Light-emitting diode effects on combined decellularization of tracheae. A novel approach to obtain biological scaffolds

Alginate-Based 3D A549 Cell Culture Model to Study Paracoccidioides Infection

A three-dimensional (3D) lung aggregate model based on sodium alginate scaffolds was developed to study the interactions between Paracoccidioides brasiliensis (Pb) and lung epithelial cells. The suitability of the 3D aggregate as an infection model was examined using cell viability (cytotoxicity), metabolic activity, and proliferation assays. Several studies exemplify the similarity between 3D cell cultures and living organisms, which can generate complementary data due to the greater complexity observed in these designed models, compared to 2D cell cultures. A 3D cell culture system of human A549 lung cell line plus sodium alginate was used to create the scaffolds that were infected with Pb18. Our results showed low cytotoxicity, evidence of increased cell density (indicative of cell proliferation), and the maintenance of cell viability for seven days. The confocal analysis revealed viable yeast within the 3D scaffold, as demonstrated in the solid BHI Agar medium cultivation. Moreover, when ECM proteins were added to the alginate scaffolds, the number of retrieved fungi was significantly higher. Our results highlight that this 3D model may be promising for in vitro studies of host-pathogen interactions.

Optimization of a decellularization protocol of porcine tracheas. Long-term effects of cryopreservation. A histological study

OBJECTIVE

The aim of this study was to optimize a decellularization protocol in the trachea of Sus scrofa domestica (pig) as well as to study the effects of long-term cryopreservation on the extracellular matrix of decellularized tracheas.

METHODS

Porcine tracheas were decellularized using Triton X-100, SDC, and SDS alone or in combination. The effect of these detergents on the extracellular matrix characteristics of decellularized porcine tracheas was evaluated at the histological, biomechanical, and biocompatibility level. Morphometric approaches were used to estimate the effect of detergents on the collagen and elastic fibers content as well as on the removal of chondrocytes from decellularized organs. Moreover, the long-term structural, ultrastructural, and biomechanical effect of cryopreservation of decellularized tracheas were also estimated.

RESULTS

Two percent SDS was the most effective detergent tested concerning cell removal and preservation of the histological and biomechanical properties of the tracheal wall. However, long-term cryopreservation had no an appreciable effect on the structure, ultrastructure, and biomechanics of decellularized tracheal rings.

CONCLUSION

The results presented here reinforce the use of SDS as a valuable decellularizing agent for porcine tracheas. Furthermore, a cryogenic preservation protocol is described, which has minimal impact on the histological and biomechanical properties of decellularized porcine tracheas.

Fabrication of Decellularized Engineered Extracellular Matrix through Bioreactor-Based Environment for Bone Tissue Engineering

Extracellular matrix (ECM)-contained grafts can be achieved by decellularization of native bones or synthetic scaffolds. Limitations associated with harvesting the native bone has raised interest in preparing in vitro ECM bioscaffold for bone tissue engineering. Here, we intend to develop an ECM-contained construct via decellularizing an engineered gelatin-coated β-tricalcium phosphate (gTCP) scaffold. In order to find an optimal protocol for decellularization of cell-loaded gTCP scaffolds, they were seeded with buccal fat pad-derived stem cells. Then, four decellularization protocols including sodium dodecyl sulfate, trypsin, Triton X-100, and combined solution methods were compared for the amounts of residual cells and remnant collagen and alteration of scaffold structure. Then, the efficacy of the selected protocol in removing cells from gTCP scaffolds incubated in a rotating and perfusion bioreactor for 24 days was evaluated and compared with static condition using histological analysis. Finally, decellularized scaffolds, reloaded with cells, and their cytotoxicity and osteoinductive capability were evaluated. Complete removal of cells from gTCP scaffolds was achieved from all protocols. However, treatment with Triton X-100 showed significantly higher amount of remnant ECM. Bioreactor-incubated scaffolds possessed greater magnitude of ECM proteins including collagen and glycosaminoglycans. Reseeding the decellularized scaffolds also represented higher osteoinductivity of bioreactor-based scaffolds. Application of Triton X-100 as decellularization protocol and usage of bioreactors are suggested as a suitable technique for designing ECM-contained grafts for bone tissue engineering.

Tissue engineering applications in otolaryngology-The state of translation

While tissue engineering holds significant potential to address current limitations in reconstructive surgery of the head and neck, few constructs have made their way into routine clinical use. In this review, we aim to appraise the state of head and neck tissue engineering over the past five years, with a specific focus on otologic, nasal, craniofacial bone, and laryngotracheal applications. A comprehensive scoping search of the PubMed database was performed and over 2000 article hits were returned with 290 articles included in the final review. These publications have addressed the hallmark characteristics of tissue engineering (cellular source, scaffold, and growth signaling) for head and neck anatomical sites. While there have been promising reports of effective tissue engineered interventions in small groups of human patients, the majority of research remains constrained to in vitro and in vivo studies aimed at furthering the understanding of the biological processes involved in tissue engineering. Further, differences in functional and cosmetic properties of the ear, nose, airway, and craniofacial bone affect the emphasis of investigation at each site. While otolaryngologists currently play a role in tissue engineering translational research, continued multidisciplinary efforts will likely be required to push the state of translation towards tissue-engineered constructs available for routine clinical use.

LEVEL OF EVIDENCE

NA.

Applications of decellularized materials in tissue engineering: advantages, drawbacks and current improvements, and future perspectives

Decellularized materials (DMs) are attracting more and more attention in tissue engineering because of their many unique advantages, and they could be further improved in some aspects through various means.

A Comparative Study of the Effects of Different Decellularization Methods and Genipin-Cross-Linking on the Properties of Tracheal Matrices

Background

Different decellularization methods can affect the integrity and the biomechanical and biocompatible properties of the tracheal matrix. Natural cross-linking with genipin can be applied to improve those properties. The goals of this study were to evaluate the effects of different decellularization methods on the properties of genipin-cross-linked decellularized tracheal matrices in rabbits.

Methods

The tracheas of New Zealand rabbits were decellularized by the Triton-X 100-processed method (TPM) and the detergent-enzymatic method (DEM) and were then cross-linked with genipin. Mechanical tests, haematoxylin-eosin staining, Masson trichrome staining, Safranin O staining, DAPI staining, scanning electronic microscopy (SEM), and biocompatibility tests were used to evaluate the treatment. The bioengineered trachea and control trachea were then implanted into allogeneic rabbits for 30 days. The structural and functional analyses were performed after transplantation.

Results

The biomechanical tests demonstrated that the biomechanical properties of the decellularized tracheas decreased and that genipin improved them (p < 0.05). The histological staining results revealed that most of the mucosal epithelial cells were removed and that the decellularized trachea had lower immunogenicity than the control group. The analysis of SEM revealed that the decellularized trachea retained the micro- and ultra-structural architectures of the trachea and that the matrices cross-linked with genipin were denser. The biocompatibility evaluation and in vivo implantation experiments showed that the decellularized trachea treated with the DEM had better biocompatibility than that treated with the TPM and that immunogenicity in the cross-linked tissues was lower than that in the uncross-linked tissues (p < 0.05).

Conclusions

Compared with the trachea treated with the TPM, the rabbit trachea processed by the DEM had better biocompatibility and lower immunogenicity, and its structural and mechanical characteristics were effectively improved after the genipin treatment, which is suitable for engineering replacement tracheal tissue.

* Extracellular Matrices for Bone Regeneration: A Literature Review

The gold standard material for bone regeneration is still autologous bone, a mesenchymal tissue that consists mainly of extracellular matrix (ECM) (90% v/v) and little cellular content (10% v/v). However, the fact that decellularized allogenic bone grafts often present a clinical performance comparable to autologous bone grafts demonstrates the crucial role of ECM in bone regeneration. For long, the mechanism by which bone allografts function was not clear, but recent research has unveiled many unique characteristics of ECM that seem to play a key role in tissue regeneration. This is further confirmed by the fact that synthetic biomaterials with composition and properties resembling bone ECM present excellent bone regeneration properties. In this context, ECM molecules such as glycosaminoglycans (GAGs) and self-assembly peptides (SAPs) can improve the performance of bone regeneration biomaterials. Moreover, decellularized ECM derived either from native tissues such as bone, cartilage, skin, and tooth germs or from cells such as osteoblasts, chondrocytes, and stem cells has shown promising results in bone regeneration applications. Understanding the role of ECM in bone regeneration is crucial for the development of the next generation of biomaterials for bone tissue engineering. In this sense, this review addresses the state-of-the-art on this subject matter.

Development of decellularized scaffolds for stem cell-driven tissue engineering

Organ transplantation is an effective treatment for chronic organ dysfunctioning conditions. However, a dearth of available donor organs for transplantation leads to the death of numerous patients waiting for a suitable organ donor. The potential of decellularized scaffolds, derived from native tissues or organs in the form of scaffolds has been evolved as a promising approach in tissue-regenerative medicine for translating functional organ replacements. In recent years, donor organs, such as heart, liver, lung and kidneys, have been reported to provide acellular extracellular matrix (ECM)-based scaffolds through the process called 'decellularization' and proved to show the potential of recellularization with selected cell populations, particularly with stem cells. In fact, decellularized stem cell matrix (DSCM) has also emerged as a potent biological scaffold for controlling stem cell fate and function during tissue organization. Despite the proven potential of decellularized scaffolds in tissue engineering, the molecular mechanism responsible for stem cell interactions with decellularized scaffolds is still unclear. Stem cells interact with, and respond to, various signals/cues emanating from their ECM. The ability to harness the regenerative potential of stem cells via decellularized ECM-based scaffolds has promising implications for tissue-regenerative medicine. Keeping these points in view, this article reviews the current status of decellularized scaffolds for stem cells, with particular focus on: (a) concept and various methods of decellularization; (b) interaction of stem cells with decellularized scaffolds; (c) current recellularization strategies, with associated challenges; and (iv) applications of the decellularized scaffolds in stem cell-driven tissue engineering and regenerative medicine. Copyright © 2015 John Wiley & Sons, Ltd.