Engineering bioactive nanoparticles to rejuvenate vascular progenitor cells

Enhancing endothelial colony-forming cells for treating diabetic vascular complications: challenges and clinical prospects

Diabetes mellitus (DM) is a metabolic disease characterized by hyperglycemia, leading to various vascular complications. Accumulating evidence indicates that endothelial colony-forming cells (ECFCs) have attractive prospects for repairing and restoring blood vessels. Thus, ECFCs may be a novel therapeutic option for diabetic patients with vascular complications who require revascularization therapy. However, it has been reported that the function of ECFCs is impaired in DM, which poses challenges for the autologous transplantation of ECFCs. In this review, we summarize the molecular mechanisms that may be responsible for ECFC dysfunction and discuss potential strategies for improving the therapeutic efficacy of ECFCs derived from patients with DM. Finally, we discuss barriers to the use of ECFCs in human studies in light of the fact that there are no published reports using these cells in humans.

Mimicking blood and lymphatic vasculatures using microfluidic systems

The role of the circulatory system, containing the blood and lymphatic vasculatures, within the body, has become increasingly focused on by researchers as dysfunction of either of the systems has been linked to serious complications and disease. Currently, in vivo models are unable to provide the sufficient monitoring and level of manipulation needed to characterize the fluidic dynamics of the microcirculation in blood and lymphatic vessels; thus in vitro models have been pursued as an alternative model. Microfluidic devices have the required properties to provide a physiologically relevant circulatory system model for research as well as the experimental tools to conduct more advanced research analyses of microcirculation flow. In this review paper, the physiological behavior of fluid flow and electrical communication within the endothelial cells of the systems are detailed and discussed to highlight their complexities. Cell co-culturing methods and other relevant organ-on-a-chip devices will be evaluated to demonstrate the feasibility and relevance of the in vitro microfluidic model. Microfluidic systems will be determined as a noteworthy model that can display physiologically relevant flow of the cardiovascular and lymphatic systems, which will enable researchers to investigate the systems' prevalence in diseases and identify potential therapeutics.

Hyaluronic Acid Hydrogels with Phototunable Supramolecular Cross-Linking for Spatially Controlled Lymphatic Tube Formation

The dynamics of the extracellular matrix (ECM) influences stem cell differentiation and morphogenesis into complex lymphatic networks. While dynamic hydrogels with stress relaxation properties have been developed, many require detailed chemical processing to tune viscoelasticity, offering a limited opportunity for in situ and spatiotemporal control. Here, a hyaluronic acid (HA) hydrogel is reported with viscoelasticity that is controlled and spatially tunable using UV light to direct the extent of supramolecular and covalent cross-linking interactions. This is achieved using UV-mediated photodimerization of a supramolecular ternary complex of pendant trans-Brooker's Merocyanine (BM) guests and a cucurbit[8]uril (CB[8]) macrocycle. The UV-mediated conversion of this supramolecular complex to its covalent photodimerized form is catalyzed by CB[8], offering a user-directed route to spatially control hydrogel dynamics in combination with orthogonal photopatterning by UV irradiation through photomasks. This material thus achieves spatial heterogeneity of substrate dynamics, recreating features of native ECM without the need for additional chemical reagents. Moreover, these dynamic hydrogels afford spatial control of substrate mechanics to direct human lymphatic endothelial cells (LECs) to form lymphatic cord-like structures (CLS). Specifically, cells cultured on viscoelastic supramolecular hydrogels have enhanced formation of CLS, arising from increased expression of key lymphatic markers, such as LYVE-1, Podoplanin, and Prox1, compared to static elastic hydrogels prepared from fully covalent cross-linking. Viscoelastic hydrogels promote lymphatic CLS formation through the expression of Nrp2, VEGFR2, and VEGFR3 to enhance the VEGF-C stimulation. Overall, viscoelastic supramolecular hydrogels offer a facile route to spatially control lymphatic CLS formation, providing a tool for future studies of basic lymphatic biology and tissue engineering applications.

The Effects of Preeclamptic Milieu on Cord Blood Derived Endothelial Colony-Forming Cells

Preeclampsia is one of the leading causes of infant and maternal mortality worldwide. Many infants born from preeclamptic pregnancies are born prematurely with higher risk of developing cardiovascular later in their life. A key mechanism by which these complications occur is through stress-induced dysfunction of endothelial progenitor cells (EPCs), including endothelial colony-forming cells (ECFCs). To gain insight into this, cord blood derived ECFCs isolated from preeclamptic pregnancies (PRECs) were analyzed and compared to their healthy counterparts. While PRECs preserve key endothelial markers, they upregulate several markers associated with oxidative stress and inflammatory response. Compared to ECFCs, PRECs also exhibit lower migratory behaviors and impaired angiogenic potential. Interestingly, treatment of neuropilin-1 can improve tube formation in vitro. Collectively, this study reports that preeclamptic milieu influence phenotypes and functionality of PRECs, which can be rejuvenated using exogenous molecules. Promising results from this study warrant future investigations on the prospect of the rejuvenated PRECs to improve lung function of infants born from preeclamptic pregnancies.

Endothelial progenitor cells in pregnancy-related diseases

Placental neovascularization plays a crucial role in fetomaternal circulation throughout pregnancy and is dysregulated in several pregnancy-related diseases, including preeclampsia, gestational diabetes mellitus, and fetal growth restriction. Endothelial progenitor cells (EPCs) are a heterogeneous population of cells that differentiate into mature endothelial cells, which influence vascular homeostasis, neovascularization, and endothelial repair. Since their discovery in 1997 by Asahara et al., the role of EPCs in vascular biology has garnered a lot of interest. However, although pregnancy-related conditions are associated with changes in the number and function of EPCs, the reported findings are conflicting. This review discusses the discovery, isolation, and classification of EPCs and highlights discrepancies between current studies. Overviews of how various diseases affect the numbers and functions of EPCs, the role of EPCs as biomarkers of pregnancy disorders, and the potential therapeutic applications involving EPCs are also provided.

Synthetic hyaluronic acid coating preserves the phenotypes of lymphatic endothelial cells

Lymphatic endothelial cells (LECs) play a critical role in the formation and maintenance of the lymphatic vasculature, which is essential for the immune system, fluid balance, and tissue repair. However, LECs are often difficult to study in vivo and in vitro models that accurately mimic their behaviors and phenotypes are limited. In particular, LECs have been shown to lose their lymphatic markers over time while being cultured in vitro, which reflect their plasticity and heterogeneity in vivo. Since LECs uniquely express lymphatic vessel endothelial hyaluronan receptor-1 (LYVE-1), we hypothesized that surface coating with hyaluronic acid (HA) can preserve LEC phenotypes and functionalities. Dopamine conjugated hyaluronic acid (HA-DP) was synthesized with 42% degree of substitution to enable surface modification and conjugation onto standard tissue culture plates. Compared to fibronectin coating and tissue culture plate controls, surface coating with HA-DP was able to preserve lymphatic markers, such as prospero homeobox protein 1 (Prox1), podoplanin (PDPN), and LYVE-1 over several passages in vitro. LECs cultured on HA-DP expressed lower levels of focal adhesion kinase (FAK) and YAP/TAZ, which may be responsible for the maintenance of the lymphatic characteristics. Collectively, the HA-DP coating may provide a novel method for culturing human LECs in vitro toward more representative studies in basic lymphatic biology and lymphatic regeneration.

Nanomedicine for Maternal and Fetal Health

Conception, pregnancy, and childbirth are complex processes that affect both mother and fetus. Thus, it is perhaps not surprising that in the United States alone, roughly 11% of women struggle with infertility and 16% of pregnancies involve some sort of complication. This presents a clear need to develop safe and effective treatment options, though the development of therapeutics for use in women's health and particularly in pregnancy is relatively limited. Physiological and biological changes during the menstrual cycle and pregnancy impact biodistribution, pharmacokinetics, and efficacy, further complicating the process of administration and delivery of therapeutics. In addition to the complex pharmacodynamics, there is also the challenge of overcoming physiological barriers that impact various routes of local and systemic administration, including the blood-follicle barrier and the placenta. Nanomedicine presents a unique opportunity to target and sustain drug delivery to the reproductive tract and other relevant organs in the mother and fetus, as well as improve the safety profile and minimize side effects. Nanomedicine-based approaches have the potential to improve the management and treatment of infertility, obstetric complications, and fetal conditions.

Current status and progress in research on dressing management for diabetic foot ulcer

Diabetic foot ulcer (DFU) is a major complication of diabetes and is associated with a high risk of lower limb amputation and mortality. During their lifetime, 19%-34% of patients with diabetes can develop DFU. It is estimated that 61% of DFU become infected and 15% of those with DFU require amputation. Furthermore, developing a DFU increases the risk of mortality by 50%-68% at 5 years, higher than some cancers. Current standard management of DFU includes surgical debridement, the use of topical dressings and wound decompression, vascular assessment, and glycemic control. Among these methods, local treatment with dressings builds a protective physical barrier, maintains a moist environment, and drains the exudate from DFU wounds. This review summarizes the development, pathophysiology, and healing mechanisms of DFU. The latest research progress and the main application of dressings in laboratory and clinical stage are also summarized. The dressings discussed in this review include traditional dressings (gauze, oil yarn, traditional Chinese medicine, and others), basic dressings (hydrogel, hydrocolloid, sponge, foam, film agents, and others), bacteriostatic dressings, composite dressings (collagen, nanomaterials, chitosan dressings, and others), bioactive dressings (scaffold dressings with stem cells, decellularized wound matrix, autologous platelet enrichment plasma, and others), and dressings that use modern technology (3D bioprinting, photothermal effects, bioelectric dressings, microneedle dressings, smart bandages, orthopedic prosthetics and regenerative medicine). The dressing management challenges and limitations are also summarized. The purpose of this review is to help readers understand the pathogenesis and healing mechanism of DFU, help physicians select dressings correctly, provide an updated overview of the potential of biomaterials and devices and their application in DFU management, and provide ideas for further exploration and development of dressings. Proper use of dressings can promote DFU healing, reduce the cost of treating DFU, and reduce patient pain.

Fractal dimension to characterize interactions between blood and lymphatic endothelial cells

Spatial patterning of different cell types is crucial for tissue engineering and is characterized by the formation of sharp boundary between segregated groups of cells of different lineages. The cell-cell boundary layers, depending on the relative adhesion forces, can result in kinks in the border, similar to fingering patterns between two viscous partially miscible fluids which can be characterized by its fractal dimension. This suggests that mathematical models used to analyze the fingering patterns can be applied to cell migration data as a metric for intercellular adhesion forces. In this study, we develop a novel computational analysis method to characterize the interactions between blood endothelial cells (BECs) and lymphatic endothelial cells (LECs), which form segregated vasculature by recognizing each other through podoplanin. We observed indiscriminate mixing with LEC-LEC and BEC-BEC pairs and a sharp boundary between LEC-BEC pair, and fingering-like patterns with pseudo-LEC-BEC pairs. We found that the box counting method yields fractal dimension between 1 for sharp boundaries and 1.3 for indiscriminate mixing, and intermediate values for fingering-like boundaries. We further verify that these results are due to differential affinity by performing random walk simulations with differential attraction to nearby cells and generate similar migration pattern, confirming that higher differential attraction between different cell types result in lower fractal dimensions. We estimate the characteristic velocity and interfacial tension for our simulated and experimental data to show that the fractal dimension negatively correlates with capillary number (Ca), further indicating that the mathematical models used to study viscous fingering pattern can be used to characterize cell-cell mixing. Taken together, these results indicate that the fractal analysis of segregation boundaries can be used as a simple metric to estimate relative cell-cell adhesion forces between different cell types.