Kathryn J. Rowland

Double-illumination photoacoustic microscopy

Recent developments of optical-resolution photoacoustic microscopy (OR-PAM) have improved its spatial resolution and imaging speed. However, the penetration depth of OR-PAM is still limited to ~1 mm in tissue, owing to the strong tissue scattering. Here, we have developed double-illumination PAM (DI-PAM), which illuminates the sample from both top and bottom sides simultaneously. Through phantom and in vivo experiments, we have demonstrated for thin targets that DI-PAM has a penetration depth of ~2 mm in tissue at 532 nm and a focal zone of 260 μm, both significant improvements over traditional reflection or transmission-mode OR-PAM.

The role of growth factors in intestinal regeneration and repair in necrotizing enterocolitis.

Necrotizing enterocolitis (NEC) is a devastating intestinal disease resulting in major neonatal morbidity and mortality. The pathology is poorly understood, and the means of preventing and treating NEC are limited. Several endogenous growth factors have been identified as having important roles in intestinal growth as well as aiding intestinal repair from injury or inflammation. In this review, we will discuss several growth factors as mediators of intestinal regeneration and repair as well as potential therapeutic agents for NEC.

Management of the Parathyroid Glands During Preventive Thyroidectomy in Patients With Multiple Endocrine Neoplasia Type 2.

OBJECTIVES Patients with multiple endocrine neoplasia type 2 (MEN2) have mutations in the RET protooncogene and virtually all of them will develop medullary thyroid carcinoma. Family members identified by genetic testing are candidates for preventive thyroidectomy. Management of the parathyroids during thyroidectomy is controversial. Some experts advocate total parathyroidectomy with autotransplantation, whereas others recommend preserving the parathyroids in situ. METHODS Between 1993 and 2000, we performed preventive thyroidectomies on 50 patients with MEN2A (group A). All patients had a central neck dissection (CND) combined with total parathyroidectomy and autotransplantation of parathyroid slivers to the nondominant forearm or to the neck. Between 2003 and the present, we performed 102 preventive thyroidectomies attempting to preserve the parathyroid glands in situ with an intact vascular pedicle (group B). Individual parathyroids were autotransplanted only if they appeared nonviable or could not be preserved intact. Central neck dissection was done only if the serum calcitonin was greater than 40 pg/mL. RESULTS Permanent hypoparathyroidism occurred in 3 (6%) of 50 patients in group A, compared with 1 (1%) of 102 patients in group B (P = 0.1). After total thyroidectomy, no patient in either group developed permanent recurrent laryngeal nerve injury or hyperparathyroidism. Immediate postoperative serum calcitonin levels were in the normal range (<5 pg/mL) in 100 of 102 patients in group B. No patients in either group have died. Oncologic follow-up of patients in group B is in progress. CONCLUSIONS In patients with MEN2A treated by preventive total thyroidectomy routine total parathyroidectomy with autotransplantation and CND gives excellent long-term results. However, preservation of the parathyroids in situ during preventive thyroidectomy combined with selective CND based on preoperative basal serum calcitonin levels is an effective and safe alternative that results in a very low incidence of hypoparathyroidism.

Immediate alterations in intestinal oxygen saturation and blood flow after massive small bowel resection as measured by photoacoustic microscopy

PURPOSE Massive small bowel resection (SBR) results in villus angiogenesis and a critical adaptation response within the remnant bowel. Previous ex vivo studies of intestinal blood flow after SBR are conflicting. We sought to determine the effect of SBR on intestinal hemodynamics using photoacoustic microscopy, a noninvasive, label-free, high-resolution in vivo hybrid imaging modality. METHODS Photoacoustic microscopy was used to image the intestine microvascular system and measure blood flow and oxygen saturation (So(2)) of the terminal mesenteric arteriole and accompanying vein in C57BL6 mice (n = 7) before and immediately after a 50% proximal SBR. A P value of less than .05 was considered significant. RESULTS Before SBR, arterial and venous So(2) were similar. Immediately after SBR, the venous So(2) decreased with an increase in the oxygen extraction fraction. In addition, the arterial and venous blood flow significantly decreased. CONCLUSION Massive SBR results in an immediate reduction in intestinal blood flow and increase in tissue oxygen utilization. These physiologic changes are observed throughout the remnant small intestine. The contribution of these early hemodynamic alterations may contribute to the induction of villus angiogenesis and the pathogenesis of normal intestinal adaptation responses.

Enterocyte Expression of Epidermal Growth Factor Receptor is Not Required for Intestinal Adaptation in Response to Massive Small Bowel Resection

PURPOSE Intestinal adaptation after massive small bowel resection (SBR) permits improved absorption of enteral nutrition despite significant loss of bowel length. Epidermal growth factor (EGF) and its receptor (EGFR) have previously been established to play major roles in the pathogenesis of adaptation. This study tested the hypothesis that EGFR signaling within the epithelial cell compartment (enterocytes) is required for intestinal adaptation. METHODS We developed a tamoxifen-inducible Villin-Cre/LoxP recombinant system for enterocyte-directed EGFR deletion using EGFR-floxed mice. Epidermal growth factor receptor-null mice and wild-type littermates underwent either 50% proximal SBR or sham operation. Ileal tissue was harvested on postoperative day 7. To assess for adaptation, villus height and crypt depth as well as rates of crypt cell proliferation and apoptosis were measured. RESULTS Adaptation after SBR occurred normally, as demonstrated by significant increases in villus height, crypt depth, and crypt proliferative and apoptotic index in both the wild-type and EGFR-null mice. CONCLUSION Enterocyte EGFR expression is not required for the adaptation response to massive SBR. This novel finding suggests that enterocyte proliferation during adaptation is regulated by EGFR signaling in cells other than enterocytes, perhaps within the mesenchymal cell compartment of the bowel wall via factor(s) that are presently unknown.

Pheochromocytoma in an 8‐year‐old patient with multiple endocrine neoplasia type 2A: Implications for screening

Childhood pheochromocytoma in the setting of multiple endocrine neoplasia type 2 (MEN2) remains rare and has not been reported under the age of 12. We present an 8‐year‐old female with known MEN 2A, C634Y RET mutation, diagnosed with a 6 cm pheochromocytoma requiring laparoscopic adrenalectomy. Given this patients age at diagnosis, screening guidelines should recommend annual screening beginning at age 8 for patients with MEN 2B or MEN 2A codons 630 or 634 RET mutations. J. Surg. Oncol. 2013 108:203–206.

Ret heterozygous mice have enhanced intestinal adaptation after massive small bowel resection

Intestinal adaptation is an important compensatory response to massive small bowel resection (SBR) and occurs because of a proliferative stimulus to crypt enterocytes by poorly understood mechanisms. Recent studies suggest the enteric nervous system (ENS) influences enterocyte proliferation. We, therefore, sought to determine whether ENS dysfunction alters resection-induced adaptation responses. Ret+/- mice with abnormal ENS function and wild-type (WT) littermates underwent sham surgery or 50% SBR. After 7 days, ileal morphology, enterocyte proliferation, apoptosis, and selected signaling proteins were characterized. Crypt depth and villus height were equivalent at baseline in WT and Ret+/- mice. In contrast after SBR, Ret+/- mice had longer villi (Ret+/- 426.7 ± 46.0 μm vs. WT 306.5 ± 7.7 μm, P < 0.001) and deeper crypts (Ret+/- 119 ± 3.4 μm vs. WT 82.4 ± 3.1 μm, P < 0.001) than WT. Crypt enterocyte proliferation was higher in Ret+/- (48.8 ± 1.3%) than WT (39.9 ± 2.1%; P < 0.001) after resection, but apoptosis rates were similar. Remnant bowel of Ret+/- mice also had higher levels of glucagon-like peptide 2 (6.2-fold, P = 0.005) and amphiregulin (4.6-fold, P < 0.001) mRNA after SBR, but serum glucagon-like peptide 2 protein levels were equal in WT and Ret+/- mice, and there was no evidence of increased c-Fos nuclear localization in submucosal neurons. Western blot confirmed higher crypt epidermal growth factor receptor (EGFR) protein levels (1.44-fold; P < 0.001) and more phosphorylated EGFR (2-fold; P = 0.003) in Ret+/- than WT mice after SBR. These data suggest that Ret heterozygosity enhances intestinal adaptation after massive SBR, likely via enhanced EGFR signaling. Reducing Ret activity or altering ENS function may provide a novel strategy to enhance adaptation attenuating morbidity in patients with short bowel syndrome.

CXCL5 is required for angiogenesis, but not structural adaptation after small bowel resection

PURPOSE Intestinal adaptation is the compensatory response to massive small bowel resection (SBR) and characterized by lengthening of villi and deepening of crypts, resulting in increased mucosal surface area. Previous studies have demonstrated increased villus capillary blood vessel density after SBR, suggesting a role for angiogenesis in the development of resection-induced adaptation. Since we have previously shown enhanced expression of the proangiogenic chemokine CXCL5 after SBR, the purpose of this study was to determine the effect of disrupted CXCL5 expression on intestinal adaptation. METHODS CXCL5 knockout (KO) and C57BL/6 wild type (WT) mice were subjected to either a 50% proximal SBR or sham operation. Ileal tissue was harvested on postoperative day 7. To assess for adaptation, villus height and crypt depth were measured. Submucosal capillary density was measured by CD31 immunohistochemistry. RESULTS Both CXCL5-KO and WT mice demonstrated normal structural features of adaptation. Submucosal capillary density increased in the WT but not in the KO mice following SBR. CONCLUSION CXCL5 is required for increased intestinal angiogenesis during resection-induced adaptation. Since adaptive villus growth occurs despite impaired CXCL5 expression and enhanced angiogenesis, this suggests that the growth of new blood vessels is not needed for resection-induced mucosal surface area expansion following massive SBR.

Hereditary thyroid cancer syndromes and genetic testing

This review focuses on both hereditary medullary thyroid cancer (MTC) and hereditary nonmedullary thyroid cancer (NMTC) and discusses the genetics, clinical diagnosis and evaluation, and surgical approach to treatment of these malignancies. Areas of innovation as well as areas of debate are highlighted and management recommendations are made. J. Surg. Oncol. 2015 111:51–60.

Up-regulation of hypoxia-inducible factor 1 alpha and hemodynamic responses following massive small bowel resection

PURPOSE Massive small bowel resection (SBR) results in an adaptive response within the remnant bowel. We have previously shown an immediate reduction in intestinal blood flow and oxygen saturation (sO2) after SBR. We therefore sought to determine the duration of resection-induced intestinal hypoxia and expression of hypoxia-inducible factors (HIFs) following SBR. METHODS C57B6 mice were subjected to 50% proximal SBR or a sham procedure. Photoacoustic microscopy (PAM) was used to measure blood flow and sO2 on postoperative days (PODs) 1, 3, and 7. Ileal tissue was harvested 6h postoperatively and on PODs 1 and 2, and HIF1α, HIF2α, and VEGF mRNA expression were assessed via RT-PCR. A p value of less than 0.05 was considered significant. RESULTS Following SBR, reduction in intestinal blood flow persists for 24h and is followed with hyperemia by POD 3. The immediate reduction in venous sO2 and increased tissue oxygen utilization continued through POD 7. Enhanced expression of HIF1α was demonstrated 6h following SBR. CONCLUSION Massive SBR results in an immediate relative hypoxic state within the remnant bowel with early enhanced expression of HIF1α. On POD 7, increased tissue oxygen extraction and elevated blood flow persist in the adapting intestine.