Meniscal repair is widely used as a treatment for meniscus injury. However, where meniscal damage has progressed such that repair is not possible, approaches for partial meniscus replacement are now being developed which have the potential to restore the functional role of the meniscus, in stabilising the knee joint, absorbing and distributing stress during loading, and prevent early degenerative joint disease. One attractive potential solution to the current lack of meniscal replacements is the use of decellularised natural biological scaffolds, derived from xenogeneic tissues, which are produced by treating the native tissue to remove the immunogenic cells. The current study investigated the effect of decellularisation on the biomechanical tensile and compressive (indentation and unconfined) properties of the porcine medial meniscus through an experimental-computational approach. The results showed that decellularised medial porcine meniscus maintained the tensile biomechanical properties of the native meniscus, but had lower tensile initial elastic modulus. In compression, decellularised medial porcine meniscus generally showed lower elastic modulus and higher permeability compared to that of the native meniscus. These changes in the biomechanical properties, which ranged from less than 1% to 40%, may be due to the reduction of glycosaminoglycans (GAG) content during the decellularisation process. The predicted biomechanical properties for the decellularised medial porcine meniscus were within the reported range for the human meniscus, making it an appropriate biological scaffold for consideration as a partial meniscus replacement.

The porcine superflexor tendon (SFT) was identified as having appropriate structure and properties for development of a decellularized device for use in anterior cruciate ligament reconstruction. SFTs were decellularized using a combination of freeze–thaw and washes in hypotonic buffer and 0.1% (w/v) sodium dodecyl sulfate in hypotonic buffer plus proteinase inhibitors, followed by nuclease treatment and sterilization using peracetic acid. The decellularized biological scaffold was devoid of cells and cell remnants and contained only 13 ng/mg (dry weight) residual total DNA. Immunohistochemistry showed retention of collagen type I and III and tenascin-C. Quantitative analysis of sulfated sugar and hydroxyproline content revealed a loss of glycosaminoglycans compared with native tissue, but no loss of collagen. The decellularized SFT was biocompatible in vitro and in vivo following implantation in a mouse subcutaneous model for 12 weeks. Uniaxial tensile testing to failure indicated that the gross material properties of decellularized SFTs were not significantly different to native tissue. Decellularized SFTs had an ultimate tensile strength of 61.8 ± 10.3 MPa (±95% confidence limits), a failure strain of 0.29 ± 0.04, and a Young's modulus of the collagen phase of 294.1 ± 61.9 MPa. Analysis of the presence of the α-Gal (galactose-α-1,3-galactose) epitope by immunohistochemistry, lectin binding, and antibody absorption assay indicated that the epitope was reduced, but still present post decellularization. This is discussed in light of the potential role of noncellular α-Gal in the acceleration of wound healing and tissue regeneration in the presence of antibodies to α-Gal.

Surgeons have used cryopreserved vascular allografts successfully for many years to treat arterial occlusive disease and to repair arterial aneurysms. Vascular allografts demonstrate high patency rates but contain viable cells, which may evoke a rejection response following implantation. Removing the cells could prevent such a response and negate the need for cryopreservation and ultra-low temperature storage. The objectives of the study were to characterize human common femoral arteries and develop a decellularization protocol with a view to the generation of biocompatible and biomechanically functional vascular grafts for use in vascular bypass and arteriovenous access. The arteries were decellularized by subjecting the tissue to a single freeze-thaw cycle followed by sequential incubation in hypotonic tris buffer and low concentration sodium dodecyl sulphate. Each artery was disinfected using 0.1% (v/v) peracetic acid. Histological analysis demonstrated a lack of cells following decellularization and confirmed the integrity of the tissue histioarchitecture and retention of major structural proteins. There was a >95% reduction in DNA levels. The acellular tissues and extracts were not cytotoxic to either mouse 3T3 or baby hamster kidney cells. Biomechanical properties were determined by burst pressure, compliance, and tensile tests, which confirmed the retention of biomechanical properties following decellularization. In conclusion the study has developed a suitable protocol for the removal of cells from human common femoral arteries without adversely affecting the biochemical or biomechanical properties. These properties indicate the potential use for acellular human common femoral arteries for vascular bypass or arteriovenous access.

The aims of this study were to determine the functional biocompatibility of low-concentration SDS-decellularized porcine aortic roots in vivo. A previously developed process was modified for 9- and 15-mm-diameter aortic roots to facilitate implantation into the porcine abdominal aorta (n=3) and juvenile sheep right ventricular outflow tract (n=7), respectively. Native allogeneic aortic roots were used as controls. Acellular porcine roots explanted from pigs at weeks were largely repopulated with stromal cells of appropriate phenotype, and there was evidence that macrophages were involved in the regenerative process. Native allogeneic roots were subject to a classic allograft rejection response. Acellular porcine roots explanted from sheep at 6 months showed evidence of appropriate cellular repopulation, again with evidence of a role for macrophages in the regenerative process. There was some degree of calcification of two of the explanted acellular roots, likely due to incomplete removal of DNA before implantation. Native allogeneic ovine roots were subject to a classic allograft rejection response involving T cells, which resulted in overtly calcified and damaged tissues. The study highlighted (1) the importance of removal of DNA from acellular porcine valved roots to avoid calcification and (2) a role for macrophages in the regeneration of low-concentration SDS-decellularized aortic roots, as has been reported for other acellular biological extracellular matrix scaffolds.

The clinical use of decellularized cardiac valve allografts is increasing. Long‐term data will be required to determine whether they outperform conventional cryopreserved allografts. Valves decellularized using different processes may show varied long‐term outcomes. It is therefore important to understand the effects of specific decellularization technologies on the characteristics of donor heart valves. Human cryopreserved aortic and pulmonary valved conduits were decellularized using hypotonic buffer, 0.1% (w/v) sodium dodecyl sulfate and nuclease digestion. The decellularized tissues were compared to cellular cryopreserved valve tissues using histology, immunohistochemistry, quantitation of total deoxyribose nucleic acid, collagen and glycosaminoglycan content, in vitro cytotoxicity assays, uniaxial tensile testing and subcutaneous implantation in mice. The decellularized tissues showed no histological evidence of cells or cell remnants and >97% deoxyribose nucleic acid removal in all regions (arterial wall, muscle, leaflet and junction). The decellularized tissues retained collagen IV and von Willebrand factor staining with some loss of fibronectin, laminin and chondroitin sulfate staining. There was an absence of major histocompatibility complex Class I staining in decellularized pulmonary valve tissues, with only residual staining in isolated areas of decellularized aortic valve tissues. The collagen content of the tissues was not decreased following decellularization however the glycosaminoglycan content was reduced. Only moderate changes in the maximum load to failure of the tissues were recorded postdecellularization. The decellularized tissues were noncytotoxic in vitro, and were biocompatible in vivo in a mouse subcutaneous implant model. The decellularization process will now be translated into a good manufacturing practices‐compatible process for donor cryopreserved valves with a view to future clinical use. Copyright © 2016 The Authors Tissue Engineering and Regenerative Medicine published by John Wiley & Sons, Ltd.