Histotripsy of the prostate using a commercial system in a canine model.

PURPOSE: Histotripsy is a focused ultrasound technology that uses controlled acoustic cavitation to homogenize targeted tissue. We assessed local and systemic effects after histotripsy treatment with the Vortx RX® system in a canine model. The system was not approved for human use at the time of the study. MATERIALS AND METHODS: Histotripsy was applied in 10 intact male dogs. The therapy transducer (36 elements, 700 kHz and 11 cm focal distance) delivered acoustic bursts (3 cycles and 500 Hz pulse repetition frequency) transabdominally to the prostate for 60 minutes. Tissue and systemic response were assessed by transrectal ultrasound, cystoscopy and interval evaluation of blood and urine parameters. Prostates were harvested on postoperative day 2 in 2 dogs and on postoperative day 28 in 8. RESULTS: A treatment cavity was apparent in each prostate on transrectal ultrasound and cystoscopy. Mean prostate volume decreased 36% (range 19% to 53%) by postoperative day 28. Although clinical symptoms were not produced, notable pathological findings at necropsy consisted of rectal wall muscle degeneration in 2 animals and concern for a potential histotripsy effect and 1 cm diameter areas of fibrosis in the abdominal rectus muscle in 2 animals suggestive of thermal injury along the acoustic propagation path to the prostate. CONCLUSIONS: Extracorporeal application of histotripsy produced prostate debulking in all dogs. Pathological findings of collateral injury are of concern since this may represent suboptimal confinement of cavitation or heating of overlying tissue. Further study is under way to quantify the prefocal thermal fields to eliminate these effects before human application.

Salmon thrombin-fibrinogen dressing allows greater survival and preserves distal blood flow compared to standard kaolin gauze in coagulopathic Swine with a standardized lethal femoral artery injury.

We have previously shown that lyophilized salmon thrombin and fibrinogen (STF) embedded in a dissolvable dextran dressing is as efficacious as Combat Gauze (CG) with regard to controlling hemorrhage and survival in non-coagulopathic swine with femoral artery lacerations. A major limitation of currently available advanced field dressings is the inability to control hemorrhage in coagulopathic casualties because of the exhaustion of host coagulation proteins. We tested the hypothesis that the STF dressing would be better able to control hemorrhage and prolong survival in coagulopathic swine compared to CG. Survival rate was 50% in CG-treated animals versus 90% in STF-treated animals. Survival time was significantly greater in STF-treated animals. Clots formed over the arterial injury in 100% of STF-treated animals compared to 0% in CG-treated animals (p < 0.001). STF-treated animals consumed less host coagulation factors, including platelets (p = 0.03). Survival after limb manipulation that simulated casualty evacuation was significantly higher with the STF dressing (p < 0.005). Angiographic observation of distal blood flow was seen twice as often with the STF dressing as with CG. The STF dressing allows a high survival rate, significantly greater survival time, and a significantly more stable dressing than CG in coagulopathic swine. The clot formed by the STF dressing also enables restoration of distal blood flow to the limb potentially resulting in higher limb salvage.

A salmon thrombin-fibrinogen dressing controls hemorrhage in a swine model compared to standard kaolin-coated gauze.

BACKGROUND: Battlefield hemorrhage remains the primary cause of death in potentially survivable combat injuries with noncompressible hemorrhage. Fibrin dressings have great potential for reducing mortality, however are limited by cost, availability, and disease transmission. METHODS: Dressings comprising a soluble dextran dressing with lyophilized salmon thrombin and fibrinogen (STF) were tested against Combat Gauze (CG) as a control in a standard swine femoral artery hemorrhage model. Ten female swine were used in each arm of the study. RESULTS: Survival, blood loss, and time to hemostasis were similar between the two dressings. Two of the CGtreated animals that survived exsanguinated during the simulated walking maneuver. Three CG-treated animals formed a clot within the wound, but the clot did not adhere to the femoral artery injury. All ten of the STF-treated animals formed a clot in the wound that adhered and sealed the arterial injury site, even in three animals that did not survive. None of the STF-treated animals bled following the simulated walking maneuver. Three of five STF-treated animals reestablished blood flow distal to the injury as demonstrated by angiography. CONCLUSIONS: The STF dressing is as efficacious as CG in treating hemorrhage in this model of a lethal injury. Further, the STF dressing formed a fibrin sealant over the injury, whereas CG achieved hemostasis by occlusive compression of the artery. The sealant property of the STF dressing allowed reestablishment of antegrade blood flow into the distal limb, demonstrating that this dressing has the potential of limb salvage in addition to control of life-threatening hemorrhage.

Cardiac xenotransplantation: recent preclinical progress with 3-month median survival.

OBJECTIVES: Transplantation is limited by a lack of human organ donors. Organs derived from animals, most likely the pig, represent a potential solution to this problem. For the heart, 90-day median graft survival of life-supporting pig hearts transplanted to nonhuman primates has been considered a reasonable standard for entry into the clinical arena. Overcoming the immune barrier to successful cardiac xenotransplantation is most appropriately first explored with the non-life-supporting heterotopic model. METHODS: We performed a series of 7 heterotopic heart transplantations from CD46 transgenic pigs to baboons using a combination of therapeutic agents largely targeted at controlling the synthesis of anti-pig antibodies. Rituximab (anti-CD20) and Thymoglobulin (rabbit antithymocyte globulin [ATG]; SangStat Medical Corp, Fremont, Calif) were used as induction therapy. Baseline immunosuppression consisted of splenectomy, tacrolimus, sirolimus, steroids, and TPC (an anti-Gal antibody therapeutic). Rejection events were not treated. RESULTS: By using Kaplan-Meier analysis, median graft survival was 96 days (range, 15-137 days; 95% confidence interval, 38-99 days). Only 2 grafts were lost as a result of rejection, as defined by cessation of graft palpation. There was no evidence of a consumptive coagulopathy, infectious complications were treatable, and no posttransplantation lymphoproliferative disorders occurred. No cellular infiltration was observed. CONCLUSIONS: This study reports the longest median survival to date (96 days) of pig hearts transplanted heterotopically into baboons. Duplication of these results in the orthotopic life-supporting position could bring cardiac xenotransplantation to the threshold of clinical application.

Prevention, detection, and management of early bacterial and fungal infections in a preclinical cardiac xenotransplantation model that achieves prolonged survival.

BACKGROUND: We analyzed bacterial and fungal infectious complications in a cohort of 16 consecutive experiments with the longest surviving cardiac xenografts to date. METHODS: Transgenic, porcine-to-baboon, heterotopic (abdomen) cardiac xenotransplantation was performed in 16 consecutive experiments, using rapamycin, tacrolimus, corticosteroids, anti-CD20 monoclonal antibody, and an alpha-Gal-PEG polymer, as immunosuppression. Prophylactic anti-microbials included i.v. trimethoprim/sulfamethoxazole, oral ganciclovir/valganciclovir, and oral itraconazole. An episode of bacterial infection was defined as a positive blood and/or wound culture with: leukocytosis, fever >101.5 degrees F, and/or clinical deterioration. RESULTS: Mean graft survival was 71 +/- 29 days; the longest was 113 days. There were 23 episodes of bacterial infection; 14 resolved with treatment. The mean time to the first episode of infection was 44 +/- 21 days (n=12). Eight of 16 deaths were due to infection: two bacterial-only, two cytomegalovirus (CMV) only, four both bacterial and CMV, and none fungal. The frequency of infection was 1, 2.8, and 1.8 episodes/100 survival days, respectively, for animals whose grafts survived for 30 to 59, 60 to 89, and >90 days. CMV infection (reviewed in detail in a separate communications) was due to baboon CMV, and was associated with low serum levels of ganciclovir. CONCLUSION: In a cardiac xenograft model that achieved prolonged (>3 months) survival, bacteremia was common, but usually reversible, and fungal infection was prevented with prophylaxis. The level of immunosuppression required to achieve clinically meaningful xenograft survival is associated with a level of bacterial and fungal infectious complications that is manageable and similar to the early clinical experiences in human transplantation. Further research will determine if the viral infectious complications observed in these experiments can be reduced by optimizing blood levels of anti-viral prophylaxis and monitoring viral polymerase chain reaction levels.

Cardiac xenotransplantation: progress toward the clinic.

BACKGROUND: Animal organs could satisfy the demand for solid organ transplants, which currently exceeds the limited human donor supply. Hyperacute rejection, the initial immune barrier to successful xenotransplantation, has been overcome with pig donors transgenic for human complement regulatory proteins. Delayed xenograft rejection, thought to be mediated by anti-pig antibodies predominantly to Gal antigens, is currently regarded as the major barrier to successful xenotransplantation. A median graft survival of 90 days in the life-supporting position is considered a reasonable initial standard for consideration of entry to the clinic. METHODS: A series of 10 heterotopic heart transplants from CD46 transgenic pigs to baboons was completed. Immunosuppression consisted of splenectomy, Rituximab (Anti-CD20), tacrolimus, sirolimus, corticosteroids, and TPC. Thymoglobulin (Rabbit Anti-Thymocyte Globulin) was used to treat putative rejection episodes. RESULTS: Median graft survival was 76 days (range 56-113 days, n = 9). Only three grafts were lost to rejection. The remaining grafts lost were due to recipient mortality with baboon cytomegalovirus (BCMV) being the major cause (n = 4). No cellular infiltrates were present as a manifestation of rejection. Three hearts showed chronic graft vasculopathy. CONCLUSIONS: The median survival of 76 days in this group of heterotopic porcine-to-baboon cardiac xenografts represents a major advance over the median 27-day survival reported in the literature. Cellular rejection may not constitute a direct major barrier to xenotransplantation. A median survival of 90 days may be achievable with better control of BCMV infection. If further studies in the orthotopic position replicate these outcomes, criteria considered appropriate for clinical application of cardiac xenotransplantation would be approached.

Reactivation of porcine cytomegalovirus through allogeneic stimulation.

Reactivation of latent porcine cytomegalovirus after coculture of peripheral blood mononuclear cells (PBMCs) from pigs with different genetic backgrounds was investigated. Nine of 10 allogeneic coculture pairs were PCR (DNA) positive, whereas 7 coculture pairs had porcine cytomegalovirus (PCMV) RNA, an indication of virus replication. The cell subpopulations harboring PCMV were monocytes and CD8+ T cells.