Bone Marrow Aspirate Matrix: A Convenient Ally in Regenerative Medicine.

The rise in musculoskeletal disorders has prompted medical experts to devise novel effective alternatives to treat complicated orthopedic conditions. The ever-expanding field of regenerative medicine has allowed researchers to appreciate the therapeutic value of bone marrow-derived biological products, such as the bone marrow aspirate (BMA) clot, a potent orthobiologic which has often been dismissed and regarded as a technical complication. Numerous in vitro and in vivo studies have contributed to the expansion of medical knowledge, revealing optimistic results concerning the application of autologous bone marrow towards various impactful disorders. The bone marrow accommodates a diverse family of cell populations and a rich secretome; therefore, autologous BMA-derived products such as the "BMA Matrix", may represent a safe and viable approach, able to reduce the costs and some drawbacks linked to the expansion of bone marrow. BMA provides -it eliminates many hurdles associated with its preparation, especially in regards to regulatory compliance. The BMA Matrix represents a suitable alternative, indicated for the enhancement of tissue repair mechanisms by modulating inflammation and acting as a natural biological scaffold as well as a reservoir of cytokines and growth factors that support cell activity. Although promising, more clinical studies are warranted in order to further clarify the efficacy of this strategy.

Clinically Significant Outcomes Following the Treatment of Focal Cartilage Defects of the Knee With Microfracture Augmentation Using Cartilage Allograft Extracellular Matrix: A Multicenter Prospective Study.

PURPOSE: To determine the short-term outcomes following microfracture augmented with cartilage allograft extracellular matrix for the treatment of symptomatic focal cartilage defects of the adult knee. METHODS: Forty-eight patients enrolled by 8 surgeons from 8 separate institutions were included in this study. Patients underwent microfracture augmented by cartilage allograft extracellular matrix (BioCartilage; Arthrex, Naples, FL) and were followed at designated time points (3, 6, 12, and 24 months) to assess patient-reported outcomes (PROs), clinically significant outcomes (CSOs), and failure and complication rates. Magnetic resonance imaging (MRI) was offered at 2 years postoperatively regardless of symptomatology, and Magnetic Resonance Observation of Cartilage Repair Tissue (MOCART) 2.0 score was documented. RESULTS: PRO compliance was 81.3% at 6 months, 72.9% at 12 months, and 47.9% at 2 years. All joint-specific and function-related PROs significantly improved compared to baseline at 3, 6, 12, 18, and 24 months of follow-up (P < .01), apart from Marx activity scale, which demonstrated a significant decline in postoperative scores at 2 years (P = .034). The percentage of patients achieving CSOs (as defined for microfracture) at 2 years was 90% for minimal clinically important difference and 85% for patient acceptable symptomatic state. Patient factors including age, sex, body mass index, symptoms duration, smoking, presence of a meniscal tear, lesion size, and location were not associated with CSO achievement at 2 years. One patient (2.1%) failed treatment 9.5 months postoperatively due to graft delamination and required a reoperation consisting of arthroscopic debridement. One complication (2.1%) consisting of complaints of clicking, grinding, and crepitus 15 months following the index procedure was reported. Two-year postoperative MRI demonstrated a mean 40.5 ± 22.9 MOCART 2.0 score. CONCLUSIONS: In this preliminary study, we found cartilage allograft extracellular matrix to be associated with improvement in functional outcomes, high rates of CSO achievement, and low failure and complication rates at 2-year follow-up. LEVEL OF EVIDENCE: Level III, prospective multicenter cohort study.

A decellularized human corneal scaffold for anterior corneal surface reconstruction.

Allogenic transplants of the cornea are prone to rejection, especially in repetitive transplantation and in scarred or highly vascularized recipient sites. Patients with these ailments would particularly benefit from the possibility to use non-immunogenic decellularized tissue scaffolds for transplantation, which may be repopulated by host cells in situ or in vitro. So, the aim of this study was to develop a fast and efficient decellularization method for creating a human corneal extracellular matrix scaffold suitable for repopulation with human cells from the corneal limbus. To decellularize human donor corneas, sodium deoxycholate, deoxyribonuclease I, and dextran were assessed to remove cells and nuclei and to control tissue swelling, respectively. We evaluated the decellularization effects on the ultrastructure, optical, mechanical, and biological properties of the human cornea. Scaffold recellularization was studied using primary human limbal epithelial cells, stromal cells, and melanocytes in vitro and a lamellar transplantation approach ex vivo. Our data strongly suggest that this approach allowed the effective removal of cellular and nuclear material in a very short period of time while preserving extracellular matrix proteins, glycosaminoglycans, tissue structure, and optical transmission properties. In vitro recellularization demonstrated good biocompatibility of the decellularized human cornea and ex vivo transplantation revealed complete epithelialization and stromal repopulation from the host tissue. Thus, the generated decellularized human corneal scaffold could be a promising biological material for anterior corneal reconstruction in the treatment of corneal defects.

Engraftment of bioengineered three-dimensional scaffold from human amniotic membrane-derived extracellular matrix accelerates ischemic diabetic wound healing.

Human amniotic membrane (HAM) is traditionally used for the treatment of non-healing wounds. However, high density of HAM-matrix (HAM-M) diminishes cellular contribution for successful tissue regeneration. Herein we investigated whether a bioengineered micro-porous three-dimensional (3D) HAM-scaffold (HAM-S) could promote healing in ischemic wounds in diabetic type 1 rat. HAM-S was prepared from freshly decellularized HAM. Then, 30 days after inducing diabetes, an ischemic circular excision was generated on rats' skin. The diabetic animals were randomly divided into untreated (Diabetic group), engrafted with HAM-M (D-HAM-M group) and HAM-S (D-HAM-S group). Also, non-diabeticuntreated rats (Healthy group) were considered as control. Stereological, molecular, and tensiometrical assessments were performed on post-surgical days 7, 14, and 21. We found that the volumes of new epidermis and dermis, the numerical density of epidermal basal cells and fibroblasts, the length density of blood vessels, the numbers of proliferating cells and collagen deposition as well as biomechanical properties of healed wound were significantly higher in D-HAM-S group in most cases compared those of the diabetic group, or even in some cases compared to D-HAM-M group. Furthermore, in D-HAM-S group, the transcripts for genes contributing to regeneration (Tgf-ß, bFgf and Vegf) upregulated more than those of D-HAM-M group, when compared to diabetic ones. Overall, the HAM-S had more impact on delayed wound healing process compared to traditional use of intact HAM. It is therefore suggested that the bioengineered three dimensional micro-porous HAM-S is more suitable for cells adhesion, penetration, and migration for contributing to wounded tissue regeneration.

Extracellular Matrix Enterocutaneous Fistula Plugs Show Promise for Low-Flow Colocutaneous and Enterocutaneous Fistulae.

PURPOSE: To evaluate extracellular matrix enterocutaneous fistula plugs (ECMFPs) in treatment of enteric fistulae at a single institution. MATERIALS AND METHODS: The study included 18 patients who had an ECMFP placed between 2012 and 2018 with treatment follow-up through July 2020. Median patient age was 52.5 years (interquartile range, 11.5 y). There were 28 ECMFP procedures performed on 19 separate fistulae. Fistulae locations were gastrocutaneous (n = 4), enterocutaneous (n = 9), and colocutaneous (n = 6). Descriptive statistics were used to define closure rates, recurrence rates, and complications. RESULTS: Fistula closure was achieved in 1 of 4 gastrocutaneous (25%), 4 of 9 enterocutaneous (44%), and 3 of 6 colocutaneous (50%) locations. The median time from procedure to fistula tract closure was 29 days interquartile range 25 days. The median time from ECMFP placement to fistula recurrence was 28 days (interquartile range 27 days). Of the fistulae that eventually closed, 6 of 8 closed after the first attempt (75%), and 2 closed after the second attempt (25%). Of the procedures that resulted in complete closure, 7 of 8 were categorized as low flow, and 1 of 8 was categorized as high flow. Complications were seen in 4 patients (23%), with major complications in 3 patients (17%). CONCLUSIONS: Low-flow fistulae originating from the small bowel are most likely to have complete closure. High-flow and/or gastrocutaneous fistulae are less likely to benefit from this intervention. In patients who are not surgical candidates or who have failed surgical management, ECMFPs may provide a solution.

In vitro evaluation of surface biological properties of decellularized aorta for cardiovascular use.

The aim of this study was to determine an in vitro evaluation method that could directly predict in vivo performance of decellularized tissue for cardiovascular use. We hypothesized that key factors for in vitro evaluation would be found by in vitro assessment of decellularized aortas that previously showed good performance in vivo, such as high patency. We chose porcine aortas, decellularized using three different decellularization methods: sodium dodecyl-sulfate (SDS), freeze-thawing, and high-hydrostatic pressurization (HHP). Immunohistological staining, a blood clotting test, scanning electron microscopy (SEM) analysis, and recellularization of endothelial cells were used for the in vitro evaluation. There was a significant difference in the remaining extracellular matrix (ECM) components, ECM structure, and the luminal surface structure between the three decellularized aortas, respectively, resulting in differences in the recellularization of endothelial cells. On the other hand, there was no difference observed in the blood clotting test. These results suggested that the blood clotting test could be a key evaluation method for the prediction of in vivo performance. In addition, evaluation of the luminal surface structure and the recellularization experiment should be packaged as an in vitro evaluation because the long-term patency was probably affected. The evaluation approach in this study may be useful to establish regulations and a quality management system for a cardiovascular prosthesis.

Bioreactivity of decellularized animal, plant, and fungal scaffolds: perspectives for medical applications.

Numerous biomedical applications imply supportive materials to improve protective, antibacterial, and regenerative abilities upon surgical interventions, oncotherapy, regenerative medicine, and others. With the increasing variability of the possible sources, the materials of natural origin are among the safest and most accessible biomedical tools. Animal, plant, and fungal tissues can further undergo decellularization to improve their biocompatibility. Decellularized scaffolds lack the most reactive cellular material, nuclear and cytoplasmic components, that predominantly trigger immune responses. At the same time, the outstanding initial three-dimensional microarchitecture, biomechanical properties, and general composition of the scaffolds are preserved. These unique features make the scaffolds perfect ready-to-use platforms for various biomedical applications, implying cell growth and functionalization. Decellularized materials can be repopulated with various cells upon request, including epithelial, endothelial, muscle and neuronal cells, and applied for structural and functional biorepair within diverse biological sites, including the skin and musculoskeletal, cardiovascular, and central nervous systems. However, the molecular and cellular mechanisms behind scaffold and host tissue interactions remain not fully understood, which significantly restricts their integration into clinical practice. In this review, we address the essential aspects of decellularization, scaffold preparation techniques, and its biochemical composition and properties, which determine the biocompatibility and immunogenicity of the materials. With the integrated evaluation of the scaffold profile in living systems, decellularized animal, plant, and fungal scaffolds have the potential to become essential instruments for safe and controllable biomedical applications.

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

Decellularized materials (DMs) are attracting more and more attention because of their native structures, comparatively high bioactivity, low immunogenicity and good biodegradability, which are difficult to be imitated by synthetic materials. Recently, DMs have been demonstrated to possess great potential to overcome the disadvantages of autografts and have become a kind of promising material for tissue engineering. In this systematic review, we aimed to not only provide a quick access for understanding DMs, but also bring new ideas to utilize them more appropriately in tissue engineering. Firstly, the preparation of DMs was introduced. Then, the updated applications of DMs derived from different tissues and organs in tissue engineering were comprehensively summarized. In particular, their advantages, drawbacks and current improvements were emphasized. Moreover, we analyzed and proposed future perspectives.

Mitral Valve Replacement in Pediatrics Using an Extracellular Matrix Cylinder Valve: A Case Series.

Mitral valve replacement (MVR) in children under 2 years is associated with significant morbidity and mortality. Decellularized porcine intestinal submucosa is a commercially available formulation of an extracellular matrix (ECM) with an indication for cardiac tissue repair. The present study reports our experience using ECM cylinder valves in patients for MVR. A retrospective review of patients under 2 years who underwent ECM custom-made cylinder mitral valve (ECM-MV) replacement was performed. Clinical, demographic, operative and post-operative follow-up data, including serial echocardiographic data are presented. Eight patients (age 5.6 ± 1.6 months; weight: 6.0 ± 1.1 kg) were identified who underwent ECM-MVR. There was one in-hospital death and no major neurological events. Six patients underwent replacement of their cylinder valve with either a Melody valve inside the ECM-MVR (n = 3), a mechanical valve (n = 2), or a decellularized bovine pericardial cylinder valve (n = 1). The mean time to replacement surgery was 8.4 ± 2.6 months after ECM-MV. The indications for replacement of ECM-MV included mitral stenosis/regurgitation (n = 4) or dehiscence (n = 2). One remaining patient is 24 months from ECM-MV, with trivial regurgitation and no stenosis. Mitral valve creation using ECM is an option for MVR in pediatrics, avoiding anticoagulation, and provides a suitable construct for later placement of a Melody valve, extending surgical and non-surgical options. However, the durability of the native ECM-MV in the mitral position is concerning considering the high re-intervention rate in a relatively short time period. Further studies are needed to determine the longer-term outcomes of this valve in this complex patient population.

Pancreatic extracellular matrix and platelet-rich plasma constructing injectable hydrogel for pancreas tissue engineering.

The development of pancreatic extracellular matrices enriched with insulin-secreting ß-cells is a promising tissue engineering approach to treat type 1 diabetes. However, its long-term therapeutic efficacy is restricted by the defensive mechanism of host immune response and the lack of developed vascularization as appropriate after transplantation. Platelet-rich plasma (PRP), as an autologous platelet concentrate, contains a large number of active factors that are essential for the cell viability, vascularization, and immune regulation. In this study, we have incorporated pancreatic extracellular matrix (PEM) with PRP to develop a three-dimensional (3D) injectable PEM-PRP hydrogel to coculture and transplant rat insulinoma cells (INS-1) and human umbilical vein endothelial cells (HUVECs). Results from this study demonstrated that PEM-PRP hydrogel mimicked the biochemical compositions of native extracellular matrices, and possessed the enhanced elastic modulus and resistance to enzymatic degradation that enabled biomaterials to maintain its volume and slowly degrade. Additionally, PEM-PRP hydrogel could release growth factors in a sustained manner. In vitro, PEM-PRP hydrogel significantly promoted the viability, insulin-secreting function, and insulin gene expression of gel encapsulated INS-1 cells. Moreover, HUVECs encapsulated in PEM-PRP hydrogel were found to constitute many lumen-like structures and exhibited high expression of proangiogenic genes. In vivo transplantation of PEM-PRP hydrogel encapsulated with INS-1 cells and HUVECs improved the viability of INS-1 cells, promoted vascularization, inhibited the host inflammatory response, and reversed hyperglycemia of diabetic rats. Our study suggests that the PEM-PRP hydrogel offers excellent biocompatibility and proangiogenic property, and may serve as an effective biomaterial platform to maintain the long-term survival and function of insulin-secreting ß cells.

In vivo testing of an injectable matrix gel for the treatment of shoulder cuff muscle fatty degeneration.

INTRODUCTION: Extracellular matrix (ECM) gels have shown efficacy for the treatment of damaged tissues, most notably cardiac muscle. We hypothesized that the ECM gel prepared from skeletal muscle could be used as a treatment strategy for fatty shoulder cuff muscle degeneration. METHODS: We conducted experiments to (1) evaluate host biocompatibility to ECM gel injection using a rat model and (2) examine the effect of ECM gel injection on muscle recovery after delayed repair of a released supraspinatus (SSP) tendon using a rabbit model. RESULTS: The host biocompatibility to the ECM gel was characterized by a transient rise (first 2 weeks only) in several genes associated with macrophage infiltration, matrix deposition, and inflammatory cytokine production. By 8 weeks all genes had returned to baseline levels and no evidence of fibrosis or chronic inflammation was observed from histology. When gel injection was combined with SSP tendon repair, we observed a significant reduction (7%) in SSP muscle atrophy (24 + 3% reduction from uninjured) when compared with treatment with tendon repair only (31 + 7% reduction). Although fatty degeneration was elevated in both treatment groups, fat content trended lower (2%) in response to combined tendon repair and intramuscular ECM injection (4.1 + 2.1%) when compared with tendon repair only (6.1 + 2.9%). Transcriptome analysis revealed adipogenesis and osteoarthritis pathway activation in the repair only group. These key pathways were abrogated in response to treatment using combined repair plus gel. DISCUSSION: The findings suggest that ECM injection had a modest but positive effect on muscle mass, fatty degeneration, and key cellular signaling pathways.

Outcomes of Dog Bite Avulsion Injury Reconstruction With Urinary Bladder Matrix.

Dog bite avulsion injuries of the head and neck are difficult to manage in pediatric patients. This study assesses the outcomes of using porcine urinary bladder extracellular matrix (UBM) for reconstruction of these complete avulsion injuries. Five male pediatric patients underwent reconstruction using UBM. Two (40%) patients underwent reconstruction of the nose; the other 3 patients underwent reconstruction of the forehead, forehead/glabella, and auricle. The average size of the avulsion defect was 7.0 ± 2.4 cm2. No patient developed wound dehiscence, graft loss, or wound infection. Four (80%) patients received pulsed dye laser treatment to improve wound cosmesis. Use of UBM is a safe and effective reconstructive option after dog bite avulsion injuries of the head and neck. Given the advantages of convenient availability and avoidance of donor site morbidity, UBM can be considered for reconstruction of posttraumatic avulsion injuries or Mohs defects.

Mitral Valve Posterior Leaflet Reconstruction Using Extracellular Matrix: In Vitro Evaluation.

PURPOSE: To investigate the anatomical and functional effects of complete surgical reconstruction of the posterior mitral leaflet and associated chordae tendineae with a patch made of 2-ply small intestinal submucosal extracellular matrix in vitro. METHODS: Seven explanted mitral valves with intact subvalvular apparatus from 80-kg pigs were evaluated in a left heart simulator and served as their own controls. After testing the native valve, the mitral posterior leaflet and associated chordae tendineae were excised and reconstructed by using the 2-ply small intestinal submucosa extracellular matrix patch. The characterization of the reconstruction was based on geometric data from digital images, papillary muscle force, annular tethering force and leaflet pressure force. RESULTS: The reconstructed valves were fully functional without regurgitation, tearing or rupture during incrementally increased pressure from 0 to 120 mmHg. The leaflet areas were preserved after reconstruction, with a normal configuration of the coaptation line. However, the coaptation midpoint moved posteriorly after reconstruction (A2: 15.8 ± 1.4 vs. 18.9 ± 1.5 mm, p = 0.002, diff = 3.1 mm, 95% CI 1.3 to 4.8 mm). The anterior papillary muscle force increased significantly (3.9 vs. 4.6 N, p = 0.029, diff = 0.7 N, 95% CI 0.1 to 1.4 N at 120mmHg) after reconstruction. The posterior papillary muscle force, leaflet pressure force and annular pressure force did not change significantly. CONCLUSIONS: In this in vitro model, mitral valve anatomy and function were comparable between the native mitral valve and our new surgical technique for complete reconstruction of the posterior mitral leaflet and associated chordae tendineae. These promising results warrant further in vivo evaluation.

Fabrication of Corneal Extracellular Matrix-Derived Hydrogels.

Hydrogels derived from corneal extracellular matrix (ECM) represent a promising biomaterial for corneal repair and regeneration. To fabricate these hydrogels, first corneas need to be decellularized using repeated freeze-thaw cycles and nucleases to remove all nuclear and cellular components. The remaining corneal ECM is lyophilized to remove all water and milled into a fine powder. The ECM powder is weighed and dissolved in pepsin solution at a concentration of 20 mg/mL. Hydrogels are formed by neutralizing the pH of the solution and maintaining it at 37 °C until fibrillogenesis has occurred. Corneal stromal cells may be suspended throughout the hydrogel solution prior to gelation to generate a corneal stromal substitute.

Decellularized Scaffolds for Intervertebral Disc Regeneration.

In the last decade, intervertebral disc (IVD) decellularization has gained significant attention for tissue regenerative purposes as a successful therapeutic alternative for low back pain (LBP). We discuss the recent advances in IVD decellularization, repopulation, and sterilization procedures, highlighting the major challenges that need to be addressed for clinical translation.

Selection of biological prosthesis for abdominal wall repair on the basis of in vitro biocompatibility determination.

Research on prostheses for repairing abdominal wall defects has progressed through past decades for developing an ideal prosthesis. The study was designed to compare different extracellular matrix (ECM) derived biological prostheses as alternate to conventional synthetic polymeric prostheses for the repair of full thickness abdominal wall defects. Five biological scaffolds derived from bovine diaphragm, bovine aorta, bovine gall bladder, porcine gall bladder, and rabbit skin were prepared and screened for their in vitro biocompatibility. Decellularized ECMs were subjected to various biocompatibility analyses, namely, water absorption potential, matrix degradation analysis, biomechanical testing, and cytocompatibility analysis. Though the rabbit skin displayed maximum biomechanical strength, due to its rapid degradation, it failed to fulfill the criteria of an ideal prosthesis. ECMs derived from bovine diaphragm and aorta were found to be superior than others based upon hydration and matrix degradation analysis, with best scores for bovine diaphragm followed by bovine aorta. The bovine diaphragm and aorta also displayed sufficient biomechanical strength, with diaphragm being the second highest (next to rabbit skin), in biomechanical strength followed by aorta. None of the biological prosthesis revealed any cytotoxicity. Thus, bovine diaphragm and aorta derived ECM fulfill the necessary criteria for their use as biological prosthesis. Because these prostheses are biocompatible, apart from their low cost, ease of availability, and simple preparation, they present a potential alternative to synthetic prosthesis for repair of abdominal wall defects, especially in veterinary patients.

A multi-center, open-label, pilot study of allograft adipose matrix for the correction of atrophic temples.

BACKGROUND: Autologous fat grafting (AFG) and synthetic fillers are currently used in esthetic and reconstructive surgery. Challenges in AFG include inconsistent graft retention, donor site morbidities, insufficient harvest, and excessive harvesting times. An allograft adipose matrix (AAM) has been developed as an off-the-shelf alternative to AFG and synthetic fillers. AIMS: To evaluate the clinical safety and retention of an AAM over 24 weeks after treatment of bilateral atrophic temples. PATIENTS/METHODS: Ten subjects (nine females, one male, aged 47-69 years) with temple atrophy were enrolled in the IRB-approved study. AAM (Renuva® , MTF Biologics, Edison, NJ) was injected (<3 mL) bilaterally into the atrophic temples of each subject. Volume retention, global improvement, and safety were evaluated at 1, 4, 8, 12, 16, 20, and 24 weeks. Biopsy specimens were obtained for adipogenic and angiogenic histological evaluation. RESULTS: The mean temple volume improved over the baseline and was retained throughout the study period. Fullness (measure of volume) increased immediately from 0 pretreatment to 2.8 post-treatment (scale 0-4 = none-maximum). Fullness varied from 0.8 to 2.2 from weeks 1 through 12 and was 2.7-3.0 from weeks 16-24, around 75% increase from baseline. Furthermore, skin tone, smoothness, texture, and overall appearance also improved with 71% of subjects being satisfied to very satisfied with the results. Adverse events were minimal and histology revealed native tissue incorporation and remodeling. CONCLUSION: AAM is safe and well tolerated, provides at least 6-month volume retention, improves skin quality, and supports adipose tissue remodeling after treatment into temples.

Nanoengineered Osteoinductive Bioink for 3D Bioprinting Bone Tissue.

Bioprinting is an emerging additive manufacturing approach to the fabrication of patient-specific, implantable three-dimensional (3D) constructs for regenerative medicine. However, developing cell-compatible bioinks with high printability, structural stability, biodegradability, and bioactive characteristics is still a primary challenge for translating 3D bioprinting technology to preclinical and clinal models. To overcome this challenge, we developed a nanoengineered ionic covalent entanglement (NICE) bioink formulation for 3D bone bioprinting. The NICE bioinks allow precise control over printability, mechanical properties, and degradation characteristics, enabling custom 3D fabrication of mechanically resilient, cellularized structures. We demonstrate cell-induced remodeling of 3D bioprinted scaffolds over 60 days, demonstrating deposition of nascent extracellular matrix proteins. Interestingly, the bioprinted constructs induce endochondral differentiation of encapsulated human mesenchymal stem cells (hMSCs) in the absence of osteoinducing agent. Using next-generation transcriptome sequencing (RNA-seq) technology, we establish the role of nanosilicates, a bioactive component of NICE bioink, to stimulate endochondral differentiation at the transcriptome level. Overall, the osteoinductive bioink has the ability to induce formation of osteo-related mineralized extracellular matrix by encapsulated hMSCs in growth factor-free conditions. Furthermore, we demonstrate the ability of NICE bioink to fabricate patient-specific, implantable 3D scaffolds for repair of craniomaxillofacial bone defects. We envision development of this NICE bioink technology toward a realistic clinical process for 3D bioprinting patient-specific bone tissue for regenerative medicine.

In-vivo regeneration of bladder muscular wall with whole decellularized bladder matrix: A novel hourglass technique for duplication of bladder volume in rabbit model.

OBJECTIVE: To determine histological aspects of decellularized bladder graft to achieve a double-sized bladder by novel hourglass technique; using rabbit models. METHODS: Sixteen rabbit bladders were decellularized and underwent laboratory investigations. After making a laparotomy incision and exposure of bladders in another 16 rabbits (partial detrusor myomectomy), they were separated into two groups. The fundus of the decellularized scaffold was anastomosed to the fundus of the native bladder via the serosal layer, and the omentum and a double-J stent were placed in the decellularized bladder by no direct contact with the urine (Group A, n=8). In group B (n=8), the bladder was augmented applying the decellularized bladder that was in contact with the urine. After 6 months, the omentum was brought out of the neck of the engineered bladder and the anastomosis was opened. Biopsies were taken at 1, 3, and 9 months postoperatively. RESULTS: Cell removal with preservation of extracellular matrix structure was confirmed in decellularized bladders. Histological examination after 1 month demonstrated few cells at the border of the grafts. After 3 months, the region of the graft was indistinguishable from the natural bladder with continuity of transitional epithelium of natural bladder on the decellularized grafted scaffolds. The organization of muscle layers was similar to native bladder muscle layers after 9 months. IHC staining markers were highly expressed after 9 months. Interestingly, bladders had a high fibrosis grade in group B compared with hourglass technique. CONCLUSION: We confirmed that decellularized bladder may be a reliable scaffold and viable material for bladder augmentation.