RECASTing racial coping stress in school: Self-efficacy as buffer for adolescent agency.

Objective: The consequences of racism and racial stress on the academic and social well-being of adolescents are profound and well-documented. However, our understanding of how adolescents navigate racial stress and develop the agency to address discriminatory encounters, particularly in settings where educators struggle to intervene with microaggressions, remains limited. Research into the development of racial coping self-efficacy (RCSE) and coping skills has shown promise in enhancing the overall well-being of youth.

Human induced pluripotent stem cell-derived planar neural organoids assembled on synthetic hydrogels.

The tailorable properties of synthetic polyethylene glycol (PEG) hydrogels make them an attractive substrate for human organoid assembly. Here, we formed human neural organoids from iPSC-derived progenitor cells in two distinct formats: (i) cells seeded on a Matrigel surface; and (ii) cells seeded on a synthetic PEG hydrogel surface. Tissue assembly on synthetic PEG hydrogels resulted in three dimensional (3D) planar neural organoids with greater neuronal diversity, greater expression of neurovascular and neuroinflammatory genes, and reduced variability when compared with tissues assembled upon Matrigel.

The role of formulation approaches in presenting targeting ligands on lipid nanoparticles.

The density of functional ligands on lipid nanoparticles (LNPs) greatly determined its capability of postfunctionalization and targetability for the applications of personalized nanomedicine and drug/gene delivery. This work is to investigate whether and how formulation methods influence the presentation of surface ligands. Biotin-modified LNPs as a functional LNP model were synthesized by four different formulation methods.

A protocol for rapid pericyte differentiation of human induced pluripotent stem cells.

Pericytes play a critical role in promoting, regulating, and maintaining numerous vascular functions. Their dysfunction is a major contributor to the progression of vascular and neurodegenerative diseases, making them an ideal candidate for large-scale production for disease modeling and regenerative cell therapy. This protocol describes the rapid and robust differentiation of pericytes from human induced pluripotent stem cells (hiPSCs) while simultaneously generating a population of hiPSC-derived endothelial progenitor cells.

Synthetic alternatives to Matrigel.

Matrigel, a basement-membrane matrix extracted from Engelbreth-Holm-Swarm mouse sarcomas, has been used for more than four decades for a myriad of cell culture applications. However, Matrigel is limited in its applicability to cellular biology, therapeutic cell manufacturing and drug discovery owing to its complex, ill-defined and variable composition. Variations in the mechanical and biochemical properties within a single batch of Matrigel - and between batches - have led to uncertainty in cell culture experiments and a lack of reproducibility.

Dynamic mechanical loading and growth factors influence chondrogenesis of induced pluripotent mesenchymal progenitor cells in a cartilage-mimetic hydrogel.

Human induced pluripotent stem cells (iPSCs) have emerged as a promising alternative to bone-marrow derived mesenchymal stem/stromal cells for cartilage tissue engineering. However, the effect of biochemical and mechanical cues on iPSC chondrogenesis remains understudied. This study evaluated chondrogenesis of induced pluripotent mesenchymal progenitor cells (iPS-MPs) encapsulated in a cartilage-mimetic hydrogel under different culture conditions: free swelling versus dynamic compressive loading and different growth factors (TGFβ3 and/or BMP2).

Assessment and prevention of cartilage degeneration surrounding a focal chondral defect in the porcine model.

Focal defects in articular cartilage are unable to self-repair and, if left untreated, are a leading risk factor for osteoarthritis. This study examined cartilage degeneration surrounding a defect and then assessed whether infilling the defect prevents degeneration. We created a focal chondral defect in porcine osteochondral explants and cultured them ex vivo with and without dynamic compressive loading to decouple the role of loading.

Photopolymerizable Injectable Cartilage Mimetic Hydrogel for the Treatment of Focal Chondral Lesions: A Proof of Concept Study in a Rabbit Animal Model.

Background: In this study, we investigate the in vitro and in vivo chondrogenic capacity of a novel photopolymerizable cartilage mimetic hydrogel, enhanced with extracellular matrix analogs, for cartilage regeneration.

Purpose: To (1) determine whether mesenchymal stem cells (MSCs) embedded in a novel cartilage mimetic hydrogel support in vitro chondrogenesis, (2) demonstrate that the proposed hydrogel can be delivered in situ in a critical chondral defect in a rabbit model, and (3) determine whether the hydrogel with or without MSCs supports in vivo chondrogenesis in a critical chondral defect.

Study Design: Controlled laboratory study.

The role of chondroitin sulfate in regulating hypertrophy during MSC chondrogenesis in a cartilage mimetic hydrogel under dynamic loading.

Mesenchymal stem cells (MSCs) are promising for cartilage regeneration, but readily undergo terminal differentiation. The aim of this study was two-fold: a) investigate physiochemical cues from a cartilage-mimetic hydrogel under dynamic compressive loading on MSC chondrogenesis and hypertrophy and b) identify whether Smad signaling and p38 MAPK signaling mediate hypertrophy during MSC chondrogenesis. Human MSCs were encapsulated in photoclickable poly(ethylene glycol) hydrogels containing chondroitin sulfate and RGD, cultured under dynamic compressive loading or free swelling for three weeks, and evaluated by qPCR and immunohistochemistry.

A MMP7-sensitive photoclickable biomimetic hydrogel for MSC encapsulation towards engineering human cartilage.

Cartilage tissue engineering strategies that use in situ forming degradable hydrogels for mesenchymal stem cell (MSC) delivery are promising for treating chondral defects. Hydrogels that recapitulate aspects of the native tissue have the potential to encourage chondrogenesis, permit cellular mediated degradation, and facilitate tissue growth. This study investigated photoclickable poly(ethylene glycol) hydrogels, which were tailored to mimic the cartilage microenvironment by incorporating extracellular matrix analogs, chondroitin sulfate and RGD, and crosslinks sensitive to matrix metalloproteinase 7 (MMP7).

A Stereolithography-Based 3D Printed Hybrid Scaffold for In Situ Cartilage Defect Repair.

Damage to articular cartilage can over time cause degeneration to the tissue surrounding the injury. To address this problem, scaffolds that prevent degeneration and promote neotissue growth are needed. A new hybrid scaffold that combines a stereolithography-based 3D printed support structure with an injectable and photopolymerizable hydrogel for delivering cells to treat focal chondral defects is introduced.

Current and novel injectable hydrogels to treat focal chondral lesions: Properties and applicability.

Focal chondral lesions and early osteoarthritis (OA) are responsible for progressive joint pain and disability in millions of people worldwide, yet there is currently no surgical joint preservation treatment available to fully restore the long term functionality of cartilage. Limitations of current treatments for cartilage defects have prompted the field of cartilage tissue engineering, which seeks to integrate engineering and biological principles to promote the growth of new cartilage to replace damaged tissue. Toward improving cartilage repair, hydrogel design has advanced in recent years to improve their utility.

Enhanced mechanical properties of photo-clickable thiol-ene PEG hydrogels through repeated photopolymerization of in-swollen macromer.

Current hydrogels used for tissue engineering are limited to a single range of mechanical properties within the replicated tissue construct. We show that repeated in-swelling by a single hydrogel pre-cursor solution into an existing polymerized hydrogel followed by photo-exposure increases hydrogel mechanical properties. The process is demonstrated with a photo-clickable thiol-ene hydrogel using a biocompatible precursor solution of poly(ethylene glycol) dithiol and 8-arm poly(ethylene glycol) functionalized with norbornene.

Mechanical loading inhibits hypertrophy in chondrogenically differentiating hMSCs within a biomimetic hydrogel.

Three dimensional hydrogels are a promising vehicle for delivery of adult human bone-marrow derived mesenchymal stem cells (hMSCs) for cartilage tissue engineering. One of the challenges with using this cell type is the default pathway is terminal differentiation, a hypertrophic phenotype and precursor to endochondral ossification. We hypothesized that a synthetic hydrogel consisting of extracellular matrix (ECM) analogs derived from cartilage when combined with dynamic loading provides physiochemical cues for achieving a stable chondrogenic phenotype.

Mechanical loading regulates human MSC differentiation in a multi-layer hydrogel for osteochondral tissue engineering.

A bioinspired multi-layer hydrogel was developed for the encapsulation of human mesenchymal stem cells (hMSCs) as a platform for osteochondral tissue engineering. The spatial presentation of biochemical cues, via incorporation of extracellular matrix analogs, and mechanical cues, via both hydrogel crosslink density and externally applied mechanical loads, were characterized in each layer. A simple sequential photopolymerization method was employed to form stable poly(ethylene glycol)-based hydrogels with a soft cartilage-like layer of chondroitin sulfate and low RGD concentrations, a stiff bone-like layer with high RGD concentrations, and an intermediate interfacial layer.

Determining equilibrium osmolarity in poly(ethylene glycol)/chondrotin sulfate gels mimicking articular cartilage.

We present an experimentally guided, multi-phase, multi-species polyelectrolyte gel model to make qualitative predictions on the equilibrium electro-chemical properties of articular cartilage. The mixture theory consists of two different types of polymers: poly(ethylene gylcol) (PEG), chondrotin sulfate (ChS), water (acting as solvent) and several different ions: H(+), Na(+), Cl(-). The polymer chains have covalent cross-links whose effect on the swelling kinetics is modeled via Doi rubber elasticity theory.