Off-the-Shelf Synthetic Biodegradable Grafts Transform In Situ into a Living Arteriovenous Fistula in a Large Animal Model.

Current vascular access options require frequent interventions. In situ tissue engineering (TE) may overcome these limitations by combining the initial success of synthetic grafts with long-term advantages of autologous vessels by using biodegradable grafts that transform into autologous vascular tissue at the site of implantation. Scaffolds (6 mm-Ø) made of supramolecular polycarbonate-bisurea (PC-BU), with a polycaprolactone (PCL) anti-kinking-coil, are implanted between the carotid artery and jugular vein in goats. A subset is bio-functionalized using bisurea-modified-Stromal cell-derived factor-1α (SDF1α) derived peptides and ePTFE grafts as controls. Grafts are explanted after 1 and 3 months, and evaluated for material degradation, tissue formation, compliance, and patency. At 3 months, the scaffold is resorbed and replaced by vascular neo-tissue, including elastin, contractile markers, and endothelial lining. No dilations, ruptures, or aneurysms are observed and grafts are successfully cannulated at termination. SDF-1α-peptide-biofunctionalization does not influence outcomes. Patency is lower in TE grafts (50%) compared to controls (100% patency), predominantly caused by intimal hyperplasia. Rapid remodeling of a synthetic, biodegradable vascular scaffold into a living, compliant arteriovenous fistula is demonstrated in a large animal model. Despite lower patency compared to ePTFE, transformation into autologous and compliant living tissue with self-healing capacity may have long-term advantages.

The effect of chronic kidney disease on tissue formation of in situ tissue-engineered vascular grafts.

Vascular in situ tissue engineering encompasses a single-step approach with a wide adaptive potential and true off-the-shelf availability for vascular grafts. However, a synchronized balance between breakdown of the scaffold material and neo-tissue formation is essential. Chronic kidney disease (CKD) may influence this balance, lowering the usability of these grafts for vascular access in end-stage CKD patients on dialysis. We aimed to investigate the effects of CKD on in vivo scaffold breakdown and tissue formation in grafts made of electrospun, modular, supramolecular polycarbonate with ureido-pyrimidinone moieties (PC-UPy). We implanted PC-UPy aortic interposition grafts (n = 40) in a rat 5/6th nephrectomy model that mimics systemic conditions in human CKD patients. We studied patency, mechanical stability, extracellular matrix (ECM) components, total cellularity, vascular tissue formation, and vascular calcification in CKD and healthy rats at 2, 4, 8, and 12 weeks post-implantation. Our study shows successful in vivo application of a slow-degrading small-diameter vascular graft that supports adequate in situ vascular tissue formation. Despite systemic inflammation associated with CKD, no influence of CKD on patency (Sham: 95% vs CKD: 100%), mechanical stability, ECM formation (Sirius red+, Sham 16.5% vs CKD 25.0%-p:0.83), tissue composition, and immune cell infiltration was found. We did find a limited increase in vascular calcification at 12 weeks (Sham 0.08% vs CKD 0.80%-p:0.02) in grafts implanted in CKD animals. However, this was not associated with increased stiffness in the explants. Our findings suggest that disease-specific graft design may not be necessary for use in CKD patients on dialysis.

Protein Intake among Community-Dwelling Older Adults: The Influence of (Pre-) Motivational Determinants.

An adequate protein intake is important for healthy ageing, yet nearly 50% of Dutch community-dwelling older adults do not meet protein recommendations. This study explores protein intake in relation to eight behavioral determinants (I-Change model) among Dutch community-dwelling older adults. Data were collected through an online questionnaire from October 2019-October 2020. Protein intake was assessed by the Protein Screener 55+, indicating a high/low chance of a low protein intake (<1.0 g/kg body weight/day). The behavioral determinants of cognizance, knowledge, risk perception, perceived cues, attitude, social support, self-efficacy and intention were assessed by evaluating statements on a 7-point Likert scale. A total of 824 Dutch community-dwelling older adults were included, recruited via online newsletters, newspapers and by personal approach. Poisson regression was performed to calculate quartile-based prevalence ratios (PRs). Almost 40% of 824 respondents had a high chance of a low protein intake. Univariate analyses indicated that lower scores for all different behavioral determinants were associated with a higher chance of a low protein intake. Independent associations were observed for knowledge (Q4 OR = 0.71) and social support (Q4 OR = 0.71). Results of this study can be used in future interventions aiming to increase protein intake in which focus should lie on increasing knowledge and social support.

The protein gap-increasing protein intake in the diet of community-dwelling older adults: a simulation study.

OBJECTIVE: Approximately 50 % of Dutch community-dwelling older adults does not meet protein recommendations. This study assesses the effect of replacing low protein foods with protein-rich alternatives on the protein intake of Dutch community-dwelling older adults. DESIGN: The Dutch National Food Consumption Survey-Older Adults 2010-2012 (DNFCS-OA) was used for scenario modelling. Dietary intake was estimated based on two 24-h recalls. Commonly consumed products were replaced by comparable products rich in protein (scenario 1), foods enriched in protein (scenario 2) and a combination of both (scenario 3). Replacement scenarios were confined to participants whose dietary protein intake was < 1·0 g/kg BW/d (n 391). Habitual protein intake of all older adults was estimated, adjusting for effects of within-person variation in the 2-d intake data. SETTING: A simulation study based on the DNFCS-OA. PARTICIPANTS: 727 Dutch community-dwelling older adults aged 70+. RESULTS: Mean protein intake of the total population increased from 1·0 to 1·2 g/kg BW/d (scenarios 1 and 2) and to 1·3 g/kg BW/d (scenario 3). The percentage of participants with intakes of ≥ 1·0 g/kg BW/d increased from 47·1 % to 91·4 %, 90·2 % and 94·6 %, respectively, in scenarios 1, 2 and 3. The largest increases in protein intake were due to replacements in food groups: yoghurt, cream desserts and pudding, potatoes, vegetables and legumes and non-alcoholic beverages and milk in scenario 1 and bread; yoghurt, cream desserts and pudding and soups in scenario 2. CONCLUSIONS: This simulation model shows that replacing low protein foods with comparable alternatives rich in protein can increase the protein intake of Dutch community-dwelling older adults considerably. Results can be used as a basis for nutritional counselling.

What Is on the Menu?-A Quantitative Analysis on Label Format among (Potential) Restaurant Guests and Restaurant Owners.

About 20% of energy intake in the Netherlands is consumed out-of-home. Eating out-of-home is associated with higher energy intake and poorer nutrition. Menu labeling can be considered a promising instrument to improve dietary choices in the out-of-home sector. Effectiveness depends on the presentation format of the label and its attractiveness and usability to restaurant guests and restaurant owners. This exploratory study investigated which menu labeling format would be mostly appreciated by (a) (potential) restaurant guests (n386) and (b) the uninvestigated group of restaurant owners (n41) if menu labeling would be implemented in Dutch full-service restaurants. A cross-sectional survey design was used to investigate three distinct menu labeling formats: a simple health logo; (star) ranking and calorie information. Questionnaires were used as study tool. Ranking has been shown to be the most appreciated menu labeling format by both (potential) restaurant guests and owners. Statistical analysis showed that label preference of potential restaurant guests was significantly associated with age, possibly associated with level of education, and not associated with health consciousness. In summary, we found that ranking is the most appreciated menu label format according to both (potential) restaurant guests and restaurant owners, suggesting it to be a promising way to improve healthy eating out-of-home.

Low awareness of community-dwelling older adults on the importance of dietary protein: new insights from four qualitative studies.

Meeting the recommended daily protein intake can be a challenge for community-dwelling older adults (CDOA). In order to understand why, we studied attitudes towards protein-rich products and healthy eating in general; identified needs and preferences, barriers and promotors and knowledge regarding dietary behaviour and implementation of high protein products. Attitudes towards protein-rich products and healthy eating were evaluated in focus groups (study 1, n 17). To gain insights in the needs and preferences of older adults with regard to meals and meal products (study 2, n 30), visual information on eating behaviour was assessed using photovoicing and verified in post-photovoice interviews. In studies 3 and 4, semi-structured interviews were conducted to identify protein consumption-related barriers, opportunities (n 20) and knowledge and communication channels (n 40), respectively. Risk of low protein intake was assessed using ProteinScreener55+ (Pro55+) in studies 2-4 (n 90). Focus groups showed that participants were unaware of potential inadequate dietary protein. Photovoicing showed that sixteen of thirty participants mainly consumed traditional Dutch products. In post-photovoice interviews, participants indicated that they were satisfied with their current eating behaviour. Barriers for adequate use of protein-rich products were 'lack of knowledge', 'resistance to change habits' and 'no urge to receive dietary advice'. Promotors were 'trust in professionals' and 'product offers'. Sixty-two percent had a low risk of low protein intake. CDOA feel low urgency to increase protein intake, possibly linked to low knowledge levels. A challenge for professionals would be to motivate older adults to change their eating pattern, to optimise protein intake.

Matrix Metalloproteinases and Tissue Inhibitors of Metalloproteinases in Extracellular Matrix Remodeling during Left Ventricular Diastolic Dysfunction and Heart Failure with Preserved Ejection Fraction: A Systematic Review and Meta-Analysis.

Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) are pivotal regulators of extracellular matrix (ECM) composition and could, due to their dynamic activity, function as prognostic tools for fibrosis and cardiac function in left ventricular diastolic dysfunction (LVDD) and heart failure with preserved ejection fraction (HFpEF). We conducted a systematic review on experimental animal models of LVDD and HFpEF published in MEDLINE or Embase. Twenty-three studies were included with a total of 36 comparisons that reported established LVDD, quantification of cardiac fibrosis and cardiac MMP or TIMP expression or activity. LVDD/HFpEF models were divided based on underlying pathology: hemodynamic overload (17 comparisons), metabolic alteration (16 comparisons) or ageing (3 comparisons). Meta-analysis showed that echocardiographic parameters were not consistently altered in LVDD/HFpEF with invasive hemodynamic measurements better representing LVDD. Increased myocardial fibrotic area indicated comparable characteristics between hemodynamic and metabolic models. Regarding MMPs and TIMPs; MMP2 and MMP9 activity and protein and TIMP1 protein levels were mainly enhanced in hemodynamic models. In most cases only mRNA was assessed and there were no correlations between cardiac tissue and plasma levels. Female gender, a known risk factor for LVDD and HFpEF, was underrepresented. Novel studies should detail relevant model characteristics and focus on MMP and TIMP protein expression and activity to identify predictive circulating markers in cardiac ECM remodeling.

What do screening tools measure? Lessons learned from SCREEN II and SNAQ65.

BACKGROUND: Over the last decade, different screening tools for malnutrition have been developed. Within these tools, a distinction can be made between tools that assess nutritional risk and tools that assess protein energy malnutrition. Insights in differences in characteristics of participants at risk and in differences in prevalence rates will aid in deciding which tool(s) to use in daily practice. METHODS: Dutch community-dwelling older adults (n = 200, 78.2 ± 6.9 years), not known to have specific nutrition problems, were recruited to participate in this cross-sectional study. SNAQ65+ (low risk vs moderate/high risk) was used to assess risk of protein energy malnutrition and SCREEN II was used to assess nutrition risk (score <54 out of 64). Chi-square tests were used to test associations between demographic, health, physical and social factors and outcome of SNAQ65+ and SCREEN II. RESULTS: Of all participants 69.0% were at nutrition risk (SCREEN II), while 13.5% were at risk of protein energy malnutrition (SNAQ65+). Agreement between the two tools was poor (kappa < 0.20). Gender, BMI, living status, income, activity level and protein/energy intake were associated with SCREEN II; age, BMI, comorbidities, medication use, help at home, activity level and low basic mobility were associated with SNAQ65+. CONCLUSION: SCREEN II and SNAQ65+ measure different concepts of malnutrition and therefore identify different persons at risk. SCREEN II is more inclusive and comprises both undernutrition and overnutrition as well as different determinants that can impact on food intake, while SNAQ65+ is solely focused on protein-energy malnutrition.

The ConsuMEER study: a randomised trial towards the effectiveness of protein-rich ready-made meals and protein-rich dairy products in increasing protein intake of community-dwelling older adults after switching from self-prepared meals towards ready-made meals.

The risk of undernutrition in older community-dwelling adults increases when they are no longer able to shop or cook themselves. Home-delivered products could then possibly prevent them from becoming undernourished. This single-blind randomised trial tested the effectiveness of home-delivered protein-rich ready-made meals and dairy products in reaching the recommended intake of 1·2 g protein/kg body weight (BW) per d and ≥25 g of protein per meal. Community-dwelling older adults (n 98; mean age 80·4 (sd 6·8) years) switched from self-prepared to home-delivered hot meals and dairy products for 28 d. The intervention group received ready-made meals and dairy products high in protein; the control group received products lower in protein. Dietary intake was measured at baseline, after 2 weeks (T1), and after 4 weeks (T2). Multilevel analyses (providing one combined outcome for T1 and T2) and logistic regressions were performed. Average baseline protein intake was 1·09 (se 0·05) g protein/kg BW per d in the intervention group and 0·99 (se 0·05) g protein/kg BW per d in the control group. During the trial, protein intake of the intervention group was 1·12 (se 0·05) g protein/kg BW per d compared with 0·87 (se 0·03) g protein/kg BW per d in the control group (between-group differences P < 0·05). More participants of the intervention group reached the threshold of ≥25 g protein at dinner compared with the control group (intervention T1: 84·8 %, T2: 88·4 % v. control T1: 42·9 %, T2: 40·5 %; P < 0·05), but not at breakfast and lunch. Our findings suggest that switching from self-prepared meals to ready-made meals carries the risk of a decreasing protein intake, unless extra attention is given to protein-rich choices.

Exhaustion of the bone marrow progenitor cell reserve is associated with major events in severe limb ischemia.

Lower numbers of progenitor cells (PCs) in peripheral blood (PB) have been associated with cardiovascular events in high-risk populations. Therapies aiming to increase the numbers of PCs in circulation have been developed, but clinical trials did not result in better outcomes. It is currently unknown what causes the reduction in PB PC numbers: whether it is primary depletion of the progenitor cell reserve, or a reduced mobilization of PCs from the bone marrow (BM). In this study, we examine if PB and BM PC numbers predict Amputation-Free Survival (AFS) in patients with Severe Limb Ischemia (SLI). We obtained PB and BM from 160 patients enrolled in a clinical trial investigating BM cell therapy for SLI. Samples were incubated with antibodies against CD34, KDR, CD133, CD184, CD14, CD105, CD140b, and CD31; PC populations were enumerated by flow cytometry. Higher PB CD34+ and CD133+ PC numbers were related to AFS (Both Hazard Ratio [HRevent] = 0.56, p = 0.003 and p = 0.0007, respectively). AFS was not associated with the other cell populations in PB. BM PC numbers correlated with PB PC numbers and showed similar HRs for AFS. A further subdivision based on relative BM and PB PC numbers showed that BM PC numbers, rather than mobilization, associated with AFS. Both PB and BM PC numbers are associated with AFS independently from traditional risk factor and show very similar risk profiles. Our data suggest that depletion of the progenitor cell reserve, rather than decreased PC mobilization, underlies the association between PB PC numbers and cardiovascular risk.

Characterization of Endothelial and Smooth Muscle Cells From Different Canine Vessels.

Vasculature performs a critical function in tissue homeostasis, supply of oxygen and nutrients, and the removal of metabolic waste products. Vascular problems are implicated in a large variety of pathologies and accurate in vitro models resembling native vasculature are of great importance. Unfortunately, existing in vitro models do not sufficiently reflect their in vivo counterpart. The complexity of vasculature requires the examination of multiple cell types including endothelial cells (ECs) and vascular smooth muscle cells (VSMCs), as well as vessel location in the body from which they originate. The use of canine blood vessels provides a way to study vasculature with similar vessel size and physiology compared to human vasculature. We report an isolation procedure that provides the possibility to isolate both the endothelial and smooth muscle cells from the same vessels simultaneously, enabling new opportunities in investigating vasculature behavior. Canine primary ECs and VSMCs were isolated from the vena cava, vena porta and aorta. All tissue sources were derived from three donors for accurate comparison and to reduce inter-animal variation. The isolation and purification of the two distinct cell types was confirmed by morphology, gene- and protein-expression and function. As both cell types can be derived from the same vessel, this approach allows accurate modeling of vascular diseases and can also be used more widely, for example, in vascular bioreactors and tissue engineering designs. Additionally, we identified several new genes that were highly expressed in canine ECs, which may become candidate genes for novel EC markers. In addition, we observed transcriptional and functional differences between arterial- and venous-derived endothelium. Further exploration of the transcriptome and physiology of arteriovenous differentiation of primary cells may have important implications for a better understanding of the fundamental behavior of the vasculature and pathogenesis of vascular disease.

Effect of donor variation on osteogenesis and vasculogenesis in hydrogel cocultures.

To introduce a functional vascular network into tissue-engineered bone equivalents, human endothelial colony forming cells (ECFCs) and multipotent mesenchymal stromal cells (MSCs) can be cocultured. Here, we studied the impact of donor variation of human bone marrow-derived MSCs and cord blood-derived ECFCs on vasculogenesis and osteogenesis using a 3D in vitro coculture model. Further, to make the step towards cocultures consisting of cells derived from a single donor, we tested how induced pluripotent stem cell (iPSC)-derived human endothelial cells (iECs) performed in coculture models. Cocultures with varying combinations of human donors of MSCs, ECFCs, or iECs were prepared in Matrigel. The constructs were cultured in an osteogenic differentiation medium. Following a 10-day culture period, the length of the prevascular structures and osteogenic differentiation were evaluated for up to 21 days of culture. The particular combination of MSC and ECFC donors influenced the vasculogenic properties significantly and induced variation in osteogenic potential. In addition, the use of iECs in the cocultures resulted in prevascular structure formation in osteogenically differentiated constructs. Together, these results showed that close attention to the source of primary cells, such as ECFCs and MSCs, is critical to address variability in vasculogenic and osteogenic potential. The 3D coculture model appeared to successfully generate prevascularized constructs and were sufficient in exceeding the ~200 µm diffusion limit. In addition, iPSC-derived cell lineages may decrease variability by providing a larger and potentially more uniform source of cells for future preclinical and clinical applications.

Paracrine Proangiogenic Function of Human Bone Marrow-Derived Mesenchymal Stem Cells Is Not Affected by Chronic Kidney Disease.

BACKGROUND: Cell-based therapies are being developed to meet the need for curative therapy in chronic kidney disease (CKD). Bone marrow- (BM-) derived mesenchymal stromal cells (MSCs) enhance tissue repair and induce neoangiogenesis through paracrine action of secreted proteins and extracellular vesicles (EVs). Administration of allogeneic BM MSCs is less desirable in a patient population likely to require a kidney transplant, but potency of autologous MSCs should be confirmed, given previous indications that CKD-induced dysfunction is present. While the immunomodulatory capacity of CKD BM MSCs has been established, it is unknown whether CKD affects wound healing and angiogenic potential of MSC-derived CM and EVs. METHODS: MSCs were cultured from BM obtained from kidney transplant recipients (N = 15) or kidney donors (N = 17). Passage 3 BM MSCs and BM MSC-conditioned medium (CM) were used for experiments. EVs were isolated from CM by differential ultracentrifugation. BM MSC differentiation capacity, proliferation, and senescence-associated ß-galactosidase activity was assessed. In vitro promigratory and proangiogenic capacity of BM MSC-derived CM and EVs was assessed using an in vitro scratch wound assay and Matrigel angiogenesis assay. RESULTS: Healthy and CKD BM MSCs exhibited similar differentiation capacity, proliferation, and senescence-associated ß-galactosidase activity. Scratch wound migration was not significantly different between healthy and CKD MSCs (P = 0.18). Healthy and CKD BM MSC-derived CM induced similar tubule formation (P = 0.21). There was also no difference in paracrine regenerative function of EVs (scratch wound: P = 0.6; tubulogenesis: P = 0.46). CONCLUSIONS: Our results indicate that MSCs have an intrinsic capacity to produce proangiogenic paracrine factors, including EVs, which is not affected by donor health status regarding CKD. This suggests that autologous MSC-based therapy is a viable option in CKD.

A randomised placebo-controlled double-blind trial to assess the safety of intramuscular administration of allogeneic mesenchymal stromal cells for digital ulcers in systemic sclerosis: the MANUS Trial protocol.

INTRODUCTION: Systemic sclerosis (SSc) is an autoimmune disease characterised by inflammation, fibrosis and vasculopathy. Digital ulcers (DUs) are a frequent manifestation of vasculopathy in patients with SSc. Despite recent advances in pharmacological treatments, DU still have major health and economic implications. As there is currently no proven therapeutic strategy to promote DU healing, new treatments are urgently needed. Mesenchymal stem or stromal cells (MSCs) may provide a novel therapy for DU in SSc, because of their immunomodulatory and vasculoregenerative properties. Allogeneic MSC therapy involves functionally competent MSCs from healthy donors and may be used as 'off-the-shelf' available treatment. This study will evaluate whether allogeneic MSC therapy is a safe and potentially efficacious treatment for DU of SSc. METHODS AND ANALYSIS: The MANUS (Mesenchymal stromal cells for Angiogenesis and Neovascularization in digital Ulcers of Systemic Sclerosis) Trial is a double-blind randomised placebo-controlled trial. 20 patients with SSc with refractory DU will be randomised to receive eight intramuscular injections with either placebo or 50*106 MSCs. The primary outcome is the toxicity of the treatment at 12 weeks after administration. Secondary outcomes include (serious) adverse events, number and time to healing of DU, pain, reported hand function, quality of life and SSc disease activity. We will also evaluate changes in nailfold capillaroscopy pattern, as well as biochemical parameters and biomarkers in peripheral blood and skin biopsies. Follow-up visits will be scheduled at 48 hours and 2, 4, 8, 12, 24 and 52 weeks post-treatment. If the results confirm safety, feasibility and potential efficacy, a large multicentre randomised controlled trial with longer follow-up will be initiated focusing on efficacy. ETHICS AND DISSEMINATION: The study has been approved by the Dutch Central Committee on Research Concerning Human Subjects (protocol no: NL51705.000.15). The results will be disseminated through patient associations and conventional scientific channels. TRIAL REGISTRATION NUMBER: NCT03211793; Pre-results.

The Transcription Factor Nrf2 Protects Angiogenic Capacity of Endothelial Colony-Forming Cells in High-Oxygen Radical Stress Conditions.

BACKGROUND: Endothelial colony forming cells (ECFCs) have shown a promise in tissue engineering of vascular constructs, where they act as endothelial progenitor cells. After implantation, ECFCs are likely to be subjected to elevated reactive oxygen species (ROS). The transcription factor Nrf2 regulates the expression of antioxidant enzymes in response to ROS. METHODS: Stable knockdown of Nrf2 and Keap1 was achieved by transduction with lentiviral shRNAs; activation of Nrf2 was induced by incubation with sulforaphane (SFN). Expression of Nrf2 target genes was assessed by qPCR, oxidative stress was assessed using CM-DCFDA, and angiogenesis was quantified by scratch-wound and tubule-formation assays Results. Nrf2 knockdown led to a reduction of antioxidant gene expression and increased ROS. Angiogenesis was disturbed after Nrf2 knockdown even in the absence of ROS. Conversely, angiogenesis was preserved in high ROS conditions after knockdown of Keap1. Preincubation of ECFCs with SFN reduced intracellular ROS in the presence of H2O2 and preserved scratch-wound closure and tubule-formation. RESULTS: Nrf2 knockdown led to a reduction of antioxidant gene expression and increased ROS. Angiogenesis was disturbed after Nrf2 knockdown even in the absence of ROS. Conversely, angiogenesis was preserved in high ROS conditions after knockdown of Keap1. Preincubation of ECFCs with SFN reduced intracellular ROS in the presence of H2O2 and preserved scratch-wound closure and tubule-formation. CONCLUSION: The results of this study indicate that Nrf2 plays an important role in the angiogenic capacity of ECFCs, particularly under conditions of increased oxidative stress. Pretreatment of ECFCs with SFN prior to implantation may be a protective strategy for tissue-engineered constructs or cell therapies.

Cellular Therapies in Systemic Sclerosis: Recent Progress.

Systemic sclerosis (SSc) is a rare autoimmune connective tissue disease with a high mortality and morbidity. While progress has been made in terms of identifying high-risk patients and implementing new treatment strategies, therapeutic options remain limited. In the past few decades, various cellular therapies have emerged, which have been studied in SSc and other conditions. Here, we provide a comprehensive review of currently available cellular therapies and critically assess their merit as disease-modifying treatment for SSc. Currently, hematopoietic stem cell transplantation is the only cellular therapy that has demonstrated clinical effects on the immune system, neoangiogenesis, and fibrosis. Robust mechanistic studies as well as clinical trials are essential to move the field forward.

Lymphatic Vascular Regeneration: The Next Step in Tissue Engineering.

The lymphatic system plays a crucial role in interstitial fluid drainage, lipid absorption, and immunological defense. Lymphatic dysfunction results in lymphedema, fluid accumulation, and swelling of soft tissues, as well as a potentially impaired immune response. Lymphedema significantly reduces quality of life of patients on a physical, mental, social, and economic basis. Current therapeutic approaches in treatment of lymphatic disease are limited. Over the last decades, great progress has been made in the development of therapeutic strategies to enhance vascular regeneration. These solutions to treat vascular disease may also be applicable in the treatment of lymphatic diseases. Comparison of the organogenic process and biological organization of the vascular and lymphatic systems and studies in the regulatory mechanisms involved in lymphangiogenesis and angiogenesis show many common features. In this study, we address the similarities between both transport systems, and focus in depth on the biology of lymphatic development. Based on the current advances in vascular regeneration, we propose different strategies for lymphatic tissue engineering that may be used for treatment of primary and secondary lymphedema.

Environmental Influences on Endothelial to Mesenchymal Transition in Developing Implanted Cardiovascular Tissue-Engineered Grafts.

Tissue-engineered grafts for cardiovascular structures experience biochemical stimuli and mechanical forces that influence tissue development after implantation such as the immunological response, oxidative stress, hemodynamic shear stress, and mechanical strain. Endothelial cells are a cell source of major interest in vascular tissue engineering because of their ability to form a luminal antithrombotic monolayer. In addition, through their ability to undergo endothelial to mesenchymal transition (EndMT), endothelial cells may yield a cell type capable of increased production and remodeling of the extracellular matrix (ECM). ECM is of major importance to the mechanical function of all cardiovascular structures. Tissue engineering approaches may employ EndMT to recapitulate, in part, the embryonic development of cardiovascular structures. Improved understanding of how the environment of an implanted graft could influence EndMT in endothelial cells may lead to novel tissue engineering strategies. This review presents an overview of biochemical and mechanical stimuli capable of influencing EndMT, discusses the influence of these stimuli as found in the direct environment of cardiovascular grafts, and discusses approaches to employ EndMT in tissue-engineered constructs.

Early in-situ cellularization of a supramolecular vascular graft is modified by synthetic stromal cell-derived factor-1α derived peptides.

In an in-situ approach towards tissue engineered cardiovascular replacement grafts, cell-free scaffolds are implanted that engage in endogenous tissue formation. Bioactive molecules can be incorporated into such grafts to facilitate cellular recruitment. Stromal cell derived factor 1α (SDF1α) is a powerful chemoattractant of lymphocytes, monocytes and progenitor cells and plays an important role in cellular signaling and tissue repair. Short SDF1α-peptides derived from its receptor-activating domain are capable of activating the SDF1α-specific receptor CXCR4. Here, we show that SDF1α-derived peptides can be chemically modified with a supramolecular four-fold hydrogen bonding ureido-pyrimidinone (UPy) moiety, that allows for the convenient incorporation of the UPy-SDF1α-derived peptides into a UPy-modified polymer scaffold. We hypothesized that a UPy-modified material bioactivated with these UPy-SDF1α-derived peptides can retain and stimulate circulating cells in an anti-inflammatory, pro-tissue formation signaling environment. First, the early recruitment of human peripheral blood mononuclear cells to the scaffolds was analyzed in vitro in a custom-made mesofluidic device applying physiological pulsatile fluid flow. Preferential adhesion of lymphocytes with reduced expression of inflammatory factors TNFα, MCP1 and lymphocyte activation marker CD25 was found in the bioactivated scaffolds, indicating a reduction in inflammatory signaling. As a proof of concept, in-vivo implantation of the bioactivated scaffolds as rat abdominal aorta interposition grafts showed increased cellularity by CD68+ cells after 7 days. These results indicate that a completely synthetic, cell-free biomaterial can attract and stimulate specific leukocyte populations through supramolecular incorporation of short bioactive SDF1α derived peptides.

Ex vivo exposure of bone marrow from chronic kidney disease donor rats to pravastatin limits renal damage in recipient rats with chronic kidney disease.

INTRODUCTION: Healthy bone marrow cell (BMC) infusion improves renal function and limits renal injury in a model of chronic kidney disease (CKD) in rats. However, BMCs derived from rats with CKD fail to retain beneficial effects, demonstrating limited therapeutic efficacy. Statins have been reported to improve cellular repair mechanisms. METHODS: We studied whether exposing CKD rat BMCs ex vivo to pravastatin improved their in vivo therapeutic efficacy in CKD and compared this to systemic in vivo treatment. Six weeks after CKD induction, healthy BMCs, healthy pravastatin-pretreated BMCs, CKD BMCs or CKD pravastatin-pretreated BMCs were injected into the renal artery of CKD rats. RESULTS: At 6 weeks after BMC injection renal injury was reduced in pravastatin-pretreated CKD BMC recipients vs. CKD BMC recipients. Effective renal plasma flow was lower and filtration fraction was higher in CKD BMC recipients compared to all groups whereas there was no difference between pravastatin-pretreated CKD BMC and healthy BMC recipients. Mean arterial pressure was higher in CKD BMC recipients compared to all other groups. In contrast, 6 weeks of systemic in vivo pravastatin treatment had no effect. In vitro results showed improved migration, decreased apoptosis and lower excretion of pro-inflammatory Chemokine (C-X-C Motif) Ligand 5 in pravastatin-pretreated CKD BMCs. CONCLUSIONS: Short ex vivo exposure of CKD BMC to pravastatin improves CKD BMC function and their subsequent therapeutic efficacy in a CKD setting, whereas systemic statin treatment did not provide renal protection.