promotes the vascularization process in the AV loop by HIF-1a up-regulation and the preliminary discussion on its kinetics in rat

FLT4 causes developmental disorders of the cardiovascular and lymphovascular systems via pleiotropic molecular mechanisms

AIMS

Rare, deleterious genetic variants in FLT4 are associated with Tetralogy of Fallot (TOF), the most common cyanotic congenital heart disease. The distinct genetic variants in FLT4 are also an established cause of Milroy disease, the most prevalent form of primary hereditary lymphoedema. The phenotypic features of these two conditions are non-overlapping, implying pleiotropic cellular mechanisms during development.

METHODS AND RESULTS

In this study, we show that FLT4 variants identified in patients with TOF, when expressed in primary human endothelial cells, cause aggregation of FLT4 protein in the perinuclear endoplasmic reticulum, activating proteostatic and metabolic signalling, whereas lymphoedema-associated FLT4 variants and wild-type (WT) FLT4 do not. FLT4 TOF variants display characteristic gene expression profiles in key developmental signalling pathways, revealing a role for FLT4 in cardiogenesis distinct from its role in lymphatic development. Inhibition of proteostatic signalling abrogates these effects, identifying potential avenues for therapeutic intervention. Depletion of flt4 in zebrafish caused cardiac phenotypes of reduced heart size and altered heart looping. These phenotypes were rescued with coinjection of WT human FLT4 mRNA, but incompletely or not at all by mRNA harbouring FLT4 TOF variants.

CONCLUSION

Taken together, we identify a pathogenic mechanism for FLT4 variants predisposing to TOF that is distinct from the known dominant negative mechanism of Milroy-causative variants. FLT4 variants give rise to conditions of the two circulatory subdivisions of the vascular system via distinct developmental pleiotropic molecular mechanisms.

The Janus face of HIF-1α in ischemic stroke and the possible associated pathways

Stroke is the most devastating disease, causing paralysis and eventually death. Many clinical and experimental trials have been done in search of a new safe and efficient medicine; nevertheless, scientists have yet to discover successful remedies that are also free of adverse effects. This is owing to the variability in intensity, localization, medication routes, and each patient's immune system reaction. HIF-1α represents the modern tool employed to treat stroke diseases due to its functions: downstream genes such as glucose metabolism, angiogenesis, erythropoiesis, and cell survival. Its role can be achieved via two downstream EPO and VEGF strongly related to apoptosis and antioxidant processes. Recently, scientists paid more attention to drugs dealing with the HIF-1 pathway. This review focuses on medicines used for ischemia treatment and their potential HIF-1α pathways. Furthermore, we discussed the interaction between HIF-1α and other biological pathways such as oxidative stress; however, a spotlight has been focused on certain potential signalling contributed to the HIF-1α pathway. HIF-1α is an essential regulator of oxygen balance within cells which affects and controls the expression of thousands of genes related to sustaining homeostasis as oxygen levels fluctuate. HIF-1α's role in ischemic stroke strongly depends on the duration and severity of brain damage after onset. HIF-1α remains difficult to investigate, particularly in ischemic stroke, due to alterations in the acute and chronic phases of the disease, as well as discrepancies between the penumbra and ischemic core. This review emphasizes these contrasts and analyzes the future of this intriguing and demanding field.

Rel Family Transcription Factor NFAT5 Upregulates COX2 via HIF-1α Activity in Ishikawa and HEC1a Cells

Nuclear factor of activated T cells 5 (NFAT5) and cyclooxygenase 2 (COX2; PTGS2) both participate in diverse pathologies including cancer progression. However, the biological role of the NFAT5-COX2 signaling pathway in human endometrial cancer has remained elusive. The present study explored whether NFAT5 is expressed in endometrial tumors and if NFAT5 participates in cancer progression. To gain insights into the underlying mechanisms, NFAT5 protein abundance in endometrial cancer tissue was visualized by immunohistochemistry and endometrial cancer cells (Ishikawa and HEC1a) were transfected with NFAT5 or with an empty plasmid. As a result, NFAT5 expression is more abundant in high-grade than in low-grade endometrial cancer tissue. RNA sequencing analysis of NFAT5 overexpression in Ishikawa cells upregulated 37 genes and downregulated 20 genes. Genes affected included cyclooxygenase 2 and hypoxia inducible factor 1α (HIF1A). NFAT5 transfection and/or treatment with HIF-1α stabilizer exerted a strong stimulating effect on HIF-1α promoter activity as well as COX2 expression level and prostaglandin E2 receptor (PGE2) levels. Our findings suggest that activation of NFAT5-HIF-1α-COX2 axis could promote endometrial cancer progression.

Recent advancement in vascularized tissue-engineered bone based on materials design and modification

Bone is one of the most vascular network-rich tissues in the body and the vascular system is essential for the development, homeostasis, and regeneration of bone. When segmental irreversible damage occurs to the bone, restoring its vascular system by means other than autogenous bone grafts with vascular pedicles is a therapeutic challenge. By pre-generating the vascular network of the scaffold in vivo or in vitro, the pre-vascularization technique enables an abundant blood supply in the scaffold after implantation. However, pre-vascularization techniques are time-consuming, and in vivo pre-vascularization techniques can be damaging to the body. Critical bone deficiencies may be filled quickly with immediate implantation of a supporting bone tissue engineered scaffold. However, bone tissue engineered scaffolds generally lack vascularization, which requires modification of the scaffold to aid in enhancing internal vascularization. In this review, we summarize the relationship between the vascular system and osteogenesis and use it as a basis to further discuss surgical and cytotechnology-based pre-vascularization strategies and to describe the preparation of vascularized bone tissue engineered scaffolds that can be implanted immediately. We anticipate that this study will serve as inspiration for future vascularized bone tissue engineered scaffold construction and will aid in the achievement of clinical vascularized bone.

Single-cell profiling reveals a potent role of quercetin in promoting hair regeneration

Hair loss affects millions of people at some time in their life, and safe and efficient treatments for hair loss are a significant unmet medical need. We report that topical delivery of quercetin (Que) stimulates resting hair follicles to grow with rapid follicular keratinocyte proliferation and replenishes perifollicular microvasculature in mice. We construct dynamic single-cell transcriptome landscape over the course of hair regrowth and find that Que treatment stimulates the differentiation trajectory in the hair follicles and induces an angiogenic signature in dermal endothelial cells by activating HIF-1α in endothelial cells. Skin administration of a HIF-1α agonist partially recapitulates the pro-angiogenesis and hair-growing effects of Que. Together, these findings provide a molecular understanding for the efficacy of Que in hair regrowth, which underscores the translational potential of targeting the hair follicle niche as a strategy for regenerative medicine, and suggest a route of pharmacological intervention that may promote hair regrowth.

Focusing on the hypoxia-inducible factor pathway: role, regulation, and therapy for osteoarthritis

Osteoarthritis (OA) is a common chronic disabling disease that affects hundreds of millions of people around the world. The most important pathological feature is the rupture and loss of articular cartilage, and the characteristics of avascular joint tissues lead to limited repair ability. Currently, there is no effective treatment to prevent cartilage degeneration. Studies on the mechanism of cartilage metabolism revealed that hypoxia-inducible factors (HIFs) are key regulatory genes that maintain the balance of cartilage catabolism-matrix anabolism and are considered to be the major OA regulator and promising OA treatment target. Although the exact mechanism of HIFs in OA needs to be further clarified, many drugs that directly or indirectly act on HIF signaling pathways have been confirmed by animal experiments and regarded as promising treatments for OA. Targeting HIFs will provide a promising strategy for the development of new OA drugs. This article reviews the regulation of HIFs on intra-articular cartilage homeostasis and its influence on the progression of osteoarthritis and summarizes the recent advances in OA therapies targeting the HIF system.

Systemically injected bone marrow mononuclear cells specifically home to axially vascularized tissue engineering constructs

Inducing axial vascularisation of tissue engineering constructs is a well-established method to support tissue growth in large 3-dimensional tissues. Progenitor cell chemotaxis towards axially vascularized tissues has not been well characterized. In a prospective randomized controlled study including 32 male syngeneic Lewis rats we investigated the capability of the axially vascularized constructs to attract systemically injected bone marrow mononuclear cells (BMMNCs). The underlying mechanism for cell homing was investigated focusing on the role of hypoxia and the SDF1-CXCR4-7 axis. Sixteen animals were used as donors for BMMNCs. The other animals were subjected to implantation of a tissue engineering construct in the subcutaneous groin region. These constructs were axially vascularized either via an arteriovenous loop (AVL, n = 6) or via uninterrupted flow-through vessels (non-AVL, n = 10). BMMNCs were labelled with quantum dots (Qdot® 655) and injected 12 days after surgery either via intra-arterial or intravenous routes. 2 days after cell injection, the animals were sacrificed and examined using fluorescence microscopy. The Qdot® 655 signals were detected exclusively in the liver, spleen, AVL constructs and to a minimal extent in the non-AVL constructs. A significant difference could be detected between the number of labelled cells in the AVL and non-AVL constructs with more cells detected in the AVL constructs specially in central zones (p <0.0001). The immunohistological analysis showed a significant increase in the absolute expression of HIF-1 in the AVL group in comparison to the non-AVL group. The PCR analysis confirmed a 1.4-fold increase in HIF-1 expression in AVL constructs. Although PCR analysis showed an enhanced expression of CXCR4 and CXCR7 in AVL constructs, no significant differences in SDF1 expression were detected via immunohistological or PCR analysis. At the examined time point, the AVL constructs can attract BMMNCs in a mechanism probably related to the hypoxia associated with a robust tissue formation.

Roxadustat promotes osteoblast differentiation and prevents estrogen deficiency-induced bone loss by stabilizing HIF-1α and activating the Wnt/β-catenin signaling pathway

Background

Osteoporosis is a very common skeletal disorder that increases the risk of fractures. However, the treatment of osteoporosis is challenging. Hypoxia-inducible factor-1α (HIF-1α) plays an important role in bone metabolism. Roxadustat is a novel HIF stabilizer, and its effects on bone metabolism remain unknown. This study aimed to investigate the effects of roxadustat on osteoblast differentiation and bone remodeling in an ovariectomized (OVX) rat model.

Methods

In vitro, primary mouse calvarial osteoblasts were treated with roxadustat. Alkaline phosphatase (ALP) activity and extracellular matrix mineralization were assessed. The mRNA and protein expression levels of osteogenic markers were detected. The effects of roxadustat on the HIF-1α and Wnt/β-catenin pathways were evaluated. Furthermore, osteoblast differentiation was assessed again after HIF-1α expression knockdown or inhibition of the Wnt/β-catenin pathway. In vivo, roxadustat was administered orally to OVX rats for 12 weeks. Then, bone histomorphometric analysis was performed. The protein expression levels of the osteogenic markers HIF-1α and β-catenin in bone tissue were detected.

Results

In vitro, roxadustat significantly increased ALP staining intensity, enhanced matrix mineralization and upregulated the expression of osteogenic markers at the mRNA and protein levels in osteoblasts compared with the control group. Roxadustat activated the HIF-1α and Wnt/β-catenin pathways. HIF-1α knockdown or Wnt/β-catenin pathway inhibition significantly attenuated roxadustat-promoted osteoblast differentiation. In vivo, roxadustat administration improved bone microarchitecture deterioration and alleviated bone loss in OVX rats by promoting bone formation and inhibiting bone resorption. Roxadustat upregulated the protein expression levels of the osteogenic markers, HIF-1α and β-catenin in the bone tissue of OVX rats.

Conclusion

Roxadustat promoted osteoblast differentiation and prevented bone loss in OVX rats. The use of roxadustat may be a new promising strategy to treat osteoporosis.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13018-022-03162-w.

Bone Regeneration Exploiting Corticoperiosteal Tissue Transfer for Scaffold-Guided Bone Regeneration

Contemporary reconstructive approaches for critical size bone defects carry significant disadvantages. As a result, clinically driven research has focused on the development and translation of alternative therapeutic concepts. Scaffold-guided tissue regeneration (SGTR) is an emerging technique to heal critical size bone defects. However, issues synchronizing scaffold vascularization with bone-specific regenerative processes currently limit bone regeneration for extra large (XL, 19 cm³) critical bone defects. To address this issue, we developed a large animal model that incorporates a corticoperiosteal flap (CPF) for sustained scaffold neovascularization and bone regeneration. In 10 sheep, we demonstrated the efficacy of this approach for healing medium (M, 9 cm³) size critical bone defects as demonstrated on plain radiography, microcomputed tomography, and histology. Furthermore, in two sheep, we demonstrate how this approach can be safely extended to heal XL critical size defects. This article presents an original CPF technique in a well-described preclinical model, which can be used in conjunction with the SGTR concept, to address challenging critical size bone defects in vivo. Impact statement This article describes a novel scaffold-guided tissue engineering approach utilizing a corticoperiosteal flap for bone healing in critical size long bone defects. This approach will be of use for tissue engineers and surgeons exploring vascularized tissue transfer as an option to regenerate large volumes of bone for extensive critical size bone defects both in vivo and in the clinical arena.

Hypoxia-inducible factor (HIF)-3a2 serves as an endothelial cell fate executor during chronic hypoxia

The adaptive response to hypoxia involves the transcriptional induction of three transcription factors called hypoxia inducible factor alpha 1, 2 and 3 (HIF-1α, HIF-2α, and HIF-3α) which dimerize with constitutively expressed beta chains that together form the HIF-1, -2 and -3 transcription factors. During normoxic conditions, the alpha chain is expressed at low levels since its stability is regulated by prolyl-hydroxylation that promotes subsequent ubiquitination and degradation. During hypoxic conditions, however, the prolyl hydroxylases are less active, and the alpha chain accumulates through elevated protein stability and the elevated induction of expression. Two of the three HIFs isoforms present in mammals, HIF-1 and HIF-2, are well characterized and have overlapping functions that promote cell survival, whereas HIF-3's role remains less clear. The HIF-3 response is complicated because the HIF3A gene can utilize different promotors and alternate splicing sites that result in a number of different HIF-3α isoforms. Here, using human umbilical vein endothelial cells (HUVECs), we demonstrate that one of the isoforms of HIF-3α, isoform 2 (HIF-3α2) accumulates at a late stage of hypoxia and induces the expression of DNA damage inducible transcript 3 (DDIT4), a gene known to promote apoptosis. We also demonstrate that caspase 3/7 activity is elevated, supporting that the role of the HIF-3α2 isoform is to promote apoptosis. Furthermore, we provide evidence that HIF-3α2 is also expressed in seven other primary endothelial cell types, suggesting that this may be a common feature of HIF-3α2 in endothelial cells.

Vascularized Tumor Spheroid-on-a-Chip Model Verifies Synergistic Vasoprotective and Chemotherapeutic Effects

Prolyl hydroxylases (PHD) inhibitors have been observed to improve drug distribution in mice tumors via blood vessel normalization, increasing the effectiveness of chemotherapy. These effects are yet to be demonstrated in human cell models. Tumor spheroids are three-dimensional cell clusters that have demonstrated great potential in drug evaluation for personalized medicine. Here, we used a perfusable vascularized tumor spheroid-on-a-chip to simulate the tumor microenvironment in vivo and demonstrated that the PHD inhibitor dimethylallyl glycine prevents the degradation of normal blood vessels while enhancing the efficacy of the anticancer drugs paclitaxel and cisplatin in human esophageal carcinoma (Eca-109) spheroids. Our results point to the potential of this model to evaluate anticancer drugs under more physiologically relevant conditions.

Synergetic protective effect of remote ischemic preconditioning and prolyl 4‑hydroxylase inhibition in ischemic cardiac injury

It has been reported that hypoxia-inducible factor 1α (HIF-1α) serves a key role in the protective effect of remote ischemic preconditioning (RIP) in ischemia/reperfusion (I/R)-induced cardiac injury. Moreover, inhibition of prolyl 4-hydroxylase (PHD), an enzyme responsible for HIF-1α degradation, prevents I/R-induced cardiac injury. However, whether their protective effects are synergetic remains to be elucidated. The present study aimed to investigate the protective effect of RIP, PHD inhibition using dimethyloxalylglycine (DMOG) and their combination on I/R-induced cardiac injury. Rabbits were randomly divided into seven groups: i) Sham; ii) I/R; iii) lung RIP + I/R; iv) thigh RIP + I/R; v) DMOG + I/R; vi) DMOG + lung RIP + I/R; and vii) DMOG + thigh RIP + I/R. I/R models were established via 30 min left coronary artery occlusion and 3 h reperfusion. For lung/thigh RIP, rabbits received left pulmonary artery (or left limb) ischemia for 25 min and followed by release for 5 min. Some rabbits were administered 20 mg/kg DMOG. The results demonstrated that both lung/thigh RIP and DMOG significantly decreased myocardial infarct size, creatine kinase activity and myocardial apoptosis in I/R rabbits. Furthermore, the combination of RIP and PHD inhibition exerted synergetic protective effects on these aforementioned changes. The mechanistic study indicated that both treatments increased mRNA and protein expression levels of HIF-1α and its downstream regulators, including vascular endothelial growth factor (VEGF), AKT and endothelial nitric oxide synthase (eNOS). In conclusion, the present study demonstrated that RIP and PHD inhibition exerted synergetic protective effects on cardiac injury via activation of HIF-1α and the downstream VEGF/AKT-eNOS signaling pathway.

Regulatory effects of HIF-1α and HO-1 in hypoxia-induced proliferation of pulmonary arterial smooth muscle cells in yak

Hypoxia-inducible factor-1α (HIF-1α) and heme oxygenase-1 (HO-1) are important transcription regulators in hypoxic cells and for maintaining cellular homeostasis, but it is unclear whether they participate in hypoxia-induced excessive proliferation of yak pulmonary artery smooth muscle cells (PASMCs). In this study, we identified distribution of HIF-1α and HO-1 in yak lungs. Immunohistochemistry and immunofluorescence results revealed that both HIF-1α and HO-1 were mainly concentrated in the medial layer of small pulmonary arteries. Furthermore, under induced-hypoxic conditions, we investigated HIF-1α and HO-1 protein expression and studied their potential involvement in yak PASMCs proliferation and apoptosis. Western blot results also showed that both factors significantly increased in age-dependent manner and upregulated in hypoxic PASMCs (which exhibited obvious proliferation and anti-apoptosis phenomena). HIF-1α up-regulation by DMOG increased the proliferation and anti-apoptosis of PASMCs, while HIF-1α down-regulation by LW6 decreased proliferation and promoted apoptosis. More so, treatment with ZnPP under hypoxic conditions down-regulated HO-1 expression, stimulated proliferation, and resisted apoptosis in yak PASMCs. Taken together, our study demonstrated that both HIF-1α and HO-1 participated in PASMCs proliferation and apoptosis, suggesting that HO-1 is important for inhibition of yak PASMCs proliferation while HIF-1α promoted hypoxia-induced yak PASMCs proliferation.

Heme oxygenase-1(HO-1) regulates Golgi stress and attenuates endotoxin-induced acute lung injury through hypoxia inducible factor-1α (HIF-1α)/HO-1 signaling pathway

Sepsis caused acute lung injury (ALI) is a kind of serious disease in critically ill patients with very high morbidity and mortality. Recently, it has been demonstrated that Golgi is involved in the process of oxidative stress. However, whether Golgi stress is associated with oxidative stress in septic induced acute lung injury has not been elucidated. In this research, we found that lipopolysaccharide (LPS) induced oxidative stress, apoptosis, inflammation and Golgi morphology changes in acute lung injury both in vivo and in vitro. The knockout of heme oxygenase-1(HO-1) aggravated oxidative stress, inflammation, apoptosis and reduced the expression of Golgi matrix protein 130 (GM130), mannosidase Ⅱ, Golgi-associated protein golgin A1 (Golgin 97), and increased the expression of Golgi phosphoprotein 3 (GOLPH3), which caused the fragmentation of Golgi. Furtherly, the activation of hypoxia inducible factor-1α (HIF-1α)/HO-1 pathway, attenuates Golgi stress and oxidative stress by increasing the levels of GM130, mannosidase Ⅱ, Golgin 97, and decreasing the expression of GOLPH3 both in vivo and in vitro. Therefore, the activation of HO-1 plays a crucial role in alleviating sepsis-induced acute lung injury by regulating Golgi stress, oxidative stress, which may provide a therapeutic target for the treatment of acute lung injury.

Unlocking mammalian regeneration through hypoxia inducible factor one alpha signaling

Historically, the field of regenerative medicine has aimed to heal damaged tissue through the use of biomaterials scaffolds or delivery of foreign progenitor cells. Despite 30 years of research, however, translation and commercialization of these techniques has been limited. To enable mammalian regeneration, a more practical approach may instead be to develop therapies that evoke endogenous processes reminiscent of those seen in innate regenerators. Recently, investigations into tadpole tail regrowth, zebrafish limb restoration, and the super-healing Murphy Roths Large (MRL) mouse strain, have identified ancient oxygen-sensing pathways as a possible target to achieve this goal. Specifically, upregulation of the transcription factor, hypoxia-inducible factor one alpha (HIF-1α) has been shown to modulate cell metabolism and plasticity, as well as inflammation and tissue remodeling, possibly priming injuries for regeneration. Since HIF-1α signaling is conserved across species, environmental or pharmacological manipulation of oxygen-dependent pathways may elicit a regenerative response in non-healing mammals. In this review, we will explore the emerging role of HIF-1α in mammalian healing and regeneration, as well as attempts to modulate protein stability through hyperbaric oxygen treatment, intermittent hypoxia therapy, and pharmacological targeting. We believe that these therapies could breathe new life into the field of regenerative medicine.

Application of diffusion tensor imaging and blood oxygenation level-dependent magnetic resonance imaging to assess bilateral renal function induced by Iohexol in rabbits

Background

Blood oxygenation level-dependent magnetic resonance imaging (BOLD-MRI) and diffusion tensor imaging (DTI) are useful methods for investigating the morphology and function of the kidneys, including revealing unilateral renal damage. Nevertheless, these techniques have not yet been applied for bilateral renal function. The aim of this study was to investigate whether the combination of DTI and BOLD could be used to examine different degrees of contrast-induced acute kidney injury (CI-AKI) in bilateral kidneys compared to standard methods such as serum creatinine (SCr) detection.

Methods

Forty-Two New Zealand white rabbits were divided into two groups: the experimental group and the control group. Physiological saline and iodine contrast agent (iohexol, 1.0 g iodine/kg, 1.0 ml/sec) were injected via the right renal artery. DTI and BOLD-MR data were acquired longitudinally at the baseline and 1, 24, 48, and 72 h after high-pressure syringe injection to measure the apparent diffusion coefficient (ADC), fractional anisotropy (FA) and relative transverse relaxation rate (R2*). After the MR scan at each time point, three rabbits in each group were sacrificed, and changes in SCr and hypoxia-inducible factor-1α (HIF-1α) were analyzed using histopathology and immunochemistry.

Results

Twenty-four hours after iohexol administration, the values of ADC and FA decreased significantly (P < 0.05), while R2* values increased (P < 0.05) in the renal cortex (CO), outer medulla (OM) and inner medulla (IM). Besides, significant negative correlations were observed among ADC, FA, and R2* in CO, OM, and IM (all P < 0.001, r = − 0.654–0.828).

Conclusions

DTI and BOLD can simultaneously and non-invasively assess different degrees of CI-AKI in bilateral kidneys.

HIF-1 stabilization exerts anticancer effects in breast cancer cells in vitro and in vivo

Tumor hypoxia and high activity of hypoxia-inducible factor-1 (HIF-1) correlate with adverse disease outcomes, malignancy, resistance to therapy and metastasis. Nonetheless, recent studies indicate that under certain circumstances, HIF-1 stabilization may exert protective effects and even decrease tumor cell aggressiveness. This study aimed to characterize the potential anticancer effect of molidustat (BAY 85-3934), the prolyl hydroxylase (PHD) inhibitor and HIF-1 stabilizator. We confirmed that molidustat stabilizes HIF-1α and induces the expression of vascular endothelial growth factor (VEGF) in MDA-MB-231 breast cancer cells, to a similar or even greater extent than hypoxia. Interestingly, decreased cell survival and colony formation capabilities, together with S/G2 cell cycle arrest, were observed after treatment with PHD inhibitor. Importantly, molidustat enhanced the effectiveness of the chemotherapeutic drug, gemcitabine, on cancer cells. Finally, the xenograft model revealed decreased tumor growth in vivo after molidustat treatment. Both in vitro and in vivo analysis showed no differences in the angiogenic potential of endothelial cells treated with tumor-conditioned media or vascularization of the MDA-MB-231 xenografts, respectively. In summary, molidustat treatment exhibits an inhibitory effect on breast cancer cell survival, self-renewal capacity and potentiates the efficacy of chemotherapeutic gemcitabine.

Convergence of Scaffold-Guided Bone Reconstruction and Surgical Vascularization Strategies-A Quest for Regenerative Matching Axial Vascularization

The prevalent challenge facing tissue engineering today is the lack of adequate vascularization to support the growth, function, and viability of tissue engineered constructs (TECs) that require blood vessel supply. The research and clinical community rely on the increasing knowledge of angiogenic and vasculogenic processes to stimulate a clinically-relevant vascular network formation within TECs. The regenerative matching axial vascularization approach presented in this manuscript incorporates the advantages of flap-based techniques for neo-vascularization yet also harnesses the in vivo bioreactor principle in a more directed "like for like" approach to further assist regeneration of the specific tissue type that is lost, such as a corticoperiosteal flap in critical sized bone defect reconstruction.

Application of Blood Oxygenation Level-Dependent Magnetic Resonance Imaging and Intravoxel Incoherent Motion to Assess Bilateral Renal Pathophysiological Processes Induced by Iodixanol Renal Artery First-Pass in Rabbit Model

BACKGROUND

Noninvasive blood oxygen level-dependent imaging and intravoxel incoherent motion sequences were used to assess bilateral renal oxygenation, hemodynamics, and proton diffusion in iodixanol renal artery first-pass in rabbit model.

METHODS

Forty-two rabbits were divided into 2 groups. Saline and iodixanol (1 g iodine/kg, left renal artery) were administered. Magnetic resonance imaging scans were acquired longitudinally at 24 hours prior to and 1, 24, 48, and 72 hours after administration to assess apparent diffusion coefficient, pure molecular diffusion (D), perfusion-related diffusion (D*), volume fraction (f), and relative spin-spin relaxation rate (R2*) values, respectively. The experiment evaluated serum creatinine, histological, and hypoxia-inducible factor 1α immunoexpression.

RESULTS

During 1 to 48 hours, the values of D, f, and D* significantly decreased (P < 0.05), but R2* values significantly increased (P < 0.05) in cortex, outer medulla, and inner medulla after administration of iodixanol through left renal artery, which showed in the 72 hours. The change of the left kidney is noteworthy. Significant negative correlations were observed between apparent diffusion coefficient, D, f, and R2* in cortex, outer medulla, and inner medulla (all P < 0.001, r = -0.635-0.697).

CONCLUSIONS

The first-pass effect of the contrast agent significantly reduces ipsilateral renal perfusion and renal oxygenation, and noninvasive monitoring can be performed by using blood oxygen level-dependent magnetic resonance imaging and intravoxel incoherent motion.

Evaluation of iodine contrast-induced acute kidney injury via different injection routes using BOLD-MRI

Objectives: The aim of this study was to evaluate and compare the severity of acute kidney injury (AKI) induced by iodine contrast agent injection via the renal artery, ear vein, and femoral artery in a rabbit model.

Methods: Blood oxygenation level-dependent (BOLD) magnetic resonance (MR) scans were performed at 24 h prior to contrast injection and 1, 24, 48, and 72 h after injection. Iodixanol injection dose was 1.0, 1.5, 2.0, and 2.5 g iodine/kg, respectively. Hypoxia-inducible factor-1α (HIF-1α) expression was determined, and the BOLD-MRI parameter R2* was used to express tissue oxygenation. Increases in R2* levels reflect reductions in tissue oxygenation. Analyses including R2* value, dose response, histology, and HIF-1α were conducted.

Result: Injection of 1.0 g iodine/kg into the left renal artery resulted in significant increases in renal R2* values after 24 h. This was equivalent to the change of R2* after 2.0 g iodine/kg femoral artery injection. Renal injury scores and HIF-1α expression scores were significantly increased at 24 h. The R2* values exhibited a positive linear correlation with histological injury scores. The maximum effects occurred 24 h after iodixanol injection and returned to baseline levels within 72 h.

Conclusions: The renal injury induced by 1.0 g iodine/kg iodixanol through renal artery injection was more significant than that caused by the same dose of femoral artery and auricular vein injection, while similar to that caused by 2.0 g iodine/kg femoral artery injection.

The pro-angiogenic role of hypoxia inducible factor stabilizer FG-4592 and its application in an in vivo tissue engineering chamber model

Tissue engineering is a promising technology used as an alternative to organ/tissue transplantation which is often limited by donor shortage. The construction of large-sized engineered tissue requires a fast and sufficient vascularization process. Previous studies have shown that hypoxia-inducible factor (HIF) -1α may promote the vascularization process implying that stabilized HIF-1α can be applied in the engineering of large-sized tissue. However, the toxicity and off-target effect of previously reported HIF-1α stabilizers limit their clinical application. FG-4592, a small molecule specific HIF stabilizer, was previously investigated as an anti-anemia drug in a phase-III clinical trial. Here we found that FG-4592 promoted tube formation in an in vitro model of angiogenesis by stabilizing HIF-1α and activating vascular endothelial growth factor (VEGF). When FG-4592 immobilized fibrin gel scaffold was implanted into a subcutaneous tissue engineering chamber, the vascularization process was significantly enhanced through the similar mechanisms which was verified in vitro. We conclude that FG-4592 may serve as a pro-angiogenic molecule for the construction of large-sized engineered tissue where intensive angiogenesis is required.

Hypoxia-inducible factor 1α (HIF-1α) is a major determinant in the enhanced function of muscle-derived progenitors from MRL/MpJ mice

Although the mouse strain Murphy Roths Large (MRL/MpJ) possesses high regenerative potential, the mechanism of tissue regeneration, including skeletal muscle, in MRL/MpJ mice after injury is still unclear. Our previous studies have shown that muscle-derived stem/progenitor cell (MDSPC) function is significantly enhanced in MRL/MpJ mice when compared with MDSPCs isolated from age-matched wild-type (WT) mice. Using mass spectrometry-based proteomic analysis, we identified increased expression of hypoxia-inducible factor (HIF) 1α target genes (expression of glycolytic factors and antioxidants) in sera from MRL/MpJ mice compared with WT mice. Therefore, we hypothesized that HIF-1α promotes the high muscle healing capacity of MRL/MpJ mice by increasing the potency of MDSPCs. We demonstrated that treating MRL/MpJ MDSPCs with dimethyloxalylglycine and CoCl₂ increased the expression of HIF-1α and target genes, including angiogenic and cell survival genes. We also observed that HIF-1α activated the expression of paired box (Pax)7 through direct interaction with the Pax7 promoter. Furthermore, we also observed a higher myogenic potential of MDSPCs derived from prolyl hydroxylase (Phd) 3-knockout (Phd3^-/-) mice, which displayed higher stability of HIF-1α. Taken together, our findings suggest that HIF-1α is a major determinant in the increased MDSPC function of MRL/MpJ mice through enhancement of cell survival, proliferation, and myogenic differentiation.-Sinha, K. M., Tseng, C., Guo, P., Lu, A., Pan, H., Gao, X., Andrews, R., Eltzschig, H., Huard, J. Hypoxia-inducible factor 1α (HIF-1α) is a major determinant in the enhanced function of muscle-derived progenitors from MRL/MpJ mice.

The impact of clay-based hypoxia mimetic hydrogel on human fibroblasts of the periodontal soft tissue

Thixotropic clays have favorable properties for tissue regeneration. Hypoxia mimetic agents showed promising results in pre-clinical models for hard and soft tissue regeneration. It is unclear if clays can be used as carrier for hypoxia mimetic agent in a periodontal regenerative setting. Here, we tested the response of human fibroblasts of the periodontal soft tissue to synthetic clay hydrogels and assessed hypoxia mimetic agent release. Cells were cultured on synthetic clay hydrogels (5.00%-0.15%). We assessed viability and differentiation capacity with resazurin-based toxicity assays, MTT staining, Live-Dead staining, and alkaline phosphatase staining. To reveal the response of fibroblasts to hypoxia mimetic agent-loaded clay hydrogels, cells were exposed to clay supplemented with dimethyloxalylglycine, deferoxamine, l-mimosine, and CoCl₂. Supernatants from hypoxia mimetic agent-loaded clay hydrogels were harvested and replaced with medium at hour 1, 3, 6, 24, 48, and 72. To reveal the hypoxia mimetic capacity of supernatants, vascular endothelial growth factor production in the fibroblasts was assessed in the culture medium. Our data show that clay did not induce relevant toxic effects in the fibroblasts which remained capable to differentiate into alkaline phosphatase-positive cells at the relevant concentrations. Fibroblasts cultured on clay hydrogel loaded with dimethyloxalylglycine, deferoxamine, l-mimosine, and CoCl₂ remained vital, however, no significant increase in vascular endothelial growth factor levels was found in the culture medium. Only dimethyloxalylglycine-loaded clay supernatants taken in the first hours stimulated vascular endothelial growth factor production in fibroblasts. In conclusion no pronounced toxic effects of synthetic clay were observed. Supplementation with dimethyloxalylglycine leads to hypoxia mimetic activity. This pilot study provides first insights into the impact of synthetic clay on periodontal tissue.

Absence of PARP-1 affects Cxcl12 expression by increasing DNA demethylation

Poly [ADP‐ribose] polymerase 1 (PARP‐1) has an inhibitory effect on C‐X‐C motif chemokine 12 gene (Cxcl12) transcription. We examined whether PARP‐1 affects the epigenetic control of Cxcl12 expression by changing its DNA methylation pattern. We observed increased expression of Cxcl12 in PARP‐1 knock‐out mouse embryonic fibroblasts (PARP1−/−) in comparison to wild‐type mouse embryonic fibroblasts (NIH3T3). In the Cxcl12 gene, a CpG island is present in the promoter, the 5′ untranslated region (5′ UTR), the first exon and in the first intron. The methylation state of Cxcl12 in each cell line was investigated by methylation‐specific PCR (MSP) and high resolution melting analysis (HRM). Both methods revealed strong demethylation in PARP1−/− compared to NIH3T3 cells in all four DNA regions. Increased expression of the Ten‐eleven translocation (Tet) genes in PARP1−/− cells indicated that TETs could be important factors in Cxcl12 demethylation in the absence of PARP‐1, accounting for its increased expression. Our results showed that PARP‐1 was a potential upstream player in (de)methylation events that modulated Cxcl12 expression.

Inhibition of prolyl hydroxylases alters cell metabolism and reverses pre-existing diastolic dysfunction in mice

BACKGROUND

Diastolic dysfunction is emerging as a leading cause of heart failure in aging population. Induction of hypoxia tolerance and reprogrammed cell metabolism have emerged as novel therapeutic strategies for the treatment of cardiovascular diseases.

METHODS AND RESULTS

In the present study, we showed that deletion of sirtuin 3 (SIRT3) resulted in a diastolic dysfunction together with a significant increase in the expression of prolyl hydroxylases (PHD) 1 and 2. We further investigated the involvement of PHD in the development of diastolic dysfunction by treating the 12-14 months old mice with a PHD inhibitor, dimethyloxalylglycine (DMOG) for 2 weeks. DMOG treatment increased the expression of hypoxia-inducible factor (HIF)-1α in the endothelium of coronary arteries. This was accompanied by a significant improvement of coronary flow reserve and diastolic function. Inhibition of PHD altered endothelial metabolism by increasing glycolysis and reducing oxygen consumption. Most importantly, treatment with DMOG completely reversed the pre-existing diastolic dysfunction in the endothelial-specific SIRT3 deficient mice.

CONCLUSIONS

Our findings demonstrate that inhibition of PHD and reprogrammed cell metabolism can reverse the pre-existed diastolic dysfunction in SIRT3 deficient mice. Our study provides a potential therapeutic strategy of induction of hypoxia tolerance for patients with diastolic dysfunction associated with coronary microvascular dysfunction, especially in the aging population with reduced SIRT3.

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

Although mammalian kidney regeneration has been reported to occur throughout life, mature kidneys in mammals are not thought to regenerate sufficiently, particularly glomeruli. In our previous work, we found that renal regeneration could be enhanced by decellularized renal scaffolds after partial nephrectomy. In this study, we verified that the enhanced renal regeneration mediated by decellularized scaffolds could be attributed to regenerated glomeruli, which were counted both indirectly and directly under a microscope. Using the isobaric tag for relative and absolute quantitation, we performed proteomics analysis and found that hypoxia-inducible factor (HIF)-1α may be a key factor involved in induced renal regeneration. Dimethyloxyallyl glycine (DMOG), a propyl hydroxylase inhibitor, was applied to stabilize constitutive expression of HIF-1α protein, and small interfering RNA was used to inhibit gene expression. Administration of DMOG to decellularized scaffold-grafted rats improved the induced renal regeneration, whereas siHif1α transfection decreased the regeneration capacity. These findings revealed the critical role of HIF-1α in renal regeneration and provided important insights into our understanding of kidney development and the treatment of various kidney diseases.

Adrenomedullin serves a role in the humoral pathway of delayed remote ischemic preconditioning via a hypoxia-inducible factor-1α-associated mechanism

Remote ischemic preconditioning (RIPC) is a minimally invasive method that provides protection by reducing injury to the heart, kidneys, brain and other tissues or organs. RIPC may improve the outcome in patients undergoing surgery. Although the role of RIPC has been studied, the results remain controversial. It is difficult to confirm whether RIPC has a kidney protective effect and the understanding of the preconditioning signal pathway involved remains unclear. In the present study, the effect of RIPC in urology was evaluated. The protection against renal damage was assessed by investigating the potential mediator, hypoxia-inducible factor-1α (HIF-1α), and the functional adrenomedullin (ADM) pathway. Male Sprague-Dawley (SD) rats were used in the present study. The animal model of kidney damage induced by ischemia reperfusion (IR) was used to investigate the protective effect of the acute and delayed phase RIPC. Furthermore, the protective effects of RIPC mediated by a HIF-1α-ADM pathway were assessed. The indexes of renal function and oxidative damage indicators were measured by Cr, BUN, mALB, β2-MG, MPO, MDA and SOD assays, and the expression of HIF-1α and ADM were detected by western blot analysis, immunohistochemistry and ELISA assays. Tubular score, determined using hematoxylin and eosin staining, was used to evaluate renal tissue damage. Applying RIPC prevented IR-induced renal dysfunction and oxidative damage by decreasing Cr, BUN, mALB, β2-MG, MPO, MDA levels and increasing SOD activity. Findings showed that delayed RIPC had an improved effect compared with acute treatment. Delayed RIPC also upregulated the expression of HIF-1α and ADM, indicating that the protective effect of the delayed RIPC may be associated with a HIF-1α-ADM-mediated mechanism. The effect of the delayed RIPC to reduce IR-induced renal damage and increase ADM expression was enhanced by HIF-1α agonists DMOG and BAY 85–3934, whereas the effect was whittled by HIF-1α antagonists YC-1 and 2-MeOE2. Furthermore, receiving ADM also offered protection to the kidney in comparison with the IR+Vehicle group. These findings suggest that RIPC prevents IR-mediated renal damage by HIF-1α via an ADM humoral pathway. In the present study, RIPC provided an effective renal protection. ADM could also offer protection regulated by HIF-1α in renal tissue. However, the mechanism of ADM as a protective factor in RIPC requires further research.

Haemodynamically stimulated and in vivo generated axially vascularized soft-tissue free flaps for closure of complex defects: Evaluation in a small animal model

The arteriovenous (AV) loop model permits the creation of significant volumes of axially vascularized tissue that represents an alternative to conventional free flaps, circumventing their common limitations. However, such AV loop-based flaps have never before been examined in standardized animal models with respect to their suitability for reconstruction of critical bone-exposing defects. In the course of our preliminary studies, we implemented a novel defect model in rats that provides standardized and critical wound conditions and evaluated whether AV loop-generated flaps are suitable for free microsurgical transfer and closure of composite defects. We compared three groups of rodents with similar scapular defects: one received the AV flap, whereas controls were left to heal by secondary intention or with supplementary acellular matrix alone. To create the flaps, AV loops were placed into subcutaneous Teflon chambers filled with acellular matrix and transferred to the thigh region. Flap maturation was evaluated by histological analysis of angiogenesis and cell migration at days 14 and 28 after loop creation. Flap transfer to the scapular region and microsurgical anastomoses were performed after 14 days. Postoperative defect closure and perfusion were continually compared between groups. Within the AV flap chamber, the mean vessel number, cell count and the proportion of proliferating cells increased significantly over time. The novel defect model revealed that stable wound coverage with homogeneous vascular integration was achieved by AV loop-vascularized soft-tissue free flaps compared with controls. In summary, our study indicates for the first time that complex composite defects in rats can successfully be treated with AV loop-based free flaps.

Flow-Induced Axial Vascularization: The Arteriovenous Loop in Angiogenesis and Tissue Engineering

Fabrication of a viable vascular network providing oxygen supply is identified as one crucial limiting factor to generate more complex three-dimensional constructs. The arteriovenous loop model provides initial blood supply and has a high angioinductive potency, making it suitable for vascularization of larger, tissue-engineered constructs. Also because of its angiogenic capabilities the arteriovenous loop is recently also used as a model to evaluate angiogenesis in vivo. This review summarizes the history of the arteriovenous loop model in research and its technical and surgical aspects. Through modifications of the isolation chamber and its containing matrices, tissue generation can be enhanced. In addition, matrices can be used as release systems for local application of growth factors, such as vascular endothelial growth factor and basic fibroblast growth factor, to affect vascular network formation. A special focus in this review is set on the assessment of angiogenesis in the arteriovenous loop model. This model provides good conditions for assessment of angiogenesis with the initial cell-free environment of the isolation chamber, which is vascularized by the arteriovenous loop. Because of the angiogenic capabilities of the arteriovenous loop model, different attempts were performed to create functional tissue in the isolation chamber for potential clinical application. Arteriovenous loops in combination with autologous bone marrow aspirate were already used to reconstruct large bone defects in humans.

Axially vascularized tissue-engineered bone constructs retain their in vivo angiogenic and osteogenic capacity after high-dose irradiation

In order to introduce bone tissue engineering to the field of oncological reconstruction, we are investigating for the first time the effect of various doses of ionizing irradiation on axially vascularized bone constructs. Synthetic bone constructs were created and implanted in 32 Lewis rats. Each construct was axially vascularized through an arteriovenous loop made by direct anastomosis of the saphenous vessels. After 2 weeks, the animals received ionizing irradiation of 9 Gy, 12 Gy and 15 Gy, and were accordingly classified to groups I, II and III, respectively. Group IV was not irradiated and acted as a control. Tissue generation, vascularity, cellular proliferation and apoptosis were investigated either 2 or 5 weeks after irradiation through micro-computed tomography, histomorphometry and real-time polymerase chain reaction (PCR). At 2 weeks after irradiation, tissue generation and central vascularity were significantly lower and apoptosis was significantly higher in groups II and III than group IV, but without signs of necrosis. Cellular proliferation was significantly lower in groups I and II. After 5 weeks, the irradiated groups showed improvement in all parameters in relation to the control group, indicating a retained capacity for angiogenesis after irradiation. PCR results confirmed the expression of osteogenesis-related genes in all irradiated groups. Dense collagen was detected 5 weeks after irradiation, and one construct showed discrete islands of bone indicating a retained osteogenic capacity after irradiation. This demonstrates for the first time that axial vascularization was capable of supporting a synthetic bone construct after a high dose of irradiation that is comparable to adjuvant radiotherapy. Copyright © 2016 John Wiley & Sons, Ltd.

Application of BOLD MRI and DTI for the evaluation of renal effect related to viscosity of iodinated contrast agent in a rat model

PURPOSE

To evaluate the effects of viscosity of contrast agent (CA) on intrarenal oxygenation and diffusion as measured by blood oxygenation level-dependent (BOLD) magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) in a rat model.

MATERIALS AND METHODS

Radiocontrast iodixanol formulated in three viscosities were designated 270, 320, and 350 (mg iodine/mL). Sixty-three male Wistar rats were divided into four groups. Saline and iodixanol (4 g iodine/kg) were administered. MR images were acquired on a 3.0T scanner at baseline and at 1 hour, 24 hours, 48 hours, and 72 hours postinjection of solutions. BOLD-MRI was performed with a multiple gradient-recalled-echo sequence. The changes in R2*, apparent diffusion coefficient (ADC), fractional anisotropy (FA), histology, and hypoxia-inducible factor-1α (HIF-1α) immunoexpression were evaluated. The R2*, ADC, and FA values were normalized to baseline to calculate ΔR2*, ΔADC, and ΔFA.

RESULTS

Compared with baseline levels, distinct elevation of ΔR2* (P < 0.05) and obvious decrease in ΔADC (P < 0.01) and ΔFA (P < 0.05) were observed in all the anatomical compartments at 1 hour after administration of CA. The absolute values in ΔR2*, ΔADC, and ΔFA increased with increases in CA viscosity, and differed significantly between the CA groups in renal cortex (CO), outer stripe of outer medulla (OSOM), and inner stripe of outer medulla (ISOM) (all P < 0.05). A significant positive correlation was observed between ΔR2* and HIF-1α expression (P < 0.001, r = 0.75). Significant negative correlations were observed between ΔADC, ΔFA, and pathologies in CO, OSOM, ISOM (all P < 0.001, r = -0.68-0.87; all P < 0.001, r = -0.60-0.66).

CONCLUSION

The effect of CA viscosity on intrarenal oxygenation and diffusion was viscosity-dependent, and was identified using BOLD-MRI and DTI.

LEVEL OF EVIDENCE

1 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2017;46:1320-1331.

Bone Tissue Engineering Under Xenogeneic-Free Conditions in a Large Animal Model as a Basis for Early Clinical Applicability

For decades, researchers have been developing a range of promising strategies in bone tissue engineering with the aim of producing a significant clinical benefit over existing therapies. However, a major problem concerns the traditional use of xenogeneic substances for the expansion of cells, which complicates direct clinical transfer. The study's aim was to establish a totally autologous sheep model as a basis for further preclinical studies and future clinical application. Ovine mesenchymal stromal cells (MSC) were cultivated in different concentrations (0%, 2%, 5%, 10%, and 25%) of either autologous serum (AS) or fetal calf serum (FCS). With an increase of serum concentration, enhanced metabolic activity and proliferation could be observed. There were minor differences between MSC cultivated in AS or FCS, comparing gene and protein expression of osteogenic and stem cell markers, morphology, and osteogenic differentiation. MSC implanted subcutaneously in the sheep model, together with a nanostructured bone substitute, either in stable block or moldable putty form, induced similar vascularization and remodeling of the bone substitute irrespective of cultivation of MSC in AS or FCS and osteogenic differentiation. The bone substitute in block form together with MSC proved particularly advantageous in the induction of ectopic bone formation compared to the cell-free control and putty form. It could be demonstrated that AS is suitable for replacement of FCS for cultivation of ovine MSC for bone tissue engineering purposes. Substantial progress has been made in the development of a strictly xenogeneic-free preclinical animal model to bring future clinical application of bone tissue engineering strategies within reach.

Hypoxia and HIF-1 activation in bacterial infections

For most of the living beings, oxygen is one of the essential elements required to sustain life. Deprivation of oxygen causes tissue hypoxia and this severely affects host cell and organ functions. Tissue hypoxia is a prominent microenvironmental condition occurring in infections and there is a body of evidence that hypoxia and inflammation are interconnected with each other. The primary key factor mediating the mammalian hypoxic response is hypoxia inducible factor (HIF)-1, which regulates oxygen homeostasis on cellular, tissue and organism level. Recent studies show that HIF-1 plays a central role in angiogenesis, cancer and cardiovascular disease but also in bacterial infections. Activation of HIF-1 depends on the nature of the pathogen and the characteristics of infections in certain hosts. Up to date, it is not completely clear whether the phenomenon of HIF-1 activation in infections has a protective or detrimental effect on the host. In this review, we give an overview of whether and how hypoxia and HIF-1 affect the course of infections.

The Arteriovenous (AV) Loop in a Small Animal Model to Study Angiogenesis and Vascularized Tissue Engineering

A functional blood vessel network is a prerequisite for the survival and growth of almost all tissues and organs in the human body. Moreover, in pathological situations such as cancer, vascularization plays a leading role in disease progression. Consequently, there is a strong need for a standardized and well-characterized in vivo model in order to elucidate the mechanisms of neovascularization and develop different vascularization approaches for tissue engineering and regenerative medicine. We describe a microsurgical approach for a small animal model for induction of a vascular axis consisting of a vein and artery that are anastomosed to an arteriovenous (AV) loop. The AV loop is transferred to an enclosed implantation chamber to create an isolated microenvironment in vivo, which is connected to the living organism only by means of the vascular axis. Using 3D imaging (MRI, micro-CT) and immunohistology, the growing vasculature can be visualized over time. By implanting different cells, growth factors and matrices, their function in blood vessel network formation can be analyzed without any disturbing influences from the surroundings in a well controllable environment. In addition to angiogenesis and antiangiogenesis studies, the AV loop model is also perfectly suited for engineering vascularized tissues. After a certain prevascularization time, the generated tissues can be transplanted into the defect site and microsurgically connected to the local vessels, thereby ensuring immediate blood supply and integration of the engineered tissue. By varying the matrices, cells, growth factors and chamber architecture, it is possible to generate various tissues, which can then be tailored to the individual patient's needs.

Role of HIF-1α signaling pathway in osteoarthritis: a systematic review

Osteoarthritis (OA) is the most common form of arthritis and is frequently diagnosed and managed in primary care; it is characterized by loss of articular hyaline cartilage, which is a unique connective tissue that physiologically lacks blood vessels. Articular cartilage survives in a microenvironment devoid of oxygen, which is regulated by hypoxia inducible factor (HIF-1α). HIF-1α is considered the main transcriptional regulator of cellular and developmental response to hypoxia. To date, the relevance of HIF-1α in the assessment of cartilage has increased since its participation is essential in the homeostasis of this tissue. Taking into account the new emerging insights of HIF-1α in the scientific literature in the last years, we focused the present review on the potential role of HIF-1α signaling pathway in OA development, especially in how some genetic factors may influence the maintenance or breakdown of articular cartilage.

Selective isolation and characterization of primary cells from normal breast and tumors reveal plasticity of adipose derived stem cells

Background

There is a need to establish more cell lines from breast tumors in contrast to immortalized cell lines from metastatic effusions in order to represent the primary tumor and not principally metastatic biology of breast cancer. This investigation describes the simultaneous isolation, characterization, growth and function of primary mammary epithelial cells (MEC), mesenchymal cells (MES) and adipose derived stem cells (ADSC) from four normal breasts, one inflammatory and one triple-negative ductal breast tumors.

Methods

A total of 17 cell lines were established and gene expression was analyzed for MEC and MES (n = 42) and ADSC (n = 48) and MUC1, pan-KRT, CD90 and GATA-3 by immunofluorescence. DNA fingerprinting to track cell line identity was performed between original primary tissues and isolates. Functional studies included ADSC differentiation, tumor MES and MEC invasion co-cultured with ADSC-conditioned media (CM) and MES adhesion and growth on 3D-printed scaffolds.

Results

Comparative analysis showed higher gene expression of EPCAM, CD49f, CDH1 and KRTs for normal MEC lines; MES lines e.g. Vimentin, CD10, ACTA2 and MMP9; and ADSC lines e.g. CD105, CD90, CDH2 and CDH11. Compared to the mean of all four normal breast cell lines, both breast tumor cell lines demonstrated significantly lower ADSC marker gene expression, but higher expression of mesenchymal and invasion gene markers like SNAI1 and MMP2. When compared with four normal ADSC differentiated lineages, both tumor ADSC showed impaired osteogenic and chondrogenic but enhanced adipogenic differentiation and endothelial-like structures, possibly due to high PDGFRB and CD34. Addressing a functional role for overproduction of adipocytes, we initiated 3D-invasion studies including different cell types from the same patient. CM from ADSC differentiating into adipocytes induced tumor MEC 3D-invasion via EMT and amoeboid phenotypes. Normal MES breast cells adhered and proliferated on 3D-printed scaffolds containing 20 fibers, but not on 2.5D-printed scaffolds with single fiber layers, important for tissue engineering.

Conclusion

Expression analyses confirmed successful simultaneous cell isolations of three different phenotypes from normal and tumor primary breast tissues. Our cell culture studies support that breast-tumor environment differentially regulates tumor ADSC plasticity as well as cell invasion and demonstrates applications for regenerative medicine.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-016-0688-2) contains supplementary material, which is available to authorized users.

Characterization of bone marrow-derived mesenchymal stem cells from dimethyloxallyl glycine-preconditioned mice: Evaluation of the feasibility of dimethyloxallyl glycine as a mobilization agent

The prolyl hydroxylase inhibitor dimethyloxallyl glycine (DMOG) has been increasingly studied with regards to stem cell therapy. Previous studies have demonstrated that endogenous mesenchymal stem cells (MSCs) may be mobilized into peripheral circulation by pharmaceutical preconditioning. In addition, our previous study confirmed that DMOG, as a novel mobilization agent, could induce mouse/rat MSC migration into peripheral blood circulation. Therefore, the present study conducted studies to characterize bone marrow-derived MSCs (BM-MSCs) collected from mice following DMOG intraperitoneal injection. The surface antigen immune phenotype, differentiation capability, proliferative ability, migratory capacity and paracrine capacity of the BM-MSCs collected from DMOG-preconditioned mice (DBM-MSCs) or normal saline-treated mice (NBM-MSCs) were evaluated by means of flow cytometry, differentiation induction, Cell Counting kit-8, Transwell assay and enzyme-linked immunosorbent assay, respectively. Compared with NBM-MSCs, DBM-MSCs displayed a similar immune phenotype and multilineage differentiation capability, reduced proliferative ability and migratory capacity, and similar transforming growth factor and platelet-derived growth factor secretion capacity. These results provide a novel insight into the biological properties of BM-MSCs from mice preconditioned with DMOG. DBM-MSCs exhibited slightly distinct characteristics to NBM-MSCs; however, they may have therapeutic potential for future stem cell therapy. In addition, the present study suggested that DMOG may be used as a novel mobilization agent in future clinical trials as no adverse effects were observed.

The potential role of telocytes in Tissue Engineering and Regenerative Medicine

Research and ideas for potential applications in the field of Tissue Engineering (TE) and Regenerative Medicine (RM) have been constantly increasing over recent years, basically driven by the fundamental human dream of repairing and regenerating lost tissue and organ functions. The basic idea of TE is to combine cells with putative stem cell properties with extracellular matrix components, growth factors and supporting matrices to achieve independently growing tissue. As a side effect, in the past years, more insights have been gained into cell-cell interaction and how to manipulate cell behavior. However, to date the ideal cell source has still to be found. Apart from commonly known various stem cell sources, telocytes (TC) have recently attracted increasing attention because they might play a potential role for TE and RM. It becomes increasingly evident that TC provide a regenerative potential and act in cellular communication through their network-forming telopodes. While TE in vitro experiments can be the first step, the key for elucidating their regenerative role will be the investigation of the interaction of TC with the surrounding tissue. For later clinical applications further steps have to include an upscaling process of vascularization of engineered tissue. Arteriovenous loop models to vascularize such constructs provide an ideal platform for preclinical testing of future therapeutic concepts in RM. The following review article should give an overview of what is known so far about the potential role of TC in TE and RM.

Dimethyloxalylglycine treatment of brain-dead donor rats improves both donor and graft left ventricular function after heart transplantation

OBJECTIVE

Hypoxia inducible factor (HIF)-1 pathway signalling has a protective effect against ischemia/reperfusion injury. The prolyl-hydroxylase inhibitor dimethyloxalylglycine (DMOG) activates the HIF-1 pathway by stabilizing HIF-1α. In a rat model of brain death (BD)-associated donor heart dysfunction we tested the hypothesis that pre-treatment of brain-dead donors with DMOG would result in a better graft heart condition.

METHODS

BD was induced in anesthetized Lewis rats by inflating a subdurally placed balloon catheter. Controls underwent sham operations. Then, rats were injected with an intravenous dose of DMOG (30 mg/kg) or an equal volume of physiologic saline. After 5 hours of BD or sham operation, hearts were perfused with a cold (4°C) preservation solution (Custodiol; Dr. Franz Köhler Chemie GmbH; Germany), explanted, stored at 4°C in Custodiol, and heterotopically transplanted. Graft function was evaluated 1.5 hours after transplantation.

RESULTS

Compared with control, BD was associated with decreased left ventricular systolic and diastolic function. DMOG treatment after BD improved contractility (end-systolic pressure volume relationship E'max: 3.7 ± 0.6 vs 3.1 ± 0.5 mm Hg/µ1; p < 0.05) and left ventricular stiffness (end-diastolic pressure volume relationship: 0.13 ± 0.03 vs 0.31 ± 0.06 mm Hg/µ1; p < 0.05) 5 hours later compared with the brain-dead group. After heart transplantation, DMOG treatment of brain-dead donors significantly improved the altered systolic function and decreased inflammatory infiltration, cardiomyocyte necrosis, and DNA strand breakage. In addition, compared with the brain-dead group, DMOG treatment moderated the pro-apoptotic changes in the gene and protein expression.

CONCLUSIONS

In a rat model of potential brain-dead heart donors, pre-treatment with DMOG resulted in improved early recovery of graft function after transplantation. These results support the hypothesis that activation of the HIF-1 pathway has a protective role against BD-associated cardiac dysfunction.