Lk Mitchard

Development of perioperative care for pigs undergoing laryngeal transplantation: a case series

Pigs are ideal animal models for airway surgical research, facilitating the successful translation of science into clinical practice. Despite their ubiquitous use, there is a paucity of information on the perioperative care of pigs, especially for major procedures. In a series of experiments to investigate laryngeal transplantation, we combined veterinary and medical experience to develop protocols for perioperative management of pigs, including high dependency care. Novel airway management methods were developed. A pain scoring system was used to direct analgesia use. Fluid balance and electrolytes were monitored closely. Recent animals received a central venous line via the femoral vein two days prior to transplantation to facilitate blood sampling and drug delivery. Intensive monitoring and airway management were required to ensure a successful outcome. Methods for optimal perioperative care are proposed. These results will help future groups wishing to use pigs in airway research, will reduce numbers of animals used and improve animal welfare.

Neonatal colonisation expands a specific intestinal antigen-presenting cell subset prior to CD4 T-cell expansion, without altering T-cell repertoire.

Interactions between the early-life colonising intestinal microbiota and the developing immune system are critical in determining the nature of immune responses in later life. Studies in neonatal animals in which this interaction can be examined are central to understanding the mechanisms by which the microbiota impacts on immune development and to developing therapies based on manipulation of the microbiome. The inbred piglet model represents a system that is comparable to human neonates and allows for control of the impact of maternal factors. Here we show that colonisation with a defined microbiota produces expansion of mucosal plasma cells and of T-lymphocytes without altering the repertoire of alpha beta T-cells in the intestine. Importantly, this is preceded by microbially-induced expansion of a signal regulatory protein α-positive (SIRPα+) antigen-presenting cell subset, whilst SIRPα−CD11R1+ antigen-presenting cells (APCs) are unaffected by colonisation. The central role of intestinal APCs in the induction and maintenance of mucosal immunity implicates SIRPα+ antigen-presenting cells as orchestrators of early-life mucosal immune development.

Effect of neurotrophin-3 on reinnervation of the larynx using the phrenic nerve transfer technique.

Current techniques for reinnervation of the larynx following recurrent laryngeal nerve (RLN) injury are limited by synkinesis, which prevents functional recovery. Treatment with neurotrophins (NT) may enhance nerve regeneration and encourage more accurate reinnervation. This study presents the results of using the phrenic nerve transfer method, combined with NT‐3 treatment, to selectively reinnervate the posterior cricoarytenoid (PCA) abductor muscle in a pig nerve injury model. RLN transection altered the phenotype and morphology of laryngeal muscles. In both the PCA and thyroarytenoid (TA) adductor muscle, fast type myosin heavy chain (MyHC) protein was decreased while slow type MyHC was increased. These changes were accompanied with a significant reduction in muscle fibre diameter. Following nerve repair there was a progressive normalization of MyHC phenotype and increased muscle fibre diameter in the PCA but not the TA muscle. This correlated with enhanced abductor function indicating the phrenic nerve accurately reinnervated the PCA muscle. Treatment with NT‐3 significantly enhanced phrenic nerve regeneration but led to only a small increase in the number of reinnervated PCA muscle fibres and minimal effect on abductor muscle phenotype and morphology. Therefore, work exploring other growth factors, either alone or in combination with NT‐3, is required.

A Model of Corneal Graft Rejection in Semi-Inbred NIH Miniature Swine: Significant T-Cell Infiltration of Clinically Accepted Allografts

PURPOSE The purpose of our study is to develop a pre-clinical model of corneal graft rejection in the semi-inbred NIH minipig as a model of human rejection. METHODS NIH minipigs received corneal allografts with MHC and minor mismatches, or minor mismatches alone. Clinical rejection was monitored, and major subsets of leukocytes and ingress of vessels were quantified post-mortem by automated digital methods. Spectratypes of recipient T-cell receptor β-subunit variable region (TRβV) were analyzed. The capacity of pig corneal endothelial cells to proliferate in vivo was assessed. RESULTS Autografts (n = 5) and SLA(cc) to SLA(cc) allografts (minor mismatches, n = 5) were not rejected. Median graft survival of SLA(dd) and SLA(bb) allografts in SLA(cc) strain recipients (major and minor mismatches) was 57 (n = 10) and 67 (n = 6) days, respectively. Rejected grafts did not recover clarity in vivo, and corneal endothelial cells did not proliferate in organ culture after cryo-injury. There were significantly more leukocytes in clinically rejected versus accepted grafts (P < 0.0001) and in transplanted versus contralateral eyes (P < 0.0001). Numbers of T-cells were significantly greater in clinically accepted grafts versus autografts and in rejected grafts versus accepted (P < 0.005 for most subsets). There were significant differences in TRβV spectratype between graft groups in cornea, but not in draining lymph node or blood (P < 0.05). CONCLUSIONS The NIH minipig offers a robust model of human rejection suitable for immunological or therapeutic studies. In particular, there is limited capacity for corneal endothelial repair in vivo, and histological evidence suggests that allosensitization of the recipient may develop in the absence of clinical rejection.

Laryngeal transplantation in minipigs: early immunological outcomes

Despite recent tissue‐engineering advances, there is no effective way of replacing all the functions of the larynx in those requiring laryngectomy. A recent clinical transplant was a success. Using quantitative immunofluorescence targeted at immunologically relevant molecules, we have studied the early (48 h and 1 week) immunological responses within larynxes transplantated between seven pairs of National Institutes of Health (NIH) minipigs fully homozygous at the major histocompatibility complex (MHC) locus. There were only small changes in expression of some molecules (relative to interindividual variation) and these were clearest in samples from the subglottic region, where the areas of co‐expression of CD25+CD45RC‐CD8‐ and of CD163+CD172+MHC‐II‐ increased at 1 week after transplant. In one case, infiltration by recipient T cells was analysed by T cell receptor (TCR) Vβ spectratype analysis; this suggested that changes in the T cell repertoire occur in the donor subglottis mucosal tissues from day 0 to day 7, but that the donor and recipient mucosal Vβ repertoires remain distinct. The observed lack of strong immunological responses to the trauma of surgery and ischaemia provides encouraging evidence to support clinical trials of laryngeal transplantation, and a basis on which to interpret future studies involving mismatches.

Genome-Wide Analysis in Swine Associates Corneal Graft Rejection with Donor-Recipient Mismatches in Three Novel Histocompatibility Regions and One Locus Homologous to the Mouse H-3 Locus

In rodents, immune responses to minor histocompatibility antigens are the most important drivers of corneal graft rejection. However, this has not been confirmed in humans or in a large animal model and the genetic loci are poorly characterised, even in mice. The gene sequence data now available for a range of relevant species permits the use of genome-wide association (GWA) techniques to identify minor antigens associated with transplant rejection. We have used this technique in a pre-clinical model of corneal transplantation in semi-inbred NIH minipigs and Babraham swine to search for novel minor histocompatibility loci and to determine whether rodent findings have wider applicability. DNA from a cohort of MHC-matched and MHC-mismatched donors and recipients was analysed for single nucleotide polymorphisms (SNPs). The level of SNP homozygosity for each line was assessed. Genome-wide analysis of the association of SNP disparities with rejection was performed using log-likelihood ratios. Four genomic blocks containing four or more SNPs significantly linked to rejection were identified (on chromosomes 1, 4, 6 and 9), none at the location of the MHC. One block of 36 SNPs spanned a region that exhibits conservation of synteny with the mouse H-3 histocompatibility locus and contains the pig homologue of the mouse Zfp106 gene, which encodes peptide epitopes known to mediate corneal graft rejection. The other three regions are novel minor histocompatibility loci. The results suggest that rejection can be predicted from SNP analysis prior to transplant in this model and that a similar GWA analysis is merited in humans.

Perioperative socialization, care and monitoring of National Institutes of Health miniature swine undergoing ocular surgery and sampling of peripheral blood

Swine are a frequent species of choice for testing new surgical procedures and for transplantation studies. However, information concerning best practice to prepare pigs for surgery and postoperative treatment and monitoring is limited, despite a perception that preoperative socialization is beneficial. Therefore we examined the effect of preoperative visits by project personnel on compliance of 26 National Institutes of Health (NIH) minipigs subject to corneal transplantation. We briefly describe sedation and anaesthesia protocols developed for surgery and multiple postoperative interventions in order to facilitate interpretation of data relating to pig compliance. Preoperative visit variables and measures of preoperative socialization were correlated with postoperative outcome. Principal component analysis (PCA) of postoperative outcome variables identified a factor accounting for 53.5% of the variance that was significantly associated with two factors derived from PCA of preoperative factors (accounting, respectively, for 54.7% and 26.0% of the variance; P = 0.019 for the overall model, P = 0.041 and 0.040 for factors 1 and 2, respectively), such that more time spent with pigs before surgery and higher socialization scores were associated with less postoperative stress and difficulty of eye medication. Moreover, two of the preoperative visit variables, time spent with only one person in the pen and time spent with two or more people in the pen, contributed predominantly to PCA factors 1 and 2, respectively, indicating that they were fulfilling two qualitatively different requirements for socialization. We conclude that NIH minipigs are fully compliant with anaesthetic and postoperative experimental procedures provided they are well-socialized to project personnel before surgery.

Erratum to: Laryngeal transplantation in minipigs: vascular, myologic and functional outcomes

The authors apologize for the following oversight during the publication process of the original article. The affiliations for three co-authors were incorrect. The correct details are provided below in the affiliations section. Although suitable permissions were obtained, the first publication and the permission granted by the publisher of the first publication were inadvertently not acknowledged for Figs. 2e and 4. The complete permission details are given below.