The use of a novel bone allograft wash process to generate a biocompatible, mechanically stable and osteoinductive biological scaffold for use in bone tissue engineering

Design, Manufacture, and Characterization of a Critical-Sized Gradient Porosity Dual-Material Tibial Defect Scaffold

This study proposed a composite tibia defect scaffold with radial gradient porosity, utilizing finite element analysis to assess stress in the tibial region with significant critical-sized defects. Simulations for scaffolds with different porosities were conducted, designing an optimal tibia defect scaffold with radial gradient porosity for repairing and replacing critical bone defects. Radial gradient porosity scaffolds resulted in a more uniform stress distribution, reducing titanium alloy stiffness and alleviating stress shielding effects. The scaffold was manufactured using selective laser melting (SLM) technology with stress relief annealing to simplify porous structure fabrication. The study used New Zealand white rabbits' tibia defect sites as simulation parameters, reconstructing the 3D model and implanting the composite scaffold. Finite element analysis in ANSYS-Workbench simulated forces under high-activity conditions, analyzing stress distribution and strain. In the simulation, the titanium alloy scaffold bore a maximum stress of 122.8626 MPa, while the centrally encapsulated HAp material delivered 27.92 MPa. The design demonstrated superior structural strength, thereby reducing stress concentration. The scaffold was manufactured using SLM, and the uniform design method was used to determine a collection of optimum annealing parameters. Nanoindentation and compression tests were used to determine the influence of annealing on the elastic modulus, hardness, and strain energy of the scaffold.

Polydopamine-Functionalized Strontium Alginate/Hydroxyapatite Composite Microhydrogel Loaded with Vascular Endothelial Growth Factor Promotes Bone Formation and Angiogenesis

Critical-size bone defects are a common and intractable clinical problem that typically requires filling in with surgical implants to facilitate bone regeneration. Considering the limitations of autologous bone and allogeneic bone in clinical applications, such as secondary damage or immunogenicity, injectable microhydrogels with osteogenic and angiogenic effects have received considerable attention. Herein, polydopamine (PDA)-functionalized strontium alginate/nanohydroxyapatite (Sr-Alg/nHA) composite microhydrogels loaded with vascular endothelial growth factor (VEGF) were prepared using microfluidic technology. This composite microhydrogel released strontium ions stably for at least 42 days to promote bone formation. The PDA coating can release VEGF in a controlled manner, effectively promote angiogenesis around bone defects, and provide nutritional support for new bone formation. In in vitro experiments, the composite microhydrogels had good biocompatibility. The PDA coating greatly improves cell adhesion on the composite microhydrogel and provides good controlled release of VEGF. Therefore, this composite microhydrogel effectively promotes osteogenic differentiation and vascularization. In in vivo experiments, composite microhydrogels were injected into critical-size bone defects in the skull of rats, and they were shown by microcomputed tomography and tissue sections to be effective in promoting bone regeneration. These findings demonstrated that this novel microhydrogel effectively promotes bone formation and angiogenesis at the site of bone defects.

A new option for bone regeneration: a rapid methodology for cellularization of allograft with human bone marrow stromal cells with in vivo bone-forming potential

The treatment of severe musculoskeletal injuries, such as loss of bone tissue and consolidation disorders, requires bone transplantation, and the success of this bone reconstruction depends on the grafts transplant's osteogenic, osteoconductive, and osteoinductive properties. Although the gold standard is autograft, it is limited by availability, morbidity, and infection risk. Despite their low capacity for osteoinduction and osteogenesis, decellularized bone allografts have been used in the search for alternative therapeutic strategies to improve bone regeneration. Considering that bone marrow stromal cells (BMSCs) are responsible for the maintenance of bone turnover throughout life, we believe that associating BMSCs with allograft could produce a material that is biologically similar to autologous bone graft. For this reason, this study evaluated the osteogenic potential of bone allograft cellularized with BMSCs. First, BMSC was characterized and allograft decellularization was confirmed by histology, scanning electron microscopy, and DNA quantification. Subsequently, the BMSCs and allografts were associated and evaluated for adhesion, proliferation, and in vitro and in vivo osteogenic potential. We demonstrated that, after 2 hours, BMSCs had already adhered to the surface of allografts and remained viable for 14 days. In vitro osteogenic assays indicated increased osteogenic potential of allografts compared with beta-tricalcium phosphate (β-TCP). In vivo transplantation assays in immunodeficient mice confirmed the allograft's potential to induce bone formation, with significantly better results than β-TCP. Finally, our results indicate that allograft can provide structural support for BMSC adhesion, offering a favorable microenvironment for cell survival and differentiation and inducing new bone formation. Taken together, our data indicate that this rapid methodology for cellularization of allograft with BMSCs might be a new therapeutic alternative in regenerative medicine and bone bioengineering.

Cost-effectiveness of decellularised bone allograft compared with fresh-frozen bone allograft for acetabular impaction bone grafting during a revision hip arthroplasty in the UK

OBJECTIVES

Fresh-frozen allograft is the gold-standard bone graft material used during revision hip arthroplasty. However, new technology has been developed to manufacture decellularised bone with potentially better graft incorporation. As these grafts cost more to manufacture, the aim of this cost-effectiveness study was to estimate whether the potential health benefit of decellularised bone allograft outweighs their increased cost.

STUDY DESIGN

A Markov model was constructed to estimate the costs and the quality-adjusted life years of impaction bone grafting during a revision hip arthroplasty.

SETTING

This study took the perspective of the National Health Service in the UK.

PARTICIPANTS

The Markov model includes patients undergoing a revision hip arthroplasty in the UK.

INTERVENTION

Impaction bone grafting during a revision hip arthroplasty using either decellularised bone allograft or fresh-frozen allograft.

MEASURES

Outcome measures included: total costs and quality-adjusted life years of both interventions over the lifetime of the model; and incremental cost-effectiveness ratios for both graft types, using base case parameters, univariate sensitivity analysis and probabilistic analysis.

RESULTS

The incremental cost-effectiveness ratio for the base case model was found to be £270 059 per quality-adjusted life year. Univariate sensitivity analysis found that changing the discount rate, the decellularised bone graft cost, age of the patient cohort and the revision rate all had a significant effect on the incremental cost-effectiveness ratio.

CONCLUSIONS

As there are no clinical studies of impaction bone grafting using a decellularised bone allograft, there is a high level of uncertainty around the costs of producing a decellularised bone allograft and the potential health benefits. However, if a decellularised bone graft was manufactured for £2887 and lowered the re-revision rate to less than 64 cases per year per 10 000 revision patients, then it would most likely be cost-effective compared with fresh-frozen allograft.

The Role of HIF-1α in Bone Regeneration: A New Direction and Challenge in Bone Tissue Engineering

The process of repairing significant bone defects requires the recruitment of a considerable number of cells for osteogenesis-related activities, which implies the consumption of a substantial amount of oxygen and nutrients. Therefore, the limited supply of nutrients and oxygen at the defect site is a vital constraint that affects the regenerative effect, which is closely related to the degree of a well-established vascular network. Hypoxia-inducible factor (HIF-1α), which is an essential transcription factor activated in hypoxic environments, plays a vital role in vascular network construction. HIF-1α, which plays a central role in regulating cartilage and bone formation, induces vascular invasion and differentiation of osteoprogenitor cells to promote and maintain extracellular matrix production by mediating the adaptive response of cells to changes in oxygen levels. However, the application of HIF-1α in bone tissue engineering is still controversial. As such, clarifying the function of HIF-1α in regulating the bone regeneration process is one of the urgent issues that need to be addressed. This review provides insight into the mechanisms of HIF-1α action in bone regeneration and related recent advances. It also describes current strategies for applying hypoxia induction and hypoxia mimicry in bone tissue engineering, providing theoretical support for the use of HIF-1α in establishing a novel and feasible bone repair strategy in clinical settings.

Towards the development of osteochondral allografts with reduced immunogenicity

Nowadays, repair and replacement of hyaline articular cartilage still challenges orthopedic surgery. Using a graft of decellularized articular cartilage as a structural scaffold is considered as a promising therapy. So far, successful cell removal has only been possible for small samples with destruction of the macrostructure or loss of biomechanics. Our aim was to develop a mild, enzyme-free chemical decellularization procedure while preserving the biomechanical properties of cartilage. Porcine osteochondral cylinders (diameter: 12 mm; height: 10 mm) were divided into four groups: Native plugs (NA), decellularized plugs treated with PBS, Triton-X-100 and SDS (DC), and plugs additionally treated with freeze-thaw-cycles of -20 °C, -80 °C or shock freezing in nitrogen (N₂) before decellularization. In a non-decalcified HE stain the decellularization efficiency (cell removal, cell size, depth of decellularization) was calculated. For biomechanics the elastic and compression modulus, transition and failure strain as well as transition and failure stress were evaluated. The -20 °C, -80 °C, and N₂ groups showed a complete decellularization of the superficial and middle zone. In the deep zone cells could not be removed in any experimental group. The biomechanical analysis showed only a reduced elastic modulus in all decellularized samples. No significant differences were found for the other biomechanical parameters.

Decellularised human bone allograft from different anatomical sites as a basis for functionally stratified repair material for bone defects

Tissue engineered bone solutions aim to overcome the limitations of autologous and allogeneic grafts. Decellularised tissues are produced by washing cellular components from human or animal tissue to produce an immunologically safe and biocompatible scaffold, capable of integration following implantation. A decellularisation procedure utilising low concentration sodium dodecyl sulphate (0.1% w/v) was applied to trabecular bone from human femoral heads (FH) and tibial plateaus (TP). Biological (histology, DNA quantification), biomechanical (compression testing) and structural (μCT) comparisons were made between decellularised and unprocessed cellular tissue. Total DNA levels of decellularised FH and TP bone were below 50 ng mg^-1 dry tissue weight and nuclear material was removed. No differences were found between cellular and decellularised bone, from each anatomical region, for all the biomechanical and structural parameters investigated. Differences were found between cellular FH and TP and between decellularised FH and TP. Decellularised FH had a higher ultimate compressive stress, Young's modulus and 0.2% proof stress than decellularised TP (p = 0.001, 0.002, 0.001, Mann Whitney U test, MWU). The mineral density of cellular and decellularised TP bone was significantly greater than cellular and decellularised FH bone respectively (cellular: p = 0.001, decellularised: p < 0.001, MWU). The bone volume fraction and trabecular thickness of cellular and decellularised FH bone were significantly greater than cellular and decellularised TP bone respectively (cellular: p = 0.001, 0.005; decellularised: p < 0.001, <0.001, MWU). Characterisation of decellularised trabecular bone from different anatomical regions offers the possibility of product stratification, allowing selection of biomechanical properties to match particular anatomical regions undergoing bone graft procedures.

Clinical Pilot Series of Non-Self-Contained Periodontal Infrabony Defects Treated with a Slowly Resorbable Bovine Pericardium Membrane in Combination with Low-Temperature-Treated Decellularized Bovine Bone Particles

The aim of this case series was to present the clinical outcomes of non-contained intrabony periodontal defects (IPDs) treated by means of papillary preservation flaps in association with a slowly resorbable bovine pericardium membrane (BPM) and a low-temperature-treated bovine bone graft (BBG). Eight healthy, non-smoking patients (two males and six females, mean age 48 ± 8 years) with stage 3 periodontitis and at least one site with residual probing depth (PD) ≥ 6 mm associated with a non-contained IPD ≥ 3 mm were treated. Two weeks after surgery, no adverse events were observed, and an early wound healing score (EHS) of 8.1 ± 1.0 was recorded. After 1 year, the mean probing depth (PD) reduction and mean clinical attachment level gain (CAL-gain) accounted for 4.8 ± 0.7 and 3.5 ± 0.7 mm, respectively, whereas the mean gingival recession (REC) was of 1.2 ± 0.3 mm. Radiographic bone fill was observed in all cases. In conclusion, the treatment of non-contained IPDs with a slowly resorbable BPM and a low-temperature-treated BBG could be considered safe and may result in significant clinical improvements 1 year after surgery.

Recent advancements in decellularized matrix technology for bone tissue engineering

The native extracellular matrix (ECM) provides a matrix to hold tissue/organ, defines the cellular fate and function, and retains growth factors. Such a matrix is considered as a most biomimetic scaffold for tissue engineering due to the biochemical and biological components, 3D hierarchical structure, and physicomechanical properties. Several attempts have been performed to decellularize allo- or xeno-graft tissues and used them for bone repairing and regeneration. Decellularized ECM (dECM) technology has been developed to create an in vivo-like microenvironment to promote cell adhesion, growth, and differentiation for tissue repair and regeneration. Decellularization is mediated through physical, chemical, and enzymatic methods. In this review, we describe the recent progress in bone decellularization and their applications as a scaffold, hydrogel, bioink, or particles in bone tissue engineering. Furthermore, we address the native dECM limitations and the potential of non-bone dECM, cell-based ECM, and engineered ECM (eECM) for in vitro osteogenic differentiation and in vivo bone regeneration.

Relation between micro- and nanostructure features and biological properties of the decellularized rat liver

Organ decellularization is one of the promising technologies of regenerative medicine, which allows obtaining cell-free extracellular matrix (ECM), which provide preservation of the composition, architecture, vascular network and biological activity of the ECM. The method of decellularization opens up wide prospects for its practical application not only in the field of creating full-scale bioengineered structures, but also in the manufacture of vessels, microcarriers, hydrogels, and coatings. The main goal of our work was the investigation of structure and biological properties of lyophilized decellularized Wistar rat liver fragments (LDLFs), as well as we assessed the regenerative potential of the obtained ECM. We obtained decellularized liver of a Wistar rat, the vascular network and the main components of the ECM of tissue were preserved. H&E staining of histological sections confirmed the removal of cells. DNA content of ECM is equal to 0.7% of native tissue DNA content. Utilizing scanning probe nanotomogrphy method, we showed sinuous, rough topography and highly nanoporous structure of ECM, which provide high level of mouse 3T3 fibroblast and Hep-G₂cells biocompatibility. Obtained LDLF had a high regenerative potential, which we studied in an experimental model of a full-thickness rat skin wound healing: we observed the acceleration of wound healing by 2.2 times in comparison with the control.

Recent Trends in the Development of Bone Regenerative Biomaterials

The goal of a biomaterial is to support the bone tissue regeneration process at the defect site and eventually degrade in situ and get replaced with the newly generated bone tissue. Biomaterials that enhance bone regeneration have a wealth of potential clinical applications from the treatment of non-union fractures to spinal fusion. The use of bone regenerative biomaterials from bioceramics and polymeric components to support bone cell and tissue growth is a longstanding area of interest. Recently, various forms of bone repair materials such as hydrogel, nanofiber scaffolds, and 3D printing composite scaffolds are emerging. Current challenges include the engineering of biomaterials that can match both the mechanical and biological context of bone tissue matrix and support the vascularization of large tissue constructs. Biomaterials with new levels of biofunctionality that attempt to recreate nanoscale topographical, biofactor, and gene delivery cues from the extracellular environment are emerging as interesting candidate bone regenerative biomaterials. This review has been sculptured around a case-by-case basis of current research that is being undertaken in the field of bone regeneration engineering. We will highlight the current progress in the development of physicochemical properties and applications of bone defect repair materials and their perspectives in bone regeneration.

Donor-Specific Human Leukocyte Antigen Antibody Formation After Allograft Glenoid Reconstruction Occurs But Does Not Impact Clinicoradiographic Outcomes

BACKGROUND

Recurrent shoulder instability is a prevalent condition, with glenoid bone loss as a common cause. Arthroscopic repair using distal tibial allografts provides long-lasting treatment by restoring glenoid surface area and presumably avoids risks of sensitization against donor human leukocyte antigen (HLA). Two case studies have challenged this assumption, suggesting that small bone allografts are able to induce host adaptive immune responses to donor HLA. The incidence of small bone allograft HLA sensitization and its effects on resorption and patient outcomes are unclear.

PURPOSE/HYPOTHESIS

The purpose was to assess the rate of sensitization against donor HLA after distal tibial allograft procedures for shoulder instability due to glenoid bone loss and to find whether HLA sensitization negatively affects patient-reported and radiographic outcomes. We hypothesized that sensitized patients would have worse radiographic and self-reported outcomes compared with nonsensitized patients.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

A total of 71 patients with a mean age of 28.85 years (range, 13.58-61.31 years) were enrolled, with 58 patients submitting sufficient pre- and postoperative blood samples for HLA antibody testing. In patients who developed HLA antibodies postoperatively, donor HLA typing was used to confirm donor-specific sensitization. Pre- and postoperative computerized tomography scans (0.9 ± 0.8 years follow-up) were used to grade resorption based on the modified Zhu resorption grade classification (ie, grade 0 = no resorption; grade 1 = less than 25% resorption; grade 2 = between 25% and 50% resorption; and grade 3 = larger than 50% resorption). The Western Ontario Shoulder Instability Index outcome scores were obtained preoperatively and at regular postoperative appointments. Resorption and outcome data were compared between sensitized and nonsensitized patients using the Fisher exact test, independent 2-tailed Student t tests, and the Wilcoxon rank-sum test to determine the effect of HLA sensitization on radiographic and patient-reported outcomes.

RESULTS

A total of 7 (12.1%) patients with sufficient HLA samples were sensitized against donor HLA postoperatively. Sensitized patients did not have significantly higher rates of resorption (21.9% vs 14.3%, 21.9% vs 28.6%, 43.8% vs 28.6%, and 12.5% vs 28.6% for respective resorption grades 0-3; P = .67; α = .05). Self-reported outcomes were not statistically significant between sensitized and nonsensitized patients (24.9 ± 27.61 vs 40.16 ± 18.99; P = .37; α = .05) and did not differ significantly based on resorption grade (47.4 ± 0.0 vs 55.2 ± 18.8, 30.4 ± 15.8 vs 39.9 ± 20.9, 41.2 ± 0.0 vs 39.1 ± 13.1, and -24.9 ± 0 vs 24.4 ± 19.6 for resorption grades 0-3; P > .05; α = .05).

CONCLUSION

Sensitization against donor HLA after small bone graft allografting was not previously considered but has been brought to light as a possibility. Aside from potential complications for future organ transplants, HLA sensitization does not introduce a risk for adverse outcomes or higher grades of resorption compared with nonsensitized patients after small bone allografting for shoulder instability.

Current concepts for tissue transplant services for developing countries

The transplantation of tissues can save lives and re-establish vital functions, where no alternatives of comparable effectiveness exist. This has led to establishment of tissue transplantation as a successful practice worldwide; however, a great variability between countries remains in terms of donation levels, safety, quality of grafts and their efficacy. Tissue transplantation requires coordination of different agencies involved in the implementation of procurement, processing, storage and distribution of tissues and cells from different hospital units that perform surgical procedures with graft-type input requirements. This biomaterial-like requirement has led to the constant development of the area and today these graft products of human origin can be the starting point for new and more advanced biotechnological products. For long-term sustainability and successful transplantation units, a process management comparable to the pharmaceutical industry in terms of quality management systems must be established to produce safe and high-quality human-derived products. This review aims to update the current concepts of tissue transplant services for its application for developing countries using the current Chilean scenario as a case study. We summarize our findings proposing a set of guidelines/actions that should be followed to ensure smooth tissue transplant services implementations with high efficiency and safe use.

Stem Cell-Friendly Scaffold Biomaterials: Applications for Bone Tissue Engineering and Regenerative Medicine

Bone is a dynamic organ with high regenerative potential and provides essential biological functions in the body, such as providing body mobility and protection of internal organs, regulating hematopoietic cell homeostasis, and serving as important mineral reservoir. Bone defects, which can be caused by trauma, cancer and bone disorders, pose formidable public health burdens. Even though autologous bone grafts, allografts, or xenografts have been used clinically, repairing large bone defects remains as a significant clinical challenge. Bone tissue engineering (BTE) emerged as a promising solution to overcome the limitations of autografts and allografts. Ideal bone tissue engineering is to induce bone regeneration through the synergistic integration of biomaterial scaffolds, bone progenitor cells, and bone-forming factors. Successful stem cell-based BTE requires a combination of abundant mesenchymal progenitors with osteogenic potential, suitable biofactors to drive osteogenic differentiation, and cell-friendly scaffold biomaterials. Thus, the crux of BTE lies within the use of cell-friendly biomaterials as scaffolds to overcome extensive bone defects. In this review, we focus on the biocompatibility and cell-friendly features of commonly used scaffold materials, including inorganic compound-based ceramics, natural polymers, synthetic polymers, decellularized extracellular matrix, and in many cases, composite scaffolds using the above existing biomaterials. It is conceivable that combinations of bioactive materials, progenitor cells, growth factors, functionalization techniques, and biomimetic scaffold designs, along with 3D bioprinting technology, will unleash a new era of complex BTE scaffolds tailored to patient-specific applications.

Decellularized Intervertebral Discs: A Potential Replacement for Degenerate Human Discs

Intervertebral disc (IVD) degeneration is a major cause of back pain. Current surgical interventions have limitations. An alternative approach is to replace degenerated IVDs with a natural biological scaffold. The removal of cellular components from human IVDs should render them nonimmunogenic upon implantation. The aim of this initial proof of technical feasibility study was to develop a decellularization protocol on bovine IVDs with endplates (EPs) and assess protocol performance before application of the protocol to human IVDs with attached EP and vertebral bone (VB). A decellularization protocol based on hypotonic low concentration sodium dodecyl sulfate (0.1% w/v) with proteinase inhibitors, freeze/thaw cycles, and nuclease and sonication treatments was applied to IVDs. Histological, biochemical, and biomechanical comparisons were made between cellular and decellularized tissue. Cell removal from bovine IVDs was demonstrated and total DNA levels of the decellularized inner annulus fibrosus (iAF), outer annulus fibrosus (oAF), and EP were 40.7 (±11.4), 25.9 (±3.8), and 29.3 (±3.1) ng.mg⁻¹ dry tissue weight, respectively (n = 6, ±95% confidence level [CL]). These values were significantly lower than in cellular tissue. No significant difference in DNA levels between bovine cellular and decellularized nucleus pulposus (NP) was found. Glycosaminoglycans (GAGs) were largely retained in the NP, iAF, and oAF. Cyclic compression testing showed sufficient sensitivity to detect an increase in stiffness of bovine IVD postdecellularization (2957.2 ± 340.8 N.mm⁻¹) (predecellularization: 2685.4 ± 263.1 N.mm⁻¹; n = 5, 95% CL), but the difference was within natural tissue variation. Total DNA levels for all decellularized tissue regions of human IVDs (NP, iAF, oAF, EP, and VB) were below 50 ng.mg⁻¹ dry tissue weight (range: 2 ng.mg⁻¹, iAF to 29 ng.mg⁻¹, VB) and the tissue retained high levels of GAGs. Further studies to assess the biocompatibility and regenerative potential of decellularized human IVDs in vitro and in vivo are now required; however, proof of technical feasibility has been demonstrated and the retention of bone in the IVD samples would allow incorporation of the tissue into the recipient spine.

Gene-modified BMSCs encapsulated with carboxymethyl cellulose facilitate osteogenesis in vitro and in vivo

Critical size bone defects are one of the most serious complications in orthopedics due to the lack of effective osteogenesis treatment. We fabricated carboxymethyl cellulose with phenol moieties (CMC-ph) microcapsules loaded with gene-modified rat bone mesenchymal stem cells (rBMSCs) that secrete hBMP2 following doxycycline (DOX) induction. The results showed that the morphology of microcapsules was spherical, and their diameters have equally distributed in the range of 100-150 μm; the viability of rBMSCs was unchanged over time. Through real-time PCR and Western blot analyses, the rBMSCs in microcapsules were found to secrete hBMP2 and to have upregulated mRNA and protein expression of osteogenesis-related genes in vitro and in vivo. Furthermore, the in vivo results suggested that the group with the middle concentration of cells expressed the highest amount of osteogenic protein over time. In this study, we showed that gene-modified rBMSCs in CMC-ph microcapsules had good morphology and viability. The BMP2-BMSCs/CMC-Ph microcapsule system could upregulate osteogenic mRNA and protein in vitro and in vivo. Further analysis demonstrated that the medium concentration of cells had a suitable density for transplantation in nude mice. Therefore, BMP2-BMSCs/CMC-Ph microcapsule constructs have potential for bone regeneration in vivo.

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

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

Collagenase treatment of cartilaginous matrix promotes fusion of adjacent cartilage

In articular cartilage-repair, grafts usually fuse unsatisfactorily with surrounding host cartilage. Enzymatic dissociation of cartilaginous matrix to free chondrocytes may benefit fusion. We tested such a hypothesis with human cartilage in vitro, and with porcine cartilage in vivo. Human articular cartilage was collected from knee surgeries, cut into disc-and-ring sets, and randomly distributed into three groups: disc-and-ring sets in Group 1 were left untreated; in Group 2 only discs, and in Group 3 both discs and rings were treated with enzyme. Each disc-and-ring reassembly was cultured in a perfusion system for 14 days; expression of cartilage marker proteins and genes was evaluated by immunohistochemistry and PCR. Porcine articular cartilage from knees was similarly fashioned into disc-and-ring combinations. Specimens were randomly distributed into a control group without further treatment, and an experimental group with both disc and ring treated with enzyme. Each disc-and-ring reassembly was transplanted into subcutaneous space of a nude mouse for 30 days, and retrieved to examine disc-ring interface. In in vitro study with human cartilage, a visible gap remained at disc-ring interfaces in Group 1, yet became indiscernible in Group 2 and 3. Marker genes, including type II collagen, aggrecan and Sox 9, were well expressed by chondrocytes in all specimens, indicating that chondrocytes’ phenotype retained regardless of enzymatic treatment. Similar results were found inin vivo study with porcine cartilage. Enzymatic dissociation of cartilaginous matrix promotes fusion of adjacent cartilage. The clinical relevance may be a novel method to facilitate integration of repaired cartilage in joints.

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Cartilage repair-patches fuse poorly to surrounding host cartilage.

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Collagenase treatment of adjacent cartilaginous tissues facilitates their fusion.

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Collagenase treatment of cartilage promotes chondrocyte proliferation and presentation.

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Collagenase treatment does not affect phenotypes of chondrocytes.

Decellularized human bone as a 3D model to study skeletal progenitor cells in a natural environment

There has been an increasing interest in exploring naturally derived extracellular matrices as an material mimicking the complexity of the cell microenvironment in vivo. Bone tissue-derived decellularized constructs are able to preserve native structural, biochemical, and biomechanical cues of the tissue, therefore providing a suitable environment to study skeletal progenitor cells. Particularly for bone decellularization, different methods have been reported in the literature. However, the used methods critically affect the final ultrastructure and surface chemistry as well as the decellularization efficiency, consequently causing complications to draw conclusions and compare results in between studies. In this chapter, an optimized protocol for the preparation of human bone derived scaffolds is described, including processing techniques and further characterization methods, which allow the final construct to be recognized as a major platform for bone therapeutic and/or diagnostic applications.

Investigating the Osteoinductive Potential of a Decellularized Xenograft Bone Substitute

Bone grafting is the second most common tissue transplantation procedure worldwide. One of the alternative methods for bone repair under investigation is a tissue-engineered bone substitute. An ideal property of tissue-engineered bone substitutes is osteoinductivity, defined as the ability to stimulate primitive cells to differentiate into a bone-forming lineage. In the current study, we use a decellularization and oxidation protocol to produce a porcine bone scaffold and examine whether it possesses osteoinductive potential and can be used to create a tissue-engineered bone microenvironment. The decellularization protocol was patented by our lab and consists of chemical decellularization and oxidation steps using combinations of deionized water, trypsin, antimicrobials, peracetic acid, and triton-X100. To test if the bone scaffold was a viable host, preosteoblasts were seeded and analyzed for markers of osteogenic differentiation. The osteoinductive potential was observed in vitro with similar osteogenic markers being expressed in preosteoblasts seeded on the scaffolds and demineralized bone matrix. To assess these properties in vivo, scaffolds with and without preosteoblasts preseeded were subcutaneously implanted in mice for 4 weeks. MicroCT scanning revealed 1.6-fold increased bone volume to total volume ratio and 1.4-fold increase in trabecular thickness in scaffolds after implantation. The histological analysis demonstrates new bone formation and blood vessel formation with pentachrome staining demonstrating osteogenesis and angiogenesis, respectively, within the scaffold. Furthermore, CD31+ staining confirmed the endothelial lining of the blood vessels. These results demonstrate that porcine bone maintains its osteoinductive properties after the application of a patented decellularization and oxidation protocol developed in our laboratory. Future work must be performed to definitively prove osteogenesis of human mesenchymal stem cells, biocompatibility in large animal models, and osteoinduction/osseointegration in a relevant clinical model in vivo. The ability to create a functional bone microenvironment using decellularized xenografts will impact regenerative medicine, orthopedic reconstruction, and could be used in the research of multiple diseases.

The efficacy and safety of core decompression for the treatment of femoral head necrosis: a systematic review and meta-analysis

BACKGROUND

Core decompression (CD) is an important method for the treatment of osteonecrosis of the femoral head (ONFH). Few articles investigate the influence of core decompression on outcomes of ONFH. This study was carried out to observe the safety and effectiveness of core decompression in the treatment of ONFH.

METHODS

A comprehensive literature search of databases including PubMed, Embase, and Cochrane Library was performed to collect the related studies. The medical subject headings used were "femur head necrosis" and "Core decompression." The relevant words in title or abstract included but not limited to "Osteonecrosis of the Femoral Head," "femoral head necrosis," "avascular necrosis of femoral head," and "ischemic necrosis of femoral head." The methodological index for nonrandomized studies was adopted for assessing the studies included in this review.

RESULTS

Thirty-two studies included 1865 patients (2441 hips). Twenty-one studies (1301 hips) using Ficat staging standard, 7 studies (338hips) using Association Research Circulation Osseous (ARCO) staging standard, and University of Pennsylvania system for staging avascular necrosis (UPSS) staging criteria for 4 studies (802 hips). All the studies recorded the treatment, 22 studies (1379 hips) were treated with core decompression (CD) alone, and 7 studies (565 hips) were treated with core decompression combined with autologous bone (CD Autologous bone). Nine subjects (497 hips) were treated with core decompression combined with autologous bone marrow (CD Marrow). Twenty-seven studies (2120 hips) documented the number of conversion to total hip replacement (THA), and 26 studies (1752hips) documented the number of radiographic progression (RP). Twenty-one studies recorded the types of complications and the number of cases, a total of 69 cases. The random-effect model was used for meta-analysis, and the results showed that the overall success rate was 65%. The rate of success showed significant difference on the outcomes of different stages. The rate of success, conversion to THA, and radiographic progression showed significant difference on the outcomes of ONFH using different treatments.

CONCLUSIONS

Core decompression is an effective and safe method of treating ONFH. The combined use of autologous bone or bone marrow can increase the success rate. For advanced femoral head necrosis, the use of CD should be cautious. High-quality randomized controlled trials and prospective studies will be necessary to clarify the effects of different etiology factors, treatments, and postoperative rehabilitation. Until then, the surgeon can choose core decompression to treat ONFH depending on the patient's condition.

LEVEL OF EVIDENCE

I Meta-analysis.

Evaluation of bone allograft processing methods: Impact on decellularization efficacy, biocompatibility and mesenchymal stem cell functionality

In an ever-aging society the demand for bone-defect filling grafts continues to gain in importance. While autologous grafting still prevails as the gold standard, allografts and xenografts present viable alternatives with promising results. Physiochemical properties of a graft strongly depend on the processing method such as the decellularization protocol. In addition, the physiochemical characteristics are critical factors for a successful integration of the graft after the implantation and might influence mesenchymal stem cell function in therapeutic approaches combining grafts and autologous mesenchymal stem cells (MSCs). Several decellularization methods have been proposed, however it still remains unclear which method results in favorable physiochemical properties or might be preferred in stem cell applications. In the first part of this study we compared two decellularization approaches resulting in chemically processed allografts (CPAs) or sonication-based processed allografts (SPAs). Each decellularization approach was compared for its decellularization efficacy and its influence on the grafts' surface texture and composition. In the second part of this study biocompatibility of grafts was assessed by testing the effect of extraction medium on MSC viability and comparing them to commercially available allografts and xenografts. Additionally, grafts' performance in terms of MSC functionality was assessed by reseeding with MSCs pre-differentiated in osteogenic medium and determining cell adhesion, proliferation, as well as alkaline phosphatase (ALP) activity and the degree of mineralization. In summary, results indicate a more effective decellularization for the SPA approach in comparison to the CPA approach. Even though SPA extracts induced a decrease in MSC viability, MSC performance after reseeding was comparable to commercially available grafts based on DNA quantification, alkaline phosphatase activity and quantification of mineralization. Commercial Tutoplast allografts showed overall the best effects on MSC functionality as indicated by extraction biocompatibility testing as well as by comparing proliferation and osteogenic differentiation.

Screen-enrich-combine circulating system to prepare MSC/β-TCP for bone repair in fractures with depressed tibial plateau

Aim: To evaluate the clinical efficacy of mesenchymal stem cell/β-tricalcium phosphate composites (MSC/β-TCP) prepared with a screen-enrich-combine circulating system (SECCS) in patients with depressed tibial plateau fractures. Materials & methods: Bone defects in depressed tibial plateaus were filled with MSC/β-TCP (n = 16) or with β-TCP only (n = 23). Enrichment efficiency and effect of enrichment on cell viability were evaluated. Clinical results were assessed by imaging examination and Lysholm score. Results: SECCS effectively integrated MSCs with β-TCP. At 18 months postimplantation, new bone ratio was significantly higher in patients treated with MSC/β-TCP than in those treated with β-TCP only (p = 0.000). Patients with MSC/β-TCP implants had better functional recovery (p = 0.028). Conclusion: MSC/β-TCP prepared by SECCS were effective in the treatment of bone defects in patients with depressed tibial plateau fractures, promoted bone regeneration and improved joint function recovery.

Applications of decellularized extracellular matrix in bone and cartilage tissue engineering

Regenerative therapies for bone and cartilage injuries are currently unable to replicate the complex microenvironment of native tissue. There are many tissue engineering approaches attempting to address this issue through the use of synthetic materials. Although synthetic materials can be modified to simulate the mechanical and biochemical properties of the cell microenvironment, they do not mimic in full the multitude of interactions that take place within tissue. Decellularized extracellular matrix (dECM) has been established as a biomaterial that preserves a tissue's native environment, promotes cell proliferation, and provides cues for cell differentiation. The potential of dECM as a therapeutic agent is rising, but there are many limitations of dECM restricting its use. This review discusses the recent progress in the utilization of bone and cartilage dECM through applications as scaffolds, particles, and supplementary factors in bone and cartilage tissue engineering.

Tissue-Engineered Grafts from Human Decellularized Extracellular Matrices: A Systematic Review and Future Perspectives

Tissue engineering and regenerative medicine involve many different artificial and biologic materials, frequently integrated in composite scaffolds, which can be repopulated with various cell types. One of the most promising scaffolds is decellularized allogeneic extracellular matrix (ECM) then recellularized by autologous or stem cells, in order to develop fully personalized clinical approaches. Decellularization protocols have to efficiently remove immunogenic cellular materials, maintaining the nonimmunogenic ECM, which is endowed with specific inductive/differentiating actions due to its architecture and bioactive factors. In the present paper, we review the available literature about the development of grafts from decellularized human tissues/organs. Human tissues may be obtained not only from surgery but also from cadavers, suggesting possible development of Human Tissue BioBanks from body donation programs. Many human tissues/organs have been decellularized for tissue engineering purposes, such as cartilage, bone, skeletal muscle, tendons, adipose tissue, heart, vessels, lung, dental pulp, intestine, liver, pancreas, kidney, gonads, uterus, childbirth products, cornea, and peripheral nerves. In vitro recellularizations have been reported with various cell types and procedures (seeding, injection, and perfusion). Conversely, studies about in vivo behaviour are poorly represented. Actually, the future challenge will be the development of human grafts to be implanted fully restored in all their structural/functional aspects.

Human bone graft cytocompatibility with mesenchymal stromal cells is comparable after thermal sterilization and washing followed by γ-irradiation: an in vitro study

Human bone allografts present a better alternative to autografts in terms of minimization of the harvesting procedure complications. Prior to the use in clinical applications, they require sterilization which aims to reduce bioburden. This often comes at the expense of their biological properties as carriers of cells. In this study, we evaluated the cytocompatibility of human bone allografts processed and sterilized by three different methods with mesenchymal stromal cells. Bone morphology, biological and biochemical properties of the extracted bone-conditioned medium and viability of cells were assessed. We found that chemical sterilization had a strong negative effect on cell viability, whereas thermal sterilization and washing with subsequent γ-irradiation both resulted in a bone graft compatible with the progenitor cells. Moreover, washing of the bone prior to sterilization allowed solid removal of cell debris and other bone marrow components. Taken together, our findings demonstrate the importance of a proper choice of the bone graft processing method for the production of the biomaterial suitable for tissue engineering.

Organic composite-mediated surface coating of human acellular bone matrix with strontium

Acellular bone matrix (ACBM) provides an osteoconductive scaffold for bone repair, but its osteoinductivity is poor. Strontium (Sr) improves the osteoinductivity of bone implants. In this study, we developed an organic composite-mediated strontium coating strategy for ACBM scaffolds by using the ion chelating ability of carboxymethyl cellulose (CMC) and the surface adhesion ability of dopamine (DOPA). The organic coating composite, termed the CMC-DOPA-Sr composite, was synthesized under a mild condition, and its chemical structure and strontium ion chelating ability were then determined. After surface decoration, the physicochemical properties of the strontium-coated ACBM (ACBM-Sr) scaffolds were characterized, and their biocompatibility and osteoinductivity were determined in vitro and in vivo. The results showed that the CMC-DOPA-Sr composite facilitated strontium coating on the surface of ACBM scaffolds. The ACBM-Sr scaffolds possessed a sustained strontium ion release profile, exhibited good cytocompatibility, and enhanced the osteogenic differentiation of mesenchymal stem cells in vitro. Furthermore, the ACBM-Sr scaffolds showed good histocompatibility after subcutaneous implantation in nude mice. Taken together, this study provided a simple and mild strategy to realize strontium coating for ACBM scaffolds, which resulted in good biocompatibility and improved osteoinductivity.

Assessment of a closed wash system developed for processing living donor femoral heads

NHS Blood and Transplant Tissue and Eye Services (TES) and Scottish National Blood Transfusion Services Tissues and Cells Directorate (TCD) currently bank whole, frozen femoral head bone from living donors who are undergoing primary hip replacement surgery. When required, the bone is issued to a surgeon still frozen on dry ice (- 79 °C). Consequently, the femoral head bone is not processed, is not sterilised and at the time of issue, it contains donor blood, bone marrow and associated cells. We have previously shown that, cut, shaped and washed bone from deceased donors can be processed to remove up to 99.9% of blood, bone marrow and associated cells (Eagle et al. 2015). However, cut and shaped bone is not suitable for some orthopaedic procedures and some orthopaedic surgeons do not wish to use irradiated bone; therefore in this report, a method has been developed in which whole femoral heads can be washed to remove donor blood and bone marrow components. Processing results in excess of 99% bone marrow component removal-soluble protein, haemoglobin and DNA; the procedure is performed inside a closed system, thereby eliminating the need for terminal sterilisation by irradiation. In addition, uniaxial testing demonstrated no difference in compressive strength between washed and unwashed bone. We suggest that this washed bone may be capable of improving incorporation after grafting without disturbing biomechanical properties of the graft.

Advances in the local and targeted delivery of anti-infective agents for management of osteomyelitis

INTRODUCTION

Osteomyelitis, a common and debilitating invasive infection of bone, is a frequent complication following orthopedic surgery and causes pathologic destruction of skeletal tissues. Bone destruction during osteomyelitis results in necrotic tissue, which is poorly penetrated by antibiotics and can serve as a nidus for relapsing infection. Osteomyelitis therefore frequently necessitates surgical debridement procedures, which provide a unique opportunity for targeted delivery of antimicrobial and adjunctive therapies. Areas covered: Following surgical debridement, tissue voids require implanted materials to facilitate the healing process. Antibiotic-loaded, non-biodegradable implants have been the standard of care. However, a new generation of biodegradable, osteoconductive materials are being developed. Additionally, in the face of widespread antimicrobial resistance, alternative therapies to traditional antibiotic regimens are being investigated, including bone targeting compounds, antimicrobial surface modifications of orthopedic implants, and anti-virulence strategies. Expert commentary: Recent advances in biodegradable drug delivery scaffolds make this technology an attractive alternative to traditional techniques for orthopedic infection that require secondary operations for removal. Advances in novel treatment methods are expanding the arsenal of viable antimicrobial treatment strategies in the face of widespread drug resistance. Despite a need for large scale clinical investigations, these strategies offer hope for future treatment of this difficult invasive disease.

Human decellularized bone scaffolds from aged donors show improved osteoinductive capacity compared to young donor bone

To improve the safe use of allograft bone, decellularization techniques may be utilized to produce acellular scaffolds. Such scaffolds should retain their innate biological and biomechanical capacity and support mesenchymal stem cell (MSC) osteogenic differentiation. However, as allograft bone is derived from a wide age-range, this study aimed to determine whether donor age impacts on the ability an osteoinductive, acellular scaffold produced from human bone to promote the osteogenic differentiation of bone marrow MSCs (BM-MSC). BM-MSCs from young and old donors were seeded on acellular bone cubes from young and old donors undergoing osteoarthritis related hip surgery. All combinations resulted in increased osteogenic gene expression, and alkaline phosphatase (ALP) enzyme activity, however BM-MSCs cultured on old donor bone displayed the largest increases. BM-MSCs cultured in old donor bone conditioned media also displayed higher osteogenic gene expression and ALP activity than those exposed to young donor bone conditioned media. ELISA and Luminex analysis of conditioned media demonstrated similar levels of bioactive factors between age groups; however, IGF binding protein 1 (IGFBP1) concentration was significantly higher in young donor samples. Additionally, structural analysis of old donor bone indicated an increased porosity compared to young donor bone. These results demonstrate the ability of a decellularized scaffold produced from young and old donors to support osteogenic differentiation of cells from young and old donors. Significantly, the older donor bone produced greater osteogenic differentiation which may be related to reduced IGFBP1 bioavailability and increased porosity, potentially explaining the excellent clinical results seen with the use of allograft from aged donors.

Preparation and characterization of cockle shell aragonite nanocomposite porous 3D scaffolds for bone repair

The demands for applicable tissue-engineered scaffolds that can be used to repair load-bearing segmental bone defects (SBDs) is vital and in increasing demand. In this study, seven different combinations of 3 dimensional (3D) novel nanocomposite porous structured scaffolds were fabricated to rebuild SBDs using an extraordinary blend of cockle shells (CaCo₃) nanoparticles (CCN), gelatin, dextran and dextrin to structure an ideal bone scaffold with adequate degradation rate using the Freeze Drying Method (FDM) and labeled as 5211, 5400, 6211, 6300, 7101, 7200 and 8100. The micron sized cockle shells powder obtained (75 µm) was made into nanoparticles using mechano-chemical, top-down method of nanoparticles synthesis with the presence of the surfactant BS-12 (dodecyl dimethyl bataine). The phase purity and crystallographic structures, the chemical functionality and the thermal characterization of the scaffolds’ powder were recognized using X-Ray Diffractometer (XRD), Fourier transform infrared (FTIR) spectrophotometer and Differential Scanning Calorimetry (DSC) respectively. Characterizations of the scaffolds were assessed by Scanning Electron Microscopy (SEM), Degradation Manner, Water Absorption Test, Swelling Test, Mechanical Test and Porosity Test. Top-down method produced cockle shell nanoparticles having averagely range 37.8±3–55.2±9 nm in size, which were determined using Transmission Electron Microscope (TEM). A mainly aragonite form of calcium carbonate was identified in both XRD and FTIR for all scaffolds, while the melting (Tm) and transition (Tg) temperatures were identified using DSC with the range of Tm 62.4–75.5 °C and of Tg 230.6–232.5 °C. The newly prepared scaffolds were with the following characteristics: (i) good biocompatibility and biodegradability, (ii) appropriate surface chemistry and (iii) highly porous, with interconnected pore network. Engineering analyses showed that scaffold 5211 possessed 3D interconnected homogenous porous structure with a porosity of about 49%, pore sizes ranging from 8.97 to 337 µm, mechanical strength 20.3 MPa, Young's Modulus 271±63 MPa and enzymatic degradation rate 22.7 within 14 days.

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An innovative mixture of nano-CaCo₃ (aragonite), gelatin, dextrin and dextran.

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Scaffold 5211 reached a tipping point in terms of ideal morphology, optimal physiochemical properties, and great mechanical strength.

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Scaffold 5211 may guarantee the achievement of the developed scaffold purposes in true biological system.

RhBMP-2 loaded MBG/PEGylated poly(glycerol sebacate) composite scaffolds for rapid bone regeneration

An rhBMP-2 loaded MBG/PEGS composite scaffold with optimal performances and rapid osteoinductive capacity was successfully designed and fabricated.

Bioinspired trimodal macro/micro/nano-porous scaffolds loading rhBMP-2 for complete regeneration of critical size bone defect

Critical size bone defects raise great demands for efficient bone substitutes. Mimicking the hierarchical porous architecture and specific biological cues of natural bone has been considered as an effective strategy to facilitate bone regeneration. Herein, a trimodal macro/micro/nano-porous scaffold loaded with recombinant human bone morphogenetic protein-2 (rhBMP-2) was developed. With mesoporous bioactive glass (MBG) as matrix, a trimodal MBG scaffold (TMS) with enhanced compressive strength (4.28 MPa, porosity of 80%) was prepared by a "viscosity controlling" and "homogeneous particle reinforcing" multi-template process. A 7.5 nm, 3D cubic (Im3m) mesoporous structure was tailored for a "size-matched entrapment" of rhBMP-2 to achieve sustained release and preserved bioactivity. RhBMP-2-loaded TMS (TMS/rhBMP-2) induced excellent cell attachment, ingrowth and osteogenesis in vitro. Further in vivo ectopic bone formation and orthotopic rabbit radius critical size defect results indicated that compared to the rhBMP-2-loaded bimodal macro/micro- and macro/nano-porous scaffolds, TMS/rhBMP-2 exhibited appealing bone regeneration capacity. Particularly, in critical size defect, complete bone reconstruction with rapid medullary cavity reunion and sclerotin maturity was observed on TMS/rhBMP-2. On the basis of these results, TMS/rhBMP-2 developed here represents a promising bone substitute for clinical application and the concepts proposed in this study might provide new thoughts on development of future orthopedic biomaterials.

STATEMENT OF SIGNIFICANCE

Limited self-regenerating capacity of human body makes the reconstruction of critical size bone defect a significant challenge. Current bone substitutes often exhibit undesirable therapeutic efficacy due to poor osteoconductivity or low osteoinductivity. Herein, TMS/rhBMP-2, an advanced mesoporous bioactive glass (MBG) scaffold with osteoconductive trimodal macro/micro/nano-porosity and osteoinductive rhBMP-2 delivery was developed. The preparative and mechanical problems of hierarchical MBG scaffold were solved without affecting its excellent biocompatibilities, and rhBMP-2 immobilization in sizematched mesopores was first explored. Combining structural and biological cues, TMS/rhBMP-2 achieved a complete regeneration with rapid medullary cavity reunion and sclerotin maturity in rabbit radius critical size defects. The design conceptions proposed in this study might provide new thoughts on development of future orthopedic biomaterials.

Evaluation of Copper and Hydrogen Peroxide Treatments on the Biology, Biomechanics, and Cytotoxicity of Decellularized Dermal Allografts

Decellularized tissue allografts are paving the way as an alternative to cellular tissue transplantation. Effective sterilization or decontamination of tissue allografts is paramount for the safety of the allograft; however, some of the current sterilization procedures have a detrimental effect on the tissue scaffold. The bactericidal and virucidal activity of copper (II) ions and hydrogen peroxide (H2O2) have been widely reported, however, their effect on the biology, biochemistry, and biocompatibility of decellularized tissue have yet to be elucidated. In this study, decellularized human dermis (dCELL human dermis) was treated with copper (II) chloride (CuCl2) and H2O2; both singly and in combination, and parameters, including concentration, pH, and synergy between CuCl2 and H2O2, were evaluated to identify conditions where any detrimental effects on the tissue scaffold were observed. Skin from 13 human donors was retrieved with appropriate consent and processed into dCELL human dermis. The dCELL human dermis was then treated for 3 h with 0.1 mg/L-1 g/L (w/v) CuCl2 and 0.01-7.5% (v/v) H2O2 and combinations of both of these in the same concentration range. dCELL human dermis treated with solutions of 0.1 mg/L-1 g/L CuCl2 or 0.01-7.5% H2O2 caused no detrimental effects on gross histology, collagen denaturation, collagen orientation, and biomechanical properties of the tissue or cytotoxicity. The highest combined concentration of CuCl2 and H2O2 demonstrated an increase in ultimate tensile strength, loss of collagen type IV immunostaining at the dermal-epidermal junction, and in vitro cytotoxicity. Combinations within the range of up to 10 mg/L CuCl2 with up to 0.5% H2O2 had no effect. The data identify the concentrations of CuCl2 and H2O2 solutions that have no effect on the biological, biomechanical, and biochemical properties of dCELL human dermis, while retaining biocompatibility. These treatments may be suitable for use as sterilization/decontamination agents on human decellularized tissues.

Development of an improved bone washing and demineralisation process to produce large demineralised human cancellous bone sponges

Shaped demineralised bone matrices (DBM) made from cancellous bone have important uses in orthopaedic and dental procedures, where the properties of the material allow its insertion into confined defects, therefore acting as a void filler and scaffold onto which new bone can form. The sponges are often small in size, <1.0 cm(3). In this study, we report on an improved bone washing and demineralisation process that allows production of larger DBM sponges (3.375 or 8.0 cm(3)) from deceased donor bone. These sponges were taken through a series of warm water washes, some with sonication, centrifugation, 100 % ethanol and two decontamination chemical washes and optimally demineralised using 0.5 N hydrochloric acid under vacuum. Demineralisation was confirmed by quantitative measurement of calcium and qualitatively by compression. Protein and DNA removal was also determined. The DBM sponges were freeze dried before terminal sterilisation with a target dose of 25 kGy gamma irradiation whilst frozen. Samples of the sponges were examined histologically for calcium, collagen and the presence of cells. The data indicated lack of cells, absence of bone marrow and a maximum of 1.5 % residual calcium.