June 19, 2017
By Dr Kulwinder S. Dua, MD, DMSc, FRCP (London), FRCP (Edinburgh), FACP, FASGE
Professor of Medicine and Pediatrics, Medical College of Wisconsin
With an annual incidence of over 400,000 cases worldwide, several patients with esophageal cancers are undergoing esophagectomy. Similar surgery is also required for children born with long-segment esophageal atresia. Gastric pull-up conduits or colon interposition to re-establish luminal continuity after esophagectomy can be associated with significant morbidities rates [up to 70%; stasis of food in the conduit, reflux, fullness, anastomotic stricture and leaks . Re-growing the esophagus to restore luminal and functional continuity would be ideal for these patients.
De-novo organogenesis is possible using principles of regenerative medicine, as validated mostly in animal studies . These principles include transplanting tissue-engineered extracellular matrix (ECM)  seeded with autologous pluripotent/stem cells. Researchers have successfully re-grown the human urinary bladder and the trachea [4, 5]. Elliott et al. transplanted decellularized cadaveric human trachea populated with recipient’s bone marrow stem-cells to re-grow the trachea in a 12 year-old child with congenital tracheal stenosis . These techniques can be demanding in terms of expertise, cost, regulations, and time.
Attempts to re-grow the human esophagus have so far been limited to only partial-thickness defects, like after endoscopic sub-mucosal dissection (ESD) or to patchy, non-circumferential transmural defects like perforations and leaks [6-9]. Circumferential ESD for superficial cancer can be associated with over 70% risk of developing a stricture. To re-grow the mucosa, Okhi et al. cultured autologous buccal mucosal cells, harvested with a swab into cell-sheets around 2 weeks before planned ESD in 9 patients . Small disks of these autologous cell-sheets were endoscopically implanted onto the raw esophageal surface immediately after ESD. Only one of the 9 patients in this cohort developed a stricture . Extracellular matrix (ECM) and autologous stromal cell therapy have also been successfully used to prevent stricture formation after ESD [6, 8, 10, 11]. Similar to partial-thickness defects, full-thickness patchy defects like perforation and leaks have also been successfully treated in human beings with devices like expandable stents, clips and suturing [9, 12, 13]. Interestingly, the majority of these lesions heal with minimal need for additional measures, such as applying tissue matrix with or without autologous pluripotent cells.
Re-growing the human esophagus after long-segment, full-thickness, circumferential (LFC) defects, such as those present after an esophagectomy, has not been attempted until recently . All previous studies concerning re-growth of LFC esophageal defects were done in animal models. The basic principles involved were transplanting ECM molded into a tubular configuration into the recipient animal after populating it with autologous pluripotent cells with or without using a non-biological scaffold (for example, a silicone stent); to maintain the three-dimensional configuration of the esophagus during the slow process of regeneration. Since the pluripotent cells are autologous, immunosuppression to prevent organ rejection is not required. Whether allogenic or xenogeneic, ECM is ideal for tissue re-generation. They provide a biological scaffold on which pluripotent cells can spatially mature into site-specific phenotypic cells resulting in de-novo organogenesis. Suggested mechanisms include release of peptides, ligands and bioactive molecules to attract endogenous stem-cells, alter immune response, induce mitosis, and provide signals to local and migrant cells to mature into a site-specific organ [2, 15, 16].
Badylak et al. resected 5-cm long esophagus segments in 22 dogs to create LFC defects. Porcine derived ECM molded into a tubular shape was used to bridge the defects . All dogs treated with EMC alone developed strictures while dogs with even as little as 30% of autologous smooth muscle cells which have pluripotent potentials colocalized with the ECM re-grew their esophagus emphasizing the importance of adding pluripotent cells to the matrix. Dogs were sacrificed at various intervals and histology confirmed re-growth of all the layers of the esophageal wall. Moreover, no porcine antigen was identified on immunohistology, thereby suggesting that the porcine ECM used to make the scaffold merely facilitated re-growth of the dog’s own tissue.
Until recently, no attempts have been made to re-grow the human esophagus using principles of regenerative medicine as validated in animal models. Availability of less than ideal alternatives like gastric pull-up conduits and the ethical concern on the uncertainty of outcomes using experimental techniques may have been the reason for this. Recently, Dua et al. reported in The Lancet the first human case of re-growing the esophagus in a young adult who had exhausted all other options, including several surgical attempts to repair a long-segment defect . The 24-year-old patient presented with a life-threatening abscess that led to a direct communication between the hypopharynx and the mediastinum. Earlier in his life, the patient had been in a car accident that required stabilization of the cervical spine with metal plates. The anterior metal plate had eroded into the hypopharynx that resulted in the infection and abscess formation. Several attempts at surgical repair failed and gastric pull-up was not possible due to the high location of the esophageal defect. On compassionate grounds, the authors attempted to re-grow a 5 cm LFC defect in the esophagus that extended up to the upper esophageal sphincter level. They used off-the-shelf, readily available, FDA approved for-human-use material. The three-dimensional configuration of the esophagus was maintained by three non-biological fully-covered expandable esophageal stents with the upper end of the proximal stent extending into the hypopharynx. FDA-approved decellularized donated human skin for tissue transplantation (AlloDerm®) was used as the ECM, to cover the defect from outside the stents. The dermal side of the matrix that attracts blood was oriented towards the mediastinum to facilitate neo-vascularization and the epithelial side that repels blood was oriented towards the lumen. To facilitate recruitment of pluripotent cells, the defect region was sprayed with the autologous platelet-rich plasma (PRP) and covered with the patient’s sternocleidomastoid muscle. Being autologous PRP, there was no risk of transmitting blood-borne infections. Platelets are known to stimulate growth and regeneration, by releasing platelet-derived growth factors, transforming growth factors, and vascular endothelial growth factors that attract mesenchymal stem-cells, endothelial cells and epidermal cells, which express receptors for these growth factors [18-20].
Initially, the patient refused to give permission to remove the stents for fear of fistula and stricture formation. Eventually all the stents were removed over three-and-half years after placement. Follow-up endoscopy/biopsy, endoscopic-ultrasound, and high-resolution impedance-manometry showed squamous epithelium, normal five-layered esophageal wall, and normal peristaltic motility with bolus transit, respectively. After almost 5 years since the stents were removed, the patient is now eating a normal diet and maintaining his weight. The authors postulate that “by maintaining the three-dimensional morphological configuration of the esophagus in its natural milieu in vivo for an extended period of time and stimulating regeneration with ECM and PRP, it is possible to structurally and functionally re-grow the human esophagus” . An added attraction of this case was that rather than using expensive tissue-engineering techniques, using non-FDA approved material followed by surgical transplantation, the authors used readily available, off-the shelf FDA approved materials implanted in-vivo. Research is actively going on in testing various biomaterials seeded with autologous pluripotent cells. Based on the lessons learnt and questions raised from this case, large-scale animal studies, followed by phase I and II clinical trials, will be required. If the results can be replicated, it will have a large impact on patients requiring esophagectomy .
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