RESUMEN
The development of hydrophobic poly(ethylene glycol) (PEG) hydrogels, which are typically hydrophilic, could significantly enhance their application as artificial extracellular matrices. In this study, we designed PEG hydrogels with enhanced hydrophobicity through gel-gel phase separation (GGPS), a phenomenon that uniquely enhances hydrophobicity under ambient conditions, and we elucidated the pivotal role of elasticity in this process. We hypothesized that increased elasticity would amplify GGPS, thereby improving the hydrophobicity and cell adhesion on PEG hydrogel surfaces, despite their inherent hydrophilicity. To test this hypothesis, we engineered dilute oligo-PEG gels via a two-step process, creating polymer networks from tetra-PEG clusters with multiple reaction points. These oligo-PEG gels exhibited significantly higher elasticity, turbidity, and shrinkage upon water immersion compared to dilute PEG gels. Detailed characterization through confocal laser scanning microscopy, rheological measurements, and cell adhesion assays revealed distinct biphasic structures, increased hydrophobicity, and enhanced cell attachability in the dilute oligo-PEG gels. Our findings confirm that elasticity is crucial for effective GGPS, providing a novel method for tailoring hydrogel properties without chemical modification. This research introduces a new paradigm for designing biomaterials with improved cell-scaffolding capabilities, offering significant potential for tissue engineering and regenerative medicine.
Asunto(s)
Adhesión Celular , Hidrogeles , Interacciones Hidrofóbicas e Hidrofílicas , Polietilenglicoles , Polietilenglicoles/química , Hidrogeles/química , Materiales Biocompatibles/química , Ingeniería de Tejidos/métodos , Reología , Elasticidad , Humanos , Animales , Ratones , Separación de FasesRESUMEN
Cosmic large-scale structures, animal flocks and living tissues can be considered non-equilibrium organized systems created by dissipative processes. Replicating such properties in artificial systems is still difficult. Herein we report a dissipative network formation process in a dilute polymer-water mixture that leads to percolation-induced gel-gel phase separation. The dilute system, which forms a monophase structure at the percolation threshold, spontaneously separates into two co-continuous gel phases with a submillimetre scale (a dilute-percolated gel) during the deswelling process after the completion of the gelation reaction. The dilute-percolated gel, which contains 99% water, exhibits unexpected hydrophobicity and induces the development of adipose-like tissues in subcutaneous tissues. These findings support the development of dissipative structures with advanced functionalities for distinct applications, ranging from physical chemistry to tissue engineering.
Asunto(s)
Polímeros , Animales , Geles/química , Polímeros/química , Interacciones Hidrofóbicas e Hidrofílicas , Agua/químicaRESUMEN
The Runt-related transcription factor (Runx) family plays various roles in the homeostasis of cartilage. Here, we examined the role of Runx2 and Runx3 for osteoarthritis development in vivo and in vitro. Runx3-knockout mice exhibited accelerated osteoarthritis following surgical induction, accompanied by decreased expression of lubricin and aggrecan. Meanwhile, Runx2 conditional knockout mice showed biphasic phenotypes: heterozygous knockout inhibited osteoarthritis and decreased matrix metallopeptidase 13 (Mmp13) expression, while homozygous knockout of Runx2 accelerated osteoarthritis and reduced type II collagen (Col2a1) expression. Comprehensive transcriptional analyses revealed lubricin and aggrecan as transcriptional target genes of Runx3, and indicated that Runx2 sustained Col2a1 expression through an intron 6 enhancer when Sox9 was decreased. Intra-articular administration of Runx3 adenovirus ameliorated development of surgically induced osteoarthritis. Runx3 protects adult articular cartilage through extracellular matrix protein production under normal conditions, while Runx2 exerts both catabolic and anabolic effects under the inflammatory condition.
Asunto(s)
Anabolizantes , Cartílago Articular , Osteoartritis , Animales , Ratones , Agrecanos/genética , Agrecanos/metabolismo , Anabolizantes/farmacología , Cartílago Articular/metabolismo , Condrocitos/metabolismo , Colágeno Tipo II/genética , Colágeno Tipo II/metabolismo , Subunidad alfa 1 del Factor de Unión al Sitio Principal/genética , Subunidad alfa 1 del Factor de Unión al Sitio Principal/metabolismo , Metaloproteinasa 13 de la Matriz/genética , Metaloproteinasa 13 de la Matriz/metabolismo , Ratones Noqueados , Osteoartritis/genética , Osteoartritis/metabolismoRESUMEN
Ectopic endochondral ossification in the tendon/ligament is caused by repetitive mechanical overload or inflammation. Tendon stem/progenitor cells (TSPCs) contribute to tissue repair, and some express lubricin [proteoglycan 4 (PRG4)]. However, the mechanisms of ectopic ossification and association of TSPCs are not yet known. Here, we investigated the characteristics of Prg4-positive (+) cells and identified that R-spondin 2 (RSPO2), a WNT activator, is specifically expressed in a distinct Prg4+ TSPC cluster. The Rspo2+ cluster was characterized as mostly undifferentiated, and RSPO2 overexpression suppressed ectopic ossification in a mouse Achilles tendon puncture model via chondrogenic differentiation suppression. RSPO2 expression levels in patients with ossification of the posterior longitudinal ligament were lower than those in spondylosis patients, and RSPO2 protein suppressed chondrogenic differentiation of human ligament cells. RSPO2 was induced by inflammatory stimulation and mechanical loading via nuclear factor κB. Rspo2+ cells may contribute to tendon/ligament homeostasis under pathogenic conditions.
RESUMEN
Purpose: We aimed to develop a rat flexor tendon repair model that could be applied to experiments in similar clinical settings. Methods: We prepared 3 different combinations of sutures in rat flexor tendons: group A had 3 single peripheral sutures plus a 2-strand core suture; group B had 3 figure-of-eight peripheral sutures alone; and group C had 3 figure-of-eight peripheral sutures plus a 2-strand core suture. We examined the in vitro tensile strength of the repaired tendons by a biomechanical test, the rerupture rate within 3 weeks, and histological findings in vivo. Results: Group C displayed the greatest ultimate strength by the mechanical test. The flexor tendons in group C did not rerupture within 3 weeks after surgery, whereas many of those in groups A and B reruptured. Fibrous scar tissue was observed in the gap of the tendon stumps in groups A and B, but not in group C. Conclusions: The combination of figure-of-eight peripheral sutures and a 2-strand core suture provided the repaired rat flexor tendon with enough strength to prevent rerupture without cast fixation or immobilization after surgery. Clinical relevance: This combination of sutures is useful to reproduce flexor tendon repair similar to that performed in clinical settings and will contribute to various translational experiments in vivo.