Assessment of the Antimicrobial Activity of Acellular Vascular Grafts

Amnion bilayer for dressing and graft replacement for delayed grafting of full-thickness burns; A study in a rat model

Burn is a common case in developing countries, with over half of fire-related deaths reported in Southeast Asia and full-thickness burns as a high mortality risk. Human amnion has been used as a wound dressing for centuries. In this study, a decellularised amnion overlaid with fibrin, “amnion bilayer (AB),” was used as a dressing immediately after burn and as a graft to replace the scar in Sprague-Dawley rats subjected to full-thickness burn model. The aim was to observe whether amnion bilayer can reduce damages in third-grade burn when skin replacement is deemed impossible. The burn was induced using an electrical solder, heated for 5 mins, and contacted on the rat’s bare skin for 20 s. AB was applied as a (i) dressing immediately after induction and graft after eschar removal. Two groups (n = 6) were compared: AB and Sofra-Tulle ^®, the National Hospital of Indonesia (NHI) protocol. Sections were stained with hematoxylin and eosin and Masson trichrome stains. Immunohistochemistry labelling was used to indicate scars (α-smooth muscle actin [α-SMA] and collagen-1) and angiogenesis (von Willebrand factor). Also, the macrophages inflammatory protein-3α (MIP-3α) indicates an early inflammatory process. The post dressing of the AB group demonstrated hair follicle remains and adipose tissue development. The NHI group appeared with a denatured matrix. Complete healing was seen in the AB group after 28 days with skin appendages similar to normal, while the NHI group showed no appendages in the centre of the actively inflamed area. The α-SMA was found in both groups. Collagen-1 was highly expressed in the NHI group, which led to a scar. Angiogenesis was found more in the AB group. The AB group had shown the capacity to accelerate complete healing and recover skin appendages better than the current protocol.

Successful treatment of left ventricular patch infection by latissimus dorsi muscle flap covering without patch removal

Removal of the infected prosthesis is considered an essential procedure in the treatment of prosthetic graft infection following cardiovascular surgery. Here, we present a case of left ventricular patch infection following repair of left ventricular rupture that was successfully treated by coverage with a latissimus dorsi muscle flap without patch removal. A 61-year-old man underwent double-patch repair for left ventricular-free wall rupture following posterior myocardial infarction. He underwent drainage and omental transposition with re-sternotomy for postoperative mediastinitis by Candida albicans, followed by pericardial fenestration via left thoracotomy for infectious pericarditis; however, left ventricular patch infection was detected. Considering the high invasiveness of a reoperation for patch removal, we preserved and covered the patch using a left pedicled latissimus dorsi muscle flap via left thoracotomy. The postoperative course was uneventful, and the patient was asymptomatic with no signs of recurrence at 30 months.

Open Repair of Mycotic Abdominal Aortic Aneurysms With Biological Grafts: An International Multicenter Study

BACKGROUND

The treatment of mycotic abdominal aortic aneurysm requires surgery and antimicrobial therapy. Since prosthetic reconstructions carry a considerable risk of reinfection, biological grafts are noteworthy alternatives. The current study evaluated the durability, infection resistance, and midterm outcome of biological grafts in treatment of mycotic abdominal aortic aneurysm.

METHODS AND RESULTS

All patients treated with biological graft in 6 countries between 2006 and 2016 were included. Primary outcome measures were 30- and 90-day survival, treatment-related mortality, and reinfection rate. Secondary outcome measures were overall mortality and graft patency. Fifty-six patients (46 males) with median age of 69 years (range 35-85) were included. Sixteen patients were immunocompromised (29%), 24 (43%) had concomitant infection, and 12 (21%) presented with rupture. Bacterial culture was isolated from 43 (77%). In-situ aortic reconstruction was performed using autologous femoral veins in 30 patients (54%), xenopericardial tube-grafts in 12 (21%), cryopreserved arterial/venous allografts in 9 (16%), and fresh arterial allografts in 5 (9%) patients. During a median follow-up of 26 months (range 3 weeks-172 months) there were no reinfections and only 3 patients (5%) required assistance with graft patency. Thirty-day survival was 95% (n=53) and 90-day survival was 91% (n=51). Treatment-related mortality was 9% (n=5). Kaplan-Meier estimation of survival at 1 year was 83% (95% confidence interval, 73%-94%) and at 5 years was 71% (52%-89%).

CONCLUSIONS

Mycotic abdominal aortic aneurysm repair with biological grafts is a durable option for patients fit for surgery presenting an excellent infection resistance and good overall survival.

Rat peripheral nerve regeneration using nerve guidance channel by porcine small intestinal submucosa

Objective

In order to develop a novel nerve guidance channel using porcine small intestinal submucosa (SIS) for nerve regeneration, we investigated the possibility of SIS, a tissue consisting of acellular collagen material without cellular immunogenicity, and containing many kinds of growth factors, as a natural material with a new bioactive functionality.

Methods

Left sciatic nerves were cut 5 mm in length, in 14 Sprague-Dawley rats. Grafts between the cut nerve ends were performed with a silicone tube (Silicon group, n=7) and rolled porcine SIS (SIS group, n=7). All rats underwent a motor function test and an electromyography (EMG) study on 4 and 10 weeks after grafting. After last EMG studies, the grafts, including proximal and distal nerve segments, were retrieved for histological analysis.

Results

Foot ulcers, due to hypesthesia, were fewer in SIS group than in Silicon group. The run time tests for motor function study were 2.67 seconds in Silicon group and 5.92 seconds in SIS group. Rats in SIS group showed a better EMG response for distal motor latency and amplitude than in Silicon group. Histologically, all grafts contained some axons and myelination. However, the number of axons and the degree of myelination were significantly higher in SIS group than Silicon group.

Conclusion

These results show that the porcine SIS was an excellent option as a natural biomaterial for peripheral nerve regeneration since this material contains many kinds of nerve growth factors. Furthermore, it could be used as a biocompatible barrier covering neural tissue.

Small intestinal submucosa segments as matrix for tissue engineering: review

Tissue engineering (TE) is an emerging interdisciplinary field aiming at the restoration or improvement of impaired tissue function. A combination of cells, scaffold materials, engineering methods, and biochemical and physiological factors is employed to generate the desired tissue substitute. Scaffolds often play a pivotal role in the engineering process supporting a three-dimensional tissue formation. The ideal scaffold should mimic the native extracellular environment providing mechanical and biological properties to allow cell attachment, migration, and differentiation, as well as remodeling by the host organism. The scaffold should be nonimmunogenic and should ideally be resorbed by the host over time, leaving behind only the regenerated tissue. More than 40 years ago, a preparation of the small intestine was introduced for the replacement of vascular structures. Since then the small intestinal submucosa (SIS) has gained a lot of interest in TE and subsequent clinical applications, as this material exhibits key features of a highly supportive scaffold. This review will focus on the general properties of the SIS and its applications in therapeutical approaches as well as in generating tissue substitutes in vitro. Furthermore, the main problem of TE, which is the insufficient nourishment of cells within three-dimensional, artificial tissues exceeding certain dimensions is addressed. To solve this issue the implementation of another small intestine-derived preparation, the biological vascularized matrix (BioVaM), could be a feasible option. The BioVaM comprises in addition to SIS the arterial and venous mesenteric pedicles and exhibits thereby a perfusable vessel bed that is preserved after decellularization.