Angiogenic Hydrogels to Accelerate Early Wound Healing.

Diabetes mellitus affects an increasing proportion of the population, and is projected to double by 2060. Comorbidities contribute to an interrupted healing process which is delayed, prolonged, and associated with increased susceptibility to infection and unresolved inflammation. This leads to chronic nonhealing wounds and potential amputation. Here, the use of a bioactive angiogenic peptide-based hydrogel, SLan, is examined to improve early wound healing in diabetic rats, and its performance is compared to clinically utilized biosynthetic peptide-based materials such as Puramatrix. Streptozotocin-treated diabetic rats underwent 8 mm biopsy wounding in their dorsum. Wounds are treated with either Low (1 w%) SLan, High (4 w%) SLan, phosphate buffered saline (PBS), Puramatrix, or K2 (an unfunctionalized nonbioactive control sequentially similar to SLan), covered with Tegaderm, and monitored on for a month; animals are sacrificed for histomorphic analyses and immunostaining. Pharmacokinetic analysis showing no trafficking of peptides from the wound into the circulation. SLan groups show similar wound contraction as control groups (Puramatrix, PBS, and K2), however, showing marked improvement in healing in earlier time points, including increased deposition of new mature blood vessels. Altogether the results suggest this material can be used to "jumpstart" the diabetic wound healing process.

Ezh2 knockout in mesenchymal cells causes enamel hyper-mineralization.

Enhancer of zeste homolog 2 (EZH2) is the catalytic core of polycomb repressive complex 2 (PRC2), which primarily methylates lysine 27 on histone H3 (H2K27me3), generating transcriptionally suppressed heterochromatin. Since EZH2 suppresses expression of genes involved in dentin formation, we examined the role of EZH2 in tooth development. Intriguingly, microCT analysis of teeth from mice with conditional Ezh2 knockout in uncommitted mesenchymal cells showed hyper-mineralization of enamel, which is produced by the epithelial-lineage cells, ameloblasts. Scanning electron microscopy analysis and nano-indentation of the incisor enamel from knockout mice revealed smaller inter-rod spaces and higher hardness compared to wild type enamel, respectively. Interestingly, expression of the calcium channel subunit gene, Orai2, was decreased compared to its competitor, Orai1, both in knockout mouse incisors and the ex vivo culture of ameloblasts with the surrounding tissues under EZH2 inhibition. Moreover, histological analysis of incisor from knockout mice showed decreased ameloblastin and expedited KLK4 expression in the ameloblasts. These observations suggest that EZH2 depletion in dental mesenchymal cells reduces enamel matrix formation and increases enamel protease activity from ameloblasts, resulting in enamel hyper-mineralization. This study demonstrates the significant role of the suppressive H3K27me3 mark for heterochromatin on enamel formation.

Angiogenic hydrogels for dental pulp revascularization.

Angiogenesis is critical for tissue healing and regeneration. Promoting angiogenesis in materials implanted within dental pulp after pulpectomy is a major clinical challenge in endodontics. We demonstrate the ability of acellular self-assembling peptide hydrogels to create extracellular matrix mimetic architectures that guide in vivo development of neovasculature and tissue deposition. The hydrogels possess facile injectability, as well as sequence-level functionalizability. We explore the therapeutic utility of an angiogenic hydrogel to regenerate vascularized pulp-like soft tissue in a large animal (canine) orthotopic model. The regenerated soft tissue recapitulates key features of native pulp, such as blood vessels, neural filaments, and an odontoblast-like layer next to dentinal tubules. Our study establishes angiogenic peptide hydrogels as potent scaffolds for promoting soft tissue regeneration in vivo. STATEMENT OF SIGNIFICANCE: A major challenge to endodontic tissue engineering is the lack of in situ angiogenesis within intracanal implants, especially after complete removal of the dental pulp. The lack of a robust vasculature in implants limit integration of matrices with the host tissue and regeneration of soft tissue. We demonstrate the development of an acellular material that promotes tissue revascularization in vivo without added growth factors, in a preclinical canine model of pulp-like soft-tissue regeneration. Such acellular biomaterials would facilitate pulp revascularization approaches in large animal models, and translation into human clinical trials.

Correction to: Green tea polyphenol treatment is chondroprotective, anti-inflammatory and palliative in a mouse posttraumatic osteoarthritis model.

Following publication of the original article [1], the authors reported an error in Figs. 2C and 5C.

Green tea polyphenol treatment is chondroprotective, anti-inflammatory and palliative in a mouse post-traumatic osteoarthritis model.

INTRODUCTION: Epigallocatechin 3-gallate (EGCG), a polyphenol present in green tea, was shown to exert chondroprotective effects in vitro. In this study, we used a post-traumatic osteoarthritis (OA) mouse model to test whether EGCG could slow the progression of OA and relieve OA-associated pain. METHODS: C57BL/6 mice were subjected to surgical destabilization of the medial meniscus (DMM) or sham surgery. EGCG (25 mg/kg) or vehicle control was administered daily for four or eight weeks by intraperitoneal injection starting on the day of surgery. OA severity was evaluated by Safranin O staining and Osteoarthritis Research Society International (OARSI) score, and by immunohistochemical analysis to detect cleaved aggrecan and type II collagen, and expression of proteolytic enzymes matrix metalloproteinase (MMP)-13 and A Disintegrin And Metalloproteinase with Thrombospondin Motifs (ADAMTS5). Real-time polymerase chain reaction (PCR) was performed to characterize the expression of genes critical for articular cartilage homeostasis. During the course of the experiments, tactile sensitivity testing (von Frey test) and open field assays were used to evaluate pain behaviors associated with OA, and expression of pain expression markers and inflammatory cytokines in the dorsal root ganglion (DRG) were determined by real-time PCR. RESULTS: Four and eight weeks after DMM surgery, the cartilage in EGCG-treated mice exhibited less Safranin O loss and cartilage erosion, and lower OARSI scores compared to vehicle-treated controls, which was associated with reduced staining for aggrecan and type II collagen cleavage epitopes, and reduced staining for MMP-13 and ADAMTS5 in the articular cartilage. Articular cartilage in the EGCG-treated mice also exhibited reduced levels of MMP-1, -3, -8, -13, ADAMTS5, interleukin (IL)-1ß, and tumor necrosis factor (TNF)-α mRNA and elevated gene expression of the MMP regulator Cbp/p300 Interacting Transactivator 2 (CITED2). Compared to vehicle controls, mice treated with EGCG exhibited reduced OA-associated pain, as indicated by higher locomotor behavior (i.e. distance traveled). Moreover, expression of chemokine receptor (CCR2), and pro-inflammatory cytokines IL-1ß and TNF-α in the DRG were significantly reduced to levels similar to sham-operated animals. CONCLUSIONS: This study provides the first evidence in an OA animal model that EGCG significantly slows OA disease progression and exerts a palliative effect.

Nutraceuticals: potential for chondroprotection and molecular targeting of osteoarthritis.

Osteoarthritis (OA) is a degenerative joint disease and a leading cause of adult disability. There is no cure for OA, and no effective treatments which arrest or slow its progression. Current pharmacologic treatments such as analgesics may improve pain relief but do not alter OA disease progression. Prolonged consumption of these drugs can result in severe adverse effects. Given the nature of OA, life-long treatment will likely be required to arrest or slow its progression. Consequently, there is an urgent need for OA disease-modifying therapies which also improve symptoms and are safe for clinical use over long periods of time. Nutraceuticals-food or food products that provide medical or health benefits, including the prevention and/or treatment of a disease-offer not only favorable safety profiles, but may exert disease- and symptom-modification effects in OA. Forty-seven percent of OA patients use alternative medications, including nutraceuticals. This review will overview the efficacy and mechanism of action of commonly used nutraceuticals, discuss recent experimental and clinical data on the effects of select nutraceuticals, such as phytoflavonoids, polyphenols, and bioflavonoids on OA, and highlight their known molecular actions and limitations of their current use. We will conclude with a proposed novel nutraceutical-based molecular targeting strategy for chondroprotection and OA treatment.

Transient exposure to TGF-ß3 improves the functional chondrogenesis of MSC-laden hyaluronic acid hydrogels.

Tissue engineering with adult stem cells is a promising approach for the restoration of focal defects in articular cartilage. For this, progenitor cells would ideally be delivered to (and maintained within) the defect site via a biocompatible material and in combination with soluble factors to promote initial cell differentiation and subsequent tissue maturation in vivo. While growth factor delivery methods are continually being optimized, most offer only a short (days to weeks) delivery profile at high doses. To address this issue, we investigated mesenchymal stem cell (MSC) differentiation and maturation in photocrosslinkable hyaluronic acid (HA) hydrogels with transient exposure to the pro-chondrogenic molecule transforming growth factor-beta3 (TGF-ß3), at varying doses (10, 50 and 100 ng/mL) and durations (3, 7, 21 and 63 days). Mechanical, biochemical, and histological outcomes were evaluated through 9 weeks of culture. Results showed that a brief exposure (7 days) to a very high level (100 ng/mL) of TGF-ß3 was sufficient to both induce and maintain cartilage formation in these 3D constructs. Indeed, this short delivery resulted in constructs with mechanical and biochemical properties that exceeded that of continuous exposure to a lower level (10 ng/mL) of TGF-ß3 over the entire 9-week time course. Of important note, the total TGF delivery in these two scenarios was roughly equivalent (200 vs. 180 ng), but the timing of delivery differed markedly. These data support the idea that acute exposure to a high dose of TGF will induce functional and long-term differentiation of stem cell populations, and further our efforts to improve cartilage repair in vivo.