Technique for the safe placement of a biodegradable stent into the common bile duct of rabbits

Recent research progresses of bioengineered biliary stents

Bile duct lesion, including benign (eg. occlusion, cholelithiasis, dilatation, malformation) and malignant (cholangiocarcinoma) diseases, is a frequently encountered challenge in hepatobiliary diseases, which can be repaired by interventional or surgical procedures. A viable cure for bile duct lesions is implantation with biliary stents. Despite the placement achieved by current clinical biliary stents, the creation of functional and readily transplantable biliary stents remains a formidable obstacle. Excellent biocompatibility, stable mechanics, and absorbability are just a few benefits of using bioengineered biliary stents, which can also support and repair damaged bile ducts that drain bile. Additionally, cell sources & organoids derived from the biliary system that are loaded onto scaffolds can encourage bile duct regeneration. Therefore, the implantation of bioengineered biliary stent is considered as an ideal treatment for bile duct lesion, holding a broad potential for clinical applications in future. In this review, we look back on the development of conventional biliary stents, biodegradable biliary stents, and bioengineered biliary stents, highlighting the crucial elements of bioengineered biliary stents in promoting bile duct regeneration. After providing an overview of the various types of cell sources & organoids and fabrication methods utilized for the bioengineering process, we present the in vitro and in vivo applications of bioengineered biliary ducts, along with the latest advances in this exciting field. Finally, we also emphasize the ongoing challenges and future development of bioengineered biliary stents.

Mechanical Enhancement of the Gelatin/Poly(zinc acrylate) Hydrogel Stent in Bile

Hydrogels with the features of softness, biocompatibility, and modifiability have emerged as excellent materials in the biomedical field. However, the poor mechanical properties of the hydrogels limit their further practical applications. Double-network and metal ion coordination, such as Cu2+ and Zn2+, have achieved a significant reinforcement of the mechanical strength of the hydrogels. Herein, we report a Zn2+-enhanced polyelectrolyte double-network hydrogel stent with a mechanical enhancement phenomenon in bile. The gelatin/poly(zinc acrylate) (PZA) stent was constructed by dip-coating and UV irradiation. Although the mechanical strength of the as-prepared stent was quite weak, it was discovered to be mechanically enhanced by the natural bile. After exploring the effect of different components on the stents according to the components of bile, we found that Ca2+ in bile made a contribution to the mechanical enhancement of the stent. It is envisioned that this bile-enhanced gelatin/PZA stent provides a train of thought for the potential application of hydrogels in the biliary environment.

Comparative assessment of the biocompatibility and degradation behavior of Zn-3Cu and JDBM alloys used for biliary surgery

This study was designed to investigate the biocompatibility and the degradation behavior of a Zn-3Cu alloy, a Zn-3Cu coating alloy, a Mg-Nd-Zn-Zr (denoted as JDBM) alloy and a JDBM coating alloy to choose the optimal alloy for common bile duct (CBD) surgery. In the in vitro degradation experiments, we observed the surface morphology of the samples and determined the elements of the corrosion products. In the in vitro cytotoxicity experiments, the cell morphology and cytotoxicity were observed and tested. In the in vivo experiments, in addition to analyzing the samples, we also analyzed the variations in serum magnesium, serum creatinine (CREA), blood urea nitrogen (BUN), total bilirubin (TB) and glutamic pyruvic transaminase (GPT). Moreover, important tissue samples from the CBD, liver, kidney and spleen were taken for histological evaluation. The in vitro degradation experiments revealed that the surface corrosion of the JDBM and JDBM coating alloys were more obvious than that of Zn-3Cu and Zn-3Cu coating alloys, and the degradation rate of the JDBM coating alloy was the slowest. The in vitro cytotoxicity assessment showed that the JDBM alloy and JDBM coating alloy extracts were biologically safe for L-929 cells, while the Zn-3Cu alloy and Zn-3Cu coating alloy extracts were harmful to L-929 cells. In the in vivo experiments, neither the JDBM alloy nor the JDBM coating alloy affected the function or morphology of the bile duct, liver, kidney or spleen. Similar to the in vitro degradation behavior, the surface corrosion of the JDBM alloy was more significant than that of the JDBM coating alloy. Our data suggested that the JDBM coating alloy is a safe, biodegradable material for CBD surgery.

Duodenum sparing technique for preventive stenting of biliary tract anastomosis in pigs

The main aim of this study was to find a standardized method for preventive stenting of biliary tract anastomosis with biodegradable self-expandable stent from polydioxanone and to evaluate the functionality of the stent. The experimental study was conducted using four pigs with a follow-up of eight weeks. The procedure was done under general anaesthesia. The function of the stent was verified by clinical stage, blood test, magnetic resonance cholangiopancreatography and necropsy. Our duodenum sparing technique was described in detail and photographically documented. All pigs finished the follow-up period without clinical, laboratory or radiologic signs of biliary obstruction. Necropsy did not reveal complication of the procedure or anastomotic stricture. In conclusion, this study demonstrated a simple new duodenum sparing method of transanastomotic insertion of a biodegradable self-expandable stent from polydioxanone. We did not find any complications during the follow-up. This method will be used in our follow-up study with an extended experimental control group of animals and a longer follow-up period to verify the preventive functionality of this stent.

Degradation of Mg-6Zn alloy stents does not influence the healing of the common bile duct in vivo

To investigate the effects of Mg-6Zn alloy on the healing of the common bile duct (CBD), Mg-6Zn alloy stents were implanted into the CBDs of rabbits. Stainless steel stents were transplanted into a second group of rabbits to serve as a control. Computed tomography (CT) scanning was performed and weight loss was recorded to evaluate the in vivo degradation process. Hematoxylin and eosin staining and immunohistochemical analyses were performed to determine the expressions of transforming growth factor (TGF)-β, vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) and evaluate CBD healing. The Mg-6Zn stents maintained ~82 and ~50% of the original length, and ~90 and ~43% of the original CT value at 1 and 2 weeks post-operatively, respectively. The residual weights of the Mg-6Zn stents were ~89, ~42 and ~9% of the original weights at 1, 2 and 3 weeks post-operatively, respectively. At 3 weeks post-surgery, the CBD was completely healed, with no wounds observed in the 3 groups. VEGF expression in the Mg-6Zn stent group was lower than that in the stainless steel stent group at 3 weeks post-surgery (P=0.002). No significant differences were observed between the mean expressions of the TGF-β1 and bFGF genes at 1 and 2 weeks post-surgery. The results of the present study suggest that degradation of the Mg-6Zn alloy may not affect healing of the CBD.

Self-expandable biodegradable biliary stents in porcine model

BACKGROUND

Treatment or prevention of a benign biliary tree stricture is an unresolved problem. A novel self-expandable biodegradable polydioxanon biliary stent in a porcine model was studied.

MATERIALS AND METHODS

This new stent was used in 23 pigs. Feasibility and safety of surgical stenting, time of biodegradation, and histologic reaction in 2, 8, 13, and 20 wk of a follow-up were studied. All stents were inserted into a common bile duct through a duodenal papilla following small dilatation. After surgical evaluation of abdominal cavities, the pigs were sacrificed to remove common bile ducts with the stents. All bile ducts were assessed by macroscopic and histopathologic examination.

RESULTS

Self-expansion was correct in all cases. Neither bile duct obstruction nor postsurgical complications were observed. Macroscopic evaluation indicated lightening of the stent color in 2 wk, a partial disintegration in 8 wk, and a complete absorption in 13 and 20 wk. Histologic evaluation in general substantiated a mild-to-moderate inflammatory reaction in the lamina propria during the whole follow up and had no clinical consequences. No cholangitis, necrosis, abscess, or excessive fibroplasia was found in a hepatoduodenal ligament.

CONCLUSIONS

Our results suggest that polydioxanon biodegradable self-expanding stents seem to be useful for biliary system implantation, offer a good biocompatibility, and completely degrade within 13 wk.