Regenerative therapy in dentistry has gained interest given the complexity to restore dental and periodontal tissues with inert materials. The best approach for regeneration requires three elements for restoring functions of affected or diseased organ tissues: cells, bioactive molecules, and scaffolds. This triad is capable of modulating the processes to replace lost or damaged tissues and restore function, as it has an impact on diverse cellular processes, influencing cell behavior positively to induce the complete restoration of function and morphology of such complex tissues. Hydrogels (HG) have shown advantages as scaffolds as they are soft and elastic three-dimensional (3D) networks formed from hydrophilic homopolymers, copolymers, or macromers. Besides simple or hybrid, HG show chemical, mechanical and biological activities such as the incorporation of cells in their structures, the retention of high-water content which enhances the transportation of cell nutrients and waste, and elastic and flexible characteristics that emulate the native extracellular matrix (ECM). HG can induce changes in cellular processes such as chemotaxis, proliferation, angiogenesis, biomineralization, and expression of specific tissue biomarkers, enhancing the regeneration process. Besides some of them have anti-inflammatory and anti-bacterial effects. This review aims to show an extensive overview of the most used hydrogels in tissue engineering, emphasizing those that are studied for the regeneration of oral tissues, their biological effects, and their clinical implications. Even though most of the HG are still under investigation, some of them have been studied in vitro and in vivo with outstanding results that may lead to preclinical studies. Besides there are HG that have shown their efficacy in patients such as hyaluronan HG that enhances the healing of gingival tissue.

BACKGROUND: The necessity to manufacture scaffolds with superior capabilities of biocompatibility and biodegradability has led to the production of extracellular matrix (ECM) scaffolds. Among their advantages, they allow better cell colonization, which enables its successful integration into the hosted tissue, surrounding the area to be repaired and their formulations facilitate placing it into irregular shapes. The ECM from porcine urinary bladder (pUBM) comprises proteins, proteoglycans and glycosaminoglycans which provide support and enable signals to the cells. These properties make it an excellent option to produce hydrogels that can be used in regenerative medicine. OBJECTIVE: The goal of this study was to assess the biocompatibility of an ECM hydrogel derived from the porcine urinary bladder (pUBMh) in vitro using fibroblasts, macrophages, and adipose-derived mesenchymal stem cells (AD-MCSs), as well as biocompatibility in vivo using Wistar rats. METHODS: Effects upon cells proliferation/viability was measured using MTT assay, cytotoxic effects were analyzed by quantifying lactate dehydrogenase release and the Live/Dead Cell Imaging assay. Macrophage activation was assessed by quantification of IL-6, IL-10, IL-12p70, MCP-1, and TNF-α using a microsphere-based cytometric bead array. For in vivo analysis, Wistar rats were inoculated into the dorsal sub-dermis with pUBMh. The specimens were sacrificed at 24 h after inoculation for histological study. RESULTS: The pUBMh obtained showed good consistency and absence of cell debris. The biocompatibility tests in vitro revealed that the pUBMh promoted cell proliferation and it is not cytotoxic on the three tested cell lines and induces the production of pro-inflammatory cytokines on macrophages, mainly TNF-α and MCP-1. In vivo, pUBMh exhibited fibroblast-like cell recruitment, without tissue damage or inflammation. CONCLUSION: The results show that pUBMh allows cell proliferation without cytotoxic effects and can be considered an excellent biomaterial for tissue engineering.

BACKGROUND: Biomaterials must allow revascularization for a successful tissue regeneration process. Biomaterials formulated from the extracellular matrix (ECM) have gained popularity in tissue engineering because of their superior biocompatibility, and due to their rheological properties, ECM-hydrogels can be easily applied in damaged areas, allowing cell colonization and integration into the host tissue. Porcine urinary bladder ECM (pUBM) retains functional signaling and structural proteins, being an excellent option in regenerative medicine. Even some small molecules, such as the antimicrobial cathelicidin-derived LL-37 peptide have proven angiogenic properties. OBJECTIVE: The objective of this study was to evaluate the biocompatibility and angiogenic potential of an ECM-hydrogel derived from the porcine urinary bladder (pUBMh) biofunctionalized with the LL-37 peptide (pUBMh/LL37). METHODS: Macrophages, fibroblasts, and adipose tissue-derived mesenchymal stem cells (AD-MSC) were exposed pUBMh/LL37, and the effect on cell proliferation was evaluated by MTT assay, cytotoxicity by quantification of lactate dehydrogenase release and the Live/Dead Cell Imaging assays. Moreover, macrophage production of IL-6, IL-10, IL-12p70, MCP-1, INF-γ, and TNF-α cytokines was quantified using a bead-based cytometric array. pUBMh/LL37 was implanted directly by dorsal subcutaneous injection in Wistar rats for 24 h to evaluate biocompatibility, and pUBMh/LL37-loaded angioreactors were implanted for 21 days for evaluation of angiogenesis. RESULTS: We found that pUBMh/LL37 did not affect cell proliferation and is cytocompatible to all tested cell lines but induces the production of TNF-α and MCP-1 in macrophages. In vivo, this ECM-hydrogel induces fibroblast-like cell recruitment within the material, without tissue damage or inflammation at 48 h. Interestingly, tissue remodeling with vasculature inside angioreactors was seen at 21 days. CONCLUSIONS: Our results showed that pUBMh/LL37 is cytologically compatible, and induces angiogenesis in vivo, showing potential for tissue regeneration therapies.

Congenital and acquired tissular losses due to disease or trauma are a major world health problem. Regenerative therapy aims to fix damaged tissues by directing the natural capacity of a host organism to use biofunctionalized artificial tissue scaffolds. These three-dimensional (3D) scaffolds can be customized with cells and/or bioactive molecules to induce cellular homing and angiogenesis, essential to ensure successful tissue regeneration. Hydrogels (HGs) scaffolds are networks of hydrophilic homopolymers, copolymers, and/or macromers with chemical and biological activities that enhance their cell colonization. The use of HGs in regenerative medicine has shown to be advantageous since HGs can be prepared under clinical-grade conditions and tailored to the specific needs of the replaced tissue. They can be made to emulate native extracellular matrices (ECMs) including physical, mechanical, and chemical cues and resilience properties. These customized HGs can reproduce the natural hygroscopic capacity of the original tissue which improves cellular anchoring, nutrition, and waste disposal. They can enable host molecular and cellular modification conducive to a natural cellular microenvironment, modifying the properties of the scaffold, and improving chemotaxis, cell adhesion, migration, proliferation, differentiation, and angiogenesis; HGs can be created and biofunctionalized with linked growth factors and synthetic peptides tailored to positively influence scaffold colonization and functional biocompatibility. This review aims to collect the most relevant information regarding biofunctionalization of HGs used for vascular tissue regeneration, their biological effects, and their clinical implications. While most biofunctionalized HGs are still under investigation, some of them have been studied in vitro, ex vivo, and in vivo with promising results. In this regard, in vivo studies have shown that biofunctionalized scaffolds with peptides such as chitosan hydrogel with LL-37 promotes angiogenesis and healing of pressure ulcers. Also, the GHK tripeptide is widely used in trials focused on guided tissue remodeling.

BACKGROUND: Nowadays, biomaterials used as a scaffold must be easy to deliver in the bone defect area. Extracellular matrix (ECM) hydrogels are highly hydrated polymers that can fill irregular shapes and act as bioactive materials. OBJECTIVE: This work aims to show the effects of ECM hydrogels derived from bovine bone (bECMh) on proliferation, cytotoxicity and expression of pro-inflammatory cytokines in three cells types involved in tissue regeneration, as well as biocompatibility in vivo. METHODS: In vitro, we used an extract of bECMh to test it on macrophages, fibroblasts, and adipose-derived mesenchymal stem cells (AD-MCSs). Cell proliferation was measured using the MTT assay, cytotoxicity was measured by quantifying lactate dehydrogenase release and the Live/Dead Cell Imaging assays. Concentrations of IL-6, IL-10, IL-12p70, MCP-1 and TNF-α were quantified in the supernatants using a microsphere-based cytometric bead array. For in vivo analysis, Wistar rats were inoculated into the dorsal sub-dermis with bECMh, taking as reference the midline of the back. The specimens were sacrificed at 24 h for histological study. RESULTS: In vitro, this hydrogel behaves as a dynamic biomaterial that increases fibroblast proliferation, induces the production of pro-inflammatory cytokines in macrophages, among which MCP-1 and TNF-α stand out. In vivo, bECMh allows the colonization of host fibroblast-like and polymorphonuclear cells, without tissue damage or inflammation. CONCLUSIONS: The results indicate that bECMh is a biocompatible material that could be used as a scaffold, alone or in conjunction with cells or functional biomolecules, enhancing proliferation and allowing the filling of bone defects to its further regeneration.