Paul Sibbons

Morphometric placental villous and vascular abnormalities in early- and late-onset pre-eclampsia with and without fetal growth restriction

Objective  To evaluate placental morphology in pregnancies complicated by early‐ and late‐onset pre‐eclampsia (PET) with and without fetal growth restriction (FGR) using stereological techniques.

Immunomodulatory effect of a decellularized skeletal muscle scaffold in a discordant xenotransplantation model

Decellularized (acellular) scaffolds, composed of natural extracellular matrix, form the basis of an emerging generation of tissue-engineered organ and tissue replacements capable of transforming healthcare. Prime requirements for allogeneic, or xenogeneic, decellularized scaffolds are biocompatibility and absence of rejection. The humoral immune response to decellularized scaffolds has been well documented, but there is a lack of data on the cell-mediated immune response toward them in vitro and in vivo. Skeletal muscle scaffolds were decellularized, characterized in vitro, and xenotransplanted. The cellular immune response toward scaffolds was evaluated by immunohistochemistry and quantified stereologically. T-cell proliferation and cytokines, as assessed by flow cytometry using carboxy-fluorescein diacetate succinimidyl ester dye and cytometric bead array, formed an in vitro surrogate marker and correlate of the in vivo host immune response toward the scaffold. Decellularized scaffolds were free of major histocompatibility complex class I and II antigens and were found to exert anti-inflammatory and immunosuppressive effects, as evidenced by delayed biodegradation time in vivo; reduced sensitized T-cell proliferative activity in vitro; reduced IL-2, IFN-γ, and raised IL-10 levels in cell-culture supernatants; polarization of the macrophage response in vivo toward an M2 phenotype; and improved survival of donor-derived xenogeneic cells at 2 and 4 wk in vivo. Decellularized scaffolds polarize host responses away from a classical TH1-proinflammatory profile and appear to down-regulate T-cell xeno responses and TH1 effector function by inducing a state of peripheral T-cell hyporesponsiveness. These results have substantial implications for the future clinical application of tissue-engineered therapies.

Effect of nanoparticulate bioactive glass particles on bioactivity and cytocompatibility of poly(3-hydroxybutyrate) composites

This work investigated the effect of adding nanoparticulate (29 nm) bioactive glass particles on the bioactivity, degradation and in vitro cytocompatibility of poly(3-hydroxybutyrate) (P(3HB)) composites/nano-sized bioactive glass (n-BG). Two different concentrations (10 and 20 wt %) of nanoscale bioactive glass particles of 45S5 Bioglass composition were used to prepare composite films. Several techniques (Raman spectroscopy, scanning electron microscopy, atomic force microscopy, energy dispersive X-ray) were used to monitor their surface and bioreactivity over a 45-day period of immersion in simulated body fluid (SBF). All results suggested the P(3HB)/n-BG composites to be highly bioactive, confirmed by the formation of hydroxyapatite on material surfaces upon immersion in SBF. The weight loss and water uptake were found to increase on increasing bioactive glass content. Cytocompatibility study (cell proliferation, cell attachment, alkaline phosphatase activity and osteocalcin production) using human MG-63 osteoblast-like cells in osteogenic and non-osteogenic medium showed that the composite substrates are suitable for cell attachment, proliferation and differentiation.

Evaluation of crosslinked and non-crosslinked biologic prostheses for abdominal hernia repair.

IntroductionAbdominal wall defects and incisional hernias represent a challenging problem. Currently, several commercially available biologic prostheses are used clinically for hernia repair. We compared the performance and efficacy of two non-crosslinked meshes in ventral hernia repair to two crosslinked prostheses in a rodent model.MethodsAnimals were divided into 12 groups (4 matrix types and 3 termination time-points per matrix). A ventral defect was carefully created and overlapped with the biologic prosthesis.ResultsMajor complications were seroma induction (3 mesh types), implant extrusion (1 mesh type), severe inflammatory and immune responses (non-crosslinked mesh), fibrosis and mineralisation (3 mesh types). After inflammation resolution, 3 of the matrices tested supported hernia healing but with marked tissue and temporal differences. AlloDerm®* and Surgisis Gold™ showed tissue reactivity with the host and a rapid rate of matrix remodelling. Bard CollaMend™* Implant proved to be inept for hernia repair under the conditions tested. Permacol™ biological implant integration with host tissue increased over time, supporting hernia healing with strength of tissue, and appears to be a safe prosthetic material for ventral hernia repair based on the results of this rodent study.

Esophageal tissue engineering: A new approach for esophageal replacement

A number of congenital and acquired disorders require esophageal tissue replacement. Various surgical techniques, such as gastric and colonic interposition, are standards of treatment, but frequently complicated by stenosis and other problems. Regenerative medicine approaches facilitate the use of biological constructs to replace or regenerate normal tissue function. We review the literature of esophageal tissue engineering, discuss its implications, compare the methodologies that have been employed and suggest possible directions for the future. Medline, Embase, the Cochrane Library, National Research Register and ClinicalTrials.gov databases were searched with the following search terms: stem cell and esophagus, esophageal replacement, esophageal tissue engineering, esophageal substitution. Reference lists of papers identified were also examined and experts in this field contacted for further information. All full-text articles in English of all potentially relevant abstracts were reviewed. Tissue engineering has involved acellular scaffolds that were either transplanted with the aim of being repopulated by host cells or seeded prior to transplantation. When acellular scaffolds were used to replace patch and short tubular defects they allowed epithelial and partial muscular migration whereas when employed for long tubular defects the results were poor leading to an increased rate of stenosis and mortality. Stenting has been shown as an effective means to reduce stenotic changes and promote cell migration, whilst omental wrapping to induce vascularization of the construct has an uncertain benefit. Decellularized matrices have been recently suggested as the optimal choice for scaffolds, but smart polymers that will incorporate signalling to promote cell-scaffold interaction may provide a more reproducible and available solution. Results in animal models that have used seeded scaffolds strongly suggest that seeding of both muscle and epithelial cells on scaffolds prior to implantation is a prerequisite for complete esophageal replacement. Novel approaches need to be designed to allow for peristalsis and vascularization in the engineered esophagus. Although esophageal tissue engineering potentially offers a real alternative to conventional treatments for severe esophageal disease, important barriers remain that need to be addressed.

An experimentally successful new sphincter-conserving treatment for anal fistula.

PURPOSE: A new sphincter-conserving treatment was evaluated in a porcine model. METHODS: A total of 36 fistulas were created by procedures that have been published previously. At fistula induction a skin biopsy was taken from which to culture fibroblasts. Four weeks after induction, when fistulas were well established, the fistula tracks were cored out. Collagen paste modified from Permacol™ injection (Covidien, Mansfield, MA) was then used as a solitary infill material in 11 tracks, cultured autologous fibroblasts being added to this in a further 18 tracks. The track was cored out in seven controls, but these tracks were not treated with infill material. All of the internal and external openings were closed. Anorectal excision was then carried out under terminal anesthesia at 2 to 12 weeks. Histologic examination of individual tracks was performed by an experienced pathologist. RESULTS: In this quadruped all of the infilled tracks healed, autologous fibroblasts having the best tissue integration, but only two of seven control tracks healed. CONCLUSIONS: Removal of the fistula track followed by injection of collagen healed all of the cases. The addition of autologous fibroblasts improved the histologic appearance of the tracks. A pilot study in human fistula patients is in progress.

The role of human-derived fibrin sealant in the reduction of postoperative flexor tendon adhesion formation in rabbits

This study assessed the role of a novel fibrin sealant (Vivostat®) in adhesion reduction after flexor tendon surgery. The deep flexor tendons of the 2nd and 4th digits of the left paw of 20 rabbits were exposed and a standard partial injury was performed on each. The rabbits were randomized to either immediate post-injury treatment with Vivostat® or no treatment. In each case active movement of the 2nd digit was prevented while the 4th digit was allowed to move normally. The two groups were assessed at 14 days for adhesion formation with a tensiometer. The right paw acted as the unoperated control. Results showed that there was no significant difference in the force needed to remove the tendon from its sheath when comparing the two Vivostat®-treated groups to the unoperated controls. There was, however, a highly significant difference in this force between the non-Vivostat®-treated groups and the unoperated controls. This suggests a beneficial effect of Vivostat® in reducing post surgical tendon adhesion formation.

Pilot study: fibrin sealant in anal fistula model.

PURPOSEThe aim of this study was to investigate the failure of fibrin sealant treatment for fistula-in-ano in an experimental porcine model and to determine histologic changes associated with the sealant and setons.METHODSThree surgically created fistulas were treated by seton drainage in each of eight male pigs. After 26 days, magnetic resonance imaging was performed and setons were removed. Two pigs were killed as controls for stereologic histologic fistula track assessment. In six, fistulas were curetted, and in four the fistulas were treated with fibrin sealant. In these four sealant and two seton pigs, magnetic resonance imaging was repeated a median of 47.5 days after fistula formation. The pigs were killed and stereologic histologic fistula track examination was performed to determine granulation tissue and fistula lumen volumes. These values were compared among control, seton, and sealant groups over time, and related to fistula volumes derived from magnetic resonance imaging.RESULTSSealant was not visible microscopically within tracks, although some sections revealed a foreign body–type reaction. On stereologic assessment, granulation tissue volumes were smaller in sealant and seton groups than in controls (median, 88 vs. 187 vs. 453 mm3, respectively; P = 0.002) and decreased over time (median, 408 and 152 mm3 (Day 42) vs. 88 and 75 (Day 53), respectively; P = 0.002). Fistula lumen (P < 0.001), and granulation tissue combined with fistula lumen volumes (P = 0.002) were similarly smaller. Magnetic resonance imaging of fistula intensity was less in the sealant group than in the seton group and controls (mean, 777 vs. 978 vs. 1214 units/mm2, P = 0.003). Magnetic resonance imaging fistula volumes were least in sealant and seton groups vs. controls (P = 0.024), decreasing significantly in the sealant group over time (P = 0.018). No direct relationship was found between imaging and histologic volumes.CONCLUSIONSIn an experimental porcine model of anal fistula, granulation tissue was still present, albeit diminished, following track curettage combined with seton or sealant therapy, and was minimal in the sealant group, confirming some benefit from this procedure. Eradication of all longstanding granulation tissue may ensure complete success of fibrin sealant therapy.

Effect of crosslinking on the performance of a collagen-derived biomaterial as an implant for soft tissue repair: A rodent model

One of the main problems in healthcare is the loss of tissues resulting from diseases, post-surgery complications or trauma. As a result there is a need for biomaterials designed to promote tissue regeneration and improve wound healing. This study assessed the effect of crosslinking of a porcine dermal collagen matrix with regard to strength of implant/host tissue integration, implant biocompatibility and general healing in a rodent model. Permacol™, a crosslinked acellular collagenous biomaterial was compared with its noncrosslinked equivalent at 3, 6, and 12 months postsubcutaneous implantation. Both matrices were well tolerated and showed no evidence of inflammation or adverse responses either in the host tissue or implants. Progressive integration of the implants with the surrounding tissue was observed. Cellular response was similar for both collagenous matrices although, at 3 and 6 months, noncrosslinked implants showed a significantly higher level of cellular penetration than crosslinked implants. However, at 12 months crosslinked implants showed significantly higher levels of cellular density, neo-vascularisation and integration with host tissue. Additionally, at long term, noncrosslinked implants lost volume suggesting some absorption. The crosslinking process does not seem to be detrimental to cellular response and biocompatibility.

Experimental model of fistula-in-ano.

PURPOSEThis study was designed to create and evaluate an experimental porcine model of fistula-in-ano.METHODSInitial cadaveric dissection enabled refinement of the technique for fistula formation and histoanatomical study of the porcine anal canal. Subsequently, three surgically created fistulas were treated by seton drainage in each of eight male pigs (weight, 38–41 kg). After 26 days, magnetic resonance imaging at 1.5 Tesla was performed and setons removed under general anesthesia, enabling clinical and microbiologic track assessment. Two pigs were killed for histologic fistula track assessment.RESULTSHistoanatomical assessment noted a rudimentary internal anal sphincter, together with structures resembling anal glands. Artificial fistulas persisted during seton drainage and were more often associated with fecal than skin-derived organisms compared with both perineal and anal canal swabs (P = 0.002). All six fistulas assessed histologically had a lumen, and abundant surrounding granulation tissue similar to that seen in human fistula-in-ano. Epithelialization was not evident in any track. Fistulas were visualized as high signal tracks using magnetic resonance imaging.CONCLUSIONSPorcine anal anatomy resembles that of humans, and an experimental model proved suitable when assessed by magnetic resonance imaging, microbiology, and histologically, which demonstrated abundant granulation tissue. This model could be further used to investigate fistula treatments.