Desferrioxamine-driven upregulation of angiogenic factor expression by human bone marrow stromal cells

Hypoxia and Hypoxia Mimetic Agents As Potential Priming Approaches to Empower Mesenchymal Stem Cells

Mesenchymal stem cells (MSC) exhibit self-renewal capacity and multilineage differentiation potential, making them attractive for research and clinical application. The properties of MSC can vary depending on specific micro-environmental factors. MSC resides in specific niches with low oxygen concentrations, where oxygen functions as a metabolic substrate and a signaling molecule. Conventional physical incubators or chemically hypoxia mimetic agents are applied in cultures to mimic the original low oxygen tension settings where MSC originated. This review aims to focus on the current knowledge of the effects of various physical hypoxic conditions and widely used hypoxia-mimetic agents-PHD inhibitors on mesenchymal stem cells at a cellular and molecular level, including proliferation, stemness, differentiation, viability, apoptosis, senescence, migration, immunomodulation behaviors, as well as epigenetic changes.

3D Biomimetic Calcified Cartilaginous Callus that Induces Type H Vessels Formation and Osteoclastogenesis

The formation of a calcified cartilaginous callus (CACC) is crucial during bone repair. CACC can stimulate the invasion of type H vessels into the callus to couple angiogenesis and osteogenesis, induce osteoclastogenesis to resorb the calcified matrix, and promote osteoclast secretion of factors to enhance osteogenesis, ultimately achieving the replacement of cartilage with bone. In this study, a porous polycaprolactone/hydroxyapatite-iminodiacetic acid-deferoxamine (PCL/HA-SF-DFO) 3D biomimetic CACC is developed using 3D printing. The porous structure can mimic the pores formed by the matrix metalloproteinase degradation of the cartilaginous matrix, HA-containing PCL can mimic the calcified cartilaginous matrix, and SF anchors DFO onto HA for the slow release of DFO. The in vitro results show that the scaffold significantly enhances angiogenesis, promotes osteoclastogenesis and resorption by osteoclasts, and enhances the osteogenic differentiation of bone marrow stromal stem cells by promoting collagen triple helix repeat-containing 1 expression by osteoclasts. The in vivo results show that the scaffold significantly promotes type H vessels formation and the expression of coupling factors to promote osteogenesis, ultimately enhancing the regeneration of large-segment bone defects in rats and preventing dislodging of the internal fixation screw. In conclusion, the scaffold inspired by biological bone repair processes effectively promotes bone regeneration.

Strategies to Promote Vascularization in 3D Printed Tissue Scaffolds: Trends and Challenges

Three-dimensional (3D) printing techniques for scaffold fabrication have shown promising advancements in recent years owing to the ability of the latest high-performance printers to mimic the native tissue down to submicron scales. Nevertheless, host integration and performance of scaffolds in vivo have been severely limited owing to the lack of robust strategies to promote vascularization in 3D printed scaffolds. As a result, researchers over the past decade have been exploring strategies that can promote vascularization in 3D printed scaffolds toward enhancing scaffold functionality and ensuring host integration. Various emerging strategies to enhance vascularization in 3D printed scaffolds are discussed. These approaches include simple strategies such as the enhancement of vascular in-growth from the host upon implantation by scaffold modifications to complex approaches wherein scaffolds are fabricated with their own vasculature that can be directly anastomosed or microsurgically connected to the host vasculature, thereby ensuring optimal integration. The key differences among the techniques, their pros and cons, and the future opportunities for utilizing each technique are highlighted here. The Review concludes with the current limitations and future directions that can help 3D printing emerge as an effective biofabrication technique to realize tissues with physiologically relevant vasculatures to ultimately accelerate clinical translation.

Bone Marrow Aspirate Concentrate: Its Uses in Osteoarthritis

Human bone marrow (BM) is a kind of source of mesenchymal stem cells (MSCs) as well as growth factors and cytokines that may aid anti-inflammation and regeneration for various tissues, including cartilage and bone. However, since MSCs in BM usually occupy only a small fraction (0.001%) of nucleated cells, bone marrow aspirate concentrate (BMAC) for cartilage pathologies, such as cartilage degeneration, defect, and osteoarthritis, have gained considerable recognition in the last few years due to its potential benefits including disease modifying and regenerative capacity. Although further research with well-designed, randomized, controlled clinical trials is needed to elucidate the exact mechanism of BMAC, this may have the most noteworthy effect in patients with osteoarthritis. The purpose of this article is to review the general characteristics of BMAC, including its constituent, action mechanisms, and related issues. Moreover, this article aims to summarize the clinical outcomes of BMAC reported to date.

Recent advances in 3D printing: vascular network for tissue and organ regeneration

Over the past years, the fabrication of adequate vascular networks has remained the main challenge in engineering tissues due to technical difficulties, while the ultimate objective of tissue engineering is to create fully functional and sustainable organs and tissues to transplant in the human body. There have been a number of studies performed to overcome this limitation, and as a result, 3D printing has become an emerging technique to serve in a variety of applications in constructing vascular networks within tissues and organs. 3D printing incorporated technical approaches allow researchers to fabricate complex and systematic architecture of vascular networks and offer various selections for fabrication materials and printing techniques. In this review, we will discuss materials and strategies for 3D printed vascular networks as well as specific applications for certain vascularized tissue and organ regeneration. We will also address the current limitations of vascular tissue engineering and make suggestions for future directions research may take.

The Reparative Abilities of Menstrual Stem Cells Modulate the Wound Matrix Signals and Improve Cutaneous Regeneration

Considerable advances have been made toward understanding the cellular and molecular mechanism of wound healing, however, treatments for chronic wounds remain elusive. Emerging concepts utilizing mesenchymal stem cells (MSCs) from umbilical cord, adipose tissue and bone marrow have shown therapeutical advantages for wound healing. Based on this positive outcome, efforts to determine the optimal sources for MSCs are required in order to improve their migratory, angiogenic, immunomodulatory, and reparative abilities. An alternative source suitable for repetitive, non-invasive collection of MSCs is from the menstrual fluid (MenSCs), displaying a major practical advantage over other sources. This study aims to compare the biological functions and the transcriptomic pattern of MenSCs with umbilical cord MSCs in conditions resembling the wound microenvironment. Consequently, we correlate the specific gene expression signature from MenSCs with changes of the wound matrix signals in vivo. The direct comparison revealed a superior clonogenic and migratory potential of MenSCs as well as a beneficial effect of their secretome on human dermal fibroblast migration in vitro. Furthermore, MenSCs showed increased immunomodulatory properties, inhibiting T-cell proliferation in co-culture. We further, investigated the expression of selected genes involved in wound repair (growth factors, cytokines, chemokines, AMPs, MMPs) and found considerably higher expression levels in MenSCs (ANGPT1 1.5-fold; PDGFA 1.8-fold; PDGFB 791-fold; MMP3 21.6-fold; ELN 13.4-fold; and MMP10 9.2-fold). This difference became more pronounced under a pro-inflammatory stimulation, resembling wound bed conditions. Locally applied in a murine excisional wound splinting model, MenSCs showed a significantly improved wound closure after 14 days, as well as enhanced neovascularization, compared to the untreated group. Interestingly, analysis of excised wound tissue revealed a significantly higher expression of VEGF (1.42-fold) among other factors, translating an important conversion of the matrix signals in the wound site. Furthermore, histological analysis of the wound tissue from MenSCs-treated group displayed a more mature robust vascular network and a genuinely higher collagen content confirming the pro-angiogenic and reparative effect of MenSCs treatment. In conclusion, the superior clonogenicity, immunosuppressive and migration potential in combination with specific paracrine signature of MenSCs, resulted in an enhanced wound healing and cutaneous regeneration process.

Preconditioning of adipose tissue-derived mesenchymal stem cells with deferoxamine increases the production of pro-angiogenic, neuroprotective and anti-inflammatory factors: Potential application in the treatment of diabetic neuropathy

Diabetic neuropathy (DN) is one of the most frequent and troublesome complications of diabetes mellitus. Evidence from diabetic animal models and diabetic patients suggests that reduced availability of neuroprotective and pro-angiogenic factors in the nerves in combination with a chronic pro-inflammatory microenvironment and high level of oxidative stress, contribute to the pathogenesis of DN. Mesenchymal stem cells (MSCs) are of great interest as therapeutic agents for regenerative purposes, since they can secrete a broad range of cytoprotective and anti-inflammatory factors. Therefore, the use of the MSC secretome may represent a promising approach for DN treatment. Recent data indicate that the paracrine potential of MSCs could be boosted by preconditioning these cells with an environmental or pharmacological stimulus, enhancing their therapeutic efficacy. In the present study, we observed that the preconditioning of human adipose tissue-derived MSCs (AD-MSCs) with 150μM or 400μM of the iron chelator deferoxamine (DFX) for 48 hours, increased the abundance of the hypoxia inducible factor 1 alpha (HIF-1α) in a concentration dependent manner, without affecting MSC morphology and survival. Activation of HIF-1α led to the up-regulation of the mRNA levels of pro-angiogenic factors like vascular endothelial growth factor alpha and angiopoietin 1. Furthermore this preconditioning increased the expression of potent neuroprotective factors, including nerve growth factor, glial cell-derived neurotrophic factor and neurotrophin-3, and cytokines with anti-inflammatory activity like IL4 and IL5. Additionally, we observed that these molecules, which could also be used as therapeutics, were also increased in the secretome of MSCs preconditioned with DFX compared to the secretome obtained from non-preconditioned cells. Moreover, DFX preconditioning significantly increased the total antioxidant capacity of the MSC secretome and they showed neuroprotective effects when evaluated in an in vitro model of DN. Altogether, our findings suggest that DFX preconditioning of AD-MSCs improves their therapeutic potential and should be considered as a potential strategy for the generation of new alternatives for DN treatment.

Angiogenic Capacity of Periodontal Ligament Stem Cells Pretreated with Deferoxamine and/or Fibroblast Growth Factor-2

Periodontal ligament stem cells (PDLSCs) represent a good source of multipotent cells for cell-based therapies in regenerative medicine. The success rate of these treatments is severely dependent on the establishment of adequate vasculature in order to provide oxygen and nutrients to the transplanted cells. Pharmacological preconditioning of stem cells has been proposed as a promising method to augment their therapeutic efficacy. In this study, the aim was to improve the intrinsic angiogenic properties of PDLSCs by in vitro pretreatment with deferoxamine (DFX; 100μM), fibroblast growth factor-2 (FGF-2; 10ng/mL) or both substances combined. An antibody array revealed the differential expression of several proteins, including vascular endothelial growth factor (VEGF) and placental growth factor (PlGF). ELISA data confirmed a 1.5 to 1.8-fold increase in VEGF for all tested conditions. Moreover, 48 hours after the removal of DFX, VEGF levels remained elevated (1.8-fold) compared to control conditions. FGF-2 and combination treatment resulted in a 5.4 to 13.1-fold increase in PlGF secretion, whereas DFX treatment had no effect. Furthermore, both PDLSCs as pretreated PDLSCs induced endothelial migration. Despite the significant elevated VEGF levels of pretreated PDLSCs, the induced endothelial migration was not higher by pretreated PDLSCs. We find that the observed induced endothelial cell motility was not dependent on VEGF, since blocking the VEGFR1-3 with Axitinib (0.5nM) did not inhibit endothelial motility towards PDLSCs. Taken together, this study provides evidence that preconditioning with DFX and/or FGF-2 significantly improves the angiogenic secretome of PDLSCs, in particular VEGF and PlGF secretion. However, our data suggest that VEGF is not the only player when it comes to influencing endothelial behavior by the PDLSCs.

Deferoxamine preconditioning to restore impaired HIF-1α-mediated angiogenic mechanisms in adipose-derived stem cells from STZ-induced type 1 diabetic rats

OBJECTIVES

Both excessive and insufficient angiogenesis are associated with progression of diabetic complications, of which poor angiogenesis is an important feature. Currently, adipose-derived stem cells (ADSCs) are considered to be a promising source to aid therapeutic neovascularization. However, functionality of these cells is impaired by diabetes which can result from a defect in hypoxia-inducible factor-1 (HIF-1), a key mediator involved in neovascularization. In the current study, we sought to explore effectiveness of pharmacological priming with deferoxamine (DFO) as a hypoxia mimetic agent, to restore the compromised angiogenic pathway, with the aid of ADSCs derived from streptozotocin (STZ)-induced type 1 diabetic rats ('diabetic ADSCs').

MATERIALS AND METHODS

Diabetic ADSCs were treated with DFO and compared to normal and non-treated diabetic ADSCs for expression of HIF-1α, VEGF, FGF-2 and SDF-1, at mRNA and protein levels, using qRT-PCR, western blotting and ELISA assay. Activity of matrix metalloproteinases -2 and -9 were measured using a gelatin zymography assay. Angiogenic potential of conditioned media derived from normal, DFO-treated and non-treated diabetic ADSCs were determined by in vitro (in HUVECs) and in vivo experiments including scratch assay, three-dimensional tube formation testing and surgical wound healing models.

RESULTS

DFO remarkably enhanced expression of noted genes by mRNA and protein levels and restored activity of matrix metalloproteinases -2 and -9. Compromised angiogenic potential of conditioned medium derived from diabetic ADSCs was restored by DFO both in vitro and in vivo experiments.

CONCLUSION

DFO preconditioning restored neovascularization potential of ADSCs derived from diabetic rats by affecting the HIF-1α pathway.

Arthroscopic Approach to Osteochondral Defects, Impingement, and Instability

Osteochondral defects, impingement, and instability of the ankle are common injuries in athletes. In this article, we review these diagnoses and their treatment options, with a focus on arthroscopic approaches. The treatment options continue to evolve, supported by innovation and outcome studies. In this article, we describe the advantages and disadvantages of both open and arthroscopic treatments using published evidence.

Local injection of deferoxamine improves neovascularization in ischemic diabetic random flap by increasing HIF-1α and VEGF expression

BACKGROUND

Although the systemic administration of deferoxamine (DFO) is protective in experimental models of normal ischemic flap and diabetic wound, its effect on diabetic flap ischemia using a local injection remains unknown.

OBJECTIVE

To explore the feasibility of local injection of DFO to improve the survival of ischemic random skin flaps in streptozotocin (STZ)-induced diabetic mice.

METHODS

Ischemic random skin flaps were made in 125 mice. Animals were divided into the DFO-treated (n = 20), PBS-treated (n = 16) and untreated (n = 16) groups. Surviving area, vessel density, and expression of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α (HIF-1α) were evaluated on the seventh day after local injection.

RESULTS

The viability of DFO-treated flap was significantly enhanced, with increased regional blood perfusion and capillary density compared with those in the two control groups. Fluorescence-activated cell sorting (FACS) analysis demonstrated a marked increase in systemic Flk-1+/CD11b- endothelial progenitor cells (EPCs) in DFO-treated mice. Furthermore, the expression of VEGF and HIF-1α was increased not only in diabetic flap tissue, but also in dermal fibroblasts cultured under hyperglycemic and hypoxic conditions.

CONCLUSIONS

Local injection of DFO could exert preventive effects against skin flap necrosis in STZ-induced diabetic mice by elevating the expression of HIF-1α and VEGF, increased EPC mobilization, which all contributed to promote ischemic diabetic flap survival.

Effects of tumor microenviromental factors on VEGF expression

The expression of vascular endothelial growth factor (VEGF) is regulated by microenvironmental factors within the tumors, such as hypoxia, free radicals, pH imbalance and nutrient deficiency. The purpose of this study was to observe VEGF activity in tumor cells under different stress conditions. A plasmid was generated, consisting of green fluorescent protein (GFP) fused to a 1,217-bp sequence, which was located downstream and upstream of the transcriptional start site of VEGF, respectively. The plasmid was stably transfected into 4T1 mouse breast carcinoma cells. Cells were cultured in a medium with nitric oxide (NO) donor sodium nitroprusside (SNP), hypoxia-mimetic agent deferoxamine mesylate (DFX), H₂O₂, absence of serum and lowered or elevated pH, or were heat-shocked, followed by measurement of VEGF activity by reverse transcription polymerase chain reaction (RT-PCR) and ELISA. Hypoxia, SNP and H₂O₂ led to increments of VEGF mRNA and protein expression, as well as of GFP expression. The pH alterations, serum deprivation and heat shock reduced VEGF mRNA expression, but had little effect on GFP expression. The results demonstrated that VEGF expression may be influenced by a number of microenvironmental factors and these factors may play important roles in regulating VEGF expression during tumorigenesis.

Physiological oxygen level is critical for modeling neuronal metabolism in vitro

In vitro models are important tools for studying the mechanisms that govern neuronal responses to injury. Most neuronal culture methods employ nonphysiological conditions with regard to metabolic parameters. Standard neuronal cell culture is performed at ambient (21%) oxygen levels, whereas actual tissue oxygen levels in the mammalian brain range from 1% to 5%. In this study, we examined the consequences of oxygen level on the viability and metabolism of primary cultures of cortical neurons. Our results indicate that physiological oxygen level (5% O(2)) has a beneficial effect on cortical neuronal survival and mitochondrial function in vitro. Moreover, oxygen level affects metabolic fluxes: glucose uptake and glycolysis was enhanced at physiological oxygen level, whereas glucose oxidation and fatty acid oxidation were reduced. Adenosine monophosphate-activated protein kinase (AMPK) was more activated in 5% O(2) and appears to play a role in these metabolic effects. Inhibiting AMPK activity with compound C decreased glucose uptake, intracellular ATP level, and viability in neurons cultured in 5% O(2). These data indicate that oxygen level is an important parameter to consider when modeling neuronal responses to stress in vitro.

The role of growth factors in cartilage repair

BACKGROUND

Full-thickness chondral defects and early osteoarthritis continue to present major challenges for the patient and the orthopaedic surgeon as a result of the limited healing potential of articular cartilage. The use of bioactive growth factors is under consideration as a potential therapy to enhance healing of chondral injuries and modify the arthritic disease process.

QUESTIONS/PURPOSES

We reviewed the role of growth factors in articular cartilage repair and identified specific growth factors and combinations of growth factors that have the capacity to improve cartilage regeneration. Additionally, we discuss the potential use of platelet-rich plasma, autologous-conditioned serum, and bone marrow concentrate preparations as methods of combined growth factor delivery.

METHODS

A PubMed search was performed using key words cartilage or chondrocyte alone and in combination with growth factor. The search was open for original manuscripts and review papers and open for all dates. From these searches we selected manuscripts investigating the effects of growth factors on extracellular matrix synthesis and excluded those investigating molecular mechanisms of action.

RESULTS

By modulating the local microenvironment, the anabolic and anticatabolic effects of a variety of growth factors have demonstrated potential in both in vitro and animal studies of cartilage injury and repair. Members of the transforming growth factor-β superfamily, fibroblast growth factor family, insulin-like growth factor-I, and platelet-derived growth factor have all been investigated as possible treatment augments in the management of chondral injuries and early arthritis.

CONCLUSIONS

The application of growth factors in the treatment of local cartilage defects as well as osteoarthritis appears promising; however, further research is needed at both the basic science and clinical levels before routine application.

Concentrated bone marrow aspirate improves full-thickness cartilage repair compared with microfracture in the equine model

BACKGROUND

The purpose of this study was to compare the outcomes of treatment with bone marrow aspirate concentrate, a simple, one-step, autogenous, and arthroscopically applicable method, with the outcomes of microfracture with regard to the repair of full-thickness cartilage defects in an equine model.

METHODS

Extensive (15-mm-diameter) full-thickness cartilage defects were created on the lateral trochlear ridge of the femur in twelve horses. Bone marrow was aspirated from the sternum and centrifuged to generate the bone marrow concentrate. The defects were treated with bone marrow concentrate and microfracture or with microfracture alone. Second-look arthroscopy was performed at three months, and the horses were killed at eight months. Repair was assessed with use of macroscopic and histological scoring systems as well as with quantitative magnetic resonance imaging.

RESULTS

No adverse reactions due to the microfracture or the bone marrow concentrate were observed. At eight months, macroscopic scores (mean and standard error of the mean, 9.4 + or - 1.2 compared with 4.4 + or - 1.2; p = 0.009) and histological scores (11.1 + or - 1.6 compared with 6.4 + or - 1.2; p = 0.02) indicated improvement in the repair tissue in the bone marrow concentrate group compared with that in the microfracture group. All scoring systems and magnetic resonance imaging data indicated that delivery of the bone marrow concentrate resulted in increased fill of the defects and improved integration of repair tissue into surrounding normal cartilage. In addition, there was greater type-II collagen content and improved orientation of the collagen as well as significantly more glycosaminoglycan in the bone marrow concentrate-treated defects than in the microfracture-treated defects.

CONCLUSIONS

Delivery of bone marrow concentrate can result in healing of acute full-thickness cartilage defects that is superior to that after microfracture alone in an equine model.

CLINICAL RELEVANCE

Delivery of bone marrow concentrate to cartilage defects has the clinical potential to improve cartilage healing, providing a simple, cost-effective, arthroscopically applicable, and clinically effective approach for cartilage repair.

Oxygen tension modulates neurite outgrowth in PC12 cells through a mechanism involving HIF and VEGF

Cell-based approaches are a promising therapeutic strategy for treating injuries to the nervous system, but the optimal means to promote neurite extension and direct cellular behavior are unclear. Previous studies have examined the behavior of neural-like cells in ambient air (21% oxygen tension), yet these conditions are not representative of the physiological oxygen microenvironment of neural tissues. We hypothesized that neuronal differentiation of a model neural cell line (PC12) could be controlled by modulating local oxygen tension. Compared to ambient conditions, PC12 cells cultured in reduced oxygen exhibited significant increases in neurite extension and total neurite length, with 4% oxygen yielding the highest levels of both indicators. We confirmed neurite extension was mediated through oxygen-responsive mechanisms using small molecules that promote or inhibit HIF-1α stabilization. The hypoxic target gene Vegf was implicated as a neurotrophic factor, as neurite formation at 21% oxygen was mimicked with exogenous VEGF, and a VEGF-neutralizing antibody attenuated neurite formation under reduced oxygen conditions. These findings demonstrate that behavior of neural-like cells is driven by the oxygen microenvironment via VEGF function, and suggest promising approaches for future applications in neural repair.