Orthogonal polarization spectral imaging: a new tool in morphologic surveillance in intestinal transplant recipients

Endoscopic Surveillance of the Intestinal Allograft: Recommendations From the Intestinal Rehabilitation and Transplant Association Working Group

Intestinal transplant (ITx) rejection lacks a reliable noninvasive biomarker and rejection surveillance relies on serial endoscopies and mucosal biopsies followed by histologic assessment. Endoscopic biopsies are also essential for identifying other ITx-related complications such as infectious, allergic, and inflammatory graft enteritis as well as post-transplant lymphoproliferative disease or graft versus host disease. In spite of its central role in ITx, published guidelines on endoscopy and biopsy are lacking and significant variability between centers in terms of timing and technical performance exists. Therefore, an international expert group convened and discussed several aspects related to the surveillance endoscopy after ITx with the aim to summarize and standardize its practice. This article summarizes these considerations on endoscopic ITx monitoring and highlights practices of surveillance and for-cause endoscopy, biopsy techniques, pathologic evaluation, potential risks and complications, outsourcing, and less-invasive monitoring techniques.

Acute Rejection After Kidney Transplantation Associates With Circulating MicroRNAs and Vascular Injury

Supplemental digital content is available in the text.

Background

Acute rejection (AR) of kidney transplants is associated with the loss of endothelial integrity, microvascular rarefaction and, ultimately, graft dysfunction. Circulating angiogenic microRNAs (miRNAs) may serve as markers for microvascular injury. Here, we investigated the short- and long-term effects of AR after kidney transplantation on systemic vascular injury and the associated circulating miRNA profile.

Methods

Systemic vascular injury was determined by measuring capillary tortuosity and density within the oral mucosa as well as by assessing circulating levels of angiopoietin-2/angiopoietin-1 ratio, vascular endothelial growth factor and soluble thrombomodulin. After a pilot study, we selected 48 miRNAs to assess the AR- and microvascular injury associated circulating miRNAs.

Results

In stable transplant recipients (n = 25) and patients with AR (n = 13), which were also studied longitudinally (1, 6, and 12 months post-AR), we found an AR-associated increase in markers of systemic vascular injury, of which vascular endothelial growth factor and soluble thrombomodulin normalized within 1 year after AR. Of the 48 selected miRNAs, 8 were either decreased (miR-135a, miR-199a-3p, and miR-15a) or increased (miR-17, miR-140-3p, miR-130b, miR-122 and miR-192) in AR. Of these, miR-130b, miR-199a, and miR-192 associated with markers of vascular injury, whereas miR-140-3p, miR-130b, miR-122, and miR-192 normalized within 1 year after AR.

Conclusions

AR after kidney transplantation is characterized by systemic microvascular injury and associates with specific circulating miRNA levels.

Everolimus Improves Microcirculatory Derangements in Experimental Postischemic Pancreatitis Modulating the Expression of Vascular Endothelial Growth Factor, Interleukin 6, and Toll-Like Receptor 4

OBJECTIVES

Ischemia/reperfusion injury (IRI) of the pancreas is a serious complication following pancreatic transplantation and hemorrhagic shock. The present study was designed to investigate the influence of the potent mammalian target of rapamycin inhibitor everolimus interfering via microvascular permeability changing key proteins hypoxia-inducible factor (HIF) and vascular endothelial growth factor on pancreatic IRI-induced microvascular disturbances.

METHODS

Anesthetized male Sprague-Dawley rats were assigned to 3 groups (n = 7/group): (1) sham, (2) 60-minute ischemia/reperfusion of the pancreas (I/R), and (3) I/R and everolimus (10 mg/kg BW orally). Quantification of the effective microvascular permeability (P), functional capillary density (FCD), and leukocyte-endothelial cell interaction (LEI) was performed using digital and analog intravital epifluorescence microscopy. Serum-amylase, lipase, interleukin 6, and vascular endothelial growth factor concentration were quantified using enzyme-linked immunosorbent assay.

RESULTS

Sham compared with I/R (P: [×10 cm/s] 0.068 ± 0.079 vs 1.516 ± 0.314; FCD: [cm/cm] 357 ± 14 vs 258 ± 13; LEI: [cells/mm] 148 ± 25 vs 349 ± 75) demonstrates a significant increase in microcirculatory damage and all previously mentioned serum parameters. Except amylase, I/R + everolimus led to a statistically significant improvement of almost all increased parameters (P: 0.434 ± 0.296, FCD: 347 ± 16, LEI: 178 ± 30).

CONCLUSIONS

Everolimus attenuated experimental microvascular and inflammatory IRI of the pancreas. Therefore, these results may warrant further investigation of everolimus as a therapeutic agent following clinical states with pancreatic ischemia/reperfusion.

Laser-Doppler flowmetry in the monitoring of the human intestinal allograft: a preliminary report

During acute rejection, graft endothelium becomes a prime target for recipient immune cells. Animal studies have shown reduced microvascular perfusion, probably due to increased endothelial-leukocyte interaction and endothelial impairment, leading to graft damage. Using laser-Doppler flowmetry (LDF), we correlated the microvascular blood flow in the intestinal mucosa of five patients receiving multivisceral grafts with clinical events and pathology results. Measurements (n = 75) were performed during the first 4 weeks posttransplantation by inserting the LDF flexible probe through the ileostomy for 25 to 30 cm. Forty-six of the 75 measurements were performed within 24 hours of endoscopy and biopsy. In uncomplicated cases, we recorded a gradual increase in mucosal perfusion during the first week posttransplantation that presumably reflected regeneration after reperfusion injury. Increased mucosal perfusion did not seem to correlate with rejection or other adverse clinical events. Sudden and sustained decreases in mucosal perfusion by 30% or more compared to the previous measurements were associated with septic episodes, rejection, or both. LDF revealed a good sensitivity in monitoring the intestinal microcirculation. It was able to indicate perfusion changes associated with acute rejection. The relatively low specificity of LDF may be compensated by the low invasivity, allowing frequent investigation. LDF may be an additional tool for routine monitoring of intestinal allografts.

Twenty-Seven Consecutive Intestinal and Multivisceral Transplants in Adult Patients: A 4-Year Clinical Experience

Adult isolated intestinal and multivisceral transplantation is gaining acceptance as the standard treatment for patients with intestinal failure with life-threatening parenteral nutrition-related complications. We report our 4-year experience with intestinal and multivisceral transplantation. We performed 20 isolated small bowel and seven multivisceral ones, including three with liver. The underlying diseases were mainly short bowel syndrome due to intestinal infarction, chronic intestinal pseudo-obstruction, and Gardner syndrome. Indications for transplant were loss of central venous access in 14 patients, recurrent sepsis in eight patients, and major electrolyte and fluid imbalance in five patients. One-year patient actuarial survival rate was 94% for isolated intestinal transplants and 42% for multivisceral recipients (P = .003), while 1-year graft actuarial survival rate was 88.4% for isolated small bowel patients and 42.8% for multivisceral ones (P = .01). The death rate was 18.5%. Our graftectomy rate was 14.8%. Our immunosuppressive protocols were based on induction agents such as alemtuzumab, daclizumab, and antithymocyte globulins. The majority of our complications were bacterial infections, followed by rejections and relaparotomies; most rejection episodes were treated with steroid boluses and tapering. We believe that our results were due to optimal candidate and donor selection, short ischemia time, and use of induction therapy. Multivisceral transplantation is a more complex procedure with less frequent clinical indications than isolated small bowel transplant, but our data concerning multivisceral transplants include only a small number of patients and require further evaluation.

Observations on the microcirculation of the human burn wound using orthogonal polarization spectral imaging

Orthogonal polarization spectral imaging (OPS) utilizes the illumination of the tissue with polarized light within the haemoglobin spectrum. We report here on OPS for the assessment of the skin microcirculation non-invasively through the surface of the human burn wound. This allows inspection of individual capillaries of the cutaneous microcirculation and flow through these vessels in real time. Two distinct microcirculatory patterns were seen. Superficial burns had small visible dermal capillaries studied throughout the field of view. The flow of individual erythrocytes through these capillaries was clearly visible in real-time. Conversely, deep burns showed large thrombosed vessel coursing in a criss-cross fashion. There was marked difference between the mean optical densities for normal skin and superficial burns (65.8+/-15.6 and 64+/-14.6, respectively) and deep burns (131.2+/-31.1). These findings indicate that OPS may have utility in the assessment of cutaneous microcirculation in burns.

Three-year experience in clinical intestinal transplantation

BACKGROUND

The purpose of this study was to evaluate the outcome of 19 patients who underwent intestinal transplantation (ITx) for intestinal failure.

METHODS

The 19 patients who underwent primary ITx between December 2000 and May 2003 were prescribed three different immunosuppressive protocols that included daclizumab, alemtuzumab, and antithymocyte globulin induction, respectively. A mucosal surveillance protocol for early detection of rejection consisted of zoom video endoscopy and serial biopsies associated with orthogonal polarization spectral imaging. Retrospective review of the clinical records was performed to assess the impact of new modalities of immunosuppression and intestinal mucosal monitoring on patient outcomes.

RESULTS

All patients were adults (mean age 35.8 years). Etiology of intestinal failure included chronic intestinal pseudo-obstruction (n = 6), intestinal angiomatosis (n = 1), Gardner syndrome (n = 2), intestinal infarction (n = 8), radiation enteritis (n = 1), and intestinal atresia (n = 1). All patients experienced complications from total parenteral nutrition (TPN). Thirteen patients (68.4%) received isolated small bowel, whereas six (31.6%) received multivisceral grafts with or without the liver. Thirteen of 19 patients experienced at least one episode of rejection (68.4%). Most ACR episodes were treated with steroid boluses and resolved completely within 5 days. The overall 1-year patient survival was 82%. All living patients are in good health with functioning grafts having been weaned off TPN after a mean of 23.7 days post-ITx.

DISCUSSION

Advances in immunosuppressive therapy with early detection and prompt treatment of rejection episodes make ITx a valuable treatment option for patients with intestinal failure and TPN-related life-threatening complications.

Minimally Invasive, In Vivo Exploration of Mouse Small Artery Reactivity

The aim of the study was to investigate in vivo arterial reactivity in the mouse hind limb using Orthogonal Polarisation Spectral (OPS) imaging, which delivers high-contrast images of vascular beds by visualizing red blood cells. After minimal skin invasion of anesthetized mice, the OPS probe was placed on the hind limb continuously superfused with physiological saline solution. Then, the response of the saphenous artery (average luminal diameter 127 +/- 3 microm; n = 15) to topical application of increasing concentrations of acetylcholine or phenylephrine was examined. Mean carotid arterial blood pressure was unaffected during the experiment. The basal diameter decreased by 70% during exposure to phenylephrine (pD2: 5.65 +/- 0.08; n = 9), while acetylcholine augmented basal diameter up to 199% (pD2: 6.55 +/- 0.12; n = 6). Application of sodium nitroprusside did not further increase arterial diameter following acetylcholine exposure. After washing out, arterial luminal diameters returned to initial values. Second exposure to vasoactive agents demonstrated that changes in diameter were reproducible with time and not different between left and right saphenous arteries. Thus, OPS imaging is an in vivo dye-free, simple and minimally invasive approach, which provides unique information regarding the behavior of vascular network within conditions of cellular and physiological homeostasis.