Extracellular matrix-derived products modulate endothelial and progenitor cell migration and proliferation in vitro and stimulate regenerative healing in vivo

The Development of a 3D PET Fibrous Scaffold Modified with an Umbilical Cord dECM for Liver Tissue Engineering

Organ and tissue dysfunction represents a clinically significant condition. By integrating cell biology with materials science, tissue engineering enables the reconstruction and restoration of damaged tissues or organs, offering a noninvasive repair approach. In our study, we replicated the cellular growth environment by utilizing a human umbilical cord-derived decellularized extracellular matrix (dECM) as a modifying agent for the polyethylene terephthalate (PET) polymeric fiber scaffold. This allowed us to create a dECM-coated polyester fiber-based scaffold, PET-dECM, tailored for liver tissue engineering purposes. We effectively produced a decellularized human umbilical cord-derived ECM through a combined decellularization process involving trypsin/EDTA, TritonX-100, and sodium deoxycholate. The application of the dECM coating onto the PET material was accomplished through several steps, such as ester hydrolysis, EDC/NHS-activated crosslinking, and dECM conjugation. The biological performance of the PET-dECM was validated using RG cell culture assays. Notably, the dECM coating significantly improved PET's hydrophilicity and biocompatibility, thereby aiding cell adhesion, proliferation, and functional differentiation (p < 0.05). It was further found that the hepatocyte function of HepaRG was significantly enhanced on the PET-dECM, which may be attributed to the dECM's ability to facilitate the restoration of cell polarity. The PET-dECM holds promise as an effective hepatocyte culture carrier and could potentially find application in liver tissue engineering.

Enhancing neuroinduction activity of PLCL-based nerve conduits through native epineurium integration

Autologous nerve grafts have been considered the gold standard for peripheral nerve grafts. However, due to drawbacks such as functional loss in the donor area and a shortage of donor sources, nerve conduits are increasingly being considered as an alternative approach. Polymer materials have been widely studied as nerve repair materials due to their excellent processing performance. However, their limited biocompatibility has restricted further clinical applications. The epineurium is a natural extra-neural wrapping structure. After undergoing decellularization, the epineurium not only reduces immune rejection but also retains certain bioactive components. In this study, decellularized epineurium (DEP) derived from the sciatic nerve of mammals was prepared, and a bilayer nerve conduit was created by electrospinning a poly (l-lactide-co-ε-caprolactone) (PLCL) membrane layer onto the outer surface of the DEP. Components of the DEP were examined; the physical properties and biosafety of the bilayer nerve conduit were evaluated; and the functionality of the nerve conduit was evaluated in rats. The results demonstrate that the developed bilayer nerve conduit exhibits excellent biocompatibility and mechanical properties. Furthermore, this bilayer nerve conduit shows significantly superior therapeutic effects for sciatic nerve defects in rats compared to the pure PLCL nerve conduit. In conclusion, this research provides a novel strategy for the design of nerve regeneration materials and holds promising potential for further clinical translation.

Composite Microparticles of Fat Graft and GFR Matrigel Improved Volume Retention by Promoting Cell Migration and Vessel Regeneration

BACKGROUND

The retention volume of autologous fat grafts decreases after transplantation due to limited nutrition infiltration and insufficient blood supply. Structural fat grafts and the 3M (multipoint, multitunnel, and multilayer) injection technique have been considered to improve the survival of grafts; however, it is difficult for surgeons to practice in the clinic because grafts tend to gather into a cluster, especially in large volume fat grafting. Therefore, we hypothesize that prefabricated microparticle fat grafts (PFMG) may improve the retention rate.

METHODS

The C57BL/6 mouse fat particles were embedded in growth factor-reduced (GFR)-Matrigel to detect cell migration by immunofluorescence staining in vitro. PFMG was prepared by mixing mouse fat particles and GFR Matrigel in a 1:1 volume ratio and injected subcutaneously into C57BL/6 mice. Fat particles mixed with PBS in equal volume served as control group. The grafts were harvested at 1, 4, 8, and 12 weeks after sacrifice. The retention rate of grafts at each time point was measured, and the structural alterations were detected by SEM. Fat necrosis and blood vessel density were evaluated by histological analysis.

RESULTS

CD34+ cells are migrated from the PFMG and formed a tree-like tubular network in the in vitro study. The retention rate was higher in the PFMG group than in the control group at week 12 (38% vs. 30%, p < 0.05). After transplantation, the dissociated structure of fat particles was maintained in PFMG by SEM analysis. Histological analysis of PFMG confirmed less fat necrosis and more blood vessel density in the PFMG group at the early stage than in the control group. The GFR Matrigel was displaced by adipose tissue with time.

CONCLUSIONS

In this study, we developed a novel fat grafting method, PFMG that dispersed fat grafts and maintained the structure after transplantation. High volume retention volume of PFMG was achieved by promoting cell migration and vessel regeneration.

NO LEVEL ASSIGNED

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Gene expression of Postn and FGF7 in canine chordae tendineae and their effects on flexor tenocyte biology

Chordae tendineae, referred to as heart tendinous cords, act as tendons connecting the papillary muscles to the valves in the heart. Their role is analogous to tendons in the musculoskeletal system. Despite being exposed to millions of cyclic tensile stretches over a human's lifetime, chordae tendineae rarely suffer from overuse injuries. On the other hand, musculoskeletal tendinopathy is very common and remains challenging in clinical treatment. The objective of this study was to investigate the mechanism behind the remarkable durability and resistance to overuse injuries of chordae tendineae, as well as to explore their effects on flexor tenocyte biology. The messenger RNA expression profiles of chordae tendineae were analyzed using RNA sequencing and verified by quantitative reverse transcription polymerase chain reaction  and immunohistochemistry. Interestingly, we found that periostin (Postn) and fibroblast growth factor 7 (FGF7) were expressed at significantly higher levels in chordae tendineae, compared to flexor tendons. We further treated flexor tenocytes in vitro with periostin and FGF7 to examine their effects on the proliferation, migration, apoptosis, and tendon-related gene expression of flexor tenocytes. The results displayed enhanced cell proliferation ability at an early stage and an antiapoptotic effect on tenocytes, while treated with periostin and/or FGF7 proteins. Furthermore, there was a trend of promoted tenocyte migration capability. These findings indicated that Postn and FGF7 may represent novel cytokines to target flexor tendon healing. Clinical significance: The preliminary discovery leads to a novel idea for treating tendinopathy in the musculoskeletal system using specific molecules identified from chordae tendineae.

Decellularized Bovine Skeletal Muscle Scaffolds: Structural Characterization and Preliminary Cytocompatibility Evaluation

Skeletal muscle degeneration is responsible for major mobility complications, and this muscle type has little regenerative capacity. Several biomaterials have been proposed to induce muscle regeneration and function restoration. Decellularized scaffolds present biological properties that allow efficient cell culture, providing a suitable microenvironment for artificial construct development and being an alternative for in vitro muscle culture. For translational purposes, biomaterials derived from large animals are an interesting and unexplored source for muscle scaffold production. Therefore, this study aimed to produce and characterize bovine muscle scaffolds to be applied to muscle cell 3D cultures. Bovine muscle fragments were immersed in decellularizing solutions for 7 days. Decellularization efficiency, structure, composition, and three-dimensionality were evaluated. Bovine fetal myoblasts were cultured on the scaffolds for 10 days to attest cytocompatibility. Decellularization was confirmed by DAPI staining and DNA quantification. Histological and immunohistochemical analysis attested to the preservation of main ECM components. SEM analysis demonstrated that the 3D structure was maintained. In addition, after 10 days, fetal myoblasts were able to adhere and proliferate on the scaffolds, attesting to their cytocompatibility. These data, even preliminary, infer that generated bovine muscular scaffolds were well structured, with preserved composition and allowed cell culture. This study demonstrated that biomaterials derived from bovine muscle could be used in tissue engineering.

High quality repair of osteochondral defects in rats using the extracellular matrix of antler stem cells

BACKGROUND

Cartilage defects are some of the most common causes of arthritis. Cartilage lesions caused by inflammation, trauma or degenerative disease normally result in osteochondral defects. Previous studies have shown that decellularized extracellular matrix (ECM) derived from autologous, allogenic, or xenogeneic mesenchymal stromal cells (MSCs) can effectively restore osteochondral integrity.

AIM

To determine whether the decellularized ECM of antler reserve mesenchymal cells (RMCs), a xenogeneic material from antler stem cells, is superior to the currently available treatments for osteochondral defects.

METHODS

We isolated the RMCs from a 60-d-old sika deer antler and cultured them in vitro to 70% confluence; 50 mg/mL L-ascorbic acid was then added to the medium to stimulate ECM deposition. Decellularized sheets of adipocyte-derived MSCs (aMSCs) and antlerogenic periosteal cells (another type of antler stem cells) were used as the controls. Three weeks after ascorbic acid stimulation, the ECM sheets were harvested and applied to the osteochondral defects in rat knee joints.

RESULTS

The defects were successfully repaired by applying the ECM-sheets. The highest quality of repair was achieved in the RMC-ECM group both in vitro (including cell attachment and proliferation), and in vivo (including the simultaneous regeneration of well-vascularized subchondral bone and avascular articular hyaline cartilage integrated with surrounding native tissues). Notably, the antler-stem-cell-derived ECM (xenogeneic) performed better than the aMSC-ECM (allogenic), while the ECM of the active antler stem cells was superior to that of the quiescent antler stem cells.

CONCLUSION

Decellularized xenogeneic ECM derived from the antler stem cell, particularly the active form (RMC-ECM), can achieve high quality repair/reconstruction of osteochondral defects, suggesting that selection of decellularized ECM for such repair should be focused more on bioactivity rather than kinship.

Decellularization and Their Significance for Tissue Regeneration in the Era of 3D Bioprinting

Three-dimensional bioprinting is an emerging technology that has high potential application in tissue engineering and regenerative medicine. Increasing advancement and improvement in the decellularization process have led to an increase in the demand for using a decellularized extracellular matrix (dECM) to fabricate tissue engineered products. Decellularization is the process of retaining the extracellular matrix (ECM) while the cellular components are completely removed to harvest the ECM for the regeneration of various tissues and across different sources. Post decellularization of tissues and organs, they act as natural biomaterials to provide the biochemical and structural support to establish cell communication. Selection of an effective method for decellularization is crucial, and various factors like tissue density, geometric organization, and ECM composition affect the regenerative potential which has an impact on the end product. The dECM is a versatile material which is added as an important ingredient to formulate the bioink component for constructing tissue and organs for various significant studies. Bioink consisting of dECM from various sources is used to generate tissue-specific bioink that is unique and to mimic different biometric microenvironments. At present, there are many different techniques applied for decellularization, and the process is not standardized and regulated due to broad application. This review aims to provide an overview of different decellularization procedures, and we also emphasize the different dECM-derived bioinks present in the current global market and the major clinical outcomes. We have also highlighted an overview of benefits and limitations of different decellularization methods and various characteristic validations of decellularization and dECM-derived bioinks.

Decellularized extracellular matrix biomaterials for regenerative therapies: Advances, challenges and clinical prospects

Tissue engineering and regenerative medicine have shown potential in the repair and regeneration of tissues and organs via the use of engineered biomaterials and scaffolds. However, current constructs face limitations in replicating the intricate native microenvironment and achieving optimal regenerative capacity and functional recovery. To address these challenges, the utilization of decellularized tissues and cell-derived extracellular matrix (ECM) has emerged as a promising approach. These biocompatible and bioactive biomaterials can be engineered into porous scaffolds and grafts that mimic the structural and compositional aspects of the native tissue or organ microenvironment, both in vitro and in vivo. Bioactive dECM materials provide a unique tissue-specific microenvironment that can regulate and guide cellular processes, thereby enhancing regenerative therapies. In this review, we explore the emerging frontiers of decellularized tissue-derived and cell-derived biomaterials and bio-inks in the field of tissue engineering and regenerative medicine. We discuss the need for further improvements in decellularization methods and techniques to retain structural, biological, and physicochemical characteristics of the dECM products in a way to mimic native tissues and organs. This article underscores the potential of dECM biomaterials to stimulate in situ tissue repair through chemotactic effects for the development of growth factor and cell-free tissue engineering strategies. The article also identifies the challenges and opportunities in developing sterilization and preservation methods applicable for decellularized biomaterials and grafts and their translation into clinical products.

The super-healing MRL strain promotes muscle growth in muscular dystrophy through a regenerative extracellular matrix

The Murphy Roths Large (MRL) mouse strain has "super-healing" properties that enhance recovery from injury. In mice, the DBA/2J strain intensifies many aspects of muscular dystrophy, so we evaluated the ability of the MRL strain to suppress muscular dystrophy in the Sgcg-null mouse model of limb girdle muscular dystrophy. A comparative analysis of Sgcg-null mice in the DBA/2J versus MRL strains showed greater myofiber regeneration, with reduced structural degradation of muscle in the MRL strain. Transcriptomic profiling of dystrophic muscle indicated strain-dependent expression of extracellular matrix (ECM) and TGF-β signaling genes. To investigate the MRL ECM, cellular components were removed from dystrophic muscle sections to generate decellularized myoscaffolds. Decellularized myoscaffolds from dystrophic mice in the protective MRL strain had significantly less deposition of collagen and matrix-bound TGF-β1 and TGF-β3 throughout the matrix. Dystrophic myoscaffolds from the MRL background, but not the DBA/2J background, were enriched in myokines like IGF-1 and IL-6. C2C12 myoblasts seeded onto decellularized matrices from Sgcg-/- MRL and Sgcg-/- DBA/2J muscles showed the MRL background induced greater myoblast differentiation compared with dystrophic DBA/2J myoscaffolds. Thus, the MRL background imparts its effect through a highly regenerative ECM, which is active even in muscular dystrophy.

Extracellular Matrices as Bioactive Materials for In Situ Tissue Regeneration

Bioactive materials based on a nature-derived extracellular matrix (NECM) represent a category of biomedical devices with versatile therapeutic applications in the realms of tissue repair and engineering. With advancements in decellularization technique, the inherent bioactive molecules and the innate nano-structural and mechanical properties are preserved in three-dimensional scaffolds mainly composed of collagens. Techniques such as electrospinning, three-dimensional printing, and the intricate fabrication of hydrogels are developed to mimic the physical structures, biosignalling and mechanical cues of ECM. Until now, there has been no approach that can fully account for the multifaceted properties and diverse applications of NECM. In this review, we introduce the main proteins composing NECMs and explicate the importance of them when used as therapeutic devices in tissue repair. Nano-structural features of NECM and their applications regarding tissue repair are summarized. The origins, degradability, and mechanical property of and immune responses to NECM are also introduced. Furthermore, we review their applications, and clinical features thereof, in the repair of acute and chronic wounds, abdominal hernia, breast deformity, etc. Some typical marketed devices based on NECM, their indications, and clinical relevance are summarized.

Combined 3D bioprinting and tissue-specific ECM system reveals the influence of brain matrix on stem cell differentiation

We have previously shown that human and murine breast extracellular matrix (ECM) can significantly impact cellular behavior, including stem cell fate determination. It has been established that tissue-specific extracellular matrix from the central nervous system has the capacity to support neuronal survival. However, the characterization of its influence on stem cell differentiation and its adaptation to robust 3D culture models is underdeveloped. To address these issues, we combined our 3D bioprinter with hydrogels containing porcine brain extracellular matrix (BMX) to test the influence of the extracellular matrix on stem cell differentiation. Our 3D bioprinting system generated reproducible 3D neural structures derived from mouse embryonic stem cells (mESCs). We demonstrate that the addition of BMX preferentially influences 3D bioprinted mESCs towards neural lineages compared to standard basement membrane (Geltrex/Matrigel) hydrogels alone. Furthermore, we demonstrate that we can transplant these 3D bioprinted neural cellular structures into a mouse's cleared mammary fat pad, where they continue to grow into larger neural outgrowths. Finally, we demonstrate that direct injection of human induced pluripotent stem cells (hiPSCS) and neural stem cells (NSCs) suspended in pure BMX formed neural structures in vivo. Combined, these findings describe a unique system for studying brain ECM/stem cell interactions and demonstrate that BMX can direct pluripotent stem cells to differentiate down a neural cellular lineage without any additional specific differentiation stimuli.

The superior healing capacity of MRL tendons is minimally influenced by the systemic environment of the MRL mouse

Murphy Roths Large mice (MRL) exhibit improved tendon healing and are often described as a "super-healer" strain. The underlying mechanisms that drive the superior healing response of MRL remain a controversial subject. We utilized a tendon transplantation model between MRL and "normal-healer" B6-mice to differentiate between the contribution of MRL's innate tendon and systemic environment to its improved healing capacity. Patellar tendons with a midsubstance punch injury were transplanted back into the same animal (autograft) or into an animal of the other strain (allograft). Findings at 4 weeks showed that the innate MRL tendon environment drives its improved healing capacity as demonstrated by improved stiffness and maximum load in MRL-grafts-in-B6-host-allografts compared to B6-autografts, and higher modulus in MRL-autografts compared to B6-graft-in-MRL-host-allografts. Groups with an MRL component showed an increase in pro-inflammatory cytokines in the 3 days after injury, suggesting an early enhanced inflammatory profile in MRL that ultimately resolves. A preserved range of motion of the knee joint in all MRL animals suggests a systemic "shielding effect" of MRL in regard to joint adhesiveness. Our findings 4-weeks post injury are consistent with previous studies showing tissue-driven improved healing and suggest that the systemic environment contributes to the overall healing process.

Evolution of biomimetic ECM scaffolds from decellularized tissue matrix for tissue engineering: A comprehensive review

Tissue engineering is essentially a technique for imitating nature. Natural tissues are made up of three parts: extracellular matrix (ECM), signaling systems, and cells. Therefore, biomimetic ECM scaffold is one of the best candidates for tissue engineering scaffolds. Among the many scaffold materials of biomimetic ECM structure, decellularized ECM scaffolds (dECMs) obtained from natural ECM after acellular treatment stand out because of their inherent natural components and microenvironment. First, an overview of the family of dECMs is provided. The principle, mechanism, advances, and shortfalls of various decellularization technologies, including physical, chemical, and biochemical methods are then critically discussed. Subsequently, a comprehensive review is provided on recent advances in the versatile applications of dECMs including but not limited to decellularized small intestinal submucosa, dermal matrix, amniotic matrix, tendon, vessel, bladder, heart valves. And detailed examples are also drawn from scientific research and practical work. Furthermore, we outline the underlying development directions of dECMs from the perspective that tissue engineering scaffolds play an important role as an important foothold and fulcrum at the intersection of materials and medicine. As scaffolds that have already found diverse applications, dECMs will continue to present both challenges and exciting opportunities for regenerative medicine and tissue engineering.

Comparison of Bovine- and Porcine-Derived Decellularized Biomaterials: Promising Platforms for Tissue Engineering Applications

Animal-derived xenogeneic biomaterials utilized in different surgeries are promising for various applications in tissue engineering. However, tissue decellularization is necessary to attain a bioactive extracellular matrix (ECM) that can be safely transplanted. The main objective of the present study is to assess the structural integrity, biocompatibility, and potential use of various acellular biomaterials for tissue engineering applications. Hence, a bovine pericardium (BP), porcine pericardium (PP), and porcine tunica vaginalis (PTV) were decellularized using a Trypsin, Triton X (TX), and sodium dodecyl sulfate (SDS) (Trypsin + TX + SDS) protocol. The results reveal effective elimination of the cellular antigens with preservation of the ECM integrity confirmed via staining and electron microscopy. The elasticity of the decellularized PP (DPP) was markedly (p < 0.0001) increased. The tensile strength of DBP, and DPP was not affected after decellularization. All decellularized tissues were biocompatible with persistent growth of the adipose stem cells over 30 days. The staining confirmed cell adherence either to the peripheries of the materials or within their matrices. Moreover, the in vivo investigation confirmed the biocompatibility and degradability of the decellularized scaffolds. Conclusively, Trypsin + TX + SDS is a successful new protocol for tissue decellularization. Moreover, decellularized pericardia and tunica vaginalis are promising scaffolds for the engineering of different tissues with higher potential for the use of DPP in cardiovascular applications and DBP and DPTV in the reconstruction of higher-stress-bearing abdominal walls.

The super-healing MRL strain promotes muscle growth in muscular dystrophy through a regenerative extracellular matrix

Genetic background shifts the severity of muscular dystrophy. In mice, the DBA/2J strain confers a more severe muscular dystrophy phenotype, whereas the Murphy's Roth Large (MRL) strain has "super-healing" properties that reduce fibrosis. A comparative analysis of the Sgcg null model of Limb Girdle Muscular Dystrophy in the DBA/2J versus MRL strain showed the MRL background was associated with greater myofiber regeneration and reduced structural degradation of muscle. Transcriptomic profiling of dystrophic muscle in the DBA/2J and MRL strains indicated strain-dependent expression of the extracellular matrix (ECM) and TGF-β signaling genes. To investigate the MRL ECM, cellular components were removed from dystrophic muscle sections to generate decellularized "myoscaffolds". Decellularized myoscaffolds from dystrophic mice in the protective MRL strain had significantly less deposition of collagen and matrix-bound TGF-β1 and TGF-β3 throughout the matrix, and dystrophic myoscaffolds from the MRL background were enriched in myokines. C2C12 myoblasts were seeded onto decellularized matrices from Sgcg-/- MRL and Sgcg-/- DBA/2J matrices. Acellular myoscaffolds from the dystrophic MRL background induced myoblast differentiation and growth compared to dystrophic myoscaffolds from the DBA/2J matrices. These studies establish that the MRL background also generates its effect through a highly regenerative ECM, which is active even in muscular dystrophy.

Prochondrogenic effect of decellularized extracellular matrix secreted from human induced pluripotent stem cell-derived chondrocytes

Cartilage is mainly composed of chondrocytes and the extracellular matrix (ECM), which exchange important biochemical and biomechanical signals necessary for differentiation and homeostasis. Human articular cartilage has a low ability for regeneration because it lacks blood vessels, nerves, and lymphatic vessels. Currently, cell therapeutics, including stem cells, provide a promising strategy for cartilage regeneration and treatment; however, there are various hurdles to overcome, such as immune rejection and teratoma formation. In this study, we assessed the applicability of the stem cell-derived chondrocyte ECM for cartilage regeneration. Human induced pluripotent stem cell (hiPSC)-derived chondrocytes (iChondrocytes) were differentiated, and decellularized ECM (dECM) was successfully isolated from cultured chondrocytes. Isolated dECM enhanced in vitro chondrogenesis of iPSCs when recellularized. Implanted dECM also restored osteochondral defects in a rat osteoarthritis model. A possible association with the glycogen synthase kinase-3 beta (GSK3β) pathway demonstrated the fate-determining importance of dECM in regulating cell differentiation. Collectively, we suggested the prochondrogenic effect of hiPSC-derived cartilage-like dECM and offered a promising approach as a non-cellular therapeutic for articular cartilage reconstruction without cell transplantation. STATEMENT OF SIGNIFICANCE: Human articular cartilage has low ability for regeneration and cell culture-based therapeutics could aid cartilage regeneration. Yet, the applicability of human induced pluripotent stem cell-derived chondrocyte (iChondrocyte) extracellular matrix (ECM) has not been elucidated. Therefore, we first differentiated iChondrocytes and isolated the secreted ECM by decellularization. Recellularization was performed to confirm the pro-chondrogenic effect of the decellularized ECM (dECM). In addition, we confirmed the possibility of cartilage repair by transplanting the dECM into the cartilage defect in osteochondral defect rat knee joint. We believe that our proof-of-concept study will serve as a basis for investigating the potential of dECM obtained from iPSC-derived differentiated cells as a non-cellular resource for tissue regeneration and other future applications.

Bioactive Spinal Cord Scaffold Releasing Neurotrophic Exosomes to Promote In Situ Centralis Neuroplasticity

Spinal cord injury (SCI), one of the most serious injuries of the central nervous system, causes physical functional dysfunction and even paralysis in millions of patients. As a matter of necessity, redressing the neuroleptic pathologic microenvironment to a neurotrophic microenvironment is essential in order to alleviate this dilemma and facilitate the recovery of the spinal cord. Herein, based on cell-sheet technology, two functional cell types─uninduced and neural-induced stem cells from human exfoliated deciduous teeth─were formed into a composite membrane that subsequently self-assembled to form a bioactive scaffold with a spinal-cord-like structure, called a spinal cord assembly (SCA). In a stable extracellular matrix microenvironment, SCA continuously released SCA-derived exosomes containing various neurotrophic factors, which effectively promoted neuronal regeneration, axonal extension, and angiogenesis and inhibited glial scar generation in a rat model of SCI. Neurotrophic exosomes significantly improved the pathological microenvironment and promoted in situ centralis neuroplasticity, ultimately eliciting a strong repair effect in this model. SCA therapy is a promising strategy for the effective treatment of SCI based on neurotrophic exosome delivery.

Use of Decellularized SMILE (Small-Incision Lenticule Extraction) Lenticules for Engineering the Corneal Endothelial Layer: A Proof-of-Concept

PURPOSE

To demonstrate the suitability of using decellularized SMILE (Small-incision Lenticule Extraction) lenticules for culturing and transplanting the corneal endothelium (CE).

METHODS

The SMILE lenticules, obtained during refractive surgery, were decellularized by incubating in CE culture medium and fetal bovine serum. Decellularization was confirmed by hematoxylin and eosin staining, DAPI staining, and gel electrophoresis. The amount of DNA per milligram of dry tissue weight was calculated to quantify the residual nuclear content. The transparency of the decellularized lenticules was determined by calculating the modulation transfer function. Immunostaining for stromal collagens and glycosaminoglycan was performed using specific antibodies. Engineered tissue was constructed by culturing the CE cells on lenticules and staining for ZO-1, Na/K ATPase, and N-cadherin. The functionality of the engineered tissues was assessed by transplanting them onto edematous human donor corneas and perfusing for 10 days ex-vivo.

RESULTS

The residual DNA per milligram of dry tissue weight was found to be significantly reduced (p < 0.0001) in serum (0.255 µg/mg) and Opti-MEM (0.140 µg/mg) when compared to fresh lenticules (3.9 µg/mg). Decellularization did not alter the arrangement of the collagen fibers or the transparency of the lenticules. CE cells attached and matured to express ZO-1, Na/K ATPase, and N-cadherin at two weeks after seeding. The engineered tissue upon transplantation significantly reduced the corneal edema (p < 0.05) and the transplanted cells remained intact on the SMILE lenticule post-transplantation.

CONCLUSION

This study demonstrates the suitability of using SMILE lenticules decellularized using a simple, chemical-free method for engineering the corneal endothelium for transplantation.

Adhesion and proliferation of bone marrow stromal cells on acellular spinal cord scaffolds

OBJECTIVES

This study aimed to produce an acellular spinal cord scaffold-bone marrow stromal cell (ASCS-BMSC) complex in which the growth of BMSCs transplanted into the spinal cord of rats could be simulated in vitro, facilitating the observation and evaluation of the growth of BMSCs on the ASCS for the first time.

METHODS

Freeze-thaw, chemical extraction and mechanical shaking approaches were used to remove the cellular components and prepare a rat ASCS containing only the extracellular matrix (ECM) structure from the rat spinal cord. BMSCs were embedded into ASCSs and freeze-dried agarose scaffolds (FASs), and cell migration and proliferation were observed via fluorescence microscopy and the MTT assay.

RESULTS

Compared with the normal rat spinal cord, the ASCS had no cell structure and retained ECM components such as type IV collagen, fibronectin and laminin, showing a three-dimensional network structure with good voids. The growth and proliferation of BMSCs on the ASCS was good, as shown by the MTT assay. Scanning electron microscopy showed that BMSCs covered 65% of the ASCS surface, and the mitochondria of BMSCs were developed and adhered to collagen fibres, as demonstrated by transmission electron microscopy. HE staining showed that BMSCs could grow inside the ASCS, and immunohistochemical staining showed that BMSCs still expressed CD44 and CD90 on the ASCS and had stem cell characteristics.

CONCLUSIONS

The results of the experiment indicate that the ASCS has the ability to improve cell adhesion and proliferation. Thus, the ASCS-BMSC combination may be used to treat spinal cord injury.

The combination of a 3D-Printed porous Ti-6Al-4V alloy scaffold and stem cell sheet technology for the construction of biomimetic engineered bone at an ectopic site

Cell sheet technology has been widely used in bone tissue engineering and regenerative medicine. However, controlling the shape and volume of large pieces of engineered bone tissue remains impossible without additional suitable scaffolds. Three-dimensional (3D) printed titanium (Ti) alloy scaffolds are mostly used as implant materials for repairing bone defects, but the unsatisfactory bioactivities of traditional Ti-based scaffolds severely limit their clinical applications. Herein, we hypothesize that the combination of bone marrow mesenchymal stem cell (BMSC) sheet technology and 3D porous Ti–6Al–4V (PT) alloy scaffolds could be used to fabricate biomimetic engineered bone. First, various concentrations of BMSCs were directly cocultured with PT scaffolds to obtain complexes of osteoblastic cell sheets and scaffolds. Then, as an experimental control, an osteoblastic BMSC sheet was prepared by continuous culturing under osteogenic conditions for 2 weeks without passaging and used to wrap the scaffolds. The BMSC sheet was composed of several layers of extracellular matrix (ECM) and a mass of BMSCs. The BMSCs exhibited excellent adherent, proliferative and osteogenic potential when cocultured with PT scaffolds, which may be attributed to the ability of the 3D microstructure of scaffolds to facilitate the biological behaviors of cells, as confirmed by the in vitro results. Moreover, the presence of BMSCs and ECM increased the angiogenic potential of PT scaffolds by the secretion of VEGF. Micro-CT and histological analysis confirmed the in vivo formation of biomimetic engineered bone when the complex of cocultured BMSCs and PT scaffolds and the scaffolds wrapped by prepared BMSC sheets were implanted subcutaneously into nude mice. Therefore, the combination of BMSC sheet technology and 3D-printed PT scaffolds could be used to construct customized biomimetic engineered bone, offering a novel and promising strategy for the precise repair of bone defects.

Human Acellular Dermal Matrix in Reconstructive Surgery-A Review

Reconstructive surgery often confronts large tissue defects. This creates a need to look for materials that are immunogenic but offer the possibility of tissue filling. ADM-acellular dermal matrix-is a biological collagen matrix without immunogenicity, which is more commonly used in surgical treatment. Reconstructive surgery is still searching for various biocompatible materials that can be widely used in surgery. The available materials have their advantages and disadvantages. This paper is a literature review on the use of human acellular dermal matrix (ADM) in reconstructive surgery (surgical oncology, plastic and reconstructive surgery, and gynecologic reconstructive surgery). ADM appears to be a material of increasing use in various fields of surgery, and thus, further research in this area is required.

Construction of biomimetic cell-sheet-engineered periosteum with a double cell sheet to repair calvarial defects of rats

Background

The periosteum plays a crucial role in the development and injury healing process of bone. The purpose of this study was to construct a biomimetic periosteum with a double cell sheet for bone tissue regeneration.

Methods

In vitro, the human amniotic mesenchymal stem cells (hAMSCs) sheet was first fabricated by adding 50 ​μg/ml ascorbic acid to the cell sheet induction medium. Characterization of the hAMSCs sheet was tested by general observation, microscopic observation, live/dead staining, scanning electron microscopy (SEM) and hematoxylin and eosin (HE) staining. Afterwards, the osteogenic cell sheet and vascular cell sheet were constructed and evaluated by general observation, alkaline phosphatase (ALP) staining, Alizarin Red S staining, SEM, live/dead staining and CD31 immunofluorescent staining for characterization. Then, we prepared the double cell sheet. In vivo, rat calvarial defect model was introduced to verify the regeneration of bone defects treated by different methods. Calvarial defects (diameter: 4 ​mm) were created of Sprague–Dawley rats. The rats were randomly divided into 4 groups: the control group, the osteogenic cell sheet group, the vascular cell sheet group and the double cell sheet group. Macroscopic, micro-CT and histological evaluations of the regenerated bone were performed to assess the treatment results at 8 weeks and 12 weeks after surgery.

Results

In vitro, hAMSCs sheet was successfully prepared. The hAMSCs sheet consisted of a large number of live hAMSCs and abundant extracellular matrix (ECM) that secreted by hAMSCs, as evidenced by macroscopic/microscopic observation, live/dead staining, SEM and HE staining. Besides, the osteogenic cell sheet and the vascular cell sheet were successfully prepared, which were verified by general observation, ALP staining, Alizarin Red S staining, SEM and CD31 immunofluorescent staining. In vivo, the macroscopic observation and micro-CT results both demonstrated that the double cell sheet group had better effect on bone regeneration than other groups. In addition, histological assessments indicated that large amounts of new bone had formed in the calvarial defects and more mature collagen in the double cell sheet group.

Conclusion

The double cell sheet could promote to repair calvarial defects of rats and accelerate bone regeneration.

The translational potential of this article

We successfully constructed a biomimetic cell-sheet-engineered periosteum with a double cell sheet by a simple, low-cost and effective method. This biomimetic periosteum may be a promising therapeutic strategy for the treatment of bone defects, which may be used in clinic in the future.

Biomaterial Design Inspired by Regenerative Research Organisms

The efficacy of implanted biomaterials is largely dependent on the response of the host's immune and stromal cells. Severe foreign body response (FBR) can impede the integration of the implant into the host tissue and compromise the intended mechanical and biochemical function. Many features of FBR, including late-stage fibrotic encapsulation of implants, parallel the formation of fibrotic scar tissue after tissue injury. Regenerative organisms like zebrafish and salamanders can avoid fibrosis after injury entirely, but FBR in these research organisms is rarely investigated because their immune competence is much lower than humans. The recent characterization of a regenerative mammal, the spiny mouse (Acomys), has inspired us to take a closer look at cellular regulation in regenerative organisms across the animal kingdom for insights into avoiding FBR in humans. Here, we highlight how major features of regeneration, such as blastema formation, macrophage polarization, and matrix composition, can be modulated across a range of regenerative research organisms to elucidate common features that may be harnessed to minimize FBR. Leveraging a deeper understanding of regenerative biology for biomaterial design may help to reduce FBR and improve device integration and performance.

Matrix Bound Nanovesicles have Tissue Specific Characteristics that Suggest a Regulatory Role

Recent studies have identified an extracellular vesicle population that is tightly anchored within the extracellular matrix of tissues and organs until released by matrix turnover events. Evidence suggests that these matrix-bound nanovesicles (MBV) are a ubiquitous component of the ECM, raising questions regarding their tissue specific identity and their biologic function(s). The primary objective of this study was to examine MBV isolated from six different tissues and compare their physical and compositional characteristics to determine the common and differentially expressed features. Accordingly, the results of this characterization show that while MBV are a ubiquitous component of the ECM they contain a protein and miRNA cargo that is tissue specific. The results furthermore suggest that MBV have an important role in regulating tissue homeostasis.

Integrity of the ECM Influences the Bone Regenerative Property of ECM/Dicalcium Phosphate Composite Scaffolds

Due to the limitation of clinical autologous bone supply and other issues, the development of bone regeneration materials is still a hot topic. Natural tissue-derived bone repair materials have good biocompatibility and degradability, but their structure and properties are likely to be adversely affected during terminal sterilization. In this study, a composite scaffold consisting of the acellular extracellular matrix and dicalcium phosphate (ECM/DCP) was fabricated and terminally sterilized by γ-ray irradiation. In addition, the ECM/DCP scaffold was saturated with water and was also sterilized by γ-ray irradiation (RX-ECM/DCP). Results showed that the triple helix structure of collagen was better maintained in RX-ECM/DCP than in ECM/DCP. The thermal stability of RX-DCP/ECM was much better than that of ECP/ECM. The in vitro and in vivo performances of both types of scaffolds were also evaluated. The RX-ECM/DCP scaffold exhibited better in vitro bioactivity than that of the ECM/DCP scaffold as evidenced by more mineral formation in the simulated body fluid. In addition, RX-ECM/DCP also induced more effective bone regeneration than the ECM/DCP scaffold did in a rat calvarial defect model. Results sufficiently demonstrated that the addition of water to the scaffold could protect the structure of the ECM/DCP scaffold from being damaged by γ-ray irradiation during the terminal sterilization process. In summary, this study demonstrated a means to protect the ECM structure, which in turn led to the improvement of bone regenerative properties of the materials during γ-ray irradiation of ECM-based bone repair materials.

Regenerative Drug Discovery Using Ear Pinna Punch Wound Model in Mice

The ear pinna is a complex tissue consisting of the dermis, cartilage, muscles, vessels, and nerves. Ear pinna healing is a model of regeneration in mammals. In some mammals, including rabbits, punch wounds in the ear pinna close spontaneously; in common-use laboratory mice, they remain for life. Agents inducing ear pinna healing are potential regenerative drugs. We tested the effects of selected bioactive agents on 2 mm ear pinna wound closure in BALB/c mice. Our previous research demonstrated that a DNA methyltransferase inhibitor, zebularine, remarkably induced ear pinna regeneration. Although experiments with two other demethylating agents, RG108 and hydralazine, were unsuccessful, a histone deacetylase inhibitor, valproic acid, was another epigenetic agent found to increase ear hole closure. In addition, we identified a pro-regenerative activity of 4-ketoretinoic acid, a retinoic acid metabolite. Attempts to counteract the regenerative effects of the demethylating agent zebularine, with folates as methyl donors, failed. Surprisingly, a high dose of methionine, another methyl donor, promoted ear hole closure. Moreover, we showed that the regenerated areas of ear pinna were supplied with nerve fibre networks and blood vessels. The ear punch model proved helpful in testing the pro-regenerative activities of small-molecule compounds and observations of peripheral nerve regeneration.

hAMSC Sheet Promotes Repair of Rabbit Osteochondral Defects

Osteochondral lesion is clinically common disease, which has been recognized as one of the contributing factors of significant morbidity. Although current treatments have achieved good outcomes, some undesirable complications and failures are not uncommon. Cell sheet technology (CST), an innovative technology to harvest seed cells and preserve abundant ECM, has been widely used in various tissue regeneration. For osteochondral lesion, many studies focus on using CST to repair osteochondral lesion and have achieved good outcomes. In the previous study, we have demonstrated that hAMSC sheet had a positive effect on osteochondral lesion. Therefore, this study is aimed at comparing the effect of noninduced hAMSC sheet with chondrogenically induced hAMSC sheet on osteochondral lesion and cartilage regeneration.

Contributions of supercritical fluid technology for advancing decellularization and postprocessing of viable biological materials

The demand for tissue and organ transplantation worldwide has led to an increased interest in the development of new therapies to restore normal tissue function through transplantation of injured tissue with biomedically engineered matrices. Among these developments is decellularization, a process that focuses on the removal of immunogenic cellular material from a tissue or organ. However, decellularization is a complex and often harsh process that frequently employs techniques that can negatively impact the properties of the materials subjected to it. The need for a more benign alternative has driven research on supercritical carbon dioxide (scCO₂) assisted decellularization. scCO₂ can achieve its critical point at relatively low temperature and pressure conditions, and for its high transfer rate and permeability. These properties make scCO₂ an appealing methodology that can replace or diminish the exposure of harsh chemicals to sensitive materials, which in turn could lead to better preservation of their biochemical and mechanical properties. The presented review covers relevant literature over the last years where scCO₂-assisted decellularization is employed, as well as discussing major topics such as the mechanism of action behind scCO₂-assisted decellularization, CO₂ and cosolvents' solvent properties, effect of the operational parameters on decellularization efficacy and on the material's properties.

A new strategy for the decellularization of whole organs by hydrostatic pressure

Tissue engineering has been able to develop novel decellularization-recellularization techniques, which facilitates the research for the generation of functional organs. This is based in the initial obtention of the organ's extracellular matrix (ECM). Therefore, any improvement in the decellularization process would have a positive impact in the results of the recellularization process. Nevertheless, commonly the methods and equipment employed for this process are expensive and thus limit the access of this technique to various research groups globally.

AIM

To develop a decellularization technique with the exclusive use of hydrostatic pressure of detergent solutions, to have an easily accessible and low-cost technique that meets the basic requirements of acellularity and functionality of the ECM.

METHODS

This experimental study was performed in 10 male Wistar rats, obtaining the liver to carry out serial washes, with 1, 2 and 3% Triton X-100 solutions and 0.1% SDS. The washes were performed by using a Gravity Perfusion System (GPS), which assured us a continuous hydrostatic pressure of 7.5 mmHg. The obtained ECM was processed using stains and immunostaining to determine the residual cell content and preservation of its components.

RESULTS

The staining showed a removal of cellular and nuclear components of approximately 97% of the acellular ECM, with an adequate three-dimensional pattern of collagen and proteoglycans. Furthermore, the acellular ECM allowed the viability of a primary hepatocyte culture.

CONCLUSIONS

The use of the GPS decellularization technique allowed us to obtain an acellular and functional ECM, drastically reducing experimentation costs. This article is protected by copyright. All rights reserved.

Bioengineering of fibroblast-conditioned Polycaprolactone/Gelatin electrospun scaffold for skin tissue engineering

BACKGROUND

Synthetic tissue engineering scaffolds has poor biocompatiblity with very low angiogenic properties. Conditioning the scaffolds with functional groups, coating with biological components, especially extracellular matrix (ECM), is an excellent strategy for improving their biomechanical and biological properties.

METHODS

In the current study, a composite of polycaprolactone and gelatin (PCL/Gel) was electrospun in the ratio of 70/30 and surface modified with 1% gelatin-coating (G-PCL/Gel) or plasma treatment (P-PCL/Gel). The surface modification was determined by SEM and ATR-FTIR spectroscopy, respectively. The scaffolds were cultured with fibroblast 3T3, then decellularized during freeze-thawing process to fabricate a fibroblast ECM-conditioned PCL/Gel scaffold (FC-PCL/Gel). The swelling and degaradtion as well as in vitro and in vivo biocompatibility and angiogenic properties of the scaffolds were evaluated.

RESULTS

The structure of the surface-modified G-PCL/Gel and P-PCL/Gel were unique and not changed compared to the PCL/Gel scaffolds. ATR-FTIR analysis admitted the formation of oxygen-containing groups, hydroxyl and carboxyl, on the surface of the P-PCL/Gel scaffold. The SEM micrographs and DAPI staining confirmed the cell attachment and the ECM deposition on the platform and successful removal of the cells after decellularization. P-PCL/Gel showed better cell attachment, ECM secretion and deposition after decellularization compared with G-PCL/Gel. The FC-PCL/Gel was considered as an optimized scaffold for further assays in this study. The FC-PCL/Gel showed increased hydrophilic behavior and cytobiocompatibility compared with P-PCL/Gel. The ECM on the FC-PCL/Gel scaffold showed a gradual degradation during 30 days degradation time, as a small amount of ECM remained over the FC-PCL/Gel scaffold at day 30. The FC-PCL/Gel showed significant biocompatibility and improved angiogenic property compared with P-PCL/Gel when subcutaneously implanted in a mouse animal model for 7 and 28 days.

CONCLUSIONS

Our findings suggest FC-PCL/Gel as an excellent biomimetic construct with high angiogenic properties. This bioengineered construct can serve as a possible application in our future pre-clinical and clinical studies for skin regeneration.

Tissue-engineered vascular grafts and regeneration mechanisms

Cardiovascular diseases (CVDs) are life-threatening diseases with high morbidity and mortality worldwide. Vascular bypass surgery is still the ultimate strategy for CVD treatment. Autografts are the gold standard for graft transplantation, but insufficient sources limit their widespread application. Therefore, alternative tissue engineered vascular grafts (TEVGs) are urgently needed. In this review, we summarize the major strategies for the preparation of vascular grafts, as well as the factors affecting their patency and tissue regeneration. Finally, the underlying mechanisms of vascular regeneration that are mediated by host cells are discussed.

Investigation of an injectable gold nanoparticle extracellular matrix

Post-traumatic osteoarthritis (PTOA) is a progressive articular degenerative disease that degrades articular cartilage and stimulates apoptosis in chondrocyte cells. An injectable decellularized, extracellular matrix (ECM) scaffold, that might be able to combat the effects of PTOA, was developed where the ECM was conjugated with 20 nm gold nanoparticles (AuNP) and supplemented with curcumin and hyaluronic acid (HA). Porcine diaphragm ECM was decellularized and homogenized; AuNPs were conjugated using chemical crosslinking followed by mixing with curcumin and/or HA. Injection force testing and scanning electron microscopy with energy-dispersive X-ray spectroscopy were utilized to characterize the ECM scaffolds. In vitro testing with L929 murine fibroblasts, equine synovial fibroblasts, and Human Chondrocytes were used to determine biocompatibility, reactive oxygen species (ROS) reduction, and chondroprotective ability. The results demonstrated that conjugation of 20 nm AuNPs to the ECM was successful without significantly altering the physical properties as noted in the low injection force. In vitro work provided evidence of biocompatibility with a propensity to reduce intracellular ROS and an ability to mitigate apoptosis of chondrocyte cells stimulated with IL-1β, a known apoptosis inducing cytokine. It was concluded that an injectable AuNP-ECM may have the ability to mitigate inflammation and apoptosis.

Novel technique of development of human derived acellular dermal matrix

Reconstructive surgery techniques have evolved exponentially in last decades. From regional flaps to free tissue transfer, tissue movilization has become the gold standart treatment in many reconstructive procedures. Main disadvantage from these techniques lies in the possibility of sequels in donor zone. Furthermore, raising comorbidities in general population and growing indications for reconstructive surgery in elder people, have triggered the development of new biomaterials which can offer support in the reconstruction while elicit donor zone morbidity. Advances in tissue decellularization techniques have brought numerous matrices which have shown effectivity in many reconstructive procedures. Use of acellular dermal matrices may become an eligible solution for many reconstructive procedures. From breast reconstruction assisted by matrices to complex wound coverage passing throught tendon repair techniques, acellular dermal matrices have shown effectiveness in last studies. Local production of this biomaterial leads to cost minimization derived from harvesting and manufacturing matrices in our centre and avoid out-of-stock and storage issues. Current original protocol proposed by our group include all steps from harvesting samples from cadaveric donors till matrix storage after decellularization proccess. The result is a high valued biomaterial in terms of biocompatibility and security profile available.

In Vivo Comparison of Three Human Acellular Dermal Matrices for Breast Reconstruction

BACKGROUND/AIM

Acellular dermal matrices (ADMs) have become popular in implant-based breast reconstruction. The aim of this study was to compare three commonly used ADM products in vivo in an animal model.

MATERIALS AND METHODS

The nucleic acid content (residual double-stranded DNA) and the levels of the remaining growth factors after decellularization were measured for each ADM. Cytocompatibility with ADMs was documented using NIH 3T3 mouse fibroblast cells. In vivo, the implanted ADMs were histologically evaluated at 1, 2, 3, and 6 months (n=5) using male 8-week-old Sprague-Dawley rats.

RESULTS

Fibroblasts grew in the SureDerm HD and DermACELL with no cytotoxicity. In a rat model, SureDerm HD and DermACELL incorporated more readily into the surrounding host tissue, as measured by rapid cell influx and collagen deposition, and showed more delayed tissue remodeling with decreased matrix metalloproteinases levels compared to AlloDerm.

CONCLUSION

SureDerm HD and DermACELL can be used as biological materials for breast reconstruction.

Transformation of acellular dermis matrix with dicalcium phosphate into 3D porous scaffold for bone regeneration

Animal derived biomaterials have attracted much attentions in treating large size bone defect due to their excellent biocompatibility and potent bioactivities offered by the biomacromolecules and growth factors contained in these materials. Dermis-derived matrix (ADM) has been used as skin grafts and wound dressings for decades, however its application in bone tissue engineering has been largely limited as ADM possesses a dense structure which does not support bone tissue ingrowth. Recently, we have successfully fabricated porous scaffold structure using an ADM with the aid of micronization technique. When integrated with inorganic components such as calcium phosphate, ADM could be transformed to bone graft substitutes with desirable osteogenic properties. While purified and chemically cross-linked collagen has lost its natural structure, our ADM successfully preserved natural tropocollagen structure, as well as other bioactive components. A composite scaffold was fabricated by incorporating dicalcium phosphate (DCP) microparticles into ADM microfibers and freeze-dried to form a highly porous structure. Unlike conventional ADM materials, this scaffold possesses high porosity with interconnected pores. More importantly, our evaluation data demonstrated that it performed much more effective in treating critical bone defects in comparison with best commercial product on the market. In a head-to-head comparison with a commercial bone graft material Bongold^®, the ADM/DCP scaffold showed superior osteogenic capacity by filling the defect with well-organized new bone tissue in a rabbit radius segmental defect model. Put together, our results exhibited a novel bone graft substitute was developed by circumventing processing barriers associated with natural ADM, which offers another novel bone graft substitute for bone regeneration.

Endogenous Repair and Regeneration of Injured Articular Cartilage: A Challenging but Promising Therapeutic Strategy

Articular cartilage (AC) has a very limited intrinsic repair capacity after injury or disease. Although exogenous cell-based regenerative approaches have obtained acceptable outcomes, they are usually associated with complicated procedures, donor-site morbidities and cell differentiation during ex vivo expansion. In recent years, endogenous regenerative strategy by recruiting resident mesenchymal stem/progenitor cells (MSPCs) into the injured sites, as a promising alternative, has gained considerable attention. It takes full advantage of body's own regenerative potential to repair and regenerate injured tissue while avoiding exogenous regenerative approach-associated limitations. Like most tissues, there are also multiple stem-cell niches in AC and its surrounding tissues. These MSPCs have the potential to migrate into injured sites to produce replacement cells under appropriate stimuli. Traditional microfracture procedure employs the concept of MSPCs recruitment usually fails to regenerate normal hyaline cartilage. The reasons for this failure might be attributed to an inadequate number of recruiting cells and adverse local tissue microenvironment after cartilage injury. A strategy that effectively improves local matrix microenvironment and recruits resident MSPCs may enhance the success of endogenous AC regeneration (EACR). In this review, we focused on the reasons why AC cannot regenerate itself in spite of potential self-repair capacity and summarized the latest developments of the three key components in the field of EACR. In addition, we discussed the challenges facing in the present EACR strategy. This review will provide an increasing understanding of EACR and attract more researchers to participate in this promising research arena.

Cell-Matrix Interactions in the Eye: From Cornea to Choroid

The extracellular matrix (ECM) plays a crucial role in all parts of the eye, from maintaining clarity and hydration of the cornea and vitreous to regulating angiogenesis, intraocular pressure maintenance, and vascular signaling. This review focuses on the interactions of the ECM for homeostasis of normal physiologic functions of the cornea, vitreous, retina, retinal pigment epithelium, Bruch's membrane, and choroid as well as trabecular meshwork, optic nerve, conjunctiva and tenon's layer as it relates to glaucoma. A variety of pathways and key factors related to ECM in the eye are discussed, including but not limited to those related to transforming growth factor-β, vascular endothelial growth factor, basic-fibroblastic growth factor, connective tissue growth factor, matrix metalloproteinases (including MMP-2 and MMP-9, and MMP-14), collagen IV, fibronectin, elastin, canonical signaling, integrins, and endothelial morphogenesis consistent of cellular activation-tubulogenesis and cellular differentiation-stabilization. Alterations contributing to disease states such as wound healing, diabetes-related complications, Fuchs endothelial corneal dystrophy, angiogenesis, fibrosis, age-related macular degeneration, retinal detachment, and posteriorly inserted vitreous base are also reviewed.

Gold Nanoparticles Promote the Bone Regeneration of Periodontal Ligament Stem Cell Sheets Through Activation of Autophagy

OBJECTIVE

Cell sheet technology (CST) is advantageous for repairing alveolar bone defects in clinical situations, and osteogenic induction before implantation may result in enhanced bone regeneration. Herein, we observed the effect of gold nanoparticles (AuNPs) on osteogenic differentiation of periodontal ligament stem cell (PDLSC) sheets and explored their potential mechanism of action.

METHODS

PDLSCs were cultured in cell sheet induction medium to obtain cell sheets. PDLSC sheets were treated with or without AuNPs. Alkaline phosphatase, alizarin red S, von Kossa, and immunofluorescence staining were used to observe the effects of AuNPs on the osteogenic differentiation of PDLSC sheets. Western blotting was performed to evaluate the osteogenic effects and autophagy activity. The cell sheets were transplanted into the dorsa of nude mice, and bone regeneration was analyzed by micro-CT and histological staining.

RESULTS

AuNPs could promote the osteogenic differentiation of PDLSC sheets by upregulating bone-related protein expression and mineralization. The 45-nm AuNPs were more effective than 13-nm AuNPs. Additional analysis demonstrated that their ability to promote differentiation could depend on activation of the autophagy pathway through upregulation of microtubule-associated protein light chain 3 and downregulation of sequestosome 1/p62. Furthermore, AuNPs significantly promoted the bone regeneration of PDLSC sheets in ectopic models.

CONCLUSION

AuNPs enhance the osteogenesis of PDLSC sheets by activating autophagy, and 45-nm AuNPs were more effective than 13-nm AuNPs. This study may provide an AuNP-based pretreatment strategy for improving the application of CST in bone repair and regeneration.

Stem cells and growth factors-based delivery approaches for chronic wound repair and regeneration: A promise to heal from within

The sophisticated chain of cellular and molecular episodes during wound healing includes cell migration, cell proliferation, deposition of extracellular matrix, and remodelling and are onerous to replicate. Encapsulation of growth factors (GFs) and Stem cell-based (SCs) has been proclaimed to accelerate healing by transforming every phase associated with wound healing to enhance skin regeneration. Therapeutic application of mesenchymal stem cells (MSCs), embryonic stem cells (ESCs) and induced pluripotent stem cells (PSCs) provides aid in wound fixing, tissue integrity restoration and function of impaired tissue. Several scientific studies have established the essential role GFs in wound healing and their reduced degree in the chronic wound. The overall limitation includes half-life, unfriendly microhabitat abundant with protease, and inadequate delivery approaches results in decreased delivery of effective amounts in a suitable time-based fashion. Advancements in the area of reformative medicine as well as tissue engineering have offered techniques competent of dispensing SCs and GFs in site-oriented manner. The progress in nanotechnology-based approaches attracts researcher to study and evaluate the potential of this SCs and GFs based therapy in chronic wounds. These techniques embrace the polymeric regime viz., nano-formulations, hydrogels, liposomes, scaffolds, nanofibers, metallic nanoparticles, lipid-based nanoparticles and dendrimers that have established better retort through targeting tissues when GFs and SCs are transported via these humans made devices. Assumed the current problems, improvements in delivery approaches and difficulties offered by chronic wounds, we hope to show that encapsulation of SCs and GFs loaded nanoformulations therapies is the rational next step in improving wound care.

The usefulness of the decellularized matrix from three-dimensional regenerative cartilage as a scaffold material

In cartilage tissue engineering, research on materials for three-dimensional (3D) scaffold has attracted attention. Decellularized matrix can be one of the candidates for the scaffold material. In this study, decellularization of regenerated cartilage was carried out and its effectiveness as a scaffold material was examined. Three-dimensionally-cultured cartilage constructs in the differentiation medium containing IGF-1 produced more cartilage matrix than those in the proliferation medium. Detergent-enzymatic method (DEM) could decellularize 3D-cultured cartilage constructs only by 1 cycle without breaking down the structure of the constructs. In vitro, newly-seeded chondrocytes were infiltrated and engrafted into decellularized constructs in the proliferation medium, and newly formed fibers were observed around the surface where newly-seeded cells were attached. Recellularized constructs could mature similarly as those without decellularization in vivo. The decellularized 3D-cultured matrix from regenerative cartilage is expected to be used as a scaffold material in the future.

Extracellular matrix derived from allogenic decellularized bone marrow mesenchymal stem cell sheets for the reconstruction of osteochondral defects in rabbits

Bioactive scaffolds from synthetical polymers or decellularized cartilage matrices have been widely used in osteochondral regeneration. However, the risks of potential immunological reactions and the inevitable donor morbidity of these scaffolds have limited their practical applications. To address these issues, a biological extracellular matrix (ECM) scaffold derived from allogenic decellularized bone marrow mesenchymal stem cell (BMSC) sheets was established for osteochondral reconstruction. BMSCs were induced to form cell sheets. Three different concentrations of sodium dodecyl sulfate (SDS), namely, 0.5%, 1%, and 3%, were used to decellularize these BMSC sheets to prepare the ECM. Histological and microstructural observations were performed in vitro and then the ECM scaffolds were implanted into osteochondral defects in rabbits to evaluate the repair effect in vivo. Treatment with 0.5% SDS not only efficiently removed BMSCs but also successfully preserved the original structure and bioactive components of the ECM When compared with the 1% and 3% SDS groups, histological observations substantiated the superior repair effect of osteochondral defects, including the simultaneous regeneration of well-vascularized subchondral bone and avascular articular cartilage integrated with native tissues in the 0.5% SDS group. Moreover, RT-PCR indicated that ECM scaffolds could promote the osteogenic differentiation potential of BMSCs under osteogenic conditions while increasing the chondrogenic differentiation potential of BMSCs under chondrogenic conditions. Allogenic BMSC sheets decellularized with 0.5% SDS treatment increased the recruitment of BMSCs and significantly improved the regeneration of osteochondral defects in rabbits, thus providing a prospective approach for both articular cartilage and subchondral bone reconstruction with cell-free transplantation.

Regeneration of critical-sized defects, in a goat model, using a dextrin-based hydrogel associated with granular synthetic bone substitute

The development of injectable bone substitutes (IBS) have obtained great importance in the bone regeneration field, as a strategy to reach hardly accessible defects using minimally invasive techniques and able to fit to irregular topographies. In this scenario, the association of injectable hydrogels and bone graft granules is emerging as a well-established trend. Particularly, in situ forming hydrogels have arisen as a new IBS generation. An in situ forming and injectable dextrin-based hydrogel (HG) was developed, aiming to act as a carrier of granular bone substitutes and bioactive agents. In this work, the HG was associated to a granular bone substitute (Bonelike^®) and implanted in goat critical-sized calvarial defects (14 mm) for 3, 6 and 12 weeks. The results showed that HG improved the handling properties of the Bonelike^® granules and did not affect its osteoconductive features, neither impairing the bone regeneration process. Human multipotent mesenchymal stromal cells from the umbilical cord, extracellular matrix hydrolysates and the pro-angiogenic peptide LLKKK18 were also combined with the IBS. These bioactive agents did not enhance the new bone formation significantly under the conditions tested, according to micro-computed tomography and histological analysis.

Potential of Soluble Decellularized Extracellular Matrix for Musculoskeletal Tissue Engineering - Comparison of Various Mesenchymal Tissues

Background

It is well studied that preparations of decellularized extracellular matrix (ECM) obtained from mesenchymal tissues can function as biological scaffolds to regenerate injured musculoskeletal tissues. Previously, we reported that soluble decellularized ECMs derived from meniscal tissue demonstrated excellent biocompatibility and produced meniscal regenerate with native meniscal anatomy and biochemical characteristics. We therefore hypothesized that decellularized mesenchymal tissue ECMs from various mesenchymal tissues should exhibit tissue-specific bioactivity. The purpose of this study was to test this hypothesis using porcine tissues, for potential applications in musculoskeletal tissue engineering.

Methods

Nine types of porcine tissue, including cartilage, meniscus, ligament, tendon, muscle, synovium, fat pad, fat, and bone, were decellularized using established methods and solubilized. Although the current trend is to develop tissue specific decellularization protocols, we selected a simple standard protocol across all tissues using Triton X-100 and DNase/RNase after mincing to compare the outcome. The content of sulfated glycosaminoglycan (sGAG) and hydroxyproline were quantified to determine the biochemical composition of each tissue. Along with the concentration of several growth factors, known to be involved in tissue repair and/or maturation, including bFGF, IGF-1, VEGF, and TGF-β1. The effect of soluble ECMs on cell differentiation was explored by combining them with 3D collagen scaffold culturing human synovium derived mesenchymal stem cells (hSMSCs).

Results

The decellularization of each tissue was performed and confirmed both histologically [hematoxylin and eosin (H&E) and 4’,6-diamidino-2-phenylindole (DAPI) staining] and on the basis of dsDNA quantification. The content of hydroxyproline of each tissue was relatively unchanged during the decellularization process when comparing the native and decellularized tissue. Cartilage and meniscus exhibited a significant decrease in sGAG content. The content of hydroxyproline in meniscus-derived ECM was the highest when compared with other tissues, while sGAG content in cartilage was the highest. Interestingly, a tissue-specific composition of most of the growth factors was measured in each soluble decellularized ECM and specific differentiation potential was particularly evident in cartilage, ligament and bone derived ECMs.

Conclusion

In this study, soluble decellularized ECMs exhibited differences based on their tissue of origin and the present results are important going forward in the field of musculoskeletal regeneration therapy.

Decellularized porcine conjunctiva as an alternative substrate for tissue-engineered epithelialized conjunctiva

PURPOSE

The long-term success of visual rehabilitation in patients with severe conjunctival scarring is reliant on the reconstruction of the conjunctiva with a suitable substitute. The purpose of this study is the development and investigation of a re-epithelialized conjunctival substitute based on porcine decellularized conjunctiva (PDC).

METHODS

PDC was re-epithelialized either with pre-expanded human conjunctival epithelial cells (PDC + HCEC) or with a human conjunctival explant placed directly on PDC (PDC + HCEx). Histology and immunohistochemistry were performed to evaluate epithelial thickness, proliferation (Ki67), apoptosis (Caspase 3), goblet cells (MUC5AC), and progenitor cells (CK15, ΔNp63, ABCG2). The superior construct (PDC + HCEx) was transplanted into a conjunctival defect of a rabbit (n = 6). Lissamine green staining verified the epithelialization in vivo. Orbital tissue was exenterated on day 10 and processed for histological and immunohistochemical analysis to examine the engrafted PDC + HCEx. A human-specific antibody was used to detect the transplanted cells.

RESULTS

From day-14 in vitro onward, a significantly thicker epithelium and greater number of cells expressing Ki67, CK15, ΔNp63, and ABCG2 were noted for PDC + HCEx versus PDC + HCEC. MUC5AC-positive cells were found only in PDC + HCEx. The PDC + HCEx-grafted rabbit conjunctivas were lissamine-negative during the evaluation period, indicating epithelial integrity. Engrafted PDC + HCEx showed preserved progenitor cell properties and an increased number of goblet cells comparable to those of native conjunctiva.

CONCLUSION

Placing and culturing a human conjunctival explant directly on PDC (PDC + HCEx) enables the generation of a stable, stratified, goblet cell-rich construct that could provide a promising alternative conjunctival substitute for patients with extensive conjunctival stem and goblet cell loss.

Construction of tissue-engineered bone with differentiated osteoblasts from adipose-derived stem cell and coral scaffolds at an ectopic site

Cell sheets from bone marrow mesenchymal stem cells (BMSC) have been widely used in the field of bone tissue engineering, although their source remains a challenging issue. In this study, adipose-derived stem cells (ADSC) were induced to differentiate into osteoblasts, and the incorporation of coral scaffolds with ADSC sheets for bone formation at an ectopic site was also investigated. First, ADSC isolated from inguinal adipose tissue of New Zealand rabbits were cultured for two weeks without passaging under osteogenic induction, and the microstructures of cell sheets were analysed by histological and scanning electron microscope (EM) observation. In addition, the activity of alkaline phosphatase (ALP) and alizarin red staining was also measured to detect their osteogenic ability. Subsequently, ADSC were proved to be able to proliferate well when seeded on the coral scaffolds. Next, coral scaffolds were wrapped in cell sheets to prepare sheet-coral complexes, which were implanted into subcutaneous pockets in nude mice. At eight weeks after implantation, gross examination, microcomputed tomography (MicroCT), and histological analysis were investigated to assess new bone formation. MicroCT scanning and histological analysis showed that there was more highly dense tissue formed in the complex group than control group (p=0.0004). These results indicated that osteoblastic ADSC sheets could be used to construct engineered bone and the incorporation of coral scaffolds with ADSC sheets significantly improved bone formation, providing a newly approach for bone tissue engineering.

Decellularized Extracellular Matrix-based Bioinks for Engineering Tissue- and Organ-specific Microenvironments

Biomaterials-based biofabrication methods have gained much attention in recent years. Among them, 3D cell printing is a pioneering technology to facilitate the recapitulation of unique features of complex human tissues and organs with high process flexibility and versatility. Bioinks, combinations of printable hydrogel and cells, can be utilized to create 3D cell-printed constructs. The bioactive cues of bioinks directly trigger cells to induce tissue morphogenesis. Among the various printable hydrogels, the tissue- and organ-specific decellularized extracellular matrix (dECM) can exert synergistic effects in supporting various cells at any component by facilitating specific physiological properties. In this review, we aim to discuss a new paradigm of dECM-based bioinks able to recapitulate the inherent microenvironmental niche in 3D cell-printed constructs. This review can serve as a toolbox for biomedical engineers who want to understand the beneficial characteristics of the dECM-based bioinks and a basic set of fundamental criteria for printing functional human tissues and organs.

A novel decellularization method to produce brain scaffolds

Scaffolds composed of extracellular matrix (ECM) can assist tissue remodeling and repair following injury. The ECM is a complex biomaterial composed of proteins, glycoproteins, proteoglycans, and glycosaminoglycans, secreted by cells. The ECM contains fundamental biological cues that modulate cell behavior and serves as a structural scaffold for cell adhesion and growth. For clinical applications, where immune rejection is a constraint, ECM can be processed using decellularization methods intended to remove cells and donor antigens from tissue or organs, while preserving native biological cues essential for cell growth and differentiation. Recent studies show bioengineered organs composed by a combination of a diversity of materials and stem cells as a possibility of new therapeutic strategies to treat diseases that affect different tissues and organs, including the central nervous system (CNS). Nevertheless, the methodologies currently described for brain decellularization involve the use of several chemical reagents with many steps that ultimately limit the process of organ or tissue recellularization. Here, we describe for the first time a fast and straightforward method for complete decellularization of mice brain by the combination of rapid freezing and thawing following the use of only one detergent (Sodium dodecyl sulfate (SDS)). Our data show that using the protocol we describe here, the brain was entirely decellularized, while still maintaining ECM components that are essential for cell survival on the scaffold. Our results also show the cell-loading of the decellularized brain matrix with Neuro2a cells, which were identified by immunohistochemistry in their undifferentiated form. We conclude that this novel and simple method for brain decellularization can be used as a scaffold for cell-loading.