In vivo implantation of a tissue engineered stem cell seeded hemi-laryngeal replacement maintains airway, phonation, and swallowing in pigs.

Laryngeal functional impairment relating to swallowing, vocalisation, and respiration can be life changing and devastating for patients. A tissue engineering approach to regenerating vocal folds would represent a significant advantage over current clinical practice. Porcine hemi-larynx were de-cellularised under negative pressure. The resultant acellular scaffold was seeded with human bone marrow derived mesenchymal stem cells and primary human epithelial cells. Seeded scaffolds were implanted orthotopically into a defect created in the thyroid cartilage in 8 pigs and monitored in vivo for 2 months. In vivo assessments consisted of mucosal brushing and bronchoscopy at 1, 2, 4, and 8 weeks post implantation followed by histological evaluation post termination. The implanted graft had no adverse effect on respiratory function in 6 of the 8 pigs; none of the pigs had problems with swallowing or vocalisation. Six out of the 8 animals survived to the planned termination date; 2 animals were terminated due to mild stenosis and deep tissue abscess formation, respectively. Human epithelial cells from mucosal brushings could only be identified at Weeks 1 and 4. The explanted tissue showed complete epithelialisation of the mucosal surface and the development of rudimentary vocal folds. However, there was no evidence of cartilage remodelling at the relatively early censor point. Single stage partial laryngeal replacement is a safe surgical procedure. Replacement with a tissue engineered laryngeal graft as a single procedure is surgically feasible and results in appropriate mucosal coverage and rudimentary vocal fold development.

Pilot study of a novel vacuum-assisted method for decellularization of tracheae for clinical tissue engineering applications.

Tissue engineered tracheae have been successfully implanted to treat a small number of patients on compassionate grounds. The treatment has not become mainstream due to the time taken to produce the scaffold and the resultant financial costs. We have developed a method for decellularization (DC) based on vacuum technology, which when combined with an enzyme/detergent protocol significantly reduces the time required to create clinically suitable scaffolds. We have applied this technology to prepare porcine tracheal scaffolds and compared the results to scaffolds produced under normal atmospheric pressures. The principal outcome measures were the reduction in time (9 days to prepare the scaffold) followed by a reduction in residual DNA levels (DC no-vac: 137.8±48.82 ng/mg vs. DC vac 36.83±18.45 ng/mg, p<0.05.). Our approach did not impact on the collagen or glycosaminoglycan content or on the biomechanical properties of the scaffolds. We applied the vacuum technology to human tracheae, which, when implanted in vivo showed no significant adverse immunological response. The addition of a vacuum to a conventional decellularization protocol significantly reduces production time, whilst providing a suitable scaffold. This increases clinical utility and lowers production costs. To our knowledge this is the first time that vacuum assisted decellularization has been explored. Copyright © 2015 John Wiley & Sons, Ltd.

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

INTRODUCTION: Abdominal 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. METHODS: Animals 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. RESULTS: Major 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.

Prolonged maintenance of neointestine using subcutaneously implanted tubular scaffolds in a rat model.

Tissue-engineered small intestine offers a possible alternative to long-term parenteral nutrition or intestinal transplantation in patients with short bowel syndrome. The aim of this study was to investigate the prolonged development of neointestine grown on subcutaneously implanted scaffolds. Tubular polylactide-coglycolide (PLGA) scaffolds were implanted into adult Lewis rats. Four weeks after scaffold implantation, a suspension of organoid units was delivered to the lumen of each scaffold. Organoid units were manufactured from small intestine harvested from neonatal Lewis rats by partial digestion using collagenase and dispase. Scaffolds were removed at 4, 8, and 12 weeks after organoid unit implantation, processed to paraffin, and sectioned. Hematoxylin and eosin staining demonstrated well-developed and well-differentiated intestinal mucosa and a vascularised submucosa within the scaffolds at 4, 8, and 12 weeks. Appearances were similar to native small intestine. Immunohistochemistry performed using primary antibody against proliferating cell nuclear antigen, a marker for cellular proliferation, demonstrated positively staining cells within the mucosa and submucosa at all time points. In the mucosal layer these positively staining cells were found primarily in the crypts. These findings show that neointestinal mucosa can be maintained for at least 12 weeks on a subcutaneous PLGA scaffold, and the presence of actively proliferating cells at 12 weeks suggests potential for further development beyond this.

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. DESIGN: A total of 69 pregnant women were studied. Twenty women had pregnancies complicated by PET, 17 by FGR and 16 by both PET and FUR; the remaining 16 were from gestational-age-matched controls. Each group was further classified into early onset (<34 weeks) and late onsets (>34 weeks) based on gestational ages. SETTING: NPIMR at Northwick Park and St Marks Hospital. POPULATION: placentae from pregnant women. METHODS: Formalin-fixed, wax-embedded sections stained with anti-CD34 antibodies and counterstained with haematoxylin. MAIN OUTCOME MEASURES: Volumes, surface areas, lengths, diameters and shape factors of the villous tissues and fetal vasculature in the intermediate and terminal villi of all the groups studied. RESULTS: Terminal villi volume and surface area were compromised in early-onset PET cases, late-onset PET had no impact on peripheral villi or vasculature features. The morphology of the vascular and villous subcomponents in the intermediate and terminal villi was significantly influenced by late-onset FGR, whereas early-onset FGR caused a reduction in placental weight. Length estimates were not influenced by PET, FGR or age of onset. Intermediate arteriole shape factor was significantly reduced in late-onset FGR. CONCLUSIONS: Isolated early-onset PET was associated with abnormal placental morphology, but placentas from late-onset PET were morphologically similar to placentas from gestational-age-matched controls, confirming the existence of two subsets of this condition and supporting the hypothesis that late-onset PET is a maternal disorder and not a placental disease.

A pilot study investigating a novel subcutaneously implanted pre-cellularised scaffold for tissue engineering of intestinal mucosa.

Tissue engineering of the small intestine offers an alternative to long-term intravenous nutrition and transplantation in patients with intestinal failure. Initial work, although encouraging, is limited by the volume of neonatal tissue required to produce a small neomucosal cyst. Our novel approach is to implant tubular poly-lactide-co-glycolide (PGLA) foam scaffolds subcutaneously. The aim of this study was to investigate whether these scaffolds would support growth of intestinal neomucosa. PGLA scaffolds were implanted subcutaneously into 8 Lewis rats; after 5 weeks, 'organoid units' were injected into the lumens. Tissue was assessed histologically after harvesting and quantitative immunohistochemistry was performed using antibodies against vascular endothelial growth factor (VEGF), vascular endothelial growth factor receptor 2 (VEGF-R2), fibroblast growth factor basic (bFGF) and fibroblast growth factor receptor 2 (FGF-R2). At 4 weeks post organoid unit implantation, clearly recognisable mucosa and submucosa was present on the luminal surface of the scaffold. Densities of VEGF and VEGF-R2 positive cells increased with time post organoid unit implantation. This pilot study demonstrates that it is possible to tissue engineer small intestinal neomucosa using subcutaneously implanted PLGA scaffolds. The yield of the process compares favourably to the published literature. Further work is required to optimise the technique.

Pre-eclampsia and fetal growth restriction: how morphometrically different is the placenta?

Both pre-eclampsia (PET) and fetal growth restriction (FGR) pose a heavy burden on fetal and maternal health and may disrupt pregnancy outcome. Using design based stereological techniques, placental vascular and villous morphology were assessed to determine the individual role played by both PET and FGR on placental growth during the third trimester. The following placentas delivered between 25 and 41 weeks of gestation were included into the study; controls (n=16), PET (n=20), FGR (n=17) and PET-FGR (n=16). Each placenta was uniformly randomly sampled and the sampled tissue processed to paraffin. Sections were stained with a CD34 antibody and the following morphometric parameters estimated: volumes, surface areas, length, diameters and the shape factor of the villous (terminal and intermediate) and vascular placental features. For stereologically estimated parameters pure PET had an effect on IVS and terminal villi volume only. FGR alone or when coexisting with PET contributed towards significant reductions in volumetric and surface area terminal villous and vascular features. FGR factors also contributed towards a significant reduction in the lengths of all parameters estimated and in the terminal villi diameter. Additionally, FGR was associated with a significant difference in shape factor indices for both intermediate and terminal villi. This study has shown that PET on its own has limited influence on the placental morphology studied, since the vascular features estimated do not differ stereologically from age matched normal controls. However, placental morphology is different between PET and PET-FGR and between PET-FGR and FGR. PET and FGR may have a cumulative effect on placental villous and vascular morphology as seen in the PET-FGR but there is no synergistic effect. These morphological abnormalities may have major physiological implications in terms of placental function and fetal growth.

Analyses of the potential oxygen transfer capability in placentae from infants succumbing to sudden infant death syndrome.

BACKGROUND: Morphometric oxygen diffusive conductance (Dp) was estimated to assess the potential efficiency of oxygen transfer across the materno-fetal interface in placentae obtained from victims of sudden infant death syndrome (SIDS). STUDY DESIGN: SIDS placentae were retrieved from archived storage and classified into normal birth weight (NBW, n=16), or small for gestational age (SGA, n=9) and compared against control placentae (n=40) or SGA (n=24) placentae. A combination of stereological techniques and physiological constants were used to estimate total Dp. RESULTS: SIDS NBW cases showed a crucial reduction in fetal capillary surface area when compared with control placentae. SIDS SGA showed a number of deficiencies in basic volumetric and surface area parameters. Values for total and specific Dp in placentae in both SIDS groups were maintained at levels comparable with control and SGA cases, respectively. CONCLUSION: Since more reductions were observed in SIDS SGA group, this suggests that factors responsible for these reductions maybe associated with SGA rather than being SIDS-specific factors.

Morphometric assessment of the oxygen diffusion conductance in placentae from pregnancies complicated by intra-uterine growth restriction.

The morphometric oxygen diffusive conductance (D(p)) of the placenta provides a measure of the efficiency of oxygen transfer between the mother and the developing fetus. Any change in the D(p)may point towards possible adaptation in the light of altered oxygen transfer. Placentae from normal (n=40) and small for gestational age SGA (n=24) pregnancies were analysed using stereological techniques. Each placenta was uniform randomly sampled and tissue samples processed to wax infiltration and embedding using conventional histological preparatory methods. A combination of stereological techniques and physiological constants were used to estimate the partial conductances across the five major tissue compartments involved in oxygen transfer. There was a significant reduction in both fetal birthweight and placental weight in the SGA group when compared with controls. A decrease in both chorionic (S(cv)) and fetal capillary (S(fc)) surface area was also observed in SGA placentae when compared with controls (P>0.001). Villous membrane harmonic thickness (T(vm)) was reduced in the SGA placentae (2.33 microm) when compared with controls (2.67 microm P=0.019). This resulted in a reduction in the minimum D(p)in SGA placentae when compared with controls (P=0.023). Adjusting for fetal weight resulted in no difference in the specific diffusive conductance. Changes in T(vm)in SGA placentae combined with changes in basic surface areas were insufficient to maintain overall D(p)values comparable with control placentae.

Quantitative neuropathological analysis of sudden infant death syndrome.

Detailed stereological analyses of specific regions of brains of children who had died from Sudden Infant Death Syndrome (SIDS) was undertaken to determine whether global evidence of an underlying pathology exists, contributing to an increased susceptibility to SIDS. A significant reduction in the total number of neocortical neurones and neurone volume was observed in SIDS normal birth weight (NBW) infants in comparison to controls. A significant reduction in both volume and total neurone number were also noted in the dorsal motor nucleus of the vagus in SIDS NBW group when compared with controls. Anomalies in regions of the brain involved with cardiorespiratory control (brainstem) and arousal (brainstem and neocortex) may play a crucial role in the chain of events resulting in a SIDS event.

Organogenesis of lung and kidney in Thoroughbreds and ponies.

Equine lung and kidney organogenesis has not previously been examined with the use of unbiased stereological techniques. The present study examined healthy (control) pony and Thoroughbred lungs and kidneys to establish baseline data of organ development from before birth until maturity at age 3-18 years. Whole left lungs and kidneys were collected from 45 equine postmortem examinations (34 Thoroughbred, 11 pony). Stereological techniques were used to estimate whole kidney, cortex and medulla volume, total glomerular number and volume-weighted mean glomerular volume, lung volume, total terminal bronchiolar duct ending number and total gas exchange surface area. Lungs were demonstrated to be more developed at birth in ponies compared with Thoroughbreds. Thoroughbreds showed continued lung development after birth, a unique micromorphogenic postnatal development. Kidneys were developed equally in ponies and Thoroughbreds. This study has provided data on the baseline development of the equiune lung and kidney which can be used in further studies to examine whether the development of these organs is affected by specific illnesses.

Estimation of mean nuclear volume of neocortical neurons in sudden infant death syndrome cases using the nucleator estimator technique.

At present, no information is available with regards to either neocortical neuronal mean nuclear volume or maturation (functional or morphological) in abnormal paediatric brains. Using the nucleator estimator technique, the mean neocortical nuclear volume was estimated in sudden infant death syndrome (SIDS) cases [10 normal birth weight (NBW) and 10 low birth weight (LBW) cases classified by birth weight for gestational age] and compared to 10 NBW control cases. Both the control and SIDS LBW cases showed an increase in mean nuclear volume with age; the SIDS NBW cases showed no increase. At 8 months, the SIDS NBW cases showed a reduced mean nuclear volume (p = 0.02) when compared to controls. The SIDS LBW cases showed no statistically significant difference (p = 0.10) when compared with controls. A deficiency in mean neuronal nuclear volume may represent a deficiency in neuronal function.

Lung development: number of terminal bronchiolar duct endings and gas exchange surface area in victims of sudden infant death syndrome.

Previous research has demonstrated impaired renal development, particularly with respect to glomerular number, in victims of sudden infant death syndrome (SIDS). The present study used stereological principles to estimate the volume of the upper lobe of the right lung, total number of terminal bronchiolar duct endings (TBDE), and gas exchange surface area of this lobe within a group of human infants. The infants were classified according to cause of death (SIDS or non-SIDS), and further subdivided according to birth-weight: normal birth-weight (NBW) or low birth-weight (LBW). The results demonstrated that TBDE density was significantly reduced in SIDS compared to non-SIDS (P = 0.014), but only reduced from non-SIDS NBW values in the SIDS NBW group (P = 0.044). Total TBDE number was significantly reduced in SIDS from non-SIDS (P = 0.001), and was significantly reduced from non-SIDS NBW values in SIDS NBW (P = 0.023). Mean gas exchange surface area per TBDE was significantly increased in SIDS compared to non-SIDS cases (P = 0.049). The results of the present study indicate developmental delay of the lung in SIDS NBW infants who had previously not been considered growth retarded based on their normal body parameters.

Stereological estimation of volume-weighted mean glomerular volume from arbitrary sections of the equine kidney.

Mean glomerular volume has previously been estimated, using stereological techniques, specifically the point-sampled intercept (PSI), either from isotropic or from vertical sections. As glomeruli are approximately spherical structures, the same stereological technique was carried out on vertical and arbitrary sections to determine whether section orientation had any effect on mean glomerular volume estimation. Equine kidneys from 10 individuals were analysed using the PSI method of estimating volume-weighted mean glomerular volume (MGV); for each kidney, arbitrary and vertical sections were analysed. MGVs were not significantly different between arbitrary and vertical sections (P = 0.691) when analysing the data with the paired t test; when plotting MGV estimates from arbitrary sections against those from vertical sections the intercept was found not to be significantly different from zero (P > 0.8) and the slope of the regression line not to be significantly different from 1.0 (P > 0.4). For the estimation of MGV in equine kidneys using PSI, arbitrary sections may be used if it is not possible to use isotropic or vertical sections, but some caution must be exercised in the interpretation of results so gained.

Terminal bronchiolar duct ending number does not increase post-natally in normal infants.

Organ development may be assessed by estimating the total number of functional units within an organ over time; the potential functional capacity of that organ may be represented by the total number of functional units present in the fully developed, mature organ. Relative development of the lung at birth is essential to provide sufficient oxygenation of body tissues and so maintain ex utero life. Estimation of the number of one type of functional unit of the lung - terminal bronchiolar duct endings - provides important information regarding development of the lung. This investigation used stereological techniques, specifically Cavalieri's Principle and the "physical disector", to estimate total number of terminal bronchiolar duct endings in the upper lobe of the right lung of a group of 14 control infants between 0 and 66 weeks post-natal age. Results demonstrate that total terminal bronchiolar duct ending number does not increase significantly over the first 24 weeks of post-natal life in normal infants (P=0.997). The unbiased, design-based techniques used in this paper confirm previous model-based research that indicates that terminal bronchiolar duct ending development is completed before birth.

Renal developmental delay expressed by reduced glomerular number and its association with growth retardation in victims of sudden infant death syndrome and in "normal" infants.

In victims of sudden infant death syndrome (SIDS), renal development has been reported to be significantly impaired. In the present study, we used stereological techniques to estimate volume of kidney cortex and total number of glomeruli in a group of human infants. Infants were classified according to cause of death-SIDS or non-SIDS. Cases were further subdivided according to birth weight-normal birth weight (NBW) or low birth weight (LBW) (we were unable to identify any non-SIDS LBW infants for our study). No significant differences were found between NBW and LBW infants (irrespective of cause of death) for cortical volume, glomerular density, or total glomerular number (p > 0.140). Kidney cortical volume, glomerular density, and total glomerular number were not significantly different between SIDS and non-SIDS infants (p > 0.510). Glomerular number was only significantly less in SIDS infants of LBW (p = 0. 032) than in controls according to the Wilcoxon rank sum test; using the Kruskal-Wallis for one-way analysis, no significant difference was found (p > 0.010). These results contrast with those from previous studies, as a reduction in glomerular number was not noted in SIDS NBW infants, and the mean value for the control (non-SIDS NBW) group was significantly reduced (p < 0.01) from those of previous studies. This indicates that glomerular number reduction is seen in SIDS NBW and non-SIDS NBW cases and is therefore directly associated with growth retardation rather than with SIDS.

Unbiased and efficient estimation of the total number of terminal bronchiolar duct endings in lung: a modified physical disector.

A novel modification of the physical disector is described which was used to estimate the total number of terminal bronchiolar duct endings (TBDEs) in human infant lung. TBDEs are closed three-dimensional space curves of complex shape that are inherently difficult to count from histological sections. However, careful consideration of the microanatomy of the terminal duct endings provides us with the opportunity to define a very simple and unbiased counting rule. To apply the rule in practice we also need to determine a suitable disector height. Owing to the complex shape of the TBDE we had no prior knowledge of what disector height would be suitable for counting the TBDE structures. Exhaustive serial sectioning of complete TBDE structures was carried out and showed that any disector height under 90 microm would give unbiased counts. A further empirical study was then undertaken to determine the most efficient disector height. This was found to be 50 micro. The total number of TBDEs in the upper lobe of the right lung of six human infants aged between 13 and 25 weeks was also estimated. The estimates of numerical density obtained with our modification of the physical disector were multiplied by estimates of lung lobe volume obtained using Cavalieri's Principle. The total number of TBDEs in the lobes ranged from 15 323 to 57 768, with a mean of 40 306. The average coefficient of error of the number estimates was 19%, which was deemed precise enough given the biological coefficient of variation between TBDE number of 36%.

Quantitative analysis of the development of experimentally induced post surgical adhesions: a microstereological study.

The aim of this study was to quantitatively define the development of post surgical adhesions (PSAs) in a well characterized experimental model and identify possible windows of pathogenesis where pharmaceutical intervention may be most effective. PSAs were induced, in an established rabbit uterine horn model, using standardized reproducible injury, in 17 experimental groups, each with 8 experimental sites and these PSAs were sampled from 30 seconds to 42 days post surgery. Using design based, unbiased stereology, mean volumes of PSAs and associated tissue damage and reaction per experimental site were calculated for each sample time point. PSA development followed the normal pattern of wound healing with surrounding adjacent tissue having a profound influence and interaction. There was a direct relationship between volume of damage (initial and subsequent) and the volume of injury tissue generated. In vivo weak fibrinous PSAs were present from 10 min following injury, with tenacious fibrinous PSAs present from 1 h and onwards. PSA development can be classified into two distinct stages: (i) PSA modelling - occurring during the first 16 h, in which maximum rate of PSA construction is achieved; and (ii) PSA remodelling - from 16 h onwards. Considering this, PSA prevention should ideally be initiated immediately post injury to prevent PSA modelling or, alternatively, during PSA modelling.