Malassezia spp. are commensal, cutaneous fungi that are implicated in seborrhoeic dermatitis. We hypothesize that the lipid-rich capsule of Malassezia spp. masks the organism from host detection, and depletion of this layer elicits an inflammatory response. To test this, preparations of capsulated or acapsular [10% (v/v) Triton X-100 treated], viable and nonviable, exponential or stationary phase Malassezia furfur, Malassezia globosa, Malassezia obtusa, Malassezia restricta, Malassezia slooffiae and Malassezia sympodialis, were incubated with normal human keratinocytes. Proinflammatory (IL-6, IL-8, IL-1alpha and tumour necrosis factor-alpha) and anti-inflammatory cytokine (IL-10) release and intracellular IL-10 concentrations were quantified using enzyme-linked immunosorbent assays. Capsulated Malassezia yeasts stimulated limited or no production of inflammatory cytokines, and increased intracellular IL-10 (P < 0.05). Removal of the capsule of many Malassezia preparations caused a significantly increased production of IL-6, IL-8 and IL-1alpha, and a decrease in intracellular IL-10. Notably, acapsular viable, stationary phase M. globosa caused a 66-fold increase in IL-8 production (P < 0.001) and acapsular nonviable, stationary phase M. furfur caused a 38-fold increase in IL-6 production (P < 0.001) and a 12-fold decrease in intracellular IL-10 (P < 0.001). These results support the hypothesis that the lipid layer of Malassezia spp. modulates cytokine production by keratinocytes. This has implications in the pathogenesis of seborrhoeic dermatitis.

The aim of this study was to investigate the suitability of decellularised porcine pericardium for heterotopic repair of the mitral valve (MV) leaflets, and its potential to regenerate through endogenous cell repopulation in vivo, or in vitro seeding and bioreactor conditioning. Anterior and posterior MV leaflets and pericardia were excised from porcine hearts within. The pericardia were decellularised according to the in-house protocol. Anterior and posterior leaflet, and decellularised and fresh pericardial samples were subjected to histology (H and E, Masson trichrome, Sirius Red, Miller’s elastin, Alcian blue-PAS), immunohistochemistry (collagen type I, III, IV, fibronectin, laminin, and chondroitin sulfate labelling), SEM, and uniaxial tensile testing. Samples were isolated along the radial and circumferential direction (leaflets), and perpendicular and parallel to the collagen fibres (pericardium). Biochemical assays for quantification of the sulphated GAG and collagen content of the tissues were also performed. Contact and extract cytotoxicity testing, and DNA quantification was performed to assess the decellularised pericardia. Histology revealed the trilaminar structure of the pericardium and quadrilaminar structure of the leaflets. Collagen type I and III was found in the fibrosa layers of both pericardium and leaflets, whereas fibronectin and laminin were found throughout the tissues. Decellularisation produced a completely acellular pericardial scaffold, which retained the histoarchitecture of the natural tissue. The biomechanics showed the anterior leaflets being stiffer along the circumferential direction. No significant anisotropy was observed in the biomechanics of the posterior leaflets, or fresh and decellularised pericardium. The anisotropy of the anterior leaflet was attributed to the orientation of the collagen (aligned along the circumferential direction). Biochemistry showed a significant increase in sulphated GAGs between the fresh leaflets and pericardium. No difference was found between the collagen content of the fresh leaflets and the fresh or decellularised pericardium. The decellularised pericardium showed a 99% reduction in DNA and a high loss in the GAG content compared to the fresh pericardium. The study showed that the MV leaflets and pericardium share similar histoarchitectures and comparable biomechanics. The similarity was more pronounced in the case of the posterior leaflet which was more isotropic both in terms of histoarchitecture and biomechanics. Apart from a decreased GAG content, the similarity was also apparent between the leaflets and the pericardial scaffolds. The decellularised pericardium has the potential to deliver the necessary biological and biomechanical cues to seeded or migrating cells, representing a plausible scaffold option for the regeneration of the MV leaflets in vitro or in vivo.

The primary objective was to evaluate performance of low concentration SDS decellularised porcine pulmonary roots in the right ventricular outflow tract of juvenile sheep. Secondary objectives were to explore the cellular population of the roots over time. Animals were monitored by echocardiography and roots explanted at 1, 3, 6 ( n = 4) and 12 months ( n = 8) for gross analysis. Explanted roots were subject to histological, immunohistochemical and quantitative calcium analysis ( n = 4 at 1, 3 and 12 months) and determination of material properties ( n = 4; 12 months). Cryopreserved ovine pulmonary root allografts ( n = 4) implanted for 12 months, and non-implanted cellular ovine roots were analysed for comparative purposes. Decellularised porcine pulmonary roots functioned well and were in very good condition with soft, thin and pliable leaflets. Morphometric analysis showed cellular population by 1 month. However, by 12 months the total number of cells was less than 50% of the total cells in non-implanted native ovine roots. Repopulation of the decellularised porcine tissues with stromal (α-SMA+; vimentin+) and progenitor cells (CD34+; CD271+) appeared to be orchestrated by macrophages (MAC 387+/ CD163low and CD163+/MAC 387−). The calcium content of the decellularised porcine pulmonary root tissues increased over the 12-month period but remained low (except suture points) at 401 ppm (wet weight) or below. The material properties of the decellularised porcine pulmonary root wall were unchanged compared to pre-implantation. There were some changes in the leaflets but importantly, the porcine tissues did not become stiffer. The decellularised porcine pulmonary roots showed good functional performance in vivo and were repopulated with ovine cells of the appropriate phenotype in a process orchestrated by M2 macrophages, highlighting the importance of these cells in the constructive tissue remodelling of cardiac root tissues.