Minna M. Wieck

Generation of tissue-engineered small intestine using embryonic stem cell-derived human intestinal organoids.

ABSTRACT Short bowel syndrome (SBS) is characterized by poor nutrient absorption due to a deficit of healthy intestine. Current treatment practices rely on providing supportive medical therapy with parenteral nutrition; while life saving, such interventions are not curative and are still associated with significant co-morbidities. As approaches to lengthen remaining intestinal tissue have been met with only limited success and intestinal transplants have poor survival outcomes, new approaches to treating SBS are necessary. Human intestine derived from embryonic stem cells (hESCs) or induced pluripotent stem cells (iPSCs), called human intestinal organoids (HIOs), have the potential to offer a personalized and scalable source of intestine for regenerative therapies. However, given that HIOs are small three-dimensional structures grown in vitro, methods to generate usable HIO-derived constructs are needed. We investigated the ability of hESCs or HIOs to populate acellular porcine intestinal matrices and artificial polyglycolic/poly L lactic acid (PGA/PLLA) scaffolds, and examined the ability of matrix/scaffolds to thrive when transplanted in vivo. Our results demonstrate that the acellular matrix alone is not sufficient to instruct hESC differentiation towards an endodermal or intestinal fate. We observed that while HIOs reseed acellular porcine matrices in vitro, the HIO-reseeded matrices do not thrive when transplanted in vivo. In contrast, HIO-seeded PGA/PLLA scaffolds thrive in vivo and develop into tissue that looks nearly identical to adult human intestinal tissue. Our results suggest that HIO-seeded PGA/PLLA scaffolds are a promising avenue for developing the mucosal component of tissue engineered human small intestine, which need to be explored further to develop them into fully functional tissue. Summary: HIO-seeded PGA/PLLA scaffolds thrive in vivo and develop into tissue that looks nearly identical to adult human intestinal tissue. These scaffolds appear to be suitable for further tissue engineering approaches to develop functional intestine.

Human and Murine Tissue-Engineered Colon Exhibit Diverse Neuronal Subtypes and Can Be Populated by Enteric Nervous System Progenitor Cells When Donor Colon Is Aganglionic.

PURPOSEnTissue-engineered colon (TEC) might potentially replace absent or injured large intestine, but the enteric nervous system (ENS), a key component, has not been investigated. In various enteric neuropathic diseases in which the TEC is derived from aganglionic donor colon, the resulting construct might also be aganglionic, limiting tissue engineering applications in conditions such as Hirschsprung disease (HD). We hypothesized that TEC might contain a diverse population of enteric neuronal subtypes, and that aganglionic TEC can be populated by neurons and glia when supplemented with ENS progenitor cells in the form of neurospheres.nnnMATERIALS AND METHODSnHuman and murine organoid units (OU) and multicellular clusters containing epithelium and mesenchyme were isolated from both mouse and human donor tissues, including from normally innervated and aganglionic colon. The OU were seeded onto a biodegradable scaffold and implanted within a host mouse, resulting in the growth of TEC. Aganglionic murine and human OU were supplemented with cultured neurospheres to populate the absent ENS not provided by the OU to rescue the HD phenotype.nnnRESULTSnTEC demonstrated abundant smooth muscle and clusters of neurons and glia beneath the epithelium and deeper within the mesenchyme. Motor and afferent neuronal subtypes were identified in TEC. Aganglionic OU formed TEC with absent neural elements, but neurons and glia were abundant when aganglionic OU were supplemented with ENS progenitor cells.nnnCONCLUSIONnMurine and human TEC contain key components of the ENS that were not previously identified, including glia, neurons, and fundamental neuronal subtypes. TEC derived from aganglionic colon can be populated with neurons and glia when supplemented with neurospheres. Combining tissue engineering and cellular replacement therapies represents a new strategy for treating enteric neuropathies, particularly HD.

Prolonged Absence of Mechanoluminal Stimulation in Human Intestine Alters the Transcriptome and Intestinal Stem Cell Niche

Background & Aims For patients with short-bowel syndrome, intestinal adaptation is required to achieve enteral independence. Although adaptation has been studied extensively in animal models, little is known about this process in human intestine. We hypothesized that analysis of matched specimens with and without luminal flow could identify new potential therapeutic pathways. Methods Fifteen paired human ileum samples were collected from children aged 2–20 months during ileostomy-reversal surgery after short-segment intestinal resection and diversion. The segment exposed to enteral feeding was denoted as fed, and the diverted segment was labeled as unfed. Morphometrics and cell differentiation were compared histologically. RNA Sequencing and Gene Ontology Enrichment Analysis identified over-represented and under-represented pathways. Immunofluorescence staining and Western blot evaluated proteins of interest. Paired data were compared with 1-tailed Wilcoxon rank-sum tests with a P value less than .05 considered significant. Results Unfed ileum contained shorter villi, shallower crypts, and fewer Paneth cells. Genes up-regulated by the absence of mechanoluminal stimulation were involved in digestion, metabolism, and transport. Messenger RNA expression of LGR5 was significantly higher in unfed intestine, accompanied by increased levels of phosphorylated signal transducer and activator of transcription 3 protein, and CCND1 and C-MYC messenger RNA. However, decreased proliferation and fewer LGR5+, OLFM4+, and SOX9+ intestinal stem cells (ISCs) were observed in unfed ileum. Conclusions Even with sufficient systemic caloric intake, human ileum responds to the chronic absence of mechanoluminal stimulation by up-regulating brush-border enzymes, transporters, structural genes, and ISC genes LGR5 and ASCL2. These data suggest that unfed intestine is primed to replenish the ISC population upon re-introduction of enteral feeding. Therefore, the elucidation of pathways involved in these processes may provide therapeutic targets for patients with intestinal failure. RNA sequencing data are available at Gene Expression Omnibus series GSE82147.

Management of pediatric intramuscular venous malformations

BACKGROUNDnIntramuscular venous malformations (VMs) are rare, but can be highly symptomatic. There are few reports on outcomes, particularly pain, functional limitations, and muscle contractures. We aimed to compare results of medical management, sclerotherapy, and surgical resection.nnnMETHODSnWe retrospectively reviewed 45 patients with an extremity or truncal intramuscular VM between June 2005 and June 2015 at a single institution. Outcomes were compared between treatment modalities with ANOVA and χ2 tests.nnnRESULTSnSix patients (13%) were treated with medical management, 4 (9%) with surgical resection, 23 (51%) with sclerotherapy, and 12 (27%) with both surgery and sclerotherapy. Sclerotherapy alone decreased pain in 72%. Only 20% of patients presented with muscle contracture. For these patients, 33% resolved with sclerotherapy, physical therapy, and aspirin; 22% resolved with surgery, and 45% had persistent contracture. 40% of patients treated with sclerotherapy then surgery developed new muscle contractures, compared to 4% of sclerotherapy only patients and 0% of surgery only patients (p=0.04).nnnCONCLUSIONSnMedical management, surgery and sclerotherapy are effective treatments for intramuscular VMs. Observation and supportive care can be a primary treatment for patients with minimal symptomatology and no functional limitations. Sclerotherapy is more effective for treating pain than contractures and when used alone, rarely causes a new muscle contracture.

The pediatric intestinal mucosal microbiome remains altered after clinical resolution of inflammatory and ischemic disease

BACKGROUNDnThe pediatric intestinal microbiome is impacted by many factors, including age, diet, antibiotics, and environment. We hypothesized that in operative patients, alterations to antibiotics and mechanoluminal stimulation would demonstrate measurable changes in the intestinal microbiome and that microbial diversity would be reduced without normal mechanoluminal stimulation and with prolonged antibiotic treatment.nnnMETHODSnBacterial 16s rRNA was extracted from swabbed samples of 43 intestines from 29 patients, aged 5xa0days to 13xa0years old. Swabs were obtained during initial resection or later stoma closure. Samples were compared using phylogenetic diversity whole tree alpha diversity and unweighted UniFrac distance beta diversity and by comparing significantly different taxonomic groups.nnnRESULTSnMicrobial community structure varied significantly between obstructive and inflammatory diseases (P = .001), with an effect size of 0.99 (0.97, 1.00). This difference persisted even 6xa0weeks after return to health. Family Enterobacter and Clostridiaceae predominated in patients with necrotizing enterocolitis or focal intestinal perforation; patients with an obstructive pathology had an abundance of Bacteroides. Comparison of UniFrac distance between paired proximal and distal intestines demonstrated that paired samples were significantly closer than any other comparison.nnnCONCLUSIONnIn infants, inflammatory and ischemic intestinal pathologies treated with prolonged courses of antibiotics durably alter the intestinal mucosal microbiome. Diversion of mechanoluminal stimulation, however, does not.

Sequestration of Vascular Endothelial Growth Factor (VEGF) Induces Late Restrictive Lung Disease.

Rationale Neonatal respiratory distress syndrome is a restrictive lung disease characterized by surfactant deficiency. Decreased vascular endothelial growth factor (VEGF), which demonstrates important roles in angiogenesis and vasculogenesis, has been implicated in the pathogenesis of restrictive lung diseases. Current animal models investigating VEGF in the etiology and outcomes of RDS require premature delivery, hypoxia, anatomically or temporally limited inhibition, or other supplemental interventions. Consequently, little is known about the isolated effects of chronic VEGF inhibition, started at birth, on subsequent developing lung structure and function. Objectives To determine whether inducible, mesenchyme-specific VEGF inhibition in the neonatal mouse lung results in long-term modulation of AECII and whole lung function. Methods Triple transgenic mice expressing the soluble VEGF receptor sFlt-1 specifically in the mesenchyme (Dermo-1/rtTA/sFlt-1) were generated and compared to littermate controls at 3 months to determine the impact of neonatal downregulation of mesenchymal VEGF expression on lung structure, cell composition and function. Reduced tissue VEGF bioavailability has previously been demonstrated with this model. Measurements and Main Results Triple transgenic mice demonstrated restrictive lung pathology. No differences in gross vascular development or protein levels of vascular endothelial markers was noted, but there was a significant decrease in perivascular smooth muscle and type I collagen. Mutants had decreased expression levels of surfactant protein C and hypoxia inducible factor 1-alpha without a difference in number of type II pneumocytes. Conclusions These data show that mesenchyme-specific inhibition of VEGF in neonatal mice results in late restrictive disease, making this transgenic mouse a novel model for future investigations on the consequences of neonatal RDS and potential interventions.

Doxycycline Sclerotherapy Is Superior in the Treatment of Pediatric Lymphatic Malformations

PURPOSEnTo evaluate efficacy of sclerotherapy with doxycycline versus sodium tetradecyl sulfate (STS) for treatment of macrocystic and mixed lymphatic malformations (LMs).nnnMATERIALS AND METHODSnThis single-center retrospective review identified 41 children (17 boys; 24 girls; age range, 1 month to 15.4 y) who underwent sclerotherapy with doxycycline (n = 32) or STS (n = 9) for macrocystic (n = 31) or mixed (n = 10) LMs. There were 114 treatments performed, averaging 2.8 treatments (range, 1-8 treatments) per patient. Average follow-up time was 10 months (range, 1-59 months). Clinical response was deemed excellent or moderate if > 90% or > 50% of LMs resolved based on visual estimate.nnnRESULTSnWith doxycycline, 87% of patients (28 of 32) had excellent or moderate response with an average of 2.8 treatments (range, 1-7 treatments); 13% required subsequent resection. With 3% STS monotherapy, only 55% of patients (5 of 9) had excellent or moderate response with an average of 2.8 treatments (range, 1-8 treatments), and 33% required subsequent resection. Significantly fewer patients treated with STS responded well compared with patients treated with doxycycline (P = .03). Patients treated with STS had significantly longer follow-up than patients treated with doxycycline (27 months vs 6 months, P = .0001).nnnCONCLUSIONSnDoxycycline monotherapy resulted in a high rate of excellent clinical outcomes after a few treatments without increased need for subsequent operative resection. These results support use of doxycycline sclerotherapy as primary treatment for macrocystic and mixed LMs in children.

Marked stem/progenitor cell expansion occurs early after murine ileostomy: a new model

BACKGROUNDnImproving treatment for short bowel syndrome requires a better understanding of how intestinal adaptation is affected by factors like mechanoluminal stimulation. We hypothesized that in mice, luminal diversion via an ileostomy would drive adaptive changes similar to those seen in human intestine after diversion while offering the opportunity to study the immediate events after resection that precede intestinal adaptation.nnnMATERIALS AND METHODSnWith Institutional Animal Care and Use Committee approval, a distal ileostomy with a long distal Hartmans was created in 9- to 14-week-old C57/B6 mice (nxa0=xa08). Control mice only had a midline laparotomy without stoma formation (nxa0=xa05). A rim of tissue from the proximal stoma was resected as a historical control for the proximal segment. Postoperatively, mice received a high-protein liquid diet and water ad libitum. On day 3, tissue from both the proximal and distal limbs were collected for histologic and RNA analysis. Morphometric measures, immunofluorescent antigen detection, and RNA expression were compared with Student paired t-tests with a P value < 0.05 considered significant.nnnRESULTSnAt 3xa0d, survival for mice with an ileostomy was 87% and average weight loss was 12.5% of initial weight compared to 6.05% for control mice. Compared to the distal limb, the proximal limb in mice with an ileostomy demonstrated significantly taller villi with deeper and wider crypts. The proximal limb also had decreased expression of intestinal stem cell markers lgr5, bmi1, sox9, and ascl2. Fewer goblet and enteroendocrine cells per hemivillus were also noted in the proximal limb. In control mice, none of these measures were significant between proximal and distal ileum except for villus height.nnnCONCLUSIONSnThis new murine ileostomy model allows study of intestinal adaptation without intestinal anastomosis, which can be technically challenging and morbid.