Porcine small intestinal submucosa as a carrier for skin flap prefabrication

Bioengineered tissue solutions for repair, correction and reconstruction in cardiovascular surgery

The treatment of cardiac alterations is still nowadays a dramatic issue in the cardiosurgical practice. Synthetic materials applied in this surgery have failed in their long-term therapeutic efficacy due to low biocompatibility and compliance, especially when used in contractile sites. In order to overcome these treatment pitfalls, novel solutions have been developed based on biological tissues. Patches in pericardium, small intestinal submucosa, as well as engineered tissues of myocardium, heart valves and blood vessels have undergone a large preclinical investigation in regenerative medicine studies. Clinical translation has been started or reached by several of these new bioengineered treatment alternatives. This review will describe the preclinical and clinical experiences realized so far with the application of biological tissues in cardiovascular surgery. It will depict the progressive steps realized in the evolution of this research, as well as it will point out the challenges yet to face in order to generate the ideal biomaterial for cardiovascular repair, corrective and reconstructive surgery.

Utilizing biologic assimilation of bovine fetal collagen in staged skin grafting

Seven patients underwent 2-stage skin grafting with bovine fetal collagen (BFC) as an initial wound cover. Split-thickness skin grafts were successfully placed on the wounds after completion of interval management. BFC proved to be a resilient acellular dermal matrix that could proceed to assimilation and skin grafting under a variety of wound conditions. BFC may prove to be a valuable material, as the role of acellular dermal matrices in skin grafting becomes better defined.

FDA approved guidance conduits and wraps for peripheral nerve injury: a review of materials and efficacy

Several nerve guidance conduits (NGCs) and nerve protectant wraps are approved by the US Food and Drug Administration (FDA) for clinical use in peripheral nerve repair. These devices cover a wide range of natural and synthetic materials, which may or may not be resorbable. This review consolidates the data pertaining to all FDA approved materials into a single reference, which emphasizes material composition alongside pre-clinical and clinical safety and efficacy (where possible). This article also summarizes the key advantages and limitations for each material as noted in the literature (with respect to the indication considered). In this context, this review provides a comprehensive reference for clinicians which may facilitate optimal material/device selection for peripheral nerve repair. For materials scientists, this review highlights predicate devices and evaluation methodologies, offering an insight into current deficiencies associated with state-of-the-art materials and may help direct new technology developments and evaluation methodologies thereof.

Structural characteristics of small intestinal submucosa constructs dictate in vivo incorporation and angiogenic response

The rate of angiogenesis and cellular infiltration into degradable biomaterials determines scaffold persistence in vivo. The ability to tune the degradation properties of naturally derived biomaterials has been a popular goal in tissue engineering, yet has often depended on chemical crosslinking. Small intestinal submucosa (SIS) is a naturally derived, collagen-based, bioactive scaffold that has broad clinical success in many therapeutic applications. Two methods for producing multilayer, non-crosslinked SIS constructs were compared in vitro and in vivo. Traditional and cryo SEM, mercury intrusion porosimetry, and a novel enzymatic degradation assay determined that lyophilization produced an open, porous scaffold, in contrast to the collapsed, denser structure of SIS constructs produced using a vacuum press process. The angiogenic responses to lyophilized and vacuum-pressed SIS constructs were evaluated in vivo using a subcutaneous implant assay in mice. Explanted samples were compared after 7 and 21 days using fluorescence microangiography and light microscopy. Capacity of the implant neovasculature was also determined. These experiments revealed that the lyophilized SIS was infiltrated and vascularized more rapidly than the vacuum pressed. These data demonstrate the tunable incorporation of a non-crosslinked ECM-based biomaterial, which may have implications for the persistence of this degradable scaffold in tissue engineering.

The porcine small intestinal submucosa (SIS) patch in foot and ankle reconstruction

We undertook a retrospective cohort study of 54 patients who underwent foot and ankle soft tissue reconstructive surgery augmented with a porcine small intestinal submucosal (SIS) patch. The mean patient age was 44 (range 17 to 68) years, there were 21 (38.89%) males in the cohort, and the mean follow-up duration was 1080 (range 365 to 1943) days. Clinical outcomes were considered excellent in 46 (85.19%) patients, good/fair in 3 (5.56%) patients, and poor in 5 (9.26%) patients; and no adverse events attributable to the xenograft were observed. Direct SIS patch failure, resulting in stretching of the repair, re-tear, or tendon stenosis, occurred in 3 (5.56%) patients, and delayed incision healing occurred in 6 (11.11%) patients. Based on our observations, we concluded that the porcine SIS xenograft, when used to augment cellular and vascular in-growth, is a viable adjunct to musculoskeletal reconstructions of the foot and ankle.

Metacarpophalangeal collateral ligament reconstruction using small intestinal submucosa in an equine model

Xenogeneic porcine small intestinal submucosa (SIS) is a natural, biodegradable matrix that has been successfully used as a scaffold for repair of tissue defects. The goal of this study was to compare a collateral ligament transection surgically reconstructed with an anchored SIS ligament to a sham-operated control procedure for the correction of joint laxity using an equine model. Ten metacarpophalangeal joints from 10 horses had complete transection of the lateral collateral ligament. In 6 horses, the collateral ligament was reconstructed with a multilaminate strip of SIS anchored with screws into bone tunnels proximal and distal to the joint. The sham controls had similar screws, but no SIS placed. Clinical compatibility and effectiveness were evaluated with lameness, incisional quality, and joint range of motion, circumference and laxity. Ligament structure and strength was quantified with serial high resolution ultrasound, histology, and mechanical testing at 8 weeks. Surgical repair with SIS eliminated joint laxity at surgery. SIS-treated joints had significantly less laxity than sham treatment at 8 weeks (p < 0.001). SIS-treated ligaments demonstrated a progressive increase in repair tissue density and fiber alignment that by week 8 were significantly greater than sham-treated ligament (p < 0.03). SIS-repaired ligament tended to have greater peak stress to failure than sham-treatment (p < 0.07). Cellularity within the ligament repair tissue and inflammation within the bone tunnel was significantly greater in the SIS-treated limbs (p < 0.017). Within the first 8 weeks of healing, SIS implanted to reinforce collateral ligament injury was biocompatible in the joint environment, restored initial loss of joint stability, and accelerated early repair tissue quality. SIS ligament reconstruction might provide benefit to early ligament healing and assist early joint stability associated with ligament injury.

Jejunal Flap as an In Vivo Vascular Carrier for Transplanted Adipose Tissue

Few manuscripts describe the construction of an adipose tissue composite flap able to create an in vivo microenvironment and a neovasculature that can grow with and service implanted adipose tissue. Creation of an in vivo vascular carrier and tissue chamber for volume-stable transplanted adipose tissue was attempted using jejunum segments with intact circulation in 18 male Wistar rats. Intestinal segments were filled with autologous adipose tissue. Histologic (hematoxylin-eosin), immunohistochemical (antibodies to leptin and to vascular endothelial growth factor) and ultrastructural analyses were used to evaluate the results at 6, 18, and 60 days after surgery. Macroscopic observation confirmed the feasibility of this prefabricated adipose tissue flap: no loss of weight or volume occurred at any time point. Histologic analysis showed normal morphologic features of transplanted adipose tissue. Immunohistochemical studies confirmed the vitality of adipose tissue and the presence of a microvascular network within the flap. Small intestinal segments denuded of the mucosal layer can support in vivo transplanted adipose tissue.

Tissue engineering a clinically useful extracellular matrix biomaterial

Implantable biomaterials are one of the most useful tools in the surgeon's armamentarium, yet there is much room for improvement. Chronic pain, tissue erosion, and late infections are just a few of the serious complications that can occur with conventional, inert materials. In contrast, tissue-inductive materials exist today. Combinations of biologically important molecules for directing cell growth and providing structural stability can be found in naturally occuring extracellular matrices. These "soft-tissue skeletons" of Mother Nature can be harvested, processed, and provided in a medically safe and biologically active form for repairing many different tissues in the human body. The future of surgical practice may well be determined by how well these new implant materials recreate the tissues they replace.

Small intestinal submucosa does not promote PAIII tumor growth in Lobund-Wistar rats

BACKGROUND

Site-specific remodeling and angiogenesis are two observations associated with the use of small intestinal submucosa (SIS) as a tissue repair graft. Its angiogenic capacity has raised questions concerning its effect on tumor growth and metastasis in clinical tumor resection cases. The effect of SIS on the ability of neoplastic (prostate adenocarcinoma) cells to establish, grow, and metastasize was examined in Lobund-Wistar (L-W) rats.

MATERIALS AND METHODS

In one study, SIS, expanded polytetrafluoroethylene (ePTFE), or human cadaveric dermis was placed in a subcutaneous pocket on the flank of L-W rats and immediately inoculated with PA-III cell suspension. Tumors were allowed to establish and metastasize for 5 weeks prior to sacrifice. Rate of tumor growth, tumor weight, and frequency of lung metastases were assessed. In a second study, SIS was placed in a resected tumor bed and tumors were allowed to recur. Rate of tumor growth, tumor weight, and frequency of lung metastases were assessed after 3 weeks.

RESULTS

ePTFE hastened the rate of formation of palpable tumors compared to controls and other materials; cadaveric dermis and SIS did not. No differences between materials were noted in final tumor weight nor in the frequency of metastasis to the lungs. Following surgical tumor resection, residual tumor cells led to recurrence of same-site tumors in all animals, but in the defects augmented with SIS, the tumors were significantly smaller than those which regrew in the resected, unaugmented group.

CONCLUSIONS

This study demonstrates that SIS does not enhance tumor establishment, growth, or metastasis in de novo tumors. Furthermore, SIS appears to reduce the rate of tumor growth, but not metastasis, when applied in direct contact with a residual tumor bed in a rat model of prostate-related tumors.