A novel biosynthetic scaffold mesh reinforcement affords the lowest hernia recurrence in the highest-risk patients

Advances, challenges, and future directions in the clinical translation of ECM biomaterials for regenerative medicine applications

Extracellular Matrix (ECM) scaffolds and biomaterials have been widely used for decades across a variety of diverse clinical applications and have been implanted in millions of patients worldwide. ECM-based biomaterials have been especially successful in soft tissue repair applications but their utility in other clinical applications such as for regeneration of bone or neural tissue is less well understood. The beneficial healing outcome with the use of ECM biomaterials is the result of their biocompatibility, their biophysical properties and their ability to modify cell behavior after injury. As a consequence of successful clinical outcomes, there has been motivation for the development of next-generation formulations of ECM materials ranging from hydrogels, bioinks, powders, to whole organ or tissue scaffolds. The continued development of novel ECM formulations as well as active research interest in these materials ensures a wealth of possibilities for future clinical translation and innovation in regenerative medicine. The clinical translation of next generation formulations ECM scaffolds faces predictable challenges such as manufacturing, manageable regulatory pathways, surgical implantation, and the cost required to address these challenges. The current status of ECM-based biomaterials, including clinical translation, novel formulations and therapies currently under development, and the challenges that limit clinical translation of ECM biomaterials are reviewed herein.

An established abdominal wall multidisciplinary team improves patient care and aids surgical decision making with complex ventral hernia patients

INTRODUCTION

Abdominal wall reconstruction (AWR) is an emerging subspecialty within general surgery. The practice of multidisciplinary team (MDT) meetings to aid decision making and improve patient care has been demonstrated, with widespread acceptance. This study presents our initial experience of over 150 cases of complex hernia patients discussed in a newly established MDT setting.

METHODS

From February 2020 to July 2022 (30-month period), abdominal wall MDTs were held bimonthly. Key stakeholders included upper and lower gastrointestinal surgeons, a gastrointestinal specialist radiologist, a plastic surgeon, a high-risk anaesthetist and two junior doctors integrated into the AWR clinical team. Meetings were held online, where patient history, past medical and surgical history, hernia characteristics and up-to-date computed tomography scans were discussed.

RESULTS

Some 156 patients were discussed over 18 meetings within the above period. Ninety-five (61%) patients were recommended for surgery, and 61 (39%) patients were recommended for conservative management or referred elsewhere. Seventy-eight (82%) patients were directly waitlisted, whereas seventeen (18%) required preoperative optimisation: three (18%) for smoking cessation, eleven (65%) for weight-loss management and three (18%) for specialist diabetic assessment and management. In total, 92 (59%) patients (including operative and nonoperative management) have been discharged to primary care.

DISCUSSION

A multidisciplinary forum for complex abdominal wall patients is a safe process that facilitates decision making, promotes education and improves patient care. As the AWR subspecialty evolves, our view is that the "complex hernia MDT" will become commonplace. We present our experience and share advice for others planning to establish an AWR centre.

Semiresorbable biologic hybrid meshes for ventral abdominal hernia repair in potentially contaminated settings: lower risk of recurrence

In case of potential contamination, implantation of synthetic meshes in hernia and abdominal wall surgery is problematic due to a higher risk of mesh infection. As an alternative, a variety of different biologic meshes have been used. However, relevant data comparing outcome after implantation of these meshes are lacking. Between January 2012 and October 2021, biologic meshes were used for reconstruction of the abdominal wall in 71 patients with preoperative or intraoperative abdominal contamination. In this retrospective study, semiresorbable biologic hybrid meshes (BHM) and completely resorbable meshes (CRM) were compared and analyzed using a Castor EDC database. In 28 patients, semiresorbable biologic hybrid meshes were used; in 43 patients, completely resorbable meshes were used. Both groups showed no difference in age, gender, BMI, operation duration, hernia size and Charlson comorbidity index. The risk degree of surgical-site occurrences was graded according to the Ventral Hernia Working Group (VHWG) classification, and the median value was 3 (range 2-4) in the BHM group and 3 (range 2-4) in the CRM group. Hernia recurrence within 24 months after hernia repair was significantly lower in the BHM group (3.6% vs. 28.9%; p = 0.03), while postoperative complication rate, with respect to seromas in need of therapy (61.4% vs. 55.5%, p = 0.43) and operative revision (28.6% vs. 16.3%, p = 0.22) was not different in either group. Biologic hybrid meshes can be used safely in case of possible contamination. BHM seems to reduce the risk of hernia recurrence compared to completely resorbable biologic meshes, but this has to be investigated further.

In-Vivo Evaluation of a Reinforced Ovine Biologic for Plastic and Reconstructive Procedures in a Non-human Primate Model of Soft Tissue Repair

BACKGROUND

Biologic matrices are used in plastic and reconstructive surgical procedures to aid in the kinetics of soft tissue repair and promote functional tissue formation. The human acellular dermal matrix AlloDerm is widely used; however, it is offered at a relatively high cost, and its dermal composition may not provide an ideal remodeling scaffold. OviTex Plastic and Reconstructive Surgery (PRS) Resorbable and Permanent are reinforced biologic matrices engineered with layers of ovine forestomach matrix embroidered with small amounts of polymer to optimize biophysical performance. This study compared the healing outcomes of these matrices in a non-human primate model of soft tissue repair.

METHODS

Animals were implanted with test articles in surgically created full-thickness midline abdominal wall defects and evaluated macroscopically and histologically at 2, 4, 12, and 24 weeks.

RESULTS

Both OviTex PRS Permanent and Resorbable matrices exhibited earlier host cell infiltration, neovascularization, and collagen deposition and also fully remodeled into the host tissue by 12 weeks post implantation. AlloDerm had less host cell infiltration and neovascularization at early time points and never fully integrated into the surrounding host tissue. There was no statistical difference in overall inflammation between AlloDerm and either OviTex PRS product at any time point, despite small amounts of polymer reinforcement in OviTex products.

CONCLUSIONS

In a primate soft tissue repair model, OviTex PRS Permanent and Resorbable matrices performed comparably with the leading human acellular dermal matrix. OviTex PRS Permanent and Resorbable are less expensive than alternatives like AlloDerm and may promote faster host cell proliferation and functional remodeling in some soft tissue repair applications.

Losartan modifies mesh integration after abdominal wall repair: an experimental study

PURPOSE

Angiotensin II (AT II) receptor blockers have previously shown to reduce inflammatory response in many settings. We aimed to assess the effects of ATII receptor blocker (Losartan) on mesh integration after abdominal wall repair in a rat model.

METHODS

A total of 16 Wistar-Kyoto (WKY) and 16 previously hypertensive (SHRSP) rats were isolated. An acute ventral hernia followed by a bridged repair with heavyweight polypropylene mesh was performed. Subjects received either normal saline (WKY-C n = 8 and SHRPS-C n = 8) or 40 mg/kg losartan (WKY-L n = 8) and SHRPS-L n = 8) in the postoperative period. Blood pressure was recorded preoperatively and weekly after surgery. Necropsy with en-bloc resection of the abdominal wall was performed at postoperative day 30. Macroscopic and microscopic evaluations of the specimens were conducted. H&E and Masson's trichrome were used for histologic evaluation.

RESULTS

Both groups receiving Losartan showed a significant reduction of blood pressure after surgery (WKY-L: 130/85 vs 116/81 mmHg, SHRPS-L: 176/137 vs 122/101 mmHg, p < 0.01). A significant reduction in mesh incorporation and adherence scores were also observed on macroscopic analysis in Losartan groups (p < 0.01 and p   = 0.02, respectively). Microscopically, higher immature fibroplasia was observed after Losartan, with a significant reduction in scar plate formation and inflammatory response on the prosthetic surface (p = 0.04 and p  = 0.02, respectively).

CONCLUSION

Losartan modifies the interaction between the host tissue and the prosthesis. An impairment in mesh integration and immature fibroplasia in both normotensive and hypertensive rats detected in our model warrants further research.

Clinical outcomes of open abdominal wall reconstruction with the use of a polypropylene reinforced tissue matrix: a multicenter retrospective study

Objective

To assess mesh behaviour and clinical outcomes of open complex abdominal wall reconstruction (CAWR) with the use of a polypropylene reinforced tissue matrix.

Methods

A multicenter retrospective study of adult patients who underwent open CAWR with the use of a permanent polypropylene reinforced tissue matrix (OviTex^®) between June 2019 and January 2021.

Results

Fifty-five consecutive patients from four hospitals in the Netherlands were analysed; 46 patients with a ventral hernia and 9 patients with an open abdomen. Most patients with a ventral hernia had one or more complicating comorbidities (91.3%) and one or more complicating hernia characteristics (95.7%). Most procedures were performed in a (clean) contaminated surgical field (69.6% CDC 2–4; 41.3% CDC 3–4). All nine patients with an open abdomen underwent semi-emergent surgery. Twelve out of 46 patients with a ventral hernia (26.1%) and 4 of 9 patients with an open abdomen (44.4%) developed a postoperative surgical site infection that made direct contact with the mesh as confirmed on computed tomography (CT), suspicious of mesh infection. No patient needed mesh explantation for persistent infection of the mesh. During a median follow-up of 13 months, 4 of 46 ventral hernia patients (8.7%) developed a CT confirmed hernia recurrence.

Conclusion

Polypropylene reinforced tissue matrix can withstand infectious complications and provides acceptable mid-term recurrence rates in this retrospective study on open complex abdominal wall reconstructions. Longer follow-up data from prospective studies are required to determine further risk of hernia recurrence.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10029-022-02604-y.

Chest Wall Reconstruction Utilizing Ovine-Derived Reinforced Tissue Matrix

BACKGROUND

Chest wall reconstruction (CWR) can be a challenge. The perfect material does not exist to restore CW stability. Synthetic materials have been the mainstay for reconstruction. Biological material use has increased. Recently, we initiated the use of a biosynthetic material (BSM) for CWR that is composed of ovine-derived extracellular tissue matrix and monofilament polypropylene suture.

METHODS

We respectively reviewed all patients who underwent CWR with a BSM from January 2020 - June 2021.

RESULTS

Twenty-five patients underwent CWR. Median age was 35 years (18 - 68); 64% were men. Indication for CWR was tumor resection in 10, chest wall defect after pectus repair in 7, radiation necrosis in 5, chest wall infection in 2 and lung herniation in 1. Infection was present in 28%. Median CW defect was 7 x 10 cm (3.5 - 22.5 cm). Bioabsorbable bars were used in combination with the BSM patch in 15 patients (60%) and BSM alone in 10; 5 patients underwent myocutaneous advancement flaps. There were no operative deaths. Postoperative complications occurred in 6 patients (24%). Median hospital stay was 5 days (3 - 14). Late complications occurred in 4 patients (16%). No patient developed paradoxical motion, chest wall instability, or required BSM removal at a median follow-up of 12 months (1 - 18).

CONCLUSIONS

This novel BSM combines the benefits of biologic material and polymer reinforcement to provide a more natural CWR compared to mesh products made of synthetic material alone. Early results are promising in this first series in the literature.

Further structural characterization of ovine forestomach matrix and multi-layered extracellular matrix composites for soft tissue repair

Decellularized extracellular matrix (dECM)-based biomaterials are of great clinical utility in soft tissue repair applications due to their regenerative properties. Multi-layered dECM devices have been developed for clinical indications where additional thickness and biomechanical performance are required. However, traditional approaches to the fabrication of multi-layered dECM devices introduce additional laminating materials or chemical modifications of the dECM that may impair the biological functionality of the material. Using an established dECM biomaterial, ovine forestomach matrix, a novel method for the fabrication of multi-layered dECM constructs has been developed, where layers are bonded via a physical interlocking process without the need for additional bonding materials or detrimental chemical modification of the dECM. The versatility of the interlocking process has been demonstrated by incorporating a layer of hyaluronic acid to create a composite material with additional biological functionality. Interlocked composite devices including hyaluronic acid showed improved in vitro bioactivity and moisture retention properties.

Outcomes of biosynthetic absorbable mesh use in high risk CDC Class I ventral hernia repair: a single surgeon series

PURPOSE

Biosynthetic absorbable meshes have emerged as suitable alternatives to permanent synthetic and biologic meshes in complex ventral hernia repair in contaminated wounds. Evidence regarding the use of these products in clean wounds is currently scant. This paper presents a large single surgeon series using GORE^®BIO-A^® (W.L. Gore & Associates, Newark, DE) (Bio-A) tissue reinforcement in high risk patients with predominantly CDC Class I wounds.

METHODS

Retrospective review of a prospectively maintained database of consecutive patients who underwent open ventral hernia repair with biosynthetic absorbable mesh was conducted. Ventral Hernia Working Group (VHWG) classification based on patient demographics and Centers for Disease Control (CDC) wound type were collected prospectively. All patients were followed up for a minimum of 12 months post-operatively.

RESULTS

155 patients were included with a mean post-operative follow up of 29 months (range 12-62 months). Mean age was 61.8 years with an average BMI of 33.5 kg/m². 147 patients (94.9%) were classified as VHWG 2 or 3 based on comorbidities or surgical field contamination. 69% (n = 107) of wounds were designated CDC Class I. Mean hernia size was 119.7cm² with recurrent defects comprising 32.3% (n = 50). Retrorectus mesh repair was achieved in 84.5% of patients (n  = 131). Post-operative wound events occurred in 19.3%. No mesh was explanted. Hernia recurrence rate was 9.0% with a mean time to recurrence of 14 months. There was no significant difference in recurrence rates between clean and contaminated wounds.

CONCLUSION

This study supports the use of Bio-A in high risk ventral hernias, demonstrating a safe and durable repair across all wound classes. Ongoing follow-up continues to monitor for late complications and recurrence.