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

Nontransplant Surgery for Intestinal Failure

Insufficient absorptive mucosal surface is the fundamental problem in the short bowel state. Intestinal adaptation has been well studied, and it is well recognized that it may lead to dilatation of the bowel with increased thickness of the bowel wall, resulting from both mucosal hypertrophy and hyperplasia. Autologous reconstructive surgery exploits bowel dilatation in short bowel syndrome and maximizes the absorptive potential of the available mucosal surface. Indeed, autologous gastrointestinal reconstructive procedures may be better viewed as optimizing bowel diameter rather than focusing on length, thus allowing better prograde peristalsis and improved contact between luminal nutrients and mucosa, ultimately enhancing absorption.

Composite Scaffolds Based on Intestinal Extracellular Matrices and Oxidized Polyvinyl Alcohol: A Preliminary Study for a New Regenerative Approach in Short Bowel Syndrome

Pediatric Short Bowel Syndrome is a rare malabsorption disease occurring because of massive surgical resections of the small intestine. To date, the issues related to current strategies including intestinal transplantation prompted the attention towards tissue engineering (TE). This work aimed to develop and compare two composite scaffolds for intestinal TE consisting of a novel hydrogel, that is, oxidized polyvinyl alcohol (OxPVA), cross-linked with decellularized intestinal wall as a whole (wW/OxPVA) or homogenized (hW/OxPVA). A characterization of the supports was performed by histology and Scanning Electron Microscopy and their interaction with adipose mesenchymal stem cells occurred by MTT assay. Finally, the scaffolds were implanted in the omentum of Sprague Dawley rats for 4 weeks prior to being processed by histology and immunohistochemistry (CD3; F4/80; Ki-67; desmin; α-SMA; MNF116). In vitro studies proved the effectiveness of the decellularization, highlighting the features of the matrices; moreover, both supports promoted cell adhesion/proliferation even if the wW/OxPVA ones were more effective (p < 0.01). Analysis of explants showed a continuous and relatively organized tissue wall around the supports with a connective appearance, such as myofibroblastic features, smooth muscle, and epithelial cells. Both scaffolds, albeit with some difference, were promising; nevertheless, further analysis will be necessary.

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.

Advancing Intestinal Organoid Technology Toward Regenerative Medicine

With the emergence of technologies to culture intestinal epithelial cells in vitro as various forms of intestinal organoids, there is growing interest in using such cultured intestinal cells as a source for tissue engineering and regenerative medicine. One such approach would be to combine the organoid technology with methodologies to engineer the culture environment, particularly the three-dimensional scaffold materials, to generate intestines that exquisitely recapitulate their original structures and functions. Another approach to use organoids for regenerative medicine would be to urge them to mature into functional intestines by implanting them into hosts. This process includes the tissue-engineered small intestine that uses synthetic scaffolds for tissue regeneration and direct organoid transplantation that takes advantage of submucosal tissues in the native intestines as a scaffold. Further study in these subfields could lead to the development of therapeutic options to use different types of organoids with various cell types in regenerative medicine for intestinal diseases in humans.

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.

hPSC-derived lung and intestinal organoids as models of human fetal tissue

In vitro human pluripotent stem cell (hPSC) derived tissues are excellent models to study certain aspects of normal human development. Current research in the field of hPSC derived tissues reveals these models to be inherently fetal-like on both a morphological and gene expression level. In this review we briefly discuss current methods for differentiating lung and intestinal tissue from hPSCs into individual 3-dimensional units called organoids. We discuss how these methods mirror what is known about in vivo signaling pathways of the developing embryo. Additionally, we will review how the inherent immaturity of these models lends them to be particularly valuable in the study of immature human tissues in the clinical setting of premature birth. Human lung organoids (HLOs) and human intestinal organoids (HIOs) not only model normal development, but can also be utilized to study several important diseases of prematurity such as respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD), and necrotizing enterocolitis (NEC).

Organoid Models of Human Gastrointestinal Development and Disease

We have greatly advanced our ability to grow a diverse range of tissue-derived and pluripotent stem cell-derived gastrointestinal (GI) tissues in vitro. These systems, broadly referred to as organoids, have allowed the field to move away from the often nonphysiological, transformed cell lines that have been used for decades in GI research. Organoids are derived from primary tissues and have the capacity for long-term growth. They contain varying levels of cellular complexity and physiological similarity to native organ systems. We review the latest discoveries from studies of tissue-derived and pluripotent stem cell-derived intestinal, gastric, esophageal, liver, and pancreatic organoids. These studies have provided important insights into GI development, tissue homeostasis, and disease and might be used to develop personalized medicines.

Evidence of Absorptive Function in vivo in a Neo-Formed Bio-Artificial Intestinal Segment Using a Rodent Model

A promising therapeutic approach for intestinal failure consists in elongating the intestine with a bio-engineered segment of neo-formed autologous intestine. Using an acellular biologic scaffold (ABS), we, and others, have previously developed an autologous bio-artificial intestinal segment (BIS) that is morphologically similar to normal bowel in rodents. This neo-formed BIS is constructed with the intervention of naïve stem cells that repopulate the scaffold in vivo, and over a period of time, are transformed in different cell populations typical of normal intestinal mucosa. However, no studies are available to demonstrate that such BIS possesses functional absorptive characteristics necessary to render this strategy a possible therapeutic application. The aim of this study was to demonstrate that the BIS generated has functional absorptive capacity. Twenty male August × Copenhagen-Irish (ACI) rats were used for the study. Two-centimeter sections of ABS were transplanted in the anti-mesenteric border of the small bowel. Animals were studied at 4, 8, and 12 weeks post-engraftment. Segments of intestine with preserved vascular supply and containing the BIS were isolated and compared to intestinal segments of same length in sham control animals (n = 10). D-Xylose solution was introduced in the lumen of the intestinal segments and after 2 h, urine and blood were collected to evaluate D-Xylose levels. Quantitative analysis was performed using ELISA. Morphologic, ultrastructural, and indirect functional absorption analyses were also performed. We observed neo-formed intestinal tissue with near-normal mucosa post-implantation as expected from our previously developed model. Functional characteristics such as morphologically normal enterocytes (and other cell types) with presence of brush borders and preserved microvilli by electron microscopy, preserved water, and ion transporters/channels (by aquaporin and cystic fibrosis transmembrane conductance regulator (CFTR)) were also observed. The capacity of BIS containing neo-formed mucosa to increase absorption of d-Xylose in the blood compared to normal intestine was also confirmed. With this study, we demonstrated for the first time that BIS obtained from ABS has functional characteristics of absorption confirming its potential for therapeutic interventions.

Stem cells and biopharmaceuticals: vital roles in the growth of tissue-engineered small intestine

Tissue engineering currently constitutes a complex, multidisciplinary field exploring ideal sources of cells in combination with scaffolds or delivery systems in order to form a new, functional organ to replace native organ lack or loss. Short bowel syndrome (SBS) is a life-threatening condition with high morbidity and mortality rates in children. Current therapeutic strategies consist of costly and risky allotransplants that demand lifelong immunosuppression. A promising alternative is the implantation of autologous organoid units (OU) to create a tissue-engineered small intestine (TESI). This strategy is proven to be stem cell and mesenchyme dependent. Intestinal stem cells (ISCs) are located at the base of the crypt and are responsible for repopulating the cycling mucosa up to the villus tip. The stem cell niche governs the biology of ISCs and, together with the rest of the epithelium, communicates with the underlying mesenchyme to sustain intestinal homeostasis. Biopharmaceuticals are broadly used in the clinic to activate or enhance known signaling pathways and may greatly contribute to the development of a full-thickness intestine by increasing mucosal surface area, improving blood supply, and determining stem cell fate. This review will focus on tissue engineering as a means of building the new small intestine, highlighting the importance of stem cells and recombinant peptide growth factors as biopharmaceuticals.

Gastrointestinal tissue engineering

Tissue engineering is an emerging discipline that combines engineering principles and the biological sciences toward the development of functional replacement tissue. Virtually every tissue in the body has been investigated and tremendous advances have been made in many areas. This article focuses on the gastrointestinal tract and reviews the current status of bioengineering gastrointestinal tissues, including the esophagus, stomach, small intestine and colon. Although progress has been achieved, there continues to be significant challenges that need to be addressed.

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.

Cell transplantation in surgical treatment of familial adenomatous polyposis coli

We developed a method of surgical treatment of familial adenomatous polyposis coli giving an opportunity to prevent the growth of new polyps in the preserved part of the rectum and consisting in transplantation of fetal cells of the epithelial origin into the rectum wall after mucosectomy. Since the rectum is partially preserved, ileorectal anastomosis can be formed after colectomy, which preserves natural bowel passage. Complex examination 4 weeks after surgery revealed the formation of normal rectal mucosa. No new polyps were detected in the rectum 1-3 years after surgery.

Scaffold Characteristics for Functional Hollow Organ Regeneration

Many medical conditions require surgical reconstruction of hollow organs. Tissue engineering of organs and tissues is a promising new technique without harvest site morbidity. An ideal biomaterial should be biocompatible, support tissue formation and provide adequate structural support. It should degrade gradually and provide an environment allowing for cell-cell interaction, adhesion, proliferation, migration, and differentiation. Although tissue formation is feasible, functionality has never been demonstrated. Mainly the lack of proper innervation and vascularisation are hindering contractility and normal function. In this chapter we critically review the current state of engineering hollow organs with a special focus on innervation and vascularisation.

The role of basic fibroblast growth factor to enhance fetal intestinal mucosal cell regeneration in vivo

BACKGROUND/PURPOSE

The limited application of small bowel transplantation for short bowel syndrome, mainly on the account of the morbidity and long-term implications of the procedure, has led to a search for alternative therapies. The purpose of this study was to evaluate whether basic fibroblast growth factor (bFGF) could facilitate regeneration of fetal small intestinal mucosa in vivo.

METHODS

Intestinal epithelial organoid units harvested from fetal Lewis rats were injected into adult male Lewis rats whose colon was denuded of mucosa, as syngeneic recipients. One experimental group transplanted with the addition of 50 ng/ml bFGF, was compared with a control group that were transplanted without bFGF. The grafts were harvested and analyzed using histology and immunohistochemistry 3 weeks after operation.

RESULTS

There were 4 anesthetic deaths, two in each group, and 11 deaths due to adhesive ileus. In no rat did neomucosa fully cover the denuded colonic muscle throughout the whole length of lumen. Histologically, the structure of the neomucosa, when present, was normal small intestinal mucosa. The small intestinal mucosa was partially restored in 100% (6 of 6) of bFGF, and in 28.6% (2 of 7) of those not given bFGF (P = 0.0021).

CONCLUSIONS

These data demonstrate that bFGF can facilitate the restoration of intestinal epithelial cells, at least to some degree. Potentially, refinements of this technique could be used to facilitate the physiologic tissue engineering of small intestine in a way that allows it to move peristaltically, and have an application in the management of patients with short bowel syndrome.

A perfusion bioreactor for intestinal tissue engineering

BACKGROUND

Short gut syndrome is a devastating clinical problem with limited long-term treatment options. A unique characteristic of the normal intestinal epithelium is its capacity for regeneration and adaptation. Despite this tremendous capacity in vivo, one of the major limitations in advancing the understanding of intestinal epithelial differentiation and proliferation has been the difficulty in maintaining primary cultures of normal gut epithelium in vitro. A perfusion bioreactor system has been shown to be beneficial in long-term culture and bioengineering of a variety of tissues. The purpose of this study is to design and fabricate a perfusion bioreactor for intestinal tissue engineering.

MATERIALS AND METHODS

A perfusion bioreactor is fabricated using specific parameters. Intestinal epithelial organoid units harvested from neonatal rats are seeded onto biodegradable polymer scaffolds and cultured for 2 d in the bioreactor. Cell attachment, viability, and survival are assessed using MTT assay, scanning electron micrograph, and histology.

RESULTS

A functional perfusion bioreactor was successfully designed and manufactured. MTT assay and scanning electron micrograph demonstrated successful attachment of viable cells onto the polymer scaffolds. Histology confirmed the survival of intestinal epithelial cells seeded on the scaffolds and cultured in the perfusion bioreactor for 2 days.

CONCLUSIONS

A functional perfusion bioreactor can be successfully fabricated for the in-vitro cultivation of intestinal epithelial cells. With further optimization, the perfusion bioreactor may be a useful in in-vitro system for engineering new intestinal tissue.

Endocrine Cell and Nerve Regeneration in Autologous In Situ Tissue-Engineered Small Intestine

BACKGROUND

The purpose of this study was to regenerate a larger size of small intestinal tissue than that of our previous study and to evaluate the regeneration of the endocrine cells (ECC) and nerve system of autologous tissue-engineered small intestine. The effect of implantation of large numbers of smooth muscle cells (SMC) for the regeneration of small intestine was also investigated.

METHODS

Two types of scaffolds with different cell densities were fabricated: low density (LD) of SMC in the scaffold and high density (HD) of SMC in the scaffold. Both scaffolds were implanted into defects of isolated ileum in a canine model. Animals were sacrificed at 8, 12, 18, and 24 weeks.

RESULTS

The area of engineered small intestine in the HD group was four times larger than that in the LD group, although that was smaller in size than the original size of the defect. There were no significant changes in the thickness of regenerated smooth muscle layer (SML) in the LD and HD groups. The numbers of endocrine cells gradually increased after implantation. At 18 weeks of regeneration, the number of ECC reached levels comparable to that of normal mucosa. The nerve fibers extended to the center of the graft area and were observed in regenerated SML and regenerated villi at 24 weeks.

CONCLUSIONS

The ECC and nerve fibers were regenerated in autologous in situ tissue-engineered small intestine. Seeding a large number of SMC was not sufficient for the regeneration of the small intestine in a tubular configuration.

Short bowel syndrome: current medical and surgical trends

Short bowel syndrome is a chronic malabsorptive state usually resulting from extensive small bowel resections. A combination of diarrhea, nutrient malabsorption, dysmotility, and bowel dilatation may constitute the clinical symptomatology of this syndrome. The remaining bowel undergoes a process called adaptation, which may replace lost intestinal function. Chronic complications include nutrient, electrolyte, and vitamin deficiencies. Therapy depends largely on the administration of various factors stimulating intestinal adaptation of the remaining bowel. If the patient despite medical therapy fails to return to oral diet alone, then long-term parenteral nutrition is required. However, long-term parenteral nutrition may gradually induce cholestatic liver disease. Surgical methods may be required for treatment including intestinal transplantation, as a last resort for the treatment of end-stage intestinal failure. The goal of this review is to analyze the clinical spectrum and pathophysiologic aspects of the syndrome, the process of intestinal adaptation, and to outline the medical and surgical methods currently used to treat this complicated group of patients.

Hyaluronic acid based materials for intestine tissue engineering: a morphological and biochemical study of cell-material interaction

A wide number of gastro-intestinal disorders are associated with structural alterations of this district leading to an impaired gastrointestinal function. The study of cell material interactions represents one of the major issues for the development of tissue engineering purposes. Benzyl esters of hyaluronic acid are promising materials because they exhibit good tissue compatibility and are available in various configurations. In this work they have been studied for the possible application of intestinal cell growth and functioning. The preliminary investigation on the morphologic and biochemistry data obtained by monitoring the growth and differentiation of intestinal epithelial cells on two hyaluronic acid benzyl esters is reported. Two types of materials structures were studied: a three dimensional matrix and a macroporous flat sheet membrane. Caco-2 cell line was used: these cells undergo spontaneous enterocytic differentiation after several days in culture. The differentiation status of these cells grown on different materials was used as a parameter of biocompatibility and cell functioning. The status of cell growth and differentiation was monitored by studying cell morphology using scanning electron microscopy. The results obtained were confirmed by biochemical determinations. Although both the configurations of the two polymers exhibited good compatibility with respect to intestinal cells, only the flat sheet membrane proved to induce cell differentiation, leading us to the conclusion that it is a promising substrate for the proposed application.

Experimental evaluation of Surgisis as scaffold for neointestine regeneration in a rat model

The aim of the study was to evaluate the use of Surgisis (Cook Biotech Inc.), a porcine derived extracellular matrix already used in tissue engineering, as a scaffold for neointestinal regeneration in a rat model. A 3-cm length of tubular Surgisis graft was interposed with bilateral anastomoses in the middle of an isolated ileal loop of Sprague Dawley rats with an ileostomy. The grafts were harvested and analyzed using histology and immunohistochemistry at 24 weeks after operation. Macroscopic examination revealed neither stenosis nor adhesions in the area surrounding the neointestine. The regenerated small bowel showed a mean shrinkage of 30.7% (range 20%-40%). Histologic and immunohistochemical evaluation showed a well-developed three layers of mucosa and smooth muscle and serosa in the regenerated bowel wall that were similar to those of the normal bowel with evident neovascularization. Also, the regeneration of smooth muscle fibers and innervation were evident. The preliminary results of this study showed that Surgisis allowed rapid regeneration of mucosa and smooth muscle and therefore may be a promising material for the creation of a neointestine.

Maturation of Tissue Engineered Cartilage Implanted in Injured and Osteoarthritic Human Knees

The regeneration of damaged organs requires that engineered tissues mature when implanted at sites of injury or disease. We have used new analytic techniques to determine the extent of tissue regeneration after treatment of knee injury patients with a novel cartilage tissue engineering therapy and the effect of pre-existing osteoarthritis on the regeneration process. We treated 23 patients, with a mean age of 35.6 years, presenting with knee articular cartilage defects 1.5 cm2 to 11.25 cm2 (mean, 5.0 cm2) in area. Nine of the patients had X-ray evidence of osteoarthritis. Chondrocytes were isolated from healthy cartilage removed at arthroscopy. The cells were cultured for 14 days, seeded onto esterified hyaluronic acid scaffolds (Hyalograft C), and grown for a further 14 days before implantation. A second-look biopsy was taken from each patient after 6 to 30 months (mean, 16 months). After standard histological analysis, uncut tissue was further analyzed using a newly developed biochemical protocol involving digestion with trypsin and specific, quantitative assays for type II collagen, type I collagen, and proteoglycan, as well as mature and immature collagen crosslinks. Cartilage regeneration was observed as early as 11 months after implantation and in 10 out of 23 patients. Tissue regeneration was found even when implants were placed in joints that had already progressed to osteoarthrosis. Cartilage injuries can be effectively repaired using tissue engineering, and osteoarthritis does not inhibit the regeneration process.

From the cradle to enteral autonomy: the role of autologous gastrointestinal reconstruction

The short bowel state is treatable, with acceptable long-term quality of life. Management during the first 6-12 months of life is critical but, presently, frequently compromises long-term survival and prospects. At first presentation, primary caregivers, working with specialists at designated intestinal failure centers, should develop a structured individual-oriented management plan. Preservation of venous access, "hepatosparing" parenteral nutrition, and avoidance of liver sepsis are crucial to survival. Early surgery should be limited to conservation of autologous bowel, even short bowel lengths having great potential, and to facilitating natural intestinal adaptation. Bowel expansion may be relevant prior to delayed bowel reconstruction with single or combined techniques that include bowel lengthening and/or tailoring, reversed segments, and colon interposition. Bowel transplantation, as yet not recommended for primary management, offers survival and opportunity to those with no prospect of autologous bowel autonomy or following failed autologous gastrointestinal reconstruction. This paper reviews current surgery for the short bowel state and concludes that it is presently appropriate before bowel transplantation to offer autologous gastrointestinal reconstruction, with its prospect of enteral autonomy with quality life. It emphasizes the need for an individual-oriented management plan, developed jointly at the time of first presentation between the primary caregivers and a designated multidisciplinary intestinal failure center, to enhance the prospects for enteral autonomy preferably on autologous bowel. Autologous gastrointestinal reconstruction is in its infancy and requires resources, commitment, and research from dedicated bowel reconstructive surgeons toward a better opportunity for the child and family with short bowel.

Stem cells, tissue engineering and organogenesis in transplantation

Tissue engineering is an attempt to generate living tissues for surgical transplantation. In vitro and in vivo approaches have led to the production of vascular and cardiovascular components, bones, cartilages and gastrointestinal tissues. Organogenesis has a different aim, which is to create transplantable organs from embryonic tissue implanted into the recipient's omentum. This approach has been successful in creating kidneys and pancreases in animals. The use of stem cells in organogenesis and in tissue engineering has vastly enlarged the potential for clinical applications. The technique of nuclear transfer offers the possibility of creating cells, which are genetically identical to the host. Tissue engineering and organogenesis represent the future of transplantation in medicine. The progress in this field is of tremendous importance because it can produce a new generation of morphologically complex tissues and organs. In this review, the most relevant experiences in this area are summarized, including its perspectives for therapeutical applications.

Morphologic evaluation of regenerated small bowel by small intestinal submucosa

BACKGROUND/PURPOSE

Previous studies have shown small intestinal submucosa (SIS) can be used as biodegradable scaffolds in tissue engineering small intestine. The purpose of this study is to evaluate the regeneration of neointestine and its morphology using SIS.

METHODS

A 2-cm tubular SIS graft from Sprague Dawley rat donors was interposed in the middle of a 6-cm ileal Thiry-Vella loop of Lewis rats, which was used to construct an ileostomy. The grafts were harvested at each of the time points ranging from 2 weeks to half a year after implantation, and native small intestine and grafts were investigated for morphology using histology and immunohistochemistry.

RESULTS

At the early postoperative period, SIS grafts were colonized by numerous inflammatory cells. A mucosal epithelial layer began to line the luminal surface of the graft by 4 weeks, and by 12 weeks, the luminal surface was covered completely by a layer of neomucosa. Neomucosa with typical small bowel morphology was characterized by a columnar epithelial cell layer with goblet cells, Paneth cells, absorptive enterocytes, and enteroendocrine cells. Significant differences between neomucosa by 12 weeks and 24 weeks in the measurements of mucosal thickness, villus height, and crypt depth were found. The outer walls of SIS grafts were composed of distinct bundles of well-formed smooth muscle-like cells with some fibrovascular tissue.

CONCLUSIONS

This initial study suggests that tissue engineering neointestine using SIS can develop structural features of the normal intestine. Small intestinal submucosa might be a viable material in the creation of neointestine for patients suffering short bowel syndrome.

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.

[Apoptosis participation in the acute rejection of intestinal transplantation in rats]

BACKGROUND

Intestinal transplantation is a possible treatment for patients with short bowel syndrome, aiming the reintroduction of oral diet. However, the major obstacle in this procedure is the strong rejection. Delay in rejection diagnosis may be irreversible and lethal.

AIM

To define method for early diagnosis of rejection based on the apoptosis from intestinal allograft.

MATERIAL AND METHODS

Isogenic rats Brown-Norway (BN) and Lewis (LEW) were submitted to intestinal heterotopic allotransplantation and divided in two groups: LEW donor to LEW recipient isograft group C and BN donor to LEW recipient allograft group (Tx). According to the day of sacrifice, Tx group were subdivided in three subgroups with eight animals each as follow: Tx3-- sacrificed at third postoperative day (POD), Tx5 -- sacrificed at fifth POD and Tx7 -- sacrificed at seventh POD. Eight animals from control group were subdivided in three moments according to the time of biopsy from the graft as follow: C3 -- biopsy at third POD; C5 -- biopsy at fifth POD and C7 -- biopsy at seventh POD. All animals from control group were sacrificed at seventh POD. Rejection parameters were compared between the control groups (C3 vs C5, C3 vs C7 and C5 vs C7, and allograft group (Tx3 vs Tx5, Tx3 vs Tx7 and Tx5 vs Tx7). The same parameters were analyzed between the control group and allograft groups ( C3 vs Tx3, C5 vs Tx5 and C7 vs Tx7). In C group no statistical significant difference regarding the expression of the apoptotic cells were detected, while in Tx group, the presence of apoptotic cells were remarkable since the third postoperative day.

Impaired absorption of marked oligopeptide Glycine-I Tyrosine-Glycine after successful autologous-allotopic ileal mucosa transplantation in beagles

PURPOSE

After establishing a method for ileal mucosa transplantation in an animal model, the authors investigated the absorptive capacity for oligopeptides of the transplanted mucosa.

METHODS

In 14 beagle dogs the authors transplanted ileal mucosa in a vascularized demucosed segment of the transverse colon. The colonic wall-ileal mucosa complex then was integrated in the ileal continuity. Six animals were lost owing to operative complications. Absorptive capacity for oligopeptides was measured in the remaining 8 animals with the iodine 131 (131I)-marked tripeptide glycine-tyrosine-glycine before and 4 weeks after transplantation. The results were compared and analyzed with the Student's t test for matched pairs. Blood concentrations of the marked tripeptide with P value less than .05 were considered as a significant reduction in the absorptive capacity of the transplanted ileal mucosa. After fixation with glutaraldehyd graft, uptake of the colonic wall-ileal mucosa complex was evaluated histologically in 8 animals.

RESULTS

In all 8 animals, a 100% graft uptake was verified in all sections. Fifteen minutes after application of 15 MBc Glycine-131I-Tyrosine-Glycine there was no significant difference in the absorption between normal and transplanted ileal mucosa. After 30 minutes, the absorption of the transplanted ileal mucosa showed a tendency (P < .1) for an impaired uptake of the marked tripeptide. However, 60 minutes after application the difference in the absorptive capacity of the transplanted ileal mucosa was significant (P < .05).

CONCLUSIONS

Autologous allotopic ileal mucosa transplantation is feasible; however, an impaired absorption of oligopeptides of the transplanted mucosa 4 weeks after transplantation could be observed.

Tissue regeneration based on tissue engineering technology

Recent development of biomedical engineering as well as basic biology and medicine has enabled us to induce cell-based regeneration of body tissue to self-repair defective tissue or substitute biological functions of damaged organs. For successful tissue regeneration, it is indispensable to give cells an environment suitable for regeneration induction. Tissue engineering is a newly emerging biomedical technology for creating an environment for tissue regeneration with various biomaterials. The paper presented here overviews recent research data on tissue regeneration based on tissue engineering, and briefly explains the key technology of tissue engineering.

Surgical therapy for short bowel syndrome

Patients with short bowel syndrome (SBS) suffer tremendous morbidity secondary to prolonged hospitalization and chronic parenteral nutrition (TPN). Overall, the majority of infants will adapt and ultimately become independent of TPN, but this process may require many months or years. Reasons for continued TPN dependency include bowel dysmotility, bacterial overgrowth, insufficient adaptation, or very short bowel length. It is this subpopulation of patients who may benefit from surgical procedures that optimize intestinal adaptation and increase the mucosal absorptive surface area. The goal of this review article is to summarize the process of intestinal adaptation and then to outline the surgical principles and techniques available to surgeons who treat this complicated group of patients.

Animal models for intestinal tissue engineering

Although total parenteral nutrition prevents patients with short bowel syndrome from dying of starvation, having short bowel remains a severely debilitating condition. The best current treatment for inadequate absorptive surface area is through intestinal transplantation. However, this therapy is associated with significant morbidity and patients suffer from consequences of long-term immunosuppression. Additionally, the numbers of organs are limited. A new frontier in medicine is the field of tissue engineering. We will review the progress of intestinal bioengineering with a focus on the use of animal models. Investigators initially used autologous tissue as a patch to study intestinal regeneration. Subsequent studies focused on the use of absorbable biomaterials as a patch for tissue ingrowth. The most novel methodology consists of seeding a resorbable scaffold and implanting this construct to observe the regeneration of neointestine. Successful creation of esophagus, stomach, small bowel and colon has been demonstrated. Although these studies are preliminary, the results suggest that tissue-engineered intestine will become a real therapeutic option in the not too distant future for patients with inadequate intestinal tissue.

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.

Histologic changes in neuronal innervation of the ileum mucosa after autologic-allotopic ileum mucosa transplantation

INTRODUCTION

After successful experimental autologic-allotopic ileum mucosa transplantation, we investigated the remodeling of the transplanted submucous and mucous plexus, which is essential for the motility of the created colon coat-ileum mucosa complex.

METHOD

In 8 beagles we transplanted ileum mucosa in a demucosed vascularized transverse colon segment, which was reanastomosed with the small bowel immediately after transplantation. Four weeks later the animals were sacrificed and histology specimens taken from the anastomosis site of the colon coat-ileum mucosa complex, allowed comparison between transplanted and normal mucosa in the same section. After fixation in 4% formaldehyde and PBS the samples were embedded in paraffin and 7 micro m sections were prepared. The distribution of nerve fibers and submucous ganglia were examined in dewaxed sections, using antisera against protein gene product (PGP9.5), a general neuronal marker.

RESULTS

The submucosal ganglia were prominent in all samples but they were smaller and the submucous nerve cells within the ganglia were less numerous compared to the controls. The innervation of the transplanted ileum mucosa was reduced as the number of nerve fibers in the mucosal villi was decreased. Besides these neuromorphologic changes the transplanted mucosa showed a slightly higher rate of shortened villi compared to normal ileum mucosa.

CONCLUSIONS

After ileum mucosa transplantation the submucosal ganglia are smaller and less numerous. Furthermore there is a considerable loss of nerve fibers in the mucosal layer. Additionally a loss of microvilli in the transplanted ileum mucosa was found. Whether these findings represent a state of remodeling or a slow atrophy of the enteric nervous system in the transplanted areas is currently under investigation.

Mucosal Regeneration of a Duodenal Defect Using Small Intestine Submucosa

Intestinal tissue engineering has the potential of developing new treatment strategies for patients with a deficit in intestinal surface area. The purpose of this study was to investigate the capacity of small intestine submucosa (SIS) to regenerate intestinal epithelia in a rodent model for a duodenal defect. A duodenotomy was created in 20 Sprague-Dawley rats and was repaired with a circular patch of SIS. The repaired sites were retrieved 1, 2, 4, and 12 weeks after implantation. The size of the residual mucosal defect was measured. The retrieved tissues were fixed in formalin and processed by standard histologic techniques. The animals tolerated the procedure well. The mean size of the mucosal defects significantly decreased with time. Complete epithelializa-tion of the defects was noted within 4 weeks in three of five samples. Histologically, the defects were lined with crypts and villi, but the muscularis layer did not regenerate. In the rodent model, SIS can be used as a patch to repair a duodenotomy. Mucosal regeneration was observed in the area of the defect. Further studies will determine whether SIS may be used to preserve or increase mucosal surface area in patients whose bowel length is compromised.

Experimental assessment of small intestinal submucosa as a small bowel graft in a rat model

BACKGROUND/PURPOSE

Small intestinal submucosa (SIS) is an extracellular matrix used in tissue engineering. The purpose of this study is to evaluate the feasibility of using SIS as a scafford for small bowel regeneration in a rat model.

METHODS

A 2-cm length tubular SIS graft from donor Sprague Dawley rats was interposed with bilateral anastomosis in the median tract of an isolated ileal loop of Lewis rats used to construct an ileostomy. The grafts were harvested and analyzed at each of the time-points ranging from 2 weeks to 24 weeks after operation using histology and immunohistochemistry.

RESULTS

Macroscopic examination found no adhesion in the surrounding area of neointestine by 24 weeks, and no stenosis was visible. The shrinkage of neointestine was indicated from 20% to 40%. Histologic and immunohistochemical evaluation showed that SIS grafts were colonized by numerous inflammation cells by 2 weeks. Neovascularization was evident, but the luminal surface was not epithelized. By 4 weeks, transitional mucosal epithelial layer began to line the luminal surface of the graft, and nearly 70% luminal surface of the graft had been covered by mucosal epithelium at 8 weeks. By 12 weeks, the luminal surface was covered completely by a mucosal layer with distinct bundles of smooth muscle cells in the neointestine. At 24 weeks, the neointestine wall showed 3 layers of mucosa, smooth muscle, and serosa.

CONCLUSIONS

The preliminary study suggested that SIS allow rapid regeneration of mucosa and smooth muscle and might be a viable material for the creation of neointestine.

Transplante de intestino delgado

RACIONAL: Avanços da biotecnologia e o desenvolvimento de novas drogas imunossupressoras melhoraram os resultados do transplante de intestino delgado. Esse transplante é atualmente indicado para casos especiais da falência intestinal. OBJETIVO: A presente revisão realça os recentes desenvolvimentos na área do transplante de intestino delgado. MATERIAL E MÉTODO: Mais de 600 publicações de transplante de intestino delgado foram revisadas. O desenvolvimento da pesquisa, novas estratégias de imunossupressão, monitorização do enxerto e do receptor, e avanços na técnica cirúrgica são discutidos. RESULTADOS: Realizaram-se cerca de 700 transplante de intestino delgado em 55 centros: 44% intestino-fígado, 41% enxerto intestinal isolado e 15% transplante multivisceral. Rejeição e infecção são as principais limitações desse transplante. Sobrevida de 5 anos na experiência internacional é de 46% para o transplante de intestino isolado, 43% para o intestino-fígado e de cerca de 30% para o transplante multivisceral. Sobrevidas prolongadas são mais freqüentes nos centros com maior experiência. Em série de 165 transplantes intestinais na Universidade de Pittsburgh, PA, EUA, foi relatada sobrevida do paciente maior do que 75% no primeiro ano, 54% em 5 anos e 42% em 10 anos. Mais de 90% desses pacientes assumem dieta oral irrestrita. CONCLUSÃO: O transplante de intestino delgado evoluiu de estratégia experimental para uma alternativa viável no tratamento da falência intestinal permanente. Promover o refinamento da terapia imunossupressora, do manejo e prevenção de infecções, da técnica cirúrgica e da indicação e seleção adequada dos pacientes é crucial para melhorar a sobrevida desse transplante.

An overview of the pathology and approaches to tissue engineering

In tissue engineering, there is an attempt to culture living tissues for surgical transplantation. In vitro and in vivo approaches have produced vascular and cardiovascular components, cartilage, bone, intestine, and liver. Attempts to microdesign cell-culture support scaffolds have used a new generation of biocompatible and bioabsorbable polymers. Suspensions of donor cells are seeded onto protein-coated polymer scaffolds and grown to confluence in dynamic bioreactors. In vitro techniques produce monolayers of tissues. Denser masses are achieved by implanting monolayers onto a host, or by culturing cell/polymer constructs in vivo. Existing techniques have produced functioning heart valves from sheep endothelial cells and myofibroblasts. Cultured ovine arterial cells have replaced 2-cm segments of pulmonary artery in lambs. Chondrocyte cultures have produced a human-ear-shaped construct, temporo-mandibular joint discs, meniscal replacement devices, and human-phalange-shaped constructs, complete with a joint. The culture of composite tissue types has recently been reported. Intestinal organoid units containing a mesenchymal core with surrounding polarized epithelia have been used in lieu of an ileal pouch in Lewis rats, and the long-term culture of rat hepatocytes has revealed cellular differentiation and neomorphology resembling elements of a biliary drainage system. To sustain the in vitro culture of dense tissues prior to implantation, micro-electro-mechanical systems (MEMS) fabrication technologies have been adapted to create wafers of polymer containing sealed, branching, vascular-type spaces. After seeding with rat lung endothelial cells, followed by 5 days of bioreactor culture, the result is an endothelial network with controlled blood flow rates, pressure, and hematocrit. When these customized vascular systems can be used to support in vitro culture, a new generation of dense, composite, morphologically complex tissues will be available for clinical development.

The surgical management of short bowel syndrome

Short bowel syndrome is a clinical entity that results from a diverse group of congenital and acquired conditions in the pediatric population. The pathophysiology of this syndrome is characterized by malabsorption, malnutrition, and metabolic disturbances. The vast majority of children with this condition undergo spontaneous adaptation of the intestinal remnant and achieve enteral nutritional autonomy. However, a small portion of pediatric patients develop intestinal failure and require long-term or permanent dependence on total parenteral nutrition. These children may benefit from surgical interventions that facilitate intestinal adaptation. Such adjunctive procedures facilitate nutrient absorption by improving motility, prolonging intestinal transit, and/or increasing mucosal contact time. In selected patients, this may allow them to be weaned from parenteral nutritional support or to have it discontinued. The purpose of this review is to discuss the various surgical techniques for the management of short bowel syndrome in children, along with their indications, complications, and outcomes.

Surgery of the small bowel

This review deals with various developments in the field of small-bowel surgery, including the role of ileal pouch-anal anastomosis and ileorectal anastomosis in the treatment of ulcerative colitis and familial adenomatous polyposis. We discuss modern trends in the surgical management of Crohn disease, and the increasing use of laparoscopy in the management of inflammatory bowel disease and small-bowel obstruction. In addition to looking at small-bowel tumors, this review deals with the current status of small-bowel transplantation.