Early Regenerative Response in the Intrathoracic Porcine Esophagus-The Impact of the Inflammation

A novel piglet model of esophageal stricture following variable segmental esophageal resection and re-anastomosis

BACKGROUND

Esophageal strictures following esophageal atresia repair are a source of significant morbidity. To test new therapeutic approaches, we designed a piglet model of esophageal stricture by resecting variable lengths of esophagus with subsequent re-anastomosis. This study describes the model and validates its physiologic impact by blinded analysis of the weight gains of the piglets.

METHODS

A total of 24 two-week old Pietrain piglets had esophageal resections performed, ranging from 0 to 5 cm, with the goal of inducing postoperative esophageal strictures. Postoperative body-weights were evaluated by repeated analysis of variance followed by pairwise group-comparisons based on estimated marginal means. In addition, body weight was modeled by linear-mixed model regression. Different resection lengths were compared. The esophagi were evaluated postmortem for stricture.

RESULTS

Of 24 operated piglets, 23 reached the endpoint, and 90% developed an esophageal stricture that was radiologically visible in a contrast study, as well as appreciable macroscopically in the necropsy. We found differences in pre- and postoperative body weights for all piglets (F (1, 18) = 298.54, p < 0.001), but no differences between resection lengths (F (4, 18) = 0.36, p = 0.837).

CONCLUSION

Our model of postoperative esophageal stricture offers the opportunity to investigate potential treatments for strictures associated with esophageal atresia, since it reliably induces strictures and results in minimal loss of animals. The similar body weight gain in all groups indicates that stricture is mainly the result of esophageal resection and re-anastomosis, regardless of the length of the resected segment.

Human Adipose Derived Stem Cells Enhance Healing in a Rat Model of Esophageal Injury with Stent

BACKGROUND

Mesenchymal stem cells have been proven to promote cellular recruitment and remodeling during healing. Considering challenges encountered in the healing process of esophageal injury, we sought to evaluate the effect of human adipose derived stem cells (hASC) on esophageal injury with stent and to assess the feasibility of submucosal hASC injection as a mechanism of delivery.

METHODS

An intrabdominal esophagotomy was created in rodents with placement of an expandable fully covered metal esophageal stent. A submucosal injection of 2 × 10⁶ hASC was delivered in experimental animals. Animals were sacrificed on postoperative day 3 (POD3) or 7 (POD7). Macroscopic, immunohistochemical and immunofluorescence analyses were conducted to assess for markers of healing and viability of transplanted cells.

RESULTS

hASC were identified within submucosal and muscular layers with proliferation demonstrated in respective areas on anti-Ki67 stained sections. Lower adhesion and abscess scores were observed in hASC specimens without significant statistical difference. Prevalence of submucosal collagen was increased in samples treated with hASC compared to control, with abundant collagen deposition demonstrated within the POD7 group. Granulation tissue at the site of esophageal injury was more prominent in tissue sections treated with hASC compared to control, with significantly higher density at POD3 (control 1.94 versus hASC 2.83, P < 0.01).

CONCLUSIONS

Presence of hASC at the site of an esophageal injury may enhance wound healing predominantly through increased granulation and decreased inflammation in conjunction with esophageal stent placement. Targeted submucosal injection at the time of esophageal stent placement is an effective delivery method of hASC therapy.

Using multidimensional scaling in model choice for congenital oesophageal atresia: similarity analysis of human autopsy organ weights with those from a comparative assessment of Aachen Minipig and Pietrain piglets

Swine models had been popular in paediatric oesophageal surgery in the past. Although being largely replaced by rodent models, swine experienced a revival with the establishment of minipig models. However, none of them has ever been investigated for similarity to humans. We conducted a pilot study to determine whether three-week old Pietrain piglets and three-month old Aachen Minipigs are suitable for experimental paediatric oesophageal atresia surgery. We tested the operation's feasibility, performed a necropsy, weighed organs, measured organ length and calculated relative weights and lengths, and measured laboratory parameters. We used multidimensional scaling to assess the similarity of the swine breeds with previously published human data. Pietrain piglets had a higher a priori bodyweight than Aachen Minipigs (Δ = 1.31 kg, 95% confidence interval (CI): 0.37-2.23, p = 0.015), while snout-to-tail length was similar. Pietrain piglets had higher absolute and relative oesophageal lengths (Δ = 5.43 cm, 95% CI: 2.2-8.6; p = 0.0062, q1* = 0.0083 and Δ = 11.4%, 95% CI: 5.1-17.6; p = 0.0025, q3* = 0.0053). Likewise, absolute and relative small intestinal lengths were higher in Pietrains, but all other parameters did not differ, with the exception of minor differences in laboratory parameters. Multidimensional scaling revealed three-week old Pietrain piglets to be similar to two-month old humans based on their thoracoabdominal organ weights. This result indicates three-week old Pietrain piglets are a suitable model of paediatric oesophageal atresia surgery, because clinically many procedures are performed at around eight weeks age. Three-month old Aachen Minipigs were more dissimilar to eight-week old humans than three-week old Pietrain piglets.

Beyond Magnamosis: A Method to Test Sutureless Esophageal Anastomotic Devices in Living Swine by Creating an Esophageal Bypass Loop for Natural Oral Nutrition

Introduction: Thoracoscopic esophageal atresia repair has become increasingly popular, but is still limited to a few expert centers and has some challenges and shortcomings. One of them has a longer operation time compared with conventional thoracotomy. Magnetic compression anastomosis may contribute toward shorter operation times by avoiding the time-consuming anastomotic suturing. We aimed to establish a method of testing sutureless anastomoses in parallel to having swine eating the natural way. Materials and Methods: We used four juvenile Pietrain swine-aged 8 weeks, weighing 15 kg-to establish a living animal model after preceding cadaver tests. Esophagi were fully mobilized through right-sided thoracotomy to gain sufficient length to create an esophageal loop that served as a bypass for food after magnet deployment. Six hours later, patency of the bypass esophageal loop was assessed by passing an orogastric tube and by allowing swine to drink methylene blue-stained water. We also tested the device stability using the classical burst pressure test. Results: The esophageal lumen was patent for feeding tube. Swine were able to drink and methylene blue colored fluid reached the stomach. Clinical signs of obstruction such as regurgitation or coughing were absent. Magnets sustained burst pressures up to 200,000 Pascal until they became disrupted. At 6 hours after magnet placing, we already saw subtle esophageal mucosa erosions indicating the beginning of anastomotic formation. Conclusion: This animal model is useful to test different magnet designs for sutureless esophageal anastomosis or even future devices for in vivo tissue engineering.

Macrophage Phenotype Is Associated With the Regenerative Response in Experimental Replacement of the Porcine Esophagus

A porcine model for bridging circumferential defects in the intrathoracic esophagus has been developed in order to improve the treatment of children born with long-gap esophageal atresia. The aim of this study was to identify factors beneficial for tissue regeneration in the bridging area in this model and to describe the histological progression 20 days after replacement with a silicone-stented Biodesign mesh. Resection of 3 cm of intrathoracic esophagus and replacement with a bridging graft was performed in six newly weaned piglets. They were fed through a gastrostomy for 10 days, and then had probe formula orally for another 10 days prior to sacrifice. Two out of six piglets had stent loss prior to sacrifice. In the four piglets with the stent in place, a tissue tube, with visible muscle in the wall, was seen at sacrifice. Histology showed that the wall of the healing area was well organized with layers of inflammatory cells, in-growing vessels, and smooth muscle cells. CD163+ macrophages was seen toward the esophageal lumen. In the animals where the stent was lost, the bridging area was narrow, and histology showed a less organized structure in the bridging area without the presence of CD163+ macrophages. This study indicates that regenerative healing was seen in the porcine esophagus 20 days after replacement of a part of the intrathoracic esophagus with a silicone-stented Biodesign mesh, if the bridging graft is retained. If the graft is lost, the inflammatory pattern changes with invasion of proinflammatory, M1 macrophages in the entire wall, which seems to redirect the healing process toward scar formation.

Regenerative Medicine Strategies for Esophageal Repair

Pathologies that involve the structure and/or function of the esophagus can be life-threatening. The esophagus is a complex organ comprising nonredundant tissue that does not have the ability to regenerate. Currently available interventions for esophageal pathology have limited success and are typically associated with significant morbidity. Hence, there is currently an unmet clinical need for effective methods of esophageal repair. The present article presents a review of esophageal disease along with the anatomic and functional consequences of each pathologic process, the shortcomings associated with currently available therapies, and the latest advancements in the field of regenerative medicine with respect to strategies for esophageal repair from benchtop to bedside.