Biomedical subjects

Tracy C Grikscheit

Publications and source records attributed to Tracy C Grikscheit.

10 recordsLinked to original sources

PubMed2005

Cost considerations and applicant characteristics for the Pediatric Surgery Match.

BACKGROUND/PURPOSE: Formal training in pediatric surgery is highly competitive. The limited number of accredited positions has historically favored applicants with basic science experience, numerous publications, national presentations, and exposure to well-known pediatric surgeons. This review analyzes characteristics of successful applicants and cost associated with the Match. METHODS: A survey was e-mailed to 45 applicants after the 2003 Match. Geographic provenance, demographics, qualifications, costs, and valued program characteristics were assessed. Statistics were formulated by chi2 and Student's t test. RESULTS: Thirty-six applicants (80%) responded. Successful characteristics for matched vs unmatched included number of publications, 11.2 vs 5.7 (P < .01); first-author designation, 6.4 vs 3.1 (P = .02); basic science papers, 5.7 vs 1.7 (P < .01); national presentations, 5.8 vs 2.4 (P = .02); and presentations at pediatric surgical meetings, 2.0 vs 0.6 (P = .04). Ninety percent of matched applicants took time off to perform basic science research (P < .01). Average candidate expense was $6974, which represented 14% of pretax salary. Forty-one percent of applicants noted that cost limited the number of interviews taken. Fifty percent preferred a regional interview process to limit expense. Candidates ranked case diversity, volume, and mentor's advice as the most valued program characteristics. Successful applicants matched at their fifth rank on average. Eighty-six percent of unsuccessful applicants will reapply. CONCLUSIONS: Results of this study are important to those interested in the future of pediatric surgery. Successful applicants were shown to have several national presentations and multiple scientific publications, especially in basic sciences. Applicant costs are high, totaling more than $236,000 for survey respondents.

Adult↗

PubMed2004

Lymphangiogenesis in tissue-engineered small intestine.

BACKGROUND: Lymphangiogenesis, the formation of lymphatic vessels, has not been reported in engineered tissue. The purpose of this study was to characterize lymphangiogenesis in tissue-engineered small intestine. METHODS: Biodegradable polymer scaffolds seeded with intestinal organoid units were implanted into syngenic recipient rats. Twenty-three neointestinal grafts were harvested from adult rat recipients 1 to 8 weeks postimplantation. Cells expressing the lymphatic endothelial marker vascular endothelial growth factor receptor (VEGFR)-3 were detected immunohistochemically. The lymphangiogenic growth factor VEGF-C was quantified by enzyme-linked immunoadsorbent assay. RESULTS: Between the first and eighth weeks, neointestinal cysts increased in volume and mass. Muscular and mucosal layers increased in thickness and developed to resemble normal intestine histologically. The proportion of neointestinal VEGFR-3-positive cells increased and ultimately, tubular structures developed that resembled lymphatics architecturally, were distinct from CD34-positive blood vessels, and lacked luminal erythrocytes. CONCLUSION: Lymphangiogenesis occurs in tissue-engineered small intestine. This is the first demonstration of lymphatic vessels in an engineered tissue.

Animals↗

PubMed2004

Tissue-engineered small intestine improves recovery after massive small bowel resection.

OBJECTIVE: Rescue with tissue-engineered small intestine (TESI) after massive small bowel resection (MSBR). SUMMARY BACKGROUND DATA: Short bowel syndrome is a morbid product of massive small bowel resection. We report the first replacement of a vital organ by tissue engineering with TESI after MSBR. METHODS: Ten male Lewis rats underwent TESI implantation with green fluorescent protein (GFP)-marked cells (TESI+, n = 5) or sham laparotomy (TESI-, n = 5) followed by MSBR. Side-to-side anastomosis of TESI to proximal small intestine was performed or omitted. TESIO animals underwent implantation of engineered intestine with no further surgery. Weights were measured QOD until day 40. Transit times were measured. DNA assay was performed with computer morphometry. Northern blots of RNA were probed for intestinal alkaline phosphatase (IAP) and villin. Hematoxylin and eosin, S100, and smooth muscle actin immunohistochemistry were performed. Blood was collected at sacrifice. RESULTS: All 10 rats initially lost then regained weight. The initial rate of weight loss was higher in TESI+ versus TESI-, but the nadir was reached a week earlier with more rapid weight gain subsequently to 98% preoperative weight on day 40 in animals with engineered intestine versus 76% (P < 0.03). Serum B12 was higher at 439 pg/mL versus 195.4 pg/mL. IAP mRNA appeared greater in TESI+ than TESIO, with constant villin levels. Histology revealed appropriate architecture including nerve. GFP labeling persisted. CONCLUSIONS: Anastomosis of TESI significantly improved postoperative weight and B12 absorption after MSBR. IAP, a marker of differentiation in intestinal epithelium, is present in TESI, and GFP labeling was accomplished.

Actins↗

PubMed2003

Effect of GLP-2 on mucosal morphology and SGLT1 expression in tissue-engineered neointestine.

Using tissue-engineering techniques, we have developed a neointestine that regenerates the structural and dynamic features of native small intestine. In this study, we tested neointestinal responsiveness to glucagon-like peptide 2 (GLP-2). Neointestinal cysts were engineered by seeding biodegradable polymers with neonatal rat intestinal organoid units. The cysts were matured and anastomosed to the native jejunum of syngeneic adult recipients. Animals were treated with GLP-2 [Gly2] (twice daily, 1 microg/g body wt) or vehicle alone (control) for 10 days. Rats were then killed, and tissues were harvested for analysis. Na+-glucose cotransporter (SGLT1) mRNA expression was assessed with Northern blotting and in situ hybridization. SGLT1 protein was localized by using immunofluorescence. GLP-2 administration resulted in 1.8- and 1.7-fold increases (P < 0.05) in neointestinal villus height and crypt depth, respectively. GLP-2 administration also resulted in a 2.4-fold increase (P < 0.01) in neomucosal SGLT1 mRNA expression. SGLT1 mRNA expression was localized to enterocytes throughout the villi, and SGLT1 protein was localized to the brush border of enterocytes along the entire length of villi from the neointestine of GLP-2-treated animals. The response of tissue-engineered neointestine to exogenous GLP-2 includes mucosal growth and enhanced SGLT1 expression. Therefore, tissue-engineering principles may help in dissecting the regulatory mechanisms mediating complex processes in the intestinal epithelium.

Animals↗

PubMed2003

Tissue engineering of the gastrointestinal tract for surgical replacement: a nutrition tool of the future?

Optimal nutrition depends on the multiple complex functions performed by the gastrointestinal tract, which range from basic functions such as storage, conduit and mechanical processing to more finely regulated capabilities such as vectorial transport, immune defence and cell signalling. Surgical strategies to supply lacking gastrointestinal tract tissues have relied on either replacement by proxy (surgical substitution) or the introduction of prostheses. Tissue engineering seeks to replace missing tissues with engineered tissues that more accurately reproduce the native physiological and anatomical milieu. It is now possible to engineer several areas of the gastrointestinal tract with high fidelity, and to employ tissue-engineered bowel in replacement in animal models. These replacement models have reflected excellent anatomical and physiological recapitulation of native bowel by the tissue-engineered constructs in vivo.

Animals↗

PubMed2003

Angiogenesis in tissue-engineered small intestine.

Tissue-engineered intestine offers promise as a potential novel therapy for short bowel syndrome. In this study we characterized the microvasculature and angiogenic growth factor profile of the engineered intestine. Twenty-three tissue-engineered small intestinal grafts were harvested from Lewis rat recipients 1 to 8 weeks after implantation. Architectural similarity to native bowel obtained from juvenile rats was assessed with hematoxylin and eosin-stained sections. Capillary density, measured after immunohistochemical staining for CD34, was expressed as number of capillaries per 1000 nuclei. Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) tissue levels were measured by ELISA and normalized to total protein. Over the 8-week period cysts increased in volume (0.5 cm(3) at week 1 versus 12.6 cm(3) at week 8) and mass (1.30 +/- 0.29 versus 9.74 +/- 0.3 g; mean +/- SEM). Muscular and mucosal layers increased in thickness, but capillary density remained constant (82.95 +/- 4.81 capillaries per 1000 nuclei). The VEGF level was significantly higher in juvenile rat bowel than in engineered cyst (147.6 +/- 23.9 versus 42.3 +/- 3.4 pg/mg; p < 0.001). Tissue bFGF levels were also higher (315 +/- 65.48 versus 162.3 +/- 15.09 pg/mg; p < 0.05). The mechanism driving angiogenesis differs in engineered intestine and in normal bowel. VEGF and bFGF delivery may prove useful for bioengineering of intestine.

Aging↗

PubMed2003

Tissue-engineered large intestine resembles native colon with appropriate in vitro physiology and architecture.

OBJECTIVE: Novel production and in vitro characterization of tissue engineered colon. SUMMARY BACKGROUND DATA: The colon provides important functions of short chain fatty acid production, sodium and water absorption, and storage. We report the first instance of tissue-engineered colon (TEC) production from autologous cells and its in vitro characterization. METHODS: Organoid units, mesenchymal cell cores surrounded by a polarized epithelia derived from full thickness sigmoid colon dissection from neonatal Lewis rats, adult rats, and tissue engineered colon itself, were implanted on a polymer scaffold into the omentum of syngeneic hosts. TEC was either anastomosed at 4 weeks or excised for Ussing chamber studies or histology, immunohistochemistry, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-digoxigenin nick end labeling assay. RESULTS: TEC was generated by 100% of all animals without regard to tissue source, the first instance of engineered intestine from adult cells or an engineered tissue. TEC architecture is identical to native with muscularis propria staining for actin, acetylcholinesterase detected in a linear distribution in the lamina propria, S100-positive cells, ganglion cells, and a terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-digoxigenin nick end labeling assay similar to native colon. Ussing chamber data indicated in vitro function consistent with mature colonocytes, and a positive short circuit current response to theophylline indicating intact ion transfer. TEM showed normal microarchitecture. Colon architecture was maintained in anastomosis with gross visualization of fluid uptake. CONCLUSIONS: TEC can be successfully produced with fidelity to native architecture and in vitro function from neonatal syngeneic tissue, adult tissue, and TEC itself.

Animals↗

PubMed2002

Tissue-engineered small intestine: ontogeny of the immune system.

BACKGROUND: Using tissue-engineering techniques, we have developed a that regenerates structural and transporter properties of native jejunum. The purpose of this study was to characterize the mucosal immune system of the engineered neointestine. We hypothesized that the neointestinal mucosa is capable of developing a mature immunocyte population and that exposure to luminal stimuli is critical to this development. METHODS: Neointestinal cysts were engineered by implanting polymer-organoid constructs into syngeneic adult recipients. Neointestine (cysts left nonanastomosed [NA] and cysts anastomosed to native bowel [AN]) and native jejunum were harvested serially (3-56 weeks postoperatively). Immune cell subsets were characterized by the immunohistochemical detection of cell-specific antigens (T cells [CD3], B cells [CD32], NK cells [CD56], and macrophages [CD68]) combined with computer-based morphometry. RESULTS: Intraepithelial and lamina propria immunocyte population densities and subset distributions were identical in AN cysts harvested 20 weeks postoperatively and in native jejunum. Mucosal immunocyte population densities were lower in AN cysts harvested 10 weeks postoperatively and only rudimentary in NA cysts, even those harvested 20 weeks postoperatively. CONCLUSIONS: These results suggest that tissue-engineered intestine has the capacity to develop a mucosal immune system with an immunocyte population similar to that of native small intestine. The development of this immune system is a function of both exposure to luminal stimuli and the duration of this exposure. Tissue-engineered intestine offers promise as a new therapeutic approach for patients who have intestinal insufficiency.

Anastomosis, Surgical↗

PubMed2002

The history and current status of tissue engineering: The future of pediatric surgery.

Progress in the pediatric surgical treatment of numerous tissue deficits has been achieved through the relatively new field of tissue engineering. Tissue engineering has distinct advantages over native tissue or prosthetic substitution including self-repair and growth with the patient, avoiding multiple surgeries. The application of microfabrication has allowed more precision in the control of cell interactions and resulting tissue architecture.

Animals↗

PubMed2002

Tissue-engineered colon exhibits function in vivo.

BACKGROUND: Postcolectomy morbidities include important changes in enterohepatic circulation, stool microbiology, and absorption. The surgical substitution of an ileal pouch for the absent colon also has a number of serious complications. We report in vivo colon replacement by tissue-engineered colon (TEC) in lieu of an ileal pouch. METHODS: End-ileostomies were created in 22 male Lewis rats. In 11 animals, side-to-side ileum-TEC anastomosis was performed 1 cm from the stoma. This group was compared with end-ileostomy alone. Serial weights were measured, and animals were harvested sequentially for assessment of histologic signs of pouchitis. Transit times, stool dry and wet weights, and serum and stool colon function markers were collected. RESULTS: Animals survived 41 days. Weight loss was more than 1.5 times greater in the end-ileostomy alone group compared with the ileum-TEC group. Transit times were significantly longer in the ileum-TEC group than the end-ileostomy alone group, with lower stool moisture content and higher total serum bile acids. Animals without TEC had statistically significant hyponatremia, elevated serum urea nitrogen, and lower stool short chain fatty acids (13.5 micromol/kg vs 84.2) with an abnormal distribution. CONCLUSIONS: TEC successfully recapitulates some major physiologic functions of native large intestine in vivo.

Anastomosis, Surgical↗