Regenerative medicine of the gastrointestinal tract Assoc. Prof. Prasit Suwannalert, Ph.D. (Email: prasit.suw@mahidol.ac.th) Department of Pathobiology Faculty of Science, Mahidol University (SCBM301- Tissue Regenerative Medicine: 2 nd Semester 2017) 1 Objectives: After learning, student should be able to! Describe the basic concept of regenerative medicine! Discuss the tools of regenerative medicine! Apply the tools of regenerative medicine for gastrointestinal disease 2! Regenerative medicine aims at helping the body to form new functional tissue to replace lost or defective ones; lost to age, disease, damage, or congenital defects.! It may involve: transplantation of stem cells, progenitors or tissue stimulation of endogenous repair processes e.g. with growth factors the use of cells as delivery vehicles for genes, cytokines and small molecules 3 Major tools for regenerative medicine! Tissue engineering! Stem cells Tissue engineering! Tissue engineering is an interdisciplinary field that applies the principles of engineering and the life sciences toward the development of biological substitutes that restore, maintain, or improve tissue function. 4
Stem cells! Stem cells by definition have two defining properties the capacity of self-renewal giving rise to more stem cells and to differentiate into different lineages under appropriate conditions.! There are two main types of stem cells, embryonic stem cells (ESCs) and non-embryonic stem cells (non-escs).! Embryonic stem cells (ESCs) are pluripotent and they can differentiate into all germ layers. 5 6 (http://www.twozebras.com/single-post/2015/01/07/are-human-embryonic-stem-cells-now-patentable-in-europe)!! Non-ESCs are probably lower in the stem cell hierarchy.! They are thought to have lost the pluripotent capability. However, throughout the organism s life, they maintain a multipotent differentiation potential.! Non-ESCs can be derived from several sources including amniotic fluid, umbilical cord tissue and bone marrow. 7 Gastrointestinal System! The gastrointestinal system consists of the digestive tract (or alimentary canal) and its accessory organs and is responsible for the digestion and metabolism of food, and the absorption of the resulting nutrients.! The gastrointestinal tract consists of the mouth, pharynx, oesophagus, stomach, small and large bowel, and anus.! The accessory digestive organs include the tongue, salivary glands, pancreas, liver and gallbladder and biliary tract. 8
Gastrointestinal Disorders! Gastrointestinal disorders and diseases can be the result of congenital defects, inherited gene mutations, tissue damage or loss, autoimmune diseases, and tumours. Cancer and Dysplasia! Dysplasia and cancer can occur at any point in the gastrointestinal tract and the associated organs.! Common cancers include colorectal, anal, pancreatic, oesophageal, stomach, oral, and liver cancer. 9 10 Inflammatory Bowel Disease! The two main subtypes of inflammatory bowel disease are ulcerative colitis and Crohn s disease.! They are thought to arise from a combination of defective mucosal immune regulation in the gut and exposure to unknown environmental factors.! Ulcerative colitis is characterised by mucosal inflammation of the rectum and/or colon. Typical symptoms include diarrhoea, rectal bleeding, tenesmus and increased stool urgency and frequency. Complications can include toxic megacolon and colorectal dysplasia or cancer.! Crohn s disease is characterised by transmural and sometimes granulomatous inflammation of the gastrointestinal tract, most commonly in the ileum and colon. Typical symptoms are abdominal pain, fatigue and diarrhoea. Complications can include intestinal stenosis, fistulas, intra-abdominal abscesses, peritonitis and cancer.! 11 12
Fistula-Perianal and Rectovaginal! A perianal fistula (anal fistula or fistula in ano) is an abnormal tract connecting the anorectal mucosa (epithelialized surface of the anal canal) to the perianal skin or perineum.! A rectovaginal fistula, also known as an enterovaginal fistula is a tract that connects the rectum to the vagina. Fistulas typically develop after rupture or drainage of an abscess or are associated with inflammatory bowel disease. Faecal Incontinence! The anal canal is surrounded by two layers of muscle, the involuntary internal anal (IAS) sphincter and the voluntary external anal sphincter.! Faecal incontinence is the involuntary loss of stool or flatus and may be caused by anatomical damage to these muscles resulting from trauma or a degenerative disorder affecting the smooth muscle of the IAS. 13 14 Liver Disease! The liver is affected by many conditions both acute and chronic. Liver disease can be caused in many different ways including: poor nutrition and metabolic syndrome leading to non-alcohol fatty liver disease (non-alcohol steatohepatitis), cirrhosis and liver cancer alcohol misuse and abuse leading to liver damage and liver cirrhosis acute and chronic hepatitis from viral infections or other harmful substances, which can progress to liver cirrhosis and liver cancer. inherited liver disorders such as haemochromatosis (causing the accumulation of iron), Wilson s disease (causing the accumulation of copper) and alpha-1 antitrypsin deficiency hepatic veno-occlusive disease where small veins in the liver can become obstructed. 15 16
Many products will be classified as advanced therapy medicinal products (ATMPs).! A somatic cell therapy medicinal product is a product that contains or consists of cells or tissues that have been subject to substantial manipulation so that biological characteristics, physiological functions or structural properties.! A gene therapy medicinal product is a product obtained through a set of manufacturing processes aimed at the transfer to human/animal cells and its subsequent expression in vivo. The gene transfer involves an expression system contained in a delivery system known as a vector, which can be of viral, as well as non-viral origin. The vector can also be included in a human or animal cell. 17 18! A tissue engineered product is a product that contains or consists of engineered cells or tissues, and is presented as having properties for, or is used in or administered to human beings with a view to regenerating, repairing or replacing a human tissue. A tissue engineered product may contain cells or tissues of human or animal origin, or both. It may also contain additional substances, such as cellular products, biomolecules, biomaterials, chemical substances, scaffolds or matrices. 19! Number of technologies by condition and underlying mechanism of action (Genus T., 2016) 20
! Over time (3 months), a laminarly organized neo-organ develops! Typically, healing responses within mammals are characterized by fibrosis and scar tissue formation, not regeneration.! Nevertheless, developing mammalian fetuses demonstrate wound healing without fibrosis and scar tissue formation during the first trimester (Adzick and Lorenz 1994).! Additionally, compensatory hyperplasia of mammalian liver or kidney secondary to partial hepatectomy or nephrectomy, remodeling of bone, and epidermis subsequent to injury in humans and mice following amputation are all examples of regenerative outcomes in adult mammals (Roy and Gatien 2008). (Basu J., 2014) 21 Maturation of a tubular regenerative construct into a laminarly organized neo-organ. Polymer matrix of construct degrades following implantation to be replaced by infiltrating smooth muscle cells, mesenchymal, endothelial, neuronal, and other cell populations. 22 Gastrointestinal (GI) tract:! Signaling interactions between endodermal epithelium and mesenchymal cells derived from splanchnic mesoderm mediate axial differentiation of the primitive gut tube during embryo-genesis into distinctive functional domains. 23! The molecular genetics underlying these differentiative signaling cascades is complex, but is broadly understood to involve members of the hedgehog family of ligands, including sonic hedgehog, desert hedgehog, and Indian hedgehog.! In mouse models and human patients, mutations in hedgehog signaling proteins and downstream targets lead to a variety of severe malformations of the GI tract.! In mouse models and human patients, mutations in hedgehog signaling proteins and downstream targets lead to a variety of severe malformations of the GI tract 24
!Conservation of signaling between mesenchymal and epithelial cell populations during organogenesis of bladder and GI suggests that the organ regeneration platform appropriate for bladder regeneration may also function in an independent positional context to catalyze regeneration of the GI, but not limited to small intestine and esophagus. Esophagus!In these studies, small defects were introduced within the esophagus of rodents. Injuries were subsequently repaired with cell-seeded, patch constructs and allowed to regenerate in vivo for up to 10 weeks post implantation.!evidence of early regenerative outcomes was observed at 8 days post-implantation in the form of developing bundles of smooth muscle.!complete regeneration of longitudinal and circularly oriented musculatures and luminal epithelia were observed at 10 weeks postimplantation of construct. 25 26 Early events in esophageal regeneration. Masson s trichrome stain, transverse section of rodent esophagus post-implantation of regenerative construct at injury site (top). Bundles of developing smooth muscle are evident, 10x. (Basu J., 2014) 27 Regeneration of esophagus from patch-based implant in rodent esophageal injury model, 3 months post-implant. Note development of laminarly organized, muscular layers together with luminal epithelial layer. Area of regeneration, top of section. Native control, bottom of section Masson s trichrome stain, 4x. (Basu J., 2014) 28
Small Intestine! The Lgr5 marker, typically reside at the base of intestinal villi and are capable of self-organizing in vitro into organoid structures that recapitulate the intestinal lumen, crypt, and villi domains (Sato et al. 2009).! As with the patch, complete regeneration of intestinal epithelia and partial regeneration were observed at 3 months post-implantation (Basu, Mihalko, et al. 2011). 29 Regeneration of small intestine from tube-based implant in rodent small intestine injury model, 3 months post-implant. Note development of laminarly organized, muscular layers together with luminal epithelial layer. Masson s trichrome stain, 10 x. (Basu J., 2014) 30 References! Bajada S., Mazakova I., Ashton B.A., Richardson J.B., Ashammakhi N. Stem Cells in Regenerative Medicine. Topics in Tissue Engineering, Vol. 4, 2008.! Genus T, Packer C, Simpson S. Regenerative medicine for gastrointestinal diseases. Technical Report. 2016! Basu J., Bertram T.A. Regenerative Medicine of the Gastrointestinal Tract. Toxicologic Pathology, 42: 82-90, 2014 31