Reprint of: Extracellular matrix as a biological scaffold material: Structure and function

Multimodal effects of an extracellular matrix on cellular morphology, dynamics and functionality

Articular cartilage defects can lead to pain and even disability in patients and have significant socioeconomic loss. Repairing articular cartilage defects remains a long-term challenge in medicine owing to the limited ability of cartilage to regenerate. At present, the treatment methods adopted in clinical practice have many limitations, thereby necessitating the rapid development of biomaterials. Among them, decellularized biomaterials have been particularly prominent, with numerous breakthroughs in research progress and translational applications. Although many studies show that decellularized cartilage biomaterials promote tissue regeneration, any differences in cellular morphology, dynamics, and functionality among various biomaterials upon comparison have not been reported. In this study, we prepared cartilage-derived extracellular matrix (cdECM) biomaterials with different bioactive contents and various physical properties to compare their effects on the morphology, dynamics and functionality of chondrocytes. This cellular multimodal analysis of the characteristics of cdECM biomaterials provided a theoretical basis for understanding the interactions between biomaterials and cells, thus laying an experimental foundation for the translation and application of decellularized cartilage biomaterials in the treatment of cartilage defects.

The application of small intestinal submucosa in tissue regeneration

The distinctive three-dimensional architecture, biological functionality, minimal immunogenicity, and inherent biodegradability of small intestinal submucosa extracellular matrix materials have attracted considerable interest and found wide-ranging applications in the domain of tissue regeneration engineering. This article presents a comprehensive examination of the structure and role of small intestinal submucosa, delving into diverse preparation techniques and classifications. Additionally, it proposes approaches for evaluating and modifying SIS scaffolds. Moreover, the advancements of SIS in the regeneration of skin, bone, heart valves, blood vessels, bladder, uterus, and urethra are thoroughly explored, accompanied by their respective future prospects. Consequently, this review enhances our understanding of the applications of SIS in tissue and organ repair and keeps researchers up-to-date with the latest research advancements in this area.

Application of Decellularized Adipose Matrix as a Bioscaffold in Different Tissue Engineering

With the development of tissue engineering, the application of decellularized adipose matrix as scaffold material in tissue engineering has been intensively explored due to its wide source and excellent potential in tissue regeneration. Decellularized adipose matrix is a promising candidate for adipose tissue regeneration, while modification of decellularized adipose matrix scaffold can also allow it to transcend the limitations of adipose tissue source properties and applied to other tissue engineering fields, including cartilage and bone tissue engineering, neural tissue engineering, and skin tissue engineering. In this review, we summarized the development of the applications of decellularized adipose matrix in different tissue engineering and present future perspectives.Level of Evidence III This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Fabrication and optimization of multilayered composite scaffold made of sulfated alginate-based nanofiber/decellularized Wharton's jelly ECM for tympanic membrane tissue engineering

In this study, we fabricated a novel multilayer polyvinyl alcohol (PVA)/alginate sulfate (ALG-S) nanofiber/decellularized Wharton's Jelly ECM (d-ECM) composite for tympanic membrane perforations (TMPs) tissue engineering (TE). Initially, electrospun PVA/ALG-S scaffolds with different blend ratios were fabricated. The influence of ALG-S ratio on surface morphology, mechanical, physical and biological properties of the nanofibers was studied. Secondly, 3-layer composites were developed as a combination of PVA/ALG-S nanofibers and d-ECM to take synergic advantages of electrospun mats and d-ECM. As part of the evaluation of the effects of d-ECM incorporation, the composite's mechanical properties, in vitro degradation, swelling ratio, and biological activities were assessed. The MTT assay showed that PVA/ALG-S nanofibers with 50:50 ratio provided a more desirable environment to support cell growth. A composite containing 25 mg/cm2 d-ECM was determined as the optimal composite through MTT assay, and this composite was used for animal studies inducing TMP regeneration. According to the in vivo studies, the optimal composite not only stimulated the healing of TMPs but also shortened the healing period. These results suggest that a multilayer nanofiber/hydrogel composite could be a potential platform for regenerating TMPs.

Nerve regeneration using decellularized tissues: challenges and opportunities

In tissue engineering, the decellularization of organs and tissues as a biological scaffold plays a critical role in the repair of neurodegenerative diseases. Various protocols for cell removal can distinguish the effects of treatment ability, tissue structure, and extracellular matrix (ECM) ability. Despite considerable progress in nerve regeneration and functional recovery, the slow regeneration and recovery potential of the central nervous system (CNS) remains a challenge. The success of neural tissue engineering is primarily influenced by composition, microstructure, and mechanical properties. The primary objective of restorative techniques is to guide existing axons properly toward the distal end of the damaged nerve and the target organs. However, due to the limitations of nerve autografts, researchers are seeking alternative methods with high therapeutic efficiency and without the limitations of autograft transplantation. Decellularization scaffolds, due to their lack of immunogenicity and the preservation of essential factors in the ECM and high angiogenic ability, provide a suitable three-dimensional (3D) substrate for the adhesion and growth of axons being repaired toward the target organs. This study focuses on mentioning the types of scaffolds used in nerve regeneration, and the methods of tissue decellularization, and specifically explores the use of decellularized nerve tissues (DNT) for nerve transplantation.

Urinary bladder matrix for lower extremity split-thickness skin graft donor site

Split-thickness skin grafts (STSG) are commonly used to treat soft-tissue defects. Harvesting a STSG creates an additional partial thickness wound at the donor site which must be managed. Many dressings are commercially available for the management of STSG donor sites; however, there is no evidence-based consensus on optimal dressing for site management. Urinary bladder matrix (UBM) is an extracellular matrix that acts as a structural support for tissue remodeling and provides molecular components for repair. Common clinical applications of UBM include coverage of deep wounds, burns, and irradiated skin. Skin grafting from the lower extremities poses a challenge due to the increased dermal tension. UBM-based reconstruction is an alternative method of managing lower extremity skin graft donor sites. This case study demonstrates the use of UBM in the reconstruction of a STSG donor site of the anterolateral thigh, which resulted in satisfactory healing, no pain, and excellent cosmetic and functional outcomes.

Mechanical homeostasis imbalance in hepatic stellate cells activation and hepatic fibrosis

Chronic liver disease or repeated damage to hepatocytes can give rise to hepatic fibrosis. Hepatic fibrosis (HF) is a pathological process of excessive sedimentation of extracellular matrix (ECM) proteins such as collagens, glycoproteins, and proteoglycans (PGs) in the hepatic parenchyma. Changes in the composition of the ECM lead to the stiffness of the matrix that destroys its inherent mechanical homeostasis, and a mechanical homeostasis imbalance activates hepatic stellate cells (HSCs) into myofibroblasts, which can overproliferate and secrete large amounts of ECM proteins. Excessive ECM proteins are gradually deposited in the Disse gap, and matrix regeneration fails, which further leads to changes in ECM components and an increase in stiffness, forming a vicious cycle. These processes promote the occurrence and development of hepatic fibrosis. In this review, the dynamic process of ECM remodeling of HF and the activation of HSCs into mechanotransduction signaling pathways for myofibroblasts to participate in HF are discussed. These mechanotransduction signaling pathways may have potential therapeutic targets for repairing or reversing fibrosis.

Bioactive ECM-Loaded SIS Generated by the Optimized Decellularization Process Exhibits Skin Wound Healing Ability in Type I Diabetic Rats

Patients with diabetes have 15-25% chance for developing diabetic ulcers as a severe complication and formidable challenge for clinicians. Conventional treatment for diabetic ulcers is to surgically remove the necrotic skin, clean the wound, and cover it with skin flaps. However, skin flap often has a limited efficacy, and its acquisition requires a second surgery, which may bring additional risk for the patient. Skin tissue engineering has brought a new solution for diabetic ulcers. Herein, we have developed a bioactive patch through a compound culture and the optimized decellularization strategy. The patch was prepared from porcine small intestinal submucosa (SIS) and modified by an extracellular matrix (ECM) derived from urine-derived stem cells (USCs), which have low immunogenicity while retaining cytokines for angiogenesis and tissue regeneration. The protocol included the optimization of the decellularization time and the establishment of the methods. Furthermore, the in vitro mechanism of wound healing ability of the patch was investigated, and its feasibility for skin wound healing was assessed through an antishrinkage full-thickness skin defect model in type I diabetic rats. As shown, the patch displayed comparable effectiveness to the USCs-loaded SIS. Our findings suggested that this optimized decellularization protocol may provide a strategy for cell-loaded scaffolds that require the removal of cellular material while retaining sufficient bioactive components in the ECM for further applications.

Biomechanical comparison of porcine mitral leaflets with porcine small intestinal submucosa extracellular matrix

Porcine small intestinal submucosa extracellular matrix (SIS-ECM) used for cardiac valve repair has shown conflicting clinical outcomes with respect to calcification and failure. This may be related to differences in biomechanical properties of the material compared with the host site. The aim of this study was to compare the biomechanical properties of porcine mitral valve leaflets with SIS-ECM. Fresh porcine anterior and posterior mitral leaflet samples were cut radially and circumferentially. Similarly, 2- and 4-layered SIS-ECM were cut in orthogonal directions: length and width. Samples were subjected to a uniaxial tensile test or a dynamic mechanical analysis. Results show that the load of the porcine anterior circumferential leaflet was 39.5 N (2.4-48.5 N), which was significantly higher compared with the 2-layered length SIS-ECM which was 7.5 N (7-7.9 N), and the 4- layered length SIS-ECM which was 7.5 N (7.1-8.1 N) (p < 0.001). The load of the posterior circumferential leaflet was 9.7 N (8.3-10.7 N), which is still significantly higher when compared with the two versions of SIS-ECM. The degree of anisotropy (i.e. the ratio between circumferential-radial and width-length properties) was higher for the anterior- (ratio: 19) and posterior leaflet (ratio: 6) than the 2-layered (ratio: 5.1) and 4-layered SIS-ECM (ratio: 1.9). Especially 2-layered SIS-ECM more closely resembles the posterior mitral leaflet than the anterior mitral leaflet tissue and would be more suitable as a repair material in this position. Additionally, the anisotropic properties of mitral leaflets and SIS-ECM underscore the importance of correct orientation of the implant to ensure optimal reconstruction.

Biomimetic Growth of Hydroxyapatite in Hybrid Polycaprolactone/Graphene Oxide Ultra-Porous Scaffolds

This paper reports the preparation and characterization of hybrid scaffolds composed of polycaprolactone (PCL) and different graphene oxide (GO) amounts, intending to incorporate the intrinsic characteristics of their constituents, such as bioactivity and biocidal effect. These materials were fabricated by a solvent-casting/particulate leaching technique showing a bimodal porosity (macro and micro) that was around 90%. The highly interconnected scaffolds were immersed in a simulated body fluid, promoting the growth of a hydroxyapatite (HAp) layer, making them ideal candidates for bone tissue engineering. The growth kinetics of the HAp layer was influenced by the GO content, a remarkable result. Furthermore, as expected, the addition of GO neither significantly improves nor reduces the compressive modulus of PCL scaffolds. The thermal behavior of composites was investigated by differential scanning calorimetry, showing an increase in crystallinity as the addition of GO raised, which implies that GO nanosheets can act as seeds to induce the crystallization of PCL. The improved bioactivity was demonstrated by the deposition of an HAp layer on the surface of the scaffold with GO, especially with a 0.1% GO content.

Constructing 3D In Vitro Models of Heterocellular Solid Tumors and Stromal Tissues Using Extrusion-Based Bioprinting

Malignant tumor tissues exhibit inter- and intratumoral heterogeneities, aberrant development, dynamic stromal composition, diverse tissue phenotypes, and cell populations growing within localized mechanical stresses in hypoxic conditions. Experimental tumor models employing engineered systems that isolate and study these complex variables using in vitro techniques are under development as complementary methods to preclinical in vivo models. Here, advances in extrusion bioprinting as an enabling technology to recreate the three-dimensional tumor milieu and its complex heterogeneous characteristics are reviewed. Extrusion bioprinting allows for the deposition of multiple materials, or selected cell types and concentrations, into models based upon physiological features of the tumor. This affords the creation of complex samples with representative extracellular or stromal compositions that replicate the biology of patient tissue. Biomaterial engineering of printable materials that replicate specific features of the tumor microenvironment offer experimental reproducibility, throughput, and physiological relevance compared to animal models. In this review, we describe the potential of extrusion-based bioprinting to recreate the tumor microenvironment within in vitro models.

Alternative lung cell model systems for toxicology testing strategies: Current knowledge and future outlook

Due to the current relevance of pulmonary toxicology (with focus upon air pollution and the inhalation of hazardous materials), it is important to further develop and implement physiologically relevant models of the entire respiratory tract. Lung model development has the aim to create human relevant systems that may replace animal use whilst balancing cost, laborious nature and regulatory ambition. There is an imperative need to move away from rodent models and implement models that mimic the holistic characteristics important in lung function. The purpose of this review is therefore, to describe and identify the various alternative models that are being applied towards assessing the pulmonary toxicology of inhaled substances, as well as the current and potential developments of various advanced models and how they may be applied towards toxicology testing strategies. These models aim to mimic various regions of the lung, as well as implementing different exposure methods with the addition of various physiologically relevent conditions (such as fluid-flow and dynamic movement). There is further progress in the type of models used with focus on the development of lung-on-a-chip technologies and bioprinting, as well as and the optimization of such models to fill current knowledge gaps within toxicology.

Physician antibiotic hydration preferences for biologic antibacterial envelopes during cardiac implantable device procedures

Background

Cardiac implantable electronic device (CIED) infection is a potentially serious complication of CIED procedures. Infection risk mitigation includes using guideline-recommended pre-operative intravenous antibacterial prophylaxis (IV ABX). The use of antibiotic-eluting CIED envelopes has also been shown to reduce infection risk. The relationship between and potential benefits associated with guideline-recommended IV ABX in combination with antibacterial envelopes have not been characterized.

Methods

Biologic envelopes made from non-crosslinked extracellular matrix (ECM) were implanted into 1,102 patients receiving CIEDs. The implanting physician decided patient selection for using a biologic envelope and envelope hydration solution. Observational data was analyzed on IV ABX utilization rates, antibacterial envelope usage, and infection outcomes.

Results

Overall compliance with IV ABX was 96.6%, and most patients received a biologic envelope hydrated in antibiotics (77.1%). After a mean follow-up of 223 days, infection rates were higher for sites using IV ABX <80% of the time vs. sites using ≥80% (5.6% vs. 0.8%, p = 0.008). Physicians demonstrated preference for hydration solutions containing gentamicin in higher-risk patients, which was found by multivariate analysis to be associated with a threefold reduction in infection risk (OR 3.0, 95% CI, 1.0-10.0).

Conclusion

These findings suggest that use of antibiotics, particularly gentamicin, in biologic envelope hydration solution may reduce infection risk, and use of antibacterial envelopes without adjunct IV ABX may not be sufficient to reduce CIED infections.

Clinical trial registration

[https://clinicaltrials.gov/], identifier [NCT02530970].

Proteomic Analysis of Decellularized Extracellular Matrix: Achieving a Competent Biomaterial for Osteogenesis

Decellularized ECMs have been used as biological scaffolds for tissue repair due to their tissue-specific biochemical and mechanical composition, poorly simulated by other materials. It is used as patches and powders, and it could be further processed via enzymatic digestion under acidic conditions using pepsin. However, part of the bioactivity is lost during the digestion process due to protein denaturation. Here, stepwise digestion was developed to prepare a competent biomaterial for osteogenesis from three different ECM sources. In addition, three different proteases were compared to evaluate the most effective digestion protocol for specific cellular processes. GAGs and peptide quantification showed that the stepwise method yielded a higher concentration of bioactive residues. Circular dichroism analysis also showed that the stepwise approach preserved the secondary structures better. The protein profiles of the digested ECMs were analyzed, and it was found to be highly diverse and tissue-specific. The digestion of ECM from pericardium produced peptides originated from 94 different proteins, followed by 48 proteins in ECM from tendon and 35 proteins in ECM from bone. In addition, digested products from pericardium ECM yielded increased proliferation and differentiation of bone marrow mesenchymal stem cells to mature osteoblasts.

Inflammation-mediated matrix remodeling of extracellular matrix-mimicking biomaterials in tissue engineering and regenerative medicine

Extracellular matrix (ECM)-mimicking biomaterials are considered effective tissue-engineered scaffolds for regenerative medicine because of their biocompatibility, biodegradability, and bioactivity. ECM-mimicking biomaterials preserve natural microstructures and matrix-related bioactive components and undergo continuous matrix remodeling upon transplantation. The interaction between host immune cells and transplanted ECM-mimicking biomaterials has attracted considerable attention in recent years. Transplantation of biomaterials may initiate injuries and early pro-inflammation reactions characterized by infiltration of neutrophils and M1 macrophages. Pro-inflammation reactions may lead to degradation of the transplanted biomaterial and drive the matrix into a fetal-like state. ECM degradation leads to the release of matrix-related bioactive components that act as signals for cell migration, proliferation, and differentiation. In late stages, pro-inflammatory cells fade away, and anti-inflammatory cells emerge, which involves macrophage polarization to the M2 phenotype and leukocyte activation to T helper 2 (Th2) cells. These anti-inflammatory cells interact with each other to facilitate matrix deposition and tissue reconstruction. Deposited ECM molecules serve as vital components of the mature tissue and influence tissue homeostasis. However, dysregulation of matrix remodeling results in several pathological conditions, such as aggressive inflammation, difficult healing, and non-functional fibrosis. In this review, we summarize the characteristics of inflammatory responses in matrix remodeling after transplantation of ECM-mimicking biomaterials. Additionally, we discuss the intrinsic linkages between matrix remodeling and tissue regeneration. STATEMENT OF SIGNIFICANCE: Extracellular matrix (ECM)-mimicking biomaterials are effectively used as scaffolds in tissue engineering and regenerative medicine. However, dysregulation of matrix remodeling can cause various pathological conditions. Here, the review describes the characteristics of inflammatory responses in matrix remodeling after transplantation of ECM-mimicking biomaterials. Additionally, we discuss the intrinsic linkages between matrix remodeling and tissue regeneration. We believe that understanding host immune responses to matrix remodeling of transplanted biomaterials is important for directing effective tissue regeneration of ECM-mimicking biomaterials. Considering the close relationship between immune response and matrix remodeling results, we highlight the need for studies of the effects of clinical characteristics on matrix remodeling of transplanted biomaterials.

Development and characterization of human fetal female reproductive tract organoids to understand Müllerian duct anomalies

Müllerian ducts are paired tubular structures that give rise to most of the female reproductive organs. Any abnormalities in the development and differentiation of these ducts lead to anatomical defects in the female reproductive tract organs categorized as Müllerian duct anomalies. Due to the limited access to fetal tissues, little is understood of human reproductive tract development and the associated anomalies. Although organoids represent a powerful model to decipher human development and disease, such organoids from fetal reproductive organs are not available. Here, we developed organoids from human fetal fallopian tubes and uteri and compared them with their adult counterparts. Our results demonstrate that human fetal reproductive tract epithelia do not express some of the typical markers of adult reproductive tract epithelia. Furthermore, fetal organoids are grossly, histologically, and proteomically different from adult organoids. While external supplementation of WNT ligands or activators in culture medium is an absolute requirement for the adult reproductive tract organoids, fetal organoids are able to grow in WNT-deficient conditions. We also developed decellularized tissue scaffolds from adult human fallopian tubes and uteri. Transplantation of fetal organoids onto these scaffolds led to the regeneration of the adult fallopian tube and uterine epithelia. Importantly, suppression of Wnt signaling, which is altered in patients with Müllerian duct anomalies, inhibits the regenerative ability of human fetal organoids and causes severe anatomical defects in the mouse reproductive tract. Thus, our fetal organoids represent an important platform to study the underlying basis of human female reproductive tract development and diseases.

Bioprinting Decellularized Breast Tissue for the Development of Three-Dimensional Breast Cancer Models

The tumor extracellular matrix (ECM) plays a vital role in tumor progression and drug resistance. Previous studies have shown that breast tissue-derived matrices could be an important biomaterial to recreate the complexity of the tumor ECM. We have developed a method for decellularizing and delipidating a porcine breast tissue (TDM) compatible with hydrogel formation. The addition of gelatin methacrylamide and alginate allows this TDM to be bioprinted by itself with good printability, shape fidelity, and cytocompatibility. Furthermore, this bioink has been tuned to more closely recreate the breast tumor by incorporating collagen type I (Col1). Breast cancer cells (BCCs) proliferate in both TDM bioinks forming cell clusters and spheroids. The addition of Col1 improves the printability of the bioink as well as increases BCC proliferation and reduces doxorubicin sensitivity due to a downregulation of HSP90. TDM bioinks also allow a precise three-dimensional printing of scaffolds containing BCCs and stromal cells and could be used to fabricate artificial tumors. Taken together, we have proven that these novel bioinks are good candidates for biofabricating breast cancer models.

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.

Development of a decellularized hypopharynx with vascular pedicle scaffold for use in reconstructing hypopharynx

BACKGROUND

Hypopharynx reconstruction after hypopharyngectomy is still a great challenge. Perfusion decellularization is for extracellular matrix (ECM) scaffolding and had been used in organ reconstruction. Our study aimed to prepare an acellular, natural, three-dimensional biological hypopharynx with vascular pedicle scaffold as the substitute materials to reconstruct hypopharynx.

RESULT

Scanning electron microscope and histology staining showed that the decellularized hypopharynx with vascular pedicle scaffold retained intact native anatomical ECM structure. Myoblasts were observed on the recellularized scaffolds with bone marrow mesenchymal stem cells induced by 5-azacytidine implanted in the rabbit greater omentum by immunohistochemical analysis.

CONCLUSION

The decellularized hypopharynx with vascular pedicle scaffold prepared by detergent perfusion in our study has a potential to be an alternative material to pharynx reconstruction.

Recent trends in therapeutic strategies for repairing endometrial tissue in intrauterine adhesion

Intrauterine adhesion (IUA) is a common gynaecological disease that develops from infection or trauma. IUA disease may seriously affect the physical and mental health of women of childbearing age, which may lead to symptoms such as hypomenorrhea or infertility. Presently, hysteroscopic transcervical resection of adhesion (TCRA) is the principal therapy for IUAs, although its function in preventing the recurrence of adhesion and preserving fertility is limited. Pharmaceuticals such as hormones and vasoactive agents and the placement of nondegradable stents are the most common postoperative adjuvant therapy methods. However, the repair of injured endometrium is relatively restricted due to the different anatomical structures of the endometrium. Recently, the treatment outcome of IUAs has improved with the advancement of hysteroscopic techniques. In particular, the application of bioactive scaffolds combined with tissue engineering technology has proven to have high therapeutic potential or endometrial repair in IUA treatment. Herein, this review has summarized past therapeutic strategies, including postoperative adjuvant therapy, cell or therapeutic molecular delivery therapy methods and bioactive scaffold-based tissue engineering methods. Therefore, this review presented the recent therapeutic strategies for repairing endometrium treatment and pointed out the issues of clinical concern to provide alternative methods for the management of IUAs.

Decellularized Extracellular Matrix Composite Hydrogel Bioinks for the Development of 3D Bioprinted Head and Neck in Vitro Tumor Models

Reinforced extracellular matrix (ECM)-based hydrogels recapitulate several mechanical and biochemical features found in the tumor microenvironment (TME) in vivo. While these gels retain several critical structural and bioactive molecules that promote cell-matrix interactivity, their mechanical properties tend toward the viscous regime limiting their ability to retain ordered structural characteristics when considered as architectured scaffolds. To overcome this limitation characteristic of pure ECM hydrogels, we present a composite material containing alginate, a seaweed-derived polysaccharide, and gelatin, denatured collagen, as rheological modifiers which impart mechanical integrity to the biologically active decellularized ECM (dECM). After an optimization process, the reinforced gel proposed is mechanically stable and bioprintable and has a stiffness within the expected physiological values. Our hydrogel's elastic modulus has no significant difference when compared to tumors induced in preclinical xenograft head and neck squamous cell carcinoma (HNSCC) mouse models. The bioprinted cell-laden model is highly reproducible and allows proliferation and reorganization of HNSCC cells while maintaining cell viability above 90% for periods of nearly 3 weeks. Cells encapsulated in our bioink produce spheroids of at least 3000 μm² of cross-sectional area by day 15 of culture and are positive for cytokeratin in immunofluorescence quantification, a common marker of HNSCC model validation in 2D and 3D models. We use this in vitro model system to evaluate the standard-of-care small molecule therapeutics used to treat HNSCC clinically and report a 4-fold increase in the IC₅₀ of cisplatin and an 80-fold increase for 5-fluorouracil compared to monolayer cultures. Our work suggests that fabricating in vitro models using reinforced dECM provides a physiologically relevant system to evaluate malignant neoplastic phenomena in vitro due to the physical and biological features replicated from the source tissue microenvironment.

Extracellular Matrix Hydrogels Originated from Different Organs Mediate Tissue-Specific Properties and Function

Porcine extracellular matrix (pECM)-derived hydrogels were introduced, in recent years, aiming to benefit the pECM’s microstructure and bioactivity, while controlling the biomaterial’s physical and mechanical properties. The use of pECM from different tissues, however, offers tissue-specific features that can better serve different applications. In this study, pECM hydrogels derived from cardiac, artery, pancreas, and adipose tissues were compared in terms of composition, structure, and mechanical properties. While major similarities were demonstrated between all the pECM hydrogels, their distinctive attributes were also identified, and their substantial effects on cell-ECM interactions were revealed. Furthermore, through comprehensive protein and gene expression analyses, we show, for the first time, that each pECM hydrogel supports the spontaneous differentiation of induced pluripotent stem cells towards the resident cells of its origin tissue. These findings imply that the origin of ECM should be carefully considered when designing a biomedical platform, to achieve a maximal bioactive impact.

Developing a mechanically matched decellularized spinal cord scaffold for the in situ matrix-based neural repair of spinal cord injury

Tissue engineering is a promising strategy to repair spinal cord injury (SCI). However, a bioscaffold with mechanical properties that match those of the pathological spinal cord tissue and a pro-regenerative matrix that allows robust neurogenesis for overcoming post-SCI scar formation has yet to be developed. Here, we report that a mechanically enhanced decellularized spinal cord (DSC) scaffold with a thin poly (lactic-co-glycolic acid) (PLGA) outer shell may fulfill the requirements for effective in situ neuroengineering after SCI. Using chemical extraction and electrospinning methods, we successfully constructed PLGA thin shell-ensheathed DSC scaffolds (PLGA-DSC scaffolds) in a way that removed major inhibitory components while preserving the permissive matrix. The DSCs exhibited good cytocompatibility with neural stem cells (NSCs) and significantly enhanced their differentiation toward neurons in vitro. Due to the mechanical reinforcement, the implanted PLGA-DSC scaffolds showed markedly increased resilience to infiltration by myofibroblasts and the deposition of dense collagen matrix, thereby creating a neurogenic niche favorable for the targeted migration, residence and neuronal differentiation of endogenous NSCs after SCI. Furthermore, PLGA-DSC presented a mild immunogenic property but prominent ability to polarize macrophages from the M1 phenotype to the M2 phenotype, leading to significant tissue regeneration and functional restoration after SCI. Taken together, the results demonstrate that the mechanically matched PLGA-DSC scaffolds show promise for effective tissue repair after SCI.

Prednisolone suppresses collagen-encoding gene expression causing cartilage defects in zebrafish larvae

Glucocorticoid-induced osteoporosis (GIOP) is a clinically important disease. Despite many studies, the intrinsic pathogenesis of GIOP is still not fully understood. Cartilage is the target tissue of the glucocorticoid prednisolone (PN). To explore the intrinsic mechanism of PN-induced cartilage damage, we performed cartilage staining and cell transfection experiments in zebrafish larvae treated with PN. The results showed that PN caused cartilage damage in zebrafish at 25 μM. Moreover, after treatment with PN, it was found that collagen-encoding gene expression was significantly reduced. Further research revealed that the glucocorticoid receptor (GR) mediates the transcriptional inhibition of collagen genes by PN. These results indicate that glucocorticoids cause cartilage damage by inhibiting the expression of collagen genes through their receptors. Our study provides new insights into GIOP.

Osteoblast-derived extracellular matrix coated PLLA/silk fibroin composite nanofibers promote osteogenic differentiation of bone mesenchymal stem cells

Poly-L-lactic acid (PLLA) is one of the most commonly used synthetic materials for regenerative medicine, and silk fibroin (SF) is a natural protein with excellent biocompatibility. Combination of PLLA and SF in a proper proportion by electrospinning may generate composite nanofibers that could meet the requirements of scaffolding in bone tissue engineering. The application of PLLA/SF nanofibrous scaffold for osteogenesis is well established in vitro and in vivo. However, PLLA/SF nanofibrous scaffold does not have an ideal ability to promote cell adhesion, proliferation, and differentiation. Extracellular matrix (ECM) plays a critical role in modulating cellular behavior. However, the role of combination of natural ECM with nanofibrous scaffold in regulating osteogenic differentiation is unclear. In this study, we aimed to develop a novel composite PLLA/SF nanofibrous scaffold coated with osteoblast-derived extracellular matrix (O-ECM/PLLA/SF) and analyze the effects of the modified scaffold on osteogenic differentiation of BMSCs. The surface structural features and compositions of the O-ECM/PLLA/SF scaffold were characterized by SEM and immunofluorescence staining. The capacities of the O-ECM/PLLA/SF scaffold to induce osteogenic differentiation of BMSCs were investigated by alkaline phosphatase (ALP) and alizarin red staining (ARS). The results showed BMSCs cultured on O-ECM/PLLA/SF scaffold significantly increased osteogenic differentiation compared with cells cultured individually on a scaffold or O-ECM. Collectively, these findings indicate that O-ECM-coated nanofibrous scaffold can be a promising strategy for osteogenic differentiation of BMSCs, opening a new possibility of utilizing composite scaffolds for bone tissue engineering.

Decellularized kidney extracellular matrix bioinks recapitulate renal 3D microenvironmentin vitro

Decellularized extracellular matrices (ECMs) are able to provide the necessary and specific cues for remodeling and maturation of tissue-specific cells. Nevertheless, their use for typical biofabrication applications requires chemical modification or mixing with other polymers, mainly due to the limited viscoelastic properties. In this study, we hypothesize that a bioink exclusively based on decellularized kidney ECM (dKECM) could be used to bioprint renal progenitor cells. To address these aims, porcine kidneys were decellularized, lyophilized and digested to yield a viscous solution. Then, the bioprinting process was optimized using an agarose microparticle support bath containing transglutaminase for enzymatic crosslinking of the dKECM. This methodology was highly effective to obtain constructs with good printing resolution and high structural integrity. Moreover, the encapsulation of primary renal progenitor cells resulted in high cell viability, with creation of 3D complex structures over time. More importantly, this tissue-specific matrix was also able to influence cellular growth and differentiation over time. Taken together, these results demonstrate that unmodified dKECM bioinks have great potential for bioengineering renal tissue analogs with promising translational applications and/or forin vitromodel systems. Ultimately, this strategy may have greater implications on the biomedical field for the development of bioengineered substitutes using decellularized matrices from other tissues.

Evaluation of PC12 Cells' Proliferation, Adhesion and Migration with the Use of an Extracellular Matrix (CorMatrix) for Application in Neural Tissue Engineering

The use of extracellular matrix (ECM) biomaterials for soft tissue repair has proved extremely successful in animal models and in some clinical settings. The aim of the study was to investigate the effect of the commercially obtained CorMatrix bioscaffold on the viability, proliferation and migration of rat pheochromocytoma cell line PC12. PC12 cells were plated directly onto a CorMatrix flake or the well surface of a 12-well plate and cultured in RPMI-1640 medium and a medium supplemented with the nerve growth factor (NGF). The surface of the culture plates was modified with collagen type I (Col I). The number of PC12 cells was counted at four time points and then analysed for apoptosis using a staining kit containing annexin V conjugate with fluorescein and propidium iodide (PI). The effect of CorMatrix bioscaffold on the proliferation and migration of PC12 cells was tested by staining the cells with Hoechst 33258 solution for analysis using fluorescence microscopy. The research showed that the percentage of apoptotic and necrotic cells was low (less than 7%). CorMatrix stimulates the proliferation and possibly migration of PC12 cells that populate all levels of the three-dimensional architecture of the biomaterial. Further research on the mechanical and biochemical capabilities of CorMatrix offers prospects for the use of this material in neuro-regenerative applications.

Renal Regeneration: The Role of Extracellular Matrix and Current ECM-Based Tissue Engineered Strategies

Natural extracellular matrices (ECM) are currently being studied as an alternative source for organ transplantation or as new solutions to treat kidney injuries, which can evolve to end-stage renal disease, a life devastating condition. This paper provides an overview on the current knowledge in kidney ECM and its usefulness on future investigations. The composition and structure of kidney ECM is herein associated with its intrinsic capacity of remodeling and repair after insult. Moreover, it provides a deeper insight on altered ECM components during disease. The use of decellularized kidney matrices is discussed in the second part of the review, with emphasis on how these matrices contribute to tissue-specific differentiation of embryonic, pluripotent, and other stem cells. The evolution on the field toward different uses of xenogeneic ECM as a biological scaffold material is discussed, namely the major outcomes on whole kidney recellularization and its in vivo implantation. At last, the recent literature on the use of processed kidney decellularized ECM to produce diverse biomaterial substrates, such as hydrogels, membranes, and bioinks are reviewed, with emphasis on future perspectives of its translation into the clinic.

Printing 3D vagina tissue analogues with vagina decellularized extracellular matrix bioink

A variety of factors can cause vaginal loss. The patients are suffering from great psychological and physical pain, and there is an urgent need for vagina reconstruction. 3D-bioprinting is expected to achieve vaginal morphological restoration and true functional reconstruction. The current study aimed to explore the biomimetic 3D vagina tissue printing with acellular vagina matrix (AVM) bioink. The AVM from pig was converted to bioink by 15% gelatin and 3% sodium alginate mixed with the AVM solution. Rheology, scanning electron microscopy and HE staining were performed to characterize the bioink's viscosity, morphologies and biocompatibility. After printing, the viability of bone marrow mesenchymal stem cells (BMSCs) in the printed 3D scaffolds in vitro was investigated by a live/dead assay kit. Then, subcutaneous transplantation in rats were divided randomly into 3D scaffold group and 3D scaffold encapsulating CM-Dil-labeled BMSCs group. The results of HE, immunohistochemistry and immunofluorescence staining revealed that 3D scaffold encapsulating BMSCs expressed significant effects on the vascularization and epithelization of the printed vagina tissue, and the BMSCs could acquire the phenotype of vaginal epithelial cells and endothelial-like cells. The work showed that the biomimetic 3D vagina tissue with AVM bioink encapsulating BMSCs is a promising approach for vagina reconstruction.

Rabbit as an animal model for the study of biological grafts in pelvic floor dysfunctions

The aims of this study were to evaluate the feasibility of the New Zealand White (NZW) rabbit for studying implanted biomaterials in pelvic reconstructive surgery; and to compare the occurrence of graft-related complications of a commercial polypropylene (PP) mesh and new developed human dermal matrix implanted at vaginal and abdominal level. 20 white female NZW rabbits were randomized into two groups, experimental group (human acellular dermal matrices-hADM-graft) and control group (commercial PP graft). In each animal, grafts were surgically implanted subcutaneously in the abdominal wall and in the vaginal submucosa layer for 180 days. The graft segments were then removed and the surgical and clinical results were analyzed. The main surgical challenges during graft implantation were: (a) an adequate vaginal exposure while maintaining the integrity of the vaginal mucosa layer; (b) to keep aseptic conditions; (c) to locate and dissect the breast vein abdominal surgery; and (d) to withdraw blood samples from the ear artery. The most abnormal findings during the explant surgery were found in the PP group (33% of vaginal mesh extrusion) in comparison with the hADM group (0% of vaginal graft extrusion), p = 0.015. Interestingly, macroscopic observation showed that the integration of the vaginal grafts was more common in the hADM group (40%) than in the PP group, in which the vaginal mesh was identified in 100% of the animals (p = 0.014). The NZW rabbit is a good model for assessing materials to be used as grafts for pelvic reconstructive surgery and vaginal surgery. Animals are easily managed during the procedures, including surgical intervention and vaginal mucosa approach. Additionally, hADM is associated with fewer clinical complications, as well as better macroscopic tissue integration, compared to PP mesh.

Human Bronchial Epithelial Cell Growth on Homologous Versus Heterologous Tissue Extracellular Matrix

BACKGROUND

Extracellular matrix (ECM) bioscaffolds produced by decellularization of source tissue have been effectively used for numerous clinical applications. However, decellularized tracheal constructs have been unsuccessful due to the immediate requirement of a functional airway epithelium on surgical implantation. ECM can be solubilized to form hydrogels that have been shown to support growth of many different cell types. The purpose of the present study is to compare the ability of airway epithelial cells to attach, form a confluent monolayer, and differentiate on homologous (trachea) and heterologous (urinary bladder) ECM substrates for potential application in full tracheal replacement.

MATERIALS AND METHODS

Porcine tracheas and urinary bladders were decellularized. Human bronchial epithelial cells (HBECs) were cultured under differentiation conditions on acellular tracheal ECM and urinary bladder matrix (UBM) bioscaffolds and hydrogels and were assessed by histology and immunolabeling for markers of ciliation, goblet cell formation, and basement membrane deposition.

RESULTS

Both trachea and urinary bladder tissues were successfully decellularized. HBEC formed a confluent layer on both trachea and UBM scaffolds and on hydrogels created from these bioscaffolds. Cells grown on tracheal and UBM hydrogels, but not on bioscaffolds, showed positive-acetylated tubulin staining and the presence of mucus-producing goblet cells. Collagen IV immunolabeling showed basement membrane deposition by these cells on the surface of the hydrogels.

CONCLUSIONS

ECM hydrogels supported growth and differentiation of HBEC better than decellularized ECM bioscaffolds and show potential utility as substrates for promotion of a mature respiratory epithelium for regenerative medicine applications in the trachea.

Construction of novel antimicrobial peptide-modified extracellular matrix biologic scaffold material

In the field of implantable medical devices, the antibacterial extracellular matrix (ECM) biologic scaffold, which is constructed by modifying biomaterials with antibacterial peptides, has excellent potential. An antibacterial peptide-modified ECM scaffold was formed with chitosan (CS), antimicrobial peptide (AMP), and ECM scaffold. Chitosan has a firm positive-charge surface and can combine with the ECM scaffold material to form a positive-charge layer on the surface. The surface potential was characterized using a surface potential map. Infrared spectroscopy and scanning electron microscopy (SEM) were used to observe the scaffold surface characteristics and cell morphology. Fluorescence staining and MTS assay kit were used to assess cytotoxicity and biocompatibility. To evaluate the antibacterial and repairing effects on the infected wounds in vivo, a subcutaneous antibacterial test of rabbit back was conducted. The antibacterial peptide-modified ECM scaffold was successfully formed and presented an excellent three-dimensional micro-surface porous structure. The antibacterial peptide-modified ECM scaffold could be effectively-prepared by surface modification and activation. Fluorescence staining tests showed good cell adhesion, proliferation ability, and cell affinity. The in vivo experiment indicated that the antibacterial ECM scaffold had antibacterial and healing-promotion abilities.

Adhesion of anaerobic periodontal pathogens to extracellular matrix proteins

Extracellular matrix (ECM) proteins are highly abundant in the human body and can be found in various tissues, most prominently in connective tissue and basement membrane. For invasive bacterial pathogens, these structures function as physical barriers that block access to underlying tissues. The ability to bind and degrade these barriers is important for the establishment of infections and migration to other body sites. In the oral cavity, the ECM and the basement membrane (BM) are important components of the Junctional epithelium (JE) that closes the gap between the teeth surface and the mucosa. In periodontitis, the JE is breached by invading pathogenic bacteria, particularly strict anaerobic species. In periodontitis, invading microorganisms induce an unregulated and destructive host response through polymicrobial synergism and dysbiosis that attracts immune cells and contributes to the destruction of connective tissue and bone in the periodontal pocket. Colonization of the periodontal pocket is the first step to establish this infection, and binding to ECM is a major advantage in this site. Several species of strict anaerobic bacteria are implicated in acute and chronic periodontitis, and although binding to ECM proteins was studied in these species, few adhesins were identified so far, and the mechanisms involved in adhesion are largely unidentified. This review summarizes the data available on the interaction of strict anaerobic bacteria and components of the ECM.

Thoracic aortic surgery: status and upcoming novelties

Several novel technological developments and surgical approaches have characterized the field of aortic surgery in the recent decade. The progressive introduction of endovascular procedures, minimally invasive surgical techniques and hybrid approaches have changed the practice in aortic surgery and generated new trends and questions. Also, the advancements in the manufacturing of tissue engineered vascular grafts as substitutes for aortic replacements are enlightening new avenues in the treatment of aortic disease. This review will provide an overview of the current novel perspectives, debates and trends in major thoracic aortic surgery.

Stress Urinary Incontinence and Pelvic Organ Prolapse: Biologic Graft Materials Revisited

Symptomatic stress urinary incontinence (SUI) and pelvic organ prolapse (POP) refractory to conservative management with pelvic floor muscle training or vaginal pessaries may warrant surgical intervention with different forms of biologic or synthetic material. However, in recent years, several global regulatory agencies have issued health warnings and recalled several mesh products due to an increase in complications such as mesh erosion, infection, chronic pain, and perioperative bleeding. At present, current surgical treatment strategies for SUI and POP are aimed at developing biological graft materials with similar mechanical properties to established synthetic meshes, but with improved tissue integration and minimal host response. This narrative review aims to highlight recent studies related to the development of biomimetic and biologic graft materials as alternatives to traditional synthetic materials for SUI/POP repair in female patients. We also investigate complications and technical limitations associated with synthetic mesh and biological biomaterials in conventional SUI and POP surgery. Our findings demonstrate that newly developed biologic grafts have a lower incidence of adverse events compared to synthetic biomaterials. However there remains a significant disparity between success in preclinical trials and long-term clinical translation. Further characterization on the optimal structural, integrative, and mechanical properties of biological grafts is required before they can be reliably introduced into clinical practice for SUI and POP surgery. Impact statement Our review article aims to outline the clinical history of developments and controversies associated with the use of synthetic mesh materials in the surgical treatment of stress urinary incontinence and pelvic organ prolapse, as well as highlighting recent advancements in the area of biological graft materials and their potential importance in an area that remains an enduring issue for patients and clinicians alike. This article aims to provide a concise summary of previous controversies in the field of urinary incontinence, while evaluating the future of potential biomaterials in this field.

Boosting the Osteogenic and Angiogenic Performance of Multiscale Porous Polycaprolactone Scaffolds by In Vitro Generated Extracellular Matrix Decoration

Tissue engineering (TE)-based bone grafts are favorable alternatives to autografts and allografts. Both biochemical properties and the architectural features of TE scaffolds are crucial in their design process. Synthetic polymers are attractive biomaterials to be used in the manufacturing of TE scaffolds, due to various advantages, such as being relatively inexpensive, enabling precise reproducibility, possessing tunable mechanical/chemical properties, and ease of processing. However, such scaffolds need modifications to improve their limited interaction with biological tissues. Structurally, multiscale porosity is advantageous over single-scale porosity; therefore, in this study, we have considered two key points in the design of a bone repair material; (i) manufacture of multiscale porous scaffolds made of photocurable polycaprolactone (PCL) by a combination of emulsion templating and three-dimensional (3D) printing and (ii) decoration of these scaffolds with the in vitro generated bone-like extracellular matrix (ECM) to create biohybrid scaffolds that have improved biological performance compared to PCL-only scaffolds. Multiscale porous scaffolds were fabricated, bone cells were cultured on them, and then they were decellularized. The biological performance of these constructs was tested in vitro and in vivo. Mesenchymal progenitors were seeded on PCL-only and biohybrid scaffolds. Cells not only showed improved attachment on biohybrid scaffolds but also exhibited a significantly higher rate of cell growth and osteogenic activity. The chick chorioallantoic membrane (CAM) assay was used to explore the angiogenic potential of the biohybrid scaffolds. The CAM assay indicated that the presence of the in vitro generated ECM on polymeric scaffolds resulted in higher angiogenic potential and a high degree of tissue infiltration. This study demonstrated that multiscale porous biohybrid scaffolds present a promising approach to improve bioactivity, encourage precursors to differentiate into mature bones, and to induce angiogenesis.

The importance of developing relevant animal models to assess existing and new materials

PURPOSE OF REVIEW

We summarize the recent literature on the use of different animal models for testing existing and new materials for treatment of pelvic organ prolapse.

RECENT FINDINGS

A wide spectrum of animal models is being used in urogynecology, both for the study of physiologic and pathophysiologic processes, training in surgical procedures, yet mainly to study the host response to implant materials. The quality of studies is variable, and procedures, read-outs, and reporting are not standardized. This makes comparison very difficult. The research community is experimenting with different knitting patterns, novel polymers, bioactivation, as well as resorbable rather than durable implants. Outcomes of the experiments are dependent on the location of implantation. Lighter polypropylene constructs seem to induce a less vigorous host response than elder heavier products. Modification of the surface yields contradictory findings. Resorbable acellular collagen matrices may be reintroduced as prophylactically inserted support structures.

SUMMARY

Although animal experimentation with novel candidate implants is advocated, there is a lack of standardization in reporting. The concept of resorbable construct is being revived, as durable materials have caused clinical graft-related complications. Large animal experiments seem to provide interesting and more comprehensive information, yet their use may be contested.

Bovine Decellularized Amniotic Membrane: Extracellular Matrix as Scaffold for Mammalian Skin

Decellularized membranes (DM) were obtained from bovine amniotic membranes (BAM) using four different decellularization protocols, based on physical, chemical, and mechanical treatment. The new material was used as a biological scaffold for in vitro skin cell culture. The DM were characterized using hematoxylin-eosin assay, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR-ATR), and differential scanning calorimetry (DSC). The in vitro cytotoxicity of DM was evaluated using MTT. The efficacy of decellularization process was assessed through DNA quantification and electrophoresis. All the used protocols showed a high effectiveness in terms of elimination of native cells, confirmed by DNA extraction and quantification, electrophoresis, and SEM, although protocol IV removes the cellular contents and preserve the native extracellular matrix (ECM) architecture which it can be considered as the most effective in terms of decellularization. FTIR-ATR and DSC on the other hand, revealed the effects of decellularization on the biochemical composition of the matrices. There was no cytotoxicity and the biological matrices obtained were a source of collagen for recellularization. The matrices of protocols I, II, and III were degraded at day 21 of cell culture, forming a gel. The biocompatibility in vitro was demonstrated; hence these matrices may be deemed as potential scaffold for epithelial tissue regeneration.

Preclinical evaluation of efficacy and pharmacokinetics of gentamicin containing extracellular-matrix envelope

BACKGROUND

Using synthetic antibiotic-eluting envelope (ABE) is an effective intervention for prevention of cardiovascular implantable electronic device (CIED) infection. The biologic extracellular-matrix envelope (ECME), may offer potential advantages over the synthetic ABE. To further minimize the risk of infection, the ECME can be hydrated in gentamicin prior to CIED implantation. We aimed to evaluate the efficacy and pharmacokinetics (PK) of gentamicin containing ECME in an animal model.

METHODS

For all experiments, the ECME was hydrated in gentamicin (40 mg/Ml) (treatment) for 2 min. In vitro antimicrobial efficacy against six different bacterial species was assessed. In vivo experiments were conducted using a rabbit model of CIED pocket infection. Serum and ECM gentamicin concentrations were measured. Five different organisms were inoculated into the device pocket of control (ECME hydrated in 0.9% saline) and treatment groups. Macroscopic appearance and colony forming units from CIED, ECME, and tissue were determined.

RESULTS

No bacteria were recovered from any culture after 12 h of exposure to the gentamicin containing ECME. Serum gentamicin levels dropped below the limit of quantification at 15 h after implant. Gentamicin concentration in the ECME remained relatively stable for up to 7 days. Signs of clinical infection were observed in the control but not in the treatment group. In the presence of gentamicin, statistically significant reduction was demonstrated across all tested bacterial species.

CONCLUSIONS

In this preclinical animal infection model, gentamicin containing ECME was highly effective in reducing bacterial burden in the implant pocket, while systemic exposure after implantation remained low.

Biomaterials for In Situ Tissue Regeneration: A Review

This review focuses on a somewhat unexplored strand of regenerative medicine, that is in situ tissue engineering. In this approach manufactured scaffolds are implanted in the injured region for regeneration within the patient. The scaffold is designed to attract cells to the required volume of regeneration to subsequently proliferate, differentiate, and as a consequence develop tissue within the scaffold which in time will degrade leaving just the regenerated tissue. This review highlights the wealth of information available from studies of ex-situ tissue engineering about the selection of materials for scaffolds. It is clear that there are great opportunities for the use of additive manufacturing to prepare complex personalized scaffolds and we speculate that by building on this knowledge and technology, the development of in situ tissue engineering could rapidly increase. Ex-situ tissue engineering is handicapped by the need to develop the tissue in a bioreactor where the conditions, however optimized, may not be optimum for accelerated growth and maintenance of the cell function. We identify that in both methodologies the prospect of tissue regeneration has created much promise but delivered little outside the scope of laboratory-based experiments. We propose that the design of the scaffolds and the materials selected remain at the heart of developments in this field and there is a clear need for predictive modelling which can be used in the design and optimization of materials and scaffolds.

Biomaterials for In Situ Tissue Regeneration: A Review

This review focuses on a somewhat unexplored strand of regenerative medicine, that is in situ tissue engineering. In this approach manufactured scaffolds are implanted in the injured region for regeneration within the patient. The scaffold is designed to attract cells to the required volume of regeneration to subsequently proliferate, differentiate, and as a consequence develop tissue within the scaffold which in time will degrade leaving just the regenerated tissue. This review highlights the wealth of information available from studies of ex-situ tissue engineering about the selection of materials for scaffolds. It is clear that there are great opportunities for the use of additive manufacturing to prepare complex personalized scaffolds and we speculate that by building on this knowledge and technology, the development of in situ tissue engineering could rapidly increase. Ex-situ tissue engineering is handicapped by the need to develop the tissue in a bioreactor where the conditions, however optimized, may not be optimum for accelerated growth and maintenance of the cell function. We identify that in both methodologies the prospect of tissue regeneration has created much promise but delivered little outside the scope of laboratory-based experiments. We propose that the design of the scaffolds and the materials selected remain at the heart of developments in this field and there is a clear need for predictive modelling which can be used in the design and optimization of materials and scaffolds.

Adult Stem Cells for Bone Regeneration and Repair

The regeneration of bone fractures, resulting from trauma, osteoporosis or tumors, is a major problem in our super-aging society. Bone regeneration is one of the main topics of concern in regenerative medicine. In recent years, stem cells have been employed in regenerative medicine with interesting results due to their self-renewal and differentiation capacity. Moreover, stem cells are able to secrete bioactive molecules and regulate the behavior of other cells in different host tissues. Bone regeneration process may improve effectively and rapidly when stem cells are used. To this purpose, stem cells are often employed with biomaterials/scaffolds and growth factors to accelerate bone healing at the fracture site. Briefly, this review will describe bone structure and the osteogenic differentiation of stem cells. In addition, the role of mesenchymal stem cells for bone repair/regrowth in the tissue engineering field and their recent progress in clinical applications will be discussed.

Impact of polypropylene prolapse mesh on vaginal smooth muscle in rhesus macaque

BACKGROUND

The use of polypropylene prolapse mesh to treat pelvic organ prolapse has been limited by mesh-related complications. Gynemesh PS mesh, implanted via sacrocolpopexy in rhesus macaques, had a negative impact on the vagina with thinning of vaginal muscularis and decreased vaginal smooth muscle contractility. The negative effect was attenuated when a bioscaffold derived from urinary bladder extracellular matrix was used as a composite with Gynemesh PS.

OBJECTIVE

The objective of the study was to further elucidate the impact of Gynemesh PS polypropylene mesh and MatriStem extracellular matrix bioscaffolds on the vaginal smooth muscle in terms of micromorphology of vaginal smooth muscle (muscle bundles and individual myocytes), innervation, and nerve-mediated contractile function following their implantations in a rhesus macaque model via sacrocolpopexy.

STUDY DESIGN

Thirty-two middle-aged rhesus macaques were randomized to undergo either a sham surgery (sham, n = 8), or the implantation of Gynemesh PS alone (n = 8) vs composite mesh comprised of Gynemesh PS plus 2-ply MatriStem (n = 8) vs 6-ply MatriStem alone (n = 8) via sacrocolpopexy. The graft-vagina complexes were harvested 3 months later. Histomorphometrics of smooth muscle bundles and myocytes were performed by immunofluorescent labeling of alpha smooth muscle actin, caveolin-3 (membrane protein), and cell nuclei followed by confocal imaging. The cross-sectional diameters of smooth muscle bundles and individual myocytes were quantified using images randomly taken in at least 5 areas of each section of sample. Contractile proteins alpha smooth muscle actin and smoothelin were quantified by Western immunoblotting. Nerve density was measured by immunohistochemical labeling of a pan-neuron marker, PGP9.5. Nerve-mediated smooth muscle contractility was quantified using electrical field stimulation. One-way analysis of variance and appropriate post hoc tests were used for statistical comparisons.

RESULTS

Compared with sham, the implantation of Gynemesh PS alone resulted in a disorganized smooth muscle morphology with the number of small muscle bundles (cross-sectional diameter less than 20 μm) increased 67% (P = .004) and the myocyte diameter decreased 22% (P < .001). Levels of contractile proteins were all decreased vs sham with alpha smooth muscle actin decreased by 68% (P = .009), low-molecular-weight smoothelin by 51% (P = .014), and high-molecular-weight smoothelin by 40% (P = .015). Nerve density was decreased by 48% (P = .03 vs sham) paralleled by a 63% decrease of nerve-mediated contractility (P = .02). Following the implantation of composite mesh, the results of measurements were similar to sham (all P > .05), with a 39% increase in the myocyte diameter (P < .001) and a 2-fold increase in the level of alpha smooth muscle actin relative to Gynemesh (P = .045). Following the implantation of MatriStem alone, the number of small muscle bundles were increased 54% vs sham (P = .002), while the other parameters were not significantly different from sham (all P > .05).

CONCLUSION

The implantation of Gynemesh PS had a negative impact on the structural and functional integrity of vaginal smooth muscle evidenced by atrophic macro- and microscopic muscle morphology, decreased innervation, and impaired contractile property, consistent with a maladaptive remodeling response. The extracellular matrix bioscaffold (MatriStem), when used with Gynemesh PS as a composite (2 ply), attenuated the negative impact of Gynemesh PS; when used alone (6 ply), it induced adaptive remodeling as evidenced by an increased fraction of small smooth muscle bundles with normal contractility.