Neovascularization and hematopoietic stem cells

Angiogenic Hydrogels to Accelerate Early Wound Healing

The metabolic disorder diabetes mellitus affects an increasing proportion of the population, a number projected to double by 2060. Non-life-threatening comorbidities contribute to an interrupted healing process which is first delayed, then prolonged, and associated with increased susceptibility to infection and sustained and unresolved inflammation. This leads to chronic non-healing wounds and eventually potential amputation of extremities. Here we examine the use of a bioactive angiogenic peptide-based hydrogel, SLan, to improve early wound healing in diabetic rats, and compare its performance to clinically utilized biosynthetic peptide-based materials such as Puramatrix. Streptozotocin-treated diabetic rats underwent 8 mm biopsy wounding in their dorsum to remove the epithelium, adipose tissues and muscle layer of the skin, and served as a model for diabetic wound healing. Wounds were treated with either Low (1w%) SLan, High (4w%) SLan, PBS, Puramatrix or K2 (an unfunctionalized non-bioactive control sequentially similar to SLan), covered with Tegaderm and monitored on days 0, 3, 7, 10, 14, 17, 21, 28; animals were sacrificed for histomorphic analyses and immunostaining. An LC/MS method developed to detect SLan in plasma allows pharmacokinetic analysis showing no trafficking of peptides from the wound site into the circulation. Low and High SLan groups show similar final outcomes of wound contraction as control groups (Puramatrix, PBS and K2). SLan-treated rats, however, show marked improvement in healing in earlier time points, including increased deposition of new mature blood vessels. Additionally, rats in the Low SLan treatment groups showed significantly improved wound contraction over other groups and significantly improved healing in early time points. Altogether our results suggest this material can be used to "jumpstart" the diabetic wound healing process. This article is protected by copyright. All rights reserved.

Chondrogenic Predifferentiation Inhibits Vascular Endothelial Growth Factor Angiogenic Effect in Pericranium-Derived Spheroids

Craniofacial reconstruction of critical bone defects typically requires a bone graft. As graft availability may be restricted by disease or comorbidities, tissue engineering approaches are actively sought. The pericranium could provide new bone graft material. During development and repair, bone transitions through a chondrogenic phase. However, with tissue engineering, pluripotent cells can differentiate directly into bone cells. Does ability to recapitulate bone formation in vitro affect osteogenesis and vascularization of pericranium grafts? To answer this, we obtained tissue from nine patients with preplanned craniotomy surgery and studied three-dimensional osteogenesis and angiogenesis of pericranium-derived spheroids. First, we established growth and differentiation conditions on Matrigel. For each spheroid sample, we investigated (i) continuous osteogenic differentiation (COD) and (ii) osteogenic differentiation preceded by chondrogenesis (CD → OD). The effect of vascular endothelial growth factor (VEGF) was compared to VEGF supplemented with fibroblast growth factor, interleukin (IL)-1, IL-6, platelet-derived growth factor, and tumor necrosis factor-α, a growth factor mix (GFM) with possible synergistic effects. In this limited sample, we observed no age- or sex-related differences in cell expansion. Similarly, no statistically significant differences in osteogenic or angiogenic scores between COD or CD → OD spheroids were noted with regular media. In COD, however, VEGF statistically significantly increased angiogenesis compared to control media (p = 0.007). Also, in COD, both VEGF and VEGF + GFM increased osteogenesis (p = 0.047 and p = 0.038, respectively). By contrast, in CD → OD, neither VEGF nor VEGF + GFM yielded statistically significant angiogenesis or osteogenesis scores compared to control media. To understand these results, we characterized spheroid protein expression by nanoliquid chromatography coupled to tandem mass spectrometry. Nine angiogenic proteins were either uniquely expressed or upregulated in COD compared to CD → OD: (i) endothelial markers JUP, PTGIS, PTGS2, and TYMP, (ii) tissue remodeling factors CHI3L1 and MMP14, and (iii) metabolic pathways modulators ANGPTL4, ITGA5, and WNT5A. ANGPTL4, ITGA5, PTGIS, PTGS2, and WNT5A define a conserved angiogenic network and were >2-fold increased in VEGF compared to VEGF + GFM. Finally, we examined bone formation on printable poly-(propylene-fumarate) (PPF) scaffolds for individualized grafting. Under COD + VEGF conditions, PPF scaffolds loaded with pericranium-derived cells displayed hallmarks of spongiform-like bone formation. Thus, the human pericranium may be a potential repository for bone-generating cells with applications in craniofacial bone repair using tissue printing.

Isolation of clinically relevant concentrations of bone marrow mesenchymal stem cells without centrifugation

BACKGROUND

This study examined the quality of bone marrow aspirates extracted using a novel, FDA cleared method to optimally target cells from the inner cortical iliac bone surface without the need for centrifugation. This method employs small draws from a single puncture that promote only lateral flow from multiple sites (SSLM method). The study utilized the Marrow Cellutions bone marrow aspiration system (MC system) which is based on the SSLM method and compared the MC system directly to bone marrow concentrates (BMAC) generated by centrifugation of aspirates harvested with a standard aspiration needle.

METHODS

Three direct comparisons were conducted evaluating the SSLM draws and BMACs derived from the same patient from contralateral iliac crests. The levels of TNCs/mL, CD34+ cells/mL, CD117+ cells/mL, and CFU-f/mL were compared between the various bone marrow preparations. The cellular content of a series of SSLM draws was also analyzed to determine the total nucleated cell (TNC) count and the concentration of mesenchymal stem/progenitor cells as measured by colony forming unit fibroblasts (CFU-f).

RESULTS

In direct comparisons with BMAC systems, SSLM draws yielded significantly higher CFU-f concentrations and comparable concentrations of CD34+ and CD117+ cells. In addition, the average quantity of TNCs/mL in a series of 30 patients utilizing the SSLM draw was 35.2 × 10⁶ ± 17.1 × 10⁶ and the average number of CFU-f/mL was 2885 ± 1716. There were small but significant correlations between the TNCs/mL and the CFU-fs/mL using the SSLM method as well as between the age of the patient and the CFU-fs/mL.

CONCLUSIONS

The MC Device, using the SSLM draw technique, produced concentrations of CFU-fs, CD34+ cells and CD117+ cells that were comparable or greater to BMACs derived from the same patient. Given the rapid speed and simplicity of the MC Device, we believe this novel system possesses significant practical advantages to other currently available centrifugation based systems.

Human Neural Stem Cell Therapy for Chronic Ischemic Stroke: Charting Progress from Laboratory to Patients

Chronic disability after stroke represents a major unmet neurologic need. ReNeuron's development of a human neural stem cell (hNSC) therapy for chronic disability after stroke is progressing through early clinical studies. A Phase I trial has recently been published, showing no safety concerns and some promising signs of efficacy. A single-arm Phase II multicenter trial in patients with stable upper-limb paresis has recently completed recruitment. The hNSCs administrated are from a manufactured, conditionally immortalized hNSC line (ReNeuron's CTX0E03 or CTX), generated with c-mycER^TAM technology. This technology has enabled CTX to be manufactured at large scale under cGMP conditions, ensuring sufficient supply to meets the demands of research, clinical development, and, eventually, the market. CTX has key pro-angiogenic, pro-neurogenic, and immunomodulatory characteristics that are mechanistically important in functional recovery poststroke. This review covers the progress of CTX cell therapy from its laboratory origins to the clinic, concluding with a look into the late stage clinical future.

Mesenchymal stromal cells (MSCs) induce ex vivo proliferation and erythroid commitment of cord blood haematopoietic stem cells (CB-CD34+ cells)

A human bone marrow-derived mesenchymal stromal cell (MSCs) and cord blood-derived CD34+ stem cell co-culture system was set up in order to evaluate the proliferative and differentiative effects induced by MSCs on CD34+ stem cells, and the reciprocal influences on gene expression profiles. After 10 days of co-culture, non-adherent (SN-fraction) and adherent (AD-fraction) CD34+ stem cells were collected and analysed separately. In the presence of MSCs, a significant increase in CD34+ cell number was observed (fold increase = 14.68), mostly in the SN-fraction (fold increase = 13.20). This was combined with a significant increase in CD34+ cell differentiation towards the BFU-E colonies and with a decrease in the CFU-GM. These observations were confirmed by microarray analysis. Through gene set enrichment analysis (GSEA), we noted a significant enrichment in genes involved in heme metabolism (e.g. LAMP2, CLCN3, BMP2K), mitotic spindle formation and proliferation (e.g. PALLD, SOS1, CCNA1) and TGF-beta signalling (e.g. ID1) and a down-modulation of genes participating in myeloid and lymphoid differentiation (e.g. PCGF2) in the co-cultured CD34+ stem cells. On the other hand, a significant enrichment in genes involved in oxygen-level response (e.g. TNFAIP3, SLC2A3, KLF6) and angiogenesis (e.g. VEGFA, IGF1, ID1) was found in the co-cultured MSCs. Taken together, our results suggest that MSCs can exert a priming effect on CD34+ stem cells, regulating their proliferation and erythroid differentiation. In turn, CD34+ stem cells seem to be able to polarise the BM-niche towards the vascular compartment by modulating molecular pathways related to hypoxia and angiogenesis.

Treatment of hind limb ischemia using angiogenic peptide nanofibers

For a proangiogenic therapy to be successful, it must promote the development of mature vasculature for rapid reperfusion of ischemic tissue. Whole growth factor, stem cell, and gene therapies have yet to achieve the clinical success needed to become FDA-approved revascularization therapies. Herein, we characterize a biodegradable peptide-based scaffold engineered to mimic VEGF and self-assemble into a nanofibrous, thixotropic hydrogel, SLanc. We found that this injectable hydrogel was rapidly infiltrated by host cells and could be degraded while promoting the generation of neovessels. In mice with induced hind limb ischemia, this synthetic peptide scaffold promoted angiogenesis and ischemic tissue recovery, as shown by Doppler-quantified limb perfusion and a treadmill endurance test. Thirteen-month-old mice showed significant recovery within 7 days of treatment. Biodistribution studies in healthy mice showed that the hydrogel is safe when administered intramuscularly, subcutaneously, or intravenously. These preclinical studies help establish the efficacy of this treatment for peripheral artery disease due to diminished microvascular perfusion, a necessary step before clinical translation. This peptide-based approach eliminates the need for cell transplantation or viral gene transfection (therapies currently being assessed in clinical trials) and could be a more effective regenerative medicine approach to microvascular tissue engineering.

Recent progress in understanding coxsackievirus replication, dissemination, and pathogenesis

Coxsackieviruses (CVs) are relatively common viruses associated with a number of serious human diseases, including myocarditis and meningo-encephalitis. These viruses are considered cytolytic yet can persist for extended periods of time within certain host tissues requiring evasion from the host immune response and a greatly reduced rate of replication. A member of Picornaviridae family, CVs have been historically considered non-enveloped viruses - although recent evidence suggest that CV and other picornaviruses hijack host membranes and acquire an envelope. Acquisition of an envelope might provide distinct benefits to CV virions, such as resistance to neutralizing antibodies and efficient nonlytic viral spread. CV exhibits a unique tropism for progenitor cells in the host which may help to explain the susceptibility of the young host to infection and the establishment of chronic disease in adults. CVs have also been shown to exploit autophagy to maximize viral replication and assist in unconventional release from target cells. In this article, we review recent progress in clarifying virus replication and dissemination within the host cell, identifying determinants of tropism, and defining strategies utilized by the virus to evade the host immune response. Also, we will highlight unanswered questions and provide future perspectives regarding the potential mechanisms of CV pathogenesis.

Local administration of stromal cell-derived factor-1 promotes stem cell recruitment and bone regeneration in a rat periodontal bone defect model

Stromal cell-derived factor-1 (SDF-1) recruits adult stem/progenitor cells via its specific receptor, C-X-C motif receptor 4 (CXCR4), to promote heart, kidney and tendon regeneration, but little is known about the effects of SDF-1 on bone regeneration in periodontal diseases. The objective of this study was to investigate whether local administration of SDF-1 in a collagen membrane scaffold enhanced the recruitment of host stem cells and improved periodontal bone defect repair. To this end, bone defects were established on the buccal side of bilateral mandibles in Wistar rats. After application of collagen membranes loaded with SDF-1 or phosphate-buffered saline (PBS) to the defects, the effects of SDF-1 on stem cell recruitment, inflammatory cell responses, angiogenesis, osteoclastogenesis, scaffold degradation, and bone regeneration were evaluated. It showed that SDF-1 recruited host-derived mesenchymal stem cells and hematopoietic stem cells to the wound area and significantly reduced the CD11b+ inflammatory cell response. Moreover, SDF-1 increased vascular formation, induced early bone osteoclastogenesis, accelerated scaffold degradation, and promoted the quality and quantity of regenerated bone. Our results suggest that this cell-free approach by local administration of SDF-1 may be an effective strategy for development as a simple and safe technique for periodontal bone regeneration.

Causes and consequences of epigenetic regulation in wound healing

Wound healing is a complex and systematic tissue level response to mechanical and chemical injuries that may cause the release of growth factors, cytokines, and chemokines by damaged tissues. For the complex features of these restorative processes, it is a crucial challenge to identify the relevant cell types and biochemical pathways that are involved in wound healing. Epigenetic mechanisms, such as DNA methylation, histone modification, and noncoding regulatory RNA editing, play important roles in many biological processes, including cell proliferation, migration and differentiation, signal pathway activation or inhibition, and cell senescence. Epigenetic regulations can coordinately control a considerable subset of known repair genes and thus serve as master regulators of wound healing. An abundance of evidence has also shown that epigenetic modifications participate in the short- and long-term control of crucial gene expression and cell signal transduction that are involved in the healing process. These data provide a foundation for probable epigenetic-based therapeutic strategies that are aimed at stimulating tissue regeneration. This review describes the epigenetic alterations in different cellular types at injury sites, induced signals, and resulting tissue repair. With the increased interest in the epigenetics of wound and repair processes, this field will soon begin to flourish.

Highly angiogenic peptide nanofibers

Major limitations of current tissue regeneration approaches using artificial scaffolds are fibrous encapsulation, lack of host cellular infiltration, unwanted immune responses, surface degradation preceding biointegration, and artificial degradation byproducts. Specifically, for scaffolds larger than 200-500 μm, implants must be accompanied by host angiogenesis in order to provide adequate nutrient/waste exchange in the newly forming tissue. In the current work, we design a peptide-based self-assembling nanofibrous hydrogel containing cell-mediated degradation and proangiogenic moieties that specifically address these challenges. This hydrogel can be easily delivered by syringe, is rapidly infiltrated by cells of hematopoietic and mesenchymal origin, and rapidly forms an extremely robust mature vascular network. Scaffolds show no signs of fibrous encapsulation and after 3 weeks are resorbed into the native tissue. These supramolecular assemblies may prove a vital paradigm for tissue regeneration and specifically for ischemic tissue disease.

Fibromodulin Enhances Angiogenesis during Cutaneous Wound Healing

Supplemental Digital Content is available in the text.

Background:

Fibromodulin (FMOD) plays a critical role in the wound-healing process. Our previous studies revealed that FMOD deficiency led to marked alterations in adult wound healing characterized by delayed dermal cell migration, postponed wound closure, and increased scar formation, all accompanied by impeded angiogenesis. Therefore, the aim of this study was to reveal the effect of FMOD on angiogenesis during the wound-healing process.

Methods:

In vivo angiogenic effects of FMOD were assessed by a chick embryo chorioallantoic membrane assay, a Matrigel (BD Bioscience, Franklin Lakes, N.J.) plug implant assay, and rodent primary closure wound models. In vitro angiogenic effects of FMOD were recorded by cell invasion and dimensional and topological parameters of human umbilical vein endothelial cells.

Results:

We provided evidence that FMOD significantly enhanced vascularization: first, FMOD boosted blood vessel formation on the chorioallantoic membrane; second, FMOD markedly stimulated capillary infiltration into Matrigel plugs subcutaneously implanted in adult mice; and finally, FMOD robustly promoted angiogenesis in multiple adult rodent cutaneous wound models. Furthermore, FMOD administration restored the vascularity of fmod^−/− mouse wounds. In support of this, FMOD endorsed an angiogenesis-favored microenvironment in adult rodent wounds not only by upregulating angiogenic genes but also by downregulating angiostatic genes. In addition, FMOD significantly enhanced human umbilical vein endothelial cell invasion and tube-like structure formation in vitro.

Conclusions:

Altogether, we demonstrated that in addition to reducing scar formation, FMOD also promotes angiogenesis. As blood vessels organize and regulate wound healing, its potent angiogenic properties will further expand the clinical application of FMOD for cutaneous healing of poorly vascularized wounds.

Retention of stemness and vasculogenic potential of human umbilical cord blood stem cells after repeated expansions on PES-nanofiber matrices

Despite recent advances in cardiovascular medicine, ischemic diseases remain a major cause of morbidity and mortality. Although stem cell-based therapies for the treatment of ischemic diseases show great promise, limited availability of biologically functional stem cells mired the application of stem cell-based therapies. Previously, we reported a PES-nanofiber based ex vivo stem cell expansion technology, which supports expansion of human umbilical cord blood (UCB)-derived CD133(+)/CD34(+) progenitor cells ∼225 fold. Herein, we show that using similar technology and subsequent re-expansion methods, we can achieve ∼5 million-fold yields within 24 days of the initial seeding. Interestingly, stem cell phenotype was preserved during the course of the multiple expansions. The high level of the stem cell homing receptor, CXCR4 was expressed in the primary expansion cells, and was maintained throughout the course of re-expansions. In addition, re-expanded cells preserved their multi-potential differential capabilities in vitro, such as, endothelial and smooth muscle lineages. Moreover, biological functionality of the re-expanded cells was preserved and was confirmed by a murine hind limb ischemia model for revascularization. These cells could also be genetically modified for enhanced vasculogenesis. Immunohistochemical evidences support enhanced expression of angiogenic factors responsible for this enhanced neovascularization. These data further confirms that nanofiber-based ex-vivo expansion technology can generate sufficient numbers of biologically functional stem cells for potential clinical applications.

Hypoplastic left heart syndrome - unresolved issues

Hypoplastic left heart syndrome (HLHS) is one of the most challenging congenital heart defects. At present, it is expected that - at best - 70% of newborns with HLHS will reach adulthood. This review addresses the problems of right ventricular (RV) failure and insufficient growth of pulmonary vasculature in these patients. In order to further improve long-term prognosis translational research to control RV function, growth of pulmonary arteries and progress in chronic circulatory support are clearly needed to provide a further improvement for adults with HLHS.

Number of circulating pro-angiogenic cells, growth factor and anti-oxidative gene profiles might be altered in type 2 diabetes with and without diabetic foot syndrome

Aims/Introduction

Type 2 diabetes is often complicated by diabetic foot syndrome (DFS). We analyzed the circulating stem cells, growth factor and anti‐oxidant gene expression profiles in type 2 diabetes patients without or with different forms of DFS.

Materials and Methods

Healthy volunteers (n = 13) and type 2 diabetes patients: (i) without DFS (n = 10); or with (ii) Charcot osteoneuropathy (n = 10); (iii) non‐infected (n = 17); (iv) infected (n = 11); and (v) healed ulceration were examined (n = 12). Peripheral blood endothelial progenitor cells (EPC), mesenchymal stem cells (MSC), hematopoietic stem cells (HSC) and very small embryonic‐like (VSEL) cells were phenotyped using flow cytometry. Plasma cytokine concentrations and gene expressions in blood cells were measured by Luminex and quantitative real‐time polymerase chain reaction assays, respectively.

Results

Patients with non‐complicated type 2 diabetes showed reduced HMOX1 expression, accompanied by HMOX2 upregulation, and had less circulating EPC, MSC or HSC than healthy subjects. In contrast, VSEL cells were elevated in the type 2 diabetes group. However, subjects with DFS, even with healed ulceration, had fewer VSEL cells, more CD45‐CD29⁺CD90⁺MSC, and upregulated HMOX1 when compared with the type 2 diabetes group. Patients with Charcot osteopathy had lowered plasma fibroblast growth factor‐2. Elevated plasma tumor necrosis factor‐α and decreased catalase expression was found in all diabetic patients.

Conclusions

Patients with type 2 diabetes and different forms of DFS have an altered number of circulating stem cells. Type 2 diabetes might also be associated with a changed plasma growth factor and anti‐oxidant gene expression profile. Altogether, these factors could contribute to the pathogenesis of different forms of DFS.

Macrophages and chemokines as mediators of angiogenesis

Accumulating evidence attests to the important roles of both macrophages and chemokines in angiogenesis. Tumor-associated macrophages or TAMS constitute the major fraction of tumor-infiltrating leukocytes and are recruited by a number of chemoattractants that are produced by the tumor and tumor-associated stroma. This heterogeneous cell population is activated by a variety of stimuli and becomes polarized to result in functionally different phenotypes regarding tumor progression. As opposed to classically activated or M1 macrophages that exhibit anti-tumor functions, most TAMS are considered to be of the alternatively activated or M2 phenotype, and express multiple cytokines, proteases, and chemokines that promote tumor angiogenesis. Chemokines also have disparate effects on angiogenesis regulation, as several members of the CXC and CC chemokine families are potent inducers of angiogenesis, while a subset of CXC chemokines are angiostatic. This review summarizes the current literature regarding the roles and modes of action of macrophage-derived chemokines as mediators of angiogenesis.

Endothelial progenitor cell dysfunction in cardiovascular diseases: role of reactive oxygen species and inflammation

Endothelial progenitor cells (EPCs) move towards injured endothelium or inflamed tissues and incorporate into foci of neovascularisation, thereby improving blood flow and tissue repair. Patients with cardiovascular diseases have been shown to exhibit reduced EPC number and function. It has become increasingly apparent that these changes may be effected in response to enhanced oxidative stress, possibly as a result of systemic and localised inflammatory responses. The interplay between inflammation and oxidative stress affects the initiation, progression, and complications of cardiovascular diseases. Recent studies suggest that inflammation and oxidative stress modulate EPC bioactivity. Clinical medications with anti-inflammatory and antioxidant properties, such as statins, thiazolidinediones, angiotensin II receptor 1 blockers, and angiotensin-converting enzyme inhibitors, are currently administered to patients with cardiovascular diseases. These medications appear to exert beneficial effects on EPC biology. This review focuses on EPC biology and explores the links between oxidative stress, inflammation, and development of cardiovascular diseases.

Role of pigment epithelium-derived factor in stem/progenitor cell-associated neovascularization

Pigment epithelium-derived factor (PEDF) was first identified in retinal pigment epithelium cells. It is an endogenously produced protein that is widely expressed throughout the human body such as in the eyes, liver, heart, and adipose tissue; it exhibits multiple and varied biological activities. PEDF is a multifunctional protein with antiangiogenic, antitumorigenic, antioxidant, anti-inflammatory, antithrombotic, neurotrophic, and neuroprotective properties. More recently, PEDF has been shown to be the most potent inhibitor of stem/progenitor cell-associated neovascularization. Neovascularization is a complex process regulated by a large, interacting network of molecules from stem/progenitor cells. PEDF is also involved in the pathogenesis of angiogenic eye disease, tumor growth, and cardiovascular disease. Novel antiangiogenic agents with tolerable side effects are desired for the treatment of patients with various diseases. Here, we review the value of PEDF as an important endogenous antiangiogenic molecule; we focus on the recently identified role of PEDF as a possible new target molecule to influence stem/progenitor cell-related neovascularization.