The Regenerative Scaffold Stenting & Shielding Hernia System for Abdominal Hernioplasty Promotes Extensive Neo-Angiogenesis in an Experimental Porcine Model

1. Introduction

The conventional approach to abdominal wall hernia repair relies on the use of synthetic flat meshes, predominantly made of polypropylene, to reinforce the groin by inducing the ingrowth of a fibrotic scar plate. [1,2] Despite ongoing advancements in techniques and materials, frequent complications continue to affect both intra- and post-operative outcomes, diminishing patient quality of life and increasing healthcare costs. Among the debated causes of these poor outcomes, the uncontrolled and suboptimal biological response of conventional hernia meshes—exacerbated by the challenges of mesh fixation in the highly mobile abdominal wall —plays a significant role. This inadequate response is often linked to unpleasant complications such as postoperative discomfort and chronic pain. [3,4,5,6]

Moreover, the widely accepted term “reinforcement” of the weakened groin may be misleading. The fibrotic ingrowth that is typical of flat, static meshes does not genuinely reinforce the herniated abdominal barrier but instead represents a foreign body reaction. When considering the relationship between this treatment approach and the underlying pathology of hernia protrusion, it becomes clear that conventional flat meshes fail to address the degenerative source of the condition. [7,8,9,10,11,12,13,14] Instead of “reinforcing” the herniated groin with avascular, stiff, and shrunken fibrotic tissue—leaving a patent defect—the goal should be to fill the hernial gap and promote tissue regeneration, thereby fully restoring a competent abdominal barrier.

In response to the motile nature of the abdominal wall and the degenerative pathogenesis of hernia disease, a novel treatment concept has recently emerged. This concept centers on the Stenting & Shielding (S&S) Hernia System, a newly engineered device made from injection-molded polypropylene-based Thermo-Polymer Elastomer (TPE). Unlike conventional flat meshes, this 3D-structured device is designed to be positioned without fixation, effectively obliterating the hernia opening. Its intrinsic dynamic compliance allows it to move in harmony with the abdominal wall, leading to a biological response that is markedly different from that elicited by static meshes.

Experimental investigations on porcine models have demonstrated the regenerative properties of the S&S hernia device, which functions as a regenerative scaffold. Alongside the development of viable connective tissue, the S&S device supports the ingrowth of newly formed muscles and mature nerves. Crucially, to sustain the function of these specialized tissues, the concurrent development and maturation of a suitable vascular network is essential. The present study aims to demonstrate this specific feature at defined stages following the implantation of the S&S hernia device in experimental pigs.

2. Material and Methods

The experimental study was performed in strict accordance with the Animal Care Protocol for Experimental Surgery, as required by the Italian Ministry of Health. Approval for the protocol was granted under Decree No. 379/2021-PR, dated June 1st, 2021. The study is reported in line with the ARRIVE guidelines (Animals in Research: Reporting In Vivo Experiments. [15]

Between February 2022 and July 2024, ten female pigs with bilaterally created muscular defects in the lower abdomen were selected for the study. Each pig received laparoscopic placement of two Stenting & Shielding (S&S) Hernia Devices. The S&S device, designed to allow atraumatic and dissection-free repair of several types of abdominal wall hernias—in particular inguinal, but also incisional, femoral, Spigelian, and obturator hernias—was employed for this purpose.

Aged between 4 and 6 months, the animals had a body weight ranging from 40 to 60 kg. All laparoscopic interventions were carried out under general anesthesia that included premedication with zolazepam and tiletamine (6.3 mg/kg) and xylazine (2.3 mg/kg), followed by induction with propofol (0.5 mg/kg) and maintenance with isoflurane combined with pancuronium (0.07 mg/kg). Postoperative care included antibiotic prophylaxis with oxytetracycline (20 mg/kg/day) for three days.

2.1. Stenting & Shielding Hernia System: Structure

The S&S Hernia System used in this study is fabricated from medical-grade, polypropylene-based Thermo-Polymer Elastomer (TPE). The mechanical properties of the material are presented in Table 1.

The device comprises two main components: an eight-rayed structure contouring a central mast, and a 3D oval shield dimensioned 10x8 cm with a ring positioned at its center. The mast is equipped with a button-like structure at its distal end, along with two conic enlargements (stops) in proximity of the button. Initially, the device is configured as a cylindrical unit, with the oval shield threaded onto the mast via its central ring (Figure 1A & B). This design allows the device to be delivered through a 12 mm trocar into the abdominal cavity. Once positioned inside the hernia defect, a metallic tube is used to advance the oval shield forward into the muscular defect. As the shield is moved beyond one or both conic stops on the mast, the cylindrical rayed structure expands inside the defect, creating an oval 3D scaffold that permanently occupies the hernia opening. This configuration locks the shield, preventing backward slippage, and blocks the scaffold within the defect, with the shield overlapping the muscular opening and making contact with the abdominal viscera (Figure 1C). The final diameter of the 3D scaffold used in this study is approximately 4.5 cm.

2.2. Follow-Up Protocol

Of the 10 pigs, 2 were sacrificed between 4 and 6 weeks postoperatively (short-term period), 2 between 3 and 4 months (mid-term), 5 between 6 and 8 months (long-term), and 1 at 18 months (extra-long-term). Scheduled ultrasound (Figure 1D) and laparoscopic evaluations were conducted at planned postoperative stages to confirm the proper positioning of the 3D scaffold and to visually verify if adhesions between abdominal viscera and shield were present.

At the time of euthanasia, all S&S devices were removed through an incision in the lower midline. The S&S devices were then carefully cleared of the host’s native tissue and cut in half for macroscopic evaluation of the tissue ingrown within the 3D scaffold (Figure 2).

The explanted devices were subsequently sent for a comprehensive histological evaluation regarding the development of the vascular elements.

2.3. Histology and Immunohistochemistry Methods

Tissue specimens removed from the core of the 3D scaffold of the S&S device were fixed in 10% phosphate-buffered formalin for a minimum of 12 hours before being embedded in paraffin. Sections of 4 μm thickness were cut and stored at room temperature until use. Routine histology (Hematoxylin–eosin staining, H&E) was performed to assess the histomorphological characteristics of the tissues developed within the 3D scaffold of the S&S device at the planned postoperative stages. Immunohistochemistry was carried out using CD31 (clone JC70A, 1:50 dilution, Dako-Agilent, Carpinteria, CA, USA),staining to assess the vascular density in the specimens.

2.4. Histologic and Immunohistochemical Assessment

Tissue samples were analysed by light microscopy at high magnification to examine the S&S device-tissue interface. A semi-quantitative histological analysis was conducted, focusing on the quantity and quality of the vascular elements identified in the histological slides. The morphological features of the vascular structures were assessed using digital images of the stained sections. Images were captured using a bright-light microscope, digital camera, and image capture software (Leica DMLB microscope, Nikon DS-Fi-1 digital camera, NIS Basic Research Nikon software).

2.5. Statistical Analysis

Vascular density was detected with CD 31 in 20 biopsies of the 3D dynamic implant excised at different times post implantation. Four samples 3-5 weeks (short term) post-surgery (PS), 4 samples 3-4 months PS (mid-term), 10 samples 6-8 months PS (long term) and 2 samples at 18 months post-surgery, were analyzed. A one-way ANOVA between 20 biopsies was conducted to compare the vascular density in 3D dynamic prosthesis for inguinal repair with respect to time (ST = short term, MT = mid-term, LT = long term). Moreover, the Tukey–Kramer multiple comparison test was used to assess significance of differences between stages. A p value <0.05 was considered significant. GraphPad Software (Inc., San Diego, CA, USA) was used for the analyses.

3. Results

Tissue specimens and their corresponding histological sections were evaluated by two pathologists who were blinded to the timing of the implants. Biopsies taken from the 3D scaffold of the S&S device during the short-term period (3-5 weeks post-implantation) revealed an abundant presence of early-stage vascular clusters near the scaffold material, with minimal inflammatory response observed (Figure 3, Figure 4, Figure 5 and Figure 6).

In the mid-term period (3-4 months post-implantation), H&E staining showed a significant presence of vascular structures within the S&S device. Notably, no inflammatory elements were detected at this stage. The arterial structures displayed advanced development, with well-defined endothelial and muscular layers, while the adventitia was properly enveloping the vessels. Similarly, the veins exhibited noticeable structural maturation compared to the earlier period (Figure 7, Figure 8 and Figure 9).

In the long-term period (6-8 months post-implantation), there was a complete absence of inflammation, and the newly formed arteries and veins demonstrated full structural maturation across all components (Figure 11, Figure 12, Figure 13, Figure 14 and Figure 15).

Microphotographs from the extra-long-term period highlighted a fully consolidated state of vascular maturation. At this stage, all three layers of the arteries—intima, media, and adventitia—exhibited an ideal configuration, closely resembling the typical structure of mature arteries (Figs.). This optimal structural formation was also evident in all components of the venous structures within the 3D scaffold of the S&S device (Figure 16, Figure 17, Figure 18, Figure 19 and Figure 20).

Statistical Analysis

Vascular density of 20 biopsies excised from the 3D dynamic implant at different stages post implantation were compared with one-way Anova and post hoc Tukey test. Results showed statistically significant differences between stages (Table 2) and, in particular, suggested that vascular density in the 3D scaffold of the S&S Hernia System increases over time, up to extra-long term when it was slightly reduced compared to long term stage. Specifically, these outcomes seem to prove that in the long-term vascular density is significantly greater than in the short-term.

4. Discussion

This study aimed to evaluate the integration of newly formed vascular structures within the dynamic, responsive scaffold of the Stenting & Shielding (S&S) Hernia System over defined postoperative periods: short-, mid-, long-, and extra-long-term. The rationale for selecting these specific time frames is rooted in established research, which indicates that by 6-8 months post-implantation, tissue integration with hernia implants generally reaches completion and stabilizes [16,17,18].

The importance of angiogenesis in traditional static hernia meshes has been well-documented. These conventional, flat implants prompt the early onset of vascular proliferation soon after implantation. Initially, this new vascular network supports the incorporation of the mesh through fibrotic tissue growth [17,18,19,20,21,22,23,24]. However, as the process continues, these meshes become encapsulated in a rigid, fibrotic layer, leading to implant shrinkage. [25,26,27,28,29,30,31,32,33,34] During this phase, the vascular network is reduced and primarily functions to sustain the chronic inflammatory response—characterized by macrophages, lymphocytes, and plasma cells—that is typical of these prostheses. [35,36,37] The resulting tissue is often of poor quality, forming dense, stiff scar tissue that can lead to complications such as adhesion formation and nerve entrapment, especially in the inguinal region, potentially causing discomfort and chronic pain.

Understanding the biological processes involved in neo-vessel formation within newly developed tissue is crucial for appreciating the differences observed with the S&S device. Angiogenesis, the process of new blood vessel formation, is essential for providing the necessary metabolic support to developing tissues. [38,39,40,41,42] However, in conventional hernia meshes, the vascular network often fails to fully mature; instead, it primarily supports the maintenance of chronic inflammation rather than nourishing healthy tissue growth. [43] This is not the case with the S&S Hernia System.

In contrast, the S&S device’s dynamic and responsive nature appears to foster a more robust and enhanced biological response. The progressive ingrowth of healthy tissue, supported by continuous and effective angiogenesis, is essential for the development and maturation of complex tissue structures, such as muscle and nerve fibers. The findings of this study suggest that angiogenesis within the 3D scaffold of the S&S device is not only persistent but also evolves in tandem with the development of these highly specialized tissue components.

In the short term, the histological analysis revealed the presence of immature vascular structures, indicative of early-stage angiogenesis. By the mid-term, a more extensive and organized vascular network had formed, with ongoing vascular development occurring within the 3D scaffold. In the long-term phase, the study observed the continued maturation of these vascular elements, which paralleled the development of other tissue components, particularly muscle fibers and nerves. By this stage, the muscular layer of the arterial and venous walls had fully matured, demonstrating the establishment of a competent vascular network capable of sustaining the newly formed, sophisticated tissues within the scaffold.

Finally, in the extra-long period, the vascular structures reached full maturation and appeared significantly more compact than in the previous stage. This likely explains the slight reduction in vascular density observed compared to the long-term period. In this final phase of vascular development, all vessel elements—arteries, veins, and capillaries—exhibited the structural characteristics of fully matured vessels. This well-established vascular network ensures adequate blood supply to the newly formed tissues, particularly muscle and nerve tissues, within the S&S device. All these evidences have been confirmed in detail by the statistical assessment.

Overall, the findings of this study align with previous research that highlights the regenerative capabilities of dynamic scaffolds in hernia repair. [44,45,46,47,48] The S&S Hernia System, with its ability to support ongoing angiogenesis and tissue maturation, demonstrates significant potential as a dynamic regenerative scaffold for the effective treatment of hernia defects.

5. Conclusions

The histological findings from this study suggest that the biological response to synthetic hernia implants is strongly influenced by their structural design. Traditional static and passive flat meshes consistently trigger a foreign body reaction, leading to the formation of stiff, avascular scar tissue. In contrast, when the same synthetic material is configured in a 3D, dynamic structure like the Stenting & Shielding (S&S) Hernia System, the biological response is markedly different. The S&S device, designed to move in harmony with the abdominal wall, fosters a more favorable environment for tissue regeneration. This dynamic interaction appears to promote the ingrowth of muscle fibers, innervated by mature nerve structures, all supported by a well-developed network of blood vessels. Essentially, this device functions as a regenerative scaffold, aligning with the therapeutic goals of addressing the tissue degeneration underlying hernia formation. However, a significant limitation of this study is the lack of a clear explanation for the mechanisms driving the observed neoangiogenesis. Preliminary observations suggest that tissue growth factors may play a role in enhancing the biological response and sustaining the development of new vascular structures. Further research is needed to elucidate these mechanisms. The promising results from this animal model lay a strong basis for future clinical investigations. These studies will be crucial in determining whether the positive biological responses observed here can be replicated in humans. If validated, the S&S Hernia System could represent a significant advancement in hernia repair, potentially simplifying surgical procedures and improving patient outcomes.