Anastomosis between tissue-engineered intestine and native small bowel

Effect of poly(3-hydroxyalkanoates) as natural polymers on mesenchymal stem cells

Mesenchymal stem cells (MSCs) are stromal multipotent stem cells that can differentiate into multiple cell types, including fibroblasts, osteoblasts, chondrocytes, adipocytes, and myoblasts, thus allowing them to contribute to the regeneration of various tissues, especially bone tissue. MSCs are now considered one of the most promising cell types in the field of tissue engineering. Traditional petri dish-based culture of MSCs generate heterogeneity, which leads to inconsistent efficacy of MSC applications. Biodegradable and biocompatible polymers, poly(3-hydroxyalkanoates) (PHAs), are actively used for the manufacture of scaffolds that serve as carriers for MSC growth. The growth and differentiation of MSCs grown on PHA scaffolds depend on the physicochemical properties of the polymers, the 3D and surface microstructure of the scaffolds, and the biological activity of PHAs, which was discovered in a series of investigations. The mechanisms of the biological activity of PHAs in relation to MSCs remain insufficiently studied. We suggest that this effect on MSCs could be associated with the natural properties of bacteria-derived PHAs, especially the most widespread representative poly(3-hydroxybutyrate) (PHB). This biopolymer is present in the bacteria of mammalian microbiota, whereas endogenous poly(3-hydroxybutyrate) is found in mammalian tissues. The possible association of PHA effects on MSCs with various biological functions of poly(3-hydroxybutyrate) in bacteria and eukaryotes, including in humans, is discussed in this paper.

Production of Tissue-Engineered Small Intestine in Rats with Different Ages of Cell Donors

IMPACT STATEMENT

This study compared side-by-side the impact of donor age on the production of tissue-engineered small intestine (TESI). Each age represents a specific period of life: E18 for fetuses, 5-day-old pups for neonates, 21-day-old rats for weanlings, and 6-week-old rats for adults. The TESI produced was compared macroscopically and microscopically. The mechanism(s) contributing to the differences observed was explored by detecting proliferating cells in the TESI and by analyzing intestinal stem cell gene expression in donor cells. These data may provide valuable information for future application of TESI clinically.

Tissue Engineering of the Small Intestine by Acellular Collagen Sponge Scaffold Grafting

Tissue engineering of the small intestine will prove a great benefit to patients suffering from short bowel disease. However cell seeding in tissue engineering, such as fetal cell use, is accompanied by problems of ethical issues, rejection, and short supply. To overcome these problems, we carried out an experimental study on tissue engineering of the small intestine by acellular collagen sponge scaffold grafting. We resected the 5 cm long jejunum from beagle dogs and reconstructed it by acellular collagen sponge grafting with a silicon tube stent. The graft was covered with the omentum. At 1 month after operation, the silicon stent was removed endoscopically. Animals were sacrificed 1 and 4 months after operation, and were examined microscopically. Neo-intestinal regeneration was observed and the intestinal mucosa covered the luminal side of the regenerated intestine across the anastomosis. Thus, the small intestine was regenerated by tissue engineering technology using an acellular collagen sponge scaffold.

Comparison of Different In Vivo Incubation Sites to Produce Tissue-Engineered Small Intestine

OBJECTIVE

The objective of this study was to compare the impact of different in vivo incubation sites on the production of tissue-engineered small intestine (TESI).

MATERIALS AND METHODS

Green fluorescent protein transgenic rat pups (3-5 days) were used as donors of intestinal organoids. Harvested intestine was exposed to enzymatic digestion to release intestinal stem cell-containing organoids. Organoids were purified, concentrated, and seeded onto tubular polyglycolic acid scaffolds. Seeded scaffolds were implanted in each of five locations in recipient female nude rats: wrapped with omentum, wrapped with intestinal mesentery, wrapped with uterine horn membrane, attached to the abdominal wall, and inserted into the subcutaneous space. After 4 weeks of in vivo incubation, specimens from each site were explanted for evaluation.

RESULTS

Wrapping seeded scaffolds with vascularized membranes produced TESI with variable lengths of vascularized pedicles, with the longest pedicle length from uterine horn membrane, the shortest pedicle length from intestinal mesentery, and intermediate length from omentum. The quantity of TESI, as expressed by volume and neomucosal length, was identical in TESI produced by wrapping with any of the three membranes. The smallest quantity of TESI was found in TESI produced from insertion into the subcutaneous space, with an intermediate quantity of TESI produced from attachment to the abdominal wall. Periodic acid-Schiff and immunofluorescence (IF) staining confirmed the presence of all intestinal epithelial cell lineages in TESI produced at all incubation sites. Additional IF staining demonstrated the presence of enteric nervous system components and blood vessels. Wrapping of seeded scaffolds with vascularized membranes significantly increased the density of blood vessels in the TESI produced.

CONCLUSION

Wrapping of seeded scaffolds in vascularized membranes produced the largest quantity and highest quality of TESI. Attaching seeded scaffolds to the abdominal wall produced an intermediate quantity of TESI, but the quality was still comparable to TESI produced in vascularized membranes. Insertion of seeded scaffolds into the subcutaneous space produced the smallest quantity and lowest quality of TESI. In summary, wrapping seeded scaffolds with vascularized membranes is favorable for the production of TESI, and wrapping with omentum may produce TESI that is most easily anastomosed with host intestine.

Tissue engineering for the treatment of short bowel syndrome in children

Short bowel syndrome is a major cause of morbidity and mortality in children. Despite decades of experience in the management of short bowel syndrome, current therapy is primarily supportive. Definitive treatment often requires intestinal transplantation, which is associated with significant morbidity and mortality. In order to develop novel approaches to the treatment of short bowel syndrome, we and others have focused on the development of an artificial intestine, by placing intestinal stem cells on a bioscaffold that has an absorptive surface resembling native intestine, and taking advantage of neovascularization to develop a blood supply. This review will explore recent advances in biomaterials, vascularization, and progress toward development of a functional epithelium and mesenchymal niche, highlighting both success and ongoing challenges in the field.

Tissue Engineering Functional Gastrointestinal Regions: The Importance of Stem and Progenitor Cells

The intestine shows extraordinary regenerative potential that might be harnessed to alleviate numerous morbid and lethal human diseases. The intestinal stem cells regenerate the epithelium every 5 days throughout an individual's lifetime. Understanding stem-cell signaling affords power to influence the niche environment for growing intestine. The manifold approaches to tissue engineering may be organized by variations of three basic components required for the transplantation and growth of stem/progenitor cells: (1) cell delivery materials or scaffolds; (2) donor cells including adult stem cells, induced pluripotent stem cells, and in vitro expansion of isolated or cocultured epithelial, smooth muscle, myofibroblasts, or nerve cells; and (3) environmental modulators or biopharmaceuticals. Tissue engineering has been applied to the regeneration of every major region of the gastrointestinal tract from esophagus to colon, with scientists around the world aiming to carry these techniques into human therapy.

Generation of an artificial intestine for the management of short bowel syndrome

PURPOSE OF REVIEW

This article discusses the current state of the art in artificial intestine generation in the treatment of short bowel syndrome.

RECENT FINDINGS

Short bowel syndrome defines the condition in which patients lack sufficient intestinal length to allow for adequate absorption of nutrition and fluids, and thus need parenteral support. Advances toward the development of an artificial intestine have improved dramatically since the first attempts in the 1980s, and the last decade has seen significant advances in understanding the intestinal stem cell niche, the growth of complex primary intestinal stem cells in culture, and fabrication of the biomaterials that can support the growth and differentiation of these stem cells. There has also been recent progress in understanding the role of the microbiota and the immune cells on the growth of intestinal cultures on scaffolds in animal models. Despite recent progress, there is much work to be done before the development of a functional artificial intestine for short bowel syndrome is successfully achieved.

SUMMARY

Continued concerted efforts by cell biologists, bioengineers, and clinician-scientists will be required for the development of an artificial intestine as a clinical treatment modality for short bowel syndrome.

Are synthetic scaffolds suitable for the development of clinical tissue-engineered tubular organs?

Transplantation of tissues and organs is currently the only available treatment for patients with end-stage diseases. However, its feasibility is limited by the chronic shortage of suitable donors, the need for life-long immunosuppression, and by socioeconomical and religious concerns. Recently, tissue engineering has garnered interest as a means to generate cell-seeded three-dimensional scaffolds that could replace diseased organs without requiring immunosuppression. Using a regenerative approach, scaffolds made by synthetic, nonimmunogenic, and biocompatible materials have been developed and successfully clinically implanted. This strategy, based on a viable and ready-to-use bioengineered scaffold, able to promote novel tissue formation, favoring cell adhesion and proliferation, could become a reliable alternative to allotransplatation in the next future. In this article, tissue-engineered synthetic substitutes for tubular organs (such as trachea, esophagus, bile ducts, and bowel) are reviewed, including a discussion on their morphological and functional properties.

Assessment of tissue-engineered stomach derived from isolated epithelium organoid units

OBJECTIVE

Isolated stomach epithelial organoid units developed on biodegradable polymers were transplanted to assess the feasibility of a tissue-engineered stomach.

BACKGROUND

Despite recent advances in reconstruction techniques, total gastrectomy is still accompanied by various complications. An alternative treatment would be a tissue-engineered stomach, which replaces the mechanical and metabolic functions of a normal stomach.

METHODS

Stomach epithelial organoid units isolated from neonatal rats were seeded onto biodegradable polymers. The constructs implanted into the omenta of adult rats were harvested for examination at designated times. Nine rats underwent a second operation for anastomosis.

RESULTS

The constructs resulted in cyst-like formations showing vascularized tissue with neomucosa lining the lumen. The surface morphology as assessed using scanning electron microscopy was similar to that of a native stomach. Immunohistochemical staining for alpha-actin smooth muscle and gastric mucin indicated the presence of a smooth muscle layer and a well-developed gastric epithelium, respectively. The luminal surface of the anastomosed tissue-engineered stomach was well-covered with epithelium.

CONCLUSIONS

Epithelium-derived stomach organoid units seeded on biodegradable polymers and transplanted into donor rats were shown to vascularize, survive, and regenerate into complex tissue resembling native stomach. Anastomosis between the units and native small intestine may have the potential to stimulate epithelial growth. This research may provide insight into new approaches to alleviate complications following total gastrectomy.

Long-term follow-up of tissue-engineered intestine after anastomosis to native small bowel

BACKGROUND

Our laboratory has investigated the fabrication of a tissue-engineered intestine using biodegradable polymer scaffolds. Previously we reported that isolated intestinal epithelial organoid units on biodegradable polymer scaffolds formed cysts and the neointestine was successfully anastomosed to the native small bowel. The purpose of this study was to observe the development of tissue-engineered intestine after anastomosis and to demonstrate the effect of the anastomosis over a 9-month period.

METHODS

Microporous biodegradable polymer tubes were created from polyglycolic acid. Intestinal epithelial organoid units were harvested from neonatal Lewis rats and seeded onto the polymers, which were implanted into the abdominal cavity of adult male Lewis rats followed by 75% small bowel resection (n=24). Three weeks after implantation, the unit/polymer constructs were anastomosed to the native jejunum in a side-to-side fashion. The anastomosed tissue-engineered intestine was measured by laparotomy 10, 24, and 36 weeks after the implantation (n= 14). During the laparotomy, all rats with an obstruction in their anastomosis were killed and excluded from the statistical analysis. Another five rats were also killed at 10 and 36 weeks for histological and morphometric studies.

RESULTS

All analyzed rats survived this study and significantly increased their body weight by 36 weeks. Obstruction of the anastomosis was observed in one rat at 24 weeks and in two rats at 36 weeks; however, the anastomosis was patent in the other 11 rats by 36 weeks. The tissue-engineered intestine of these 11 rats increased in length and diameter at 10, 24, and 36 weeks after anastomosis; there were statistically significant differences between each time point except between the length of 10 and 24 weeks (P<0.016 by Wilcoxon signed rank test). Histologically the inner surface of the tissue-engineered intestine was lined with well-developed neomucosa at 10 and 36 weeks; however, there were small bare areas lacking neomucosa in the tissue-engineered intestine at 36 weeks. Morphometric analysis demonstrated no significant differences in villus number, villus height, and surface length of the neomucosa at 10 and 36 weeks.

CONCLUSIONS

Anastomosis between tissue-engineered intestine and native small bowel resulted in no complications after operation and maintained a high patency rate for up to 36 weeks. The tissue-engineered intestine increased in size and was lined with well-developed neomucosa for the duration of the study.

End-to-end anastomosis between tissue-engineered intestine and native small bowel

The purpose of this study was to demonstrate the feasibility of end-to-end anastomosis between tissue-engineered intestine and native small bowel and to investigate the effect of this anastomosis on their growth. Microporous biodegradable polymer tubes were created from a fiber mesh of polyglycolic acid sprayed with 5% polylactic acid. Intestinal epithelial organoid units were harvested from neonatal Lewis rats and seeded onto polymers. These constructs were implanted into the omentum of adult Lewis rats. Three weeks after the implantation, the constructs (n = 7) were anastomosed to the native jejunum in an end-to-end fashion. Ten weeks after implantation, the tissue-engineered intestine was harvested. Four of 7 rats survived for 10 weeks and the overall patency rate of the anastomosis was 78% (11 of 14 anastomosis). The maximal length of the tissue-engineered intestine at week 3 and 10 was 1.80 +/- 0.32 and 1.93 +/- 0.39 cm (mean +/- SD). Histologically, the tissue-engineered intestine was lined with a well-developed neomucosal layer that was continuous with the native intestine. We conclude that anastomosis between tissue-engineered intestine and native small bowel had a moderately high patency rate and had a positive effect on maintenance of the size of the neointestine and development of the neomucosa.