Table 4: Xenografts.

AuthorSampleBiomechanical propertiesHost response

Badylak et al., 2001 [52]Abdominal wall defect repaired with SIS in 40 dogs randomized into 8 survival groups (1, 4, 7, and 10 days and 1, 3, 6, and 24 months).Strength was decreased from day 1 to day 10 after implantation, followed by a progressive increase, until reaching double of the original strength 24 months after implantation. Rapid degradation with associated and subsequent host remodeling.

Badylak et al., 2002 [55]Abdominal wall defect repaired with SIS in 10 dogs and 30 rats, both randomized into 4 survival groups (1 week, 1 month, 3 months, 6 months, and 2 years).(i) No shrinkage or expansion of the graft site over the 2-year period of the study.
(ii) One week after implantation, abundant levels of polymorphonuclear leukocytes diminished to negligible after 1 month.
(iii) Moderate neovascularization.
(iv) By 3 months, graft material was not recognizable and was replaced by moderately well-organized host tissues including collagenous connective tissue, adipose tissue, and skeletal muscle.

Cole et al., 2003 [60]SIS removed from a 42-year-old female patient 4 months after pubovaginal implantation of the sling due to severe obstruction.(i) Completely intact acellular sling.
(ii) Well defined fibrous capsule.
(iii) Chronic inflammatory response.

Zhang et al., 2003 [51]SIS implanted in the abdominal wall of rats for up to 2 months.SIS together with the abdominal wall has increased strength.Levels of interleukin 2 and interleukin 6 were high straight after the operation but they become normal after 2 months.

Wiedemann and Otto, 2004 [56]Biopsies taken from the implantation site of the SIS band under the vaginal mucosa from 3 patients during reoperation, at a mean of 12.7 months, after pubourethral sling procedures due to recurrent urinary stress incontinence. (i) Focal residues of SIS implant.
(ii) No evidence of a specific tissue reaction that might point to a foreign body reaction.
(iii) No evidence of any significant immunological reaction and in particular no evidence of any chronic inflammatory reaction.

Konstantinovic et al., 2005 [50]Abdominal wall defect repaired with SIS in 24 Wistar rats randomized into 4 survival groups (7, 14, 30, and 90 days).Significant increase of biomechanical properties after 90 days of implantation.(i) Moderate acute inflammatory response at day 7, decreased to minimal after 90 days.
(ii) Moderate neovascularization.
(iii) Abundant collagen deposition well organized after 90 days.

Macleod et al., 2005 [62]SIS and cross-linked porcine dermis (Permacol) implanted subcutaneously on the anterior rectus fascia of 18 rats each randomized into 5 survival groups (1, 2, 4, 10, and 20 weeks).For both grafts:
(i) absent acute inflammatory response,
(ii) from moderate chronic inflammation after 1 week of implantation to minimal after 20 weeks,
(iii) absent eosinophilic infiltration and stromal fibroblastic reaction over the entire implantation,
(iv) from moderate fibrosis and vascularity around the grafts after 1 week of implantation to minimal after 20 weeks.

Poulose et al., 2005 [57]12 female pigs were implanted with SIS intraperitoneally for up to 6 weeks.(i) Cell infiltration.
(ii) Vascularization.
(iii) Collagen deposition and remodelling.

Thiel et al., 2005 [58]SIS implanted subcutaneously on the abdominal wall of 30 rats randomized into 3 survival groups (7, 30, and 90 days).(i) Moderate inflammatory reaction increased to severe after 90 days.
(ii) 86% of the graft was replaced by new collagen fibers.

Krambeck et al., 2006 [26]SIS and porcine dermis implanted subcutaneously on the anterior rectus fascia of 10 rabbits randomized into 2 survival groups (6 and 12 weeks). (i) Porcine dermis presented moderate fibrosis which was minimal for SIS.
(ii) Minimal degree of scar for both grafts and high degree of inflammatory infiltrate.

Ko et al., 2006 [54]Abdominal wall defect repaired with 8-layer SIS in 20 domestic pigs randomized into 2 survival groups (1 and 4 months).No significant changes of biomechanical properties after 4 months of implantation.(i) Dense fibrous connective tissue ingrowth.
(ii) Minimal to mild mononuclear inflammatory cell infiltrate throughout the connective tissue.

Hilger et al., 2006 [20]Porcine dermis implanted in 20 rabbits randomized into 2 survival groups (6 and 12 weeks). Half implanted on the rectus fascia and half on the posterior vagina fascia.Very significant decrease of biomechanical properties after 12 weeks of implantation.(i) Two missing or fragmented materials 12 weeks after being implanted on the vagina.
(ii) Moderate to strong inflammatory response.
(iii) Minimal collagen ingrowth without significant cell infiltration.
(iv) Minimal neovascularization.

Kim et al., 2007 [59]SIS implanted in the subcutaneous dorsum of 3 rats sacrificed after 2 weeks. (i) Prominent infiltration and ingrowth of host cells.
(ii) Few macrophages infiltrated or accumulated around the grafts.

Rauth et al., 2007 [63]SIS implanted on the peritoneal surface of the abdominal wall of 6 pigs sacrificed 8 weeks after implantation.(i) 80% of contraction from original surface area.
(ii) Moderate neovascularization.
(iii) Densely populated by host cells with moderate amounts of new disorganized collagen deposition.

Woodruff et al., 2008 [27]Porcine dermis slings explanted after revision from 4 women, due to different complications, between 2 and 65 months after implantation.(i) Severe encapsulation.
(ii) No degradation.
(iii) No fibroblasts infiltration and neovascularization.

Sandor et al., 2008 [64]Abdominal wall defect repaired with SIS and cross-linked porcine dermis (Permacol) in 33 primates randomized into 3 survival groups (1, 3, and 6 months). (i) Considerable contraction after 1 month for both materials, but not significant change over the next 5 months.
(ii) Better integration of both materials at late stage by scar formation.
(iii) Inflammatory cells infiltration 3 months after implantation for SIS associated with formation of few blood vessels.
(iv) Acellular porcine dermis over the entire course implantation with substantial inflammation surrounding their perimeter.
(v) Partial resorption for both materials after 6 months.

Pierce et al., 2009 [65]Cross-linked porcine dermis implanted on the abdominal wall and posterior vagina of 18 rabbits sacrificed 9 months after implantation. 11 grafts remained intact without significant changes of biomechanical properties compared to the baseline values. They were just thicker and tolerated with less elongation at failure. Seven grafts were partially degraded but thicker again and with significant decrease of all biomechanical properties. (i) Host connective tissue incorporation between fibers.
(ii) Intense foreign body reaction in degraded grafts.

VandeVord et al., 2010 [39]SIS and porcine dermis implanted in 16 rats, respectively, and both randomized into 4 survival groups (2, 4, 8, and 12 weeks). Implantation around the bladder neck, anchored to the surrounding tissues. (i) Thin fibrous capsule formation.
(ii) Moderate cell infiltration and angiogenesis for SIS and minimal for porcine dermis.

Rice et al., 2010 [36]Abdominal wall defect repair with SIS (Surgisis) in 18 rats randomized into 2 survival groups (30 and 60 days). Increase of tensile strength after 30 days and, increase of tensile strength after 60 days, respectively, to 30 days.(i) Moderate amounts of collagen deposition well organized.
(ii) Abundant revascularization.

Deprest et al., 2010 [61]13 patients underwent secondary sacrocolpopexy because of a graft related complication after the initial sacrocolpopexy with porcine dermal collagen (Pelvicol) (9) or SIS (Surgisis) (4).(i) Pelvicol presented high degradation rates associated with no foreign body reaction.
(ii) Pelvicol remnants were integrated into collagen rich connective tissue with limited neovascularization (scar host tissue).
(iii) No significant body foreign reaction to Surgisis grafts.
(iv) Surgisis no longer recognizable replaced by irregularly organized connective tissue and fat tissue.

Liu et al., 2011 [49]Abdominal wall defect repaired with SIS and acellular porcine dermal matrix in 50 Sprague Dawley rats randomized into 5 survival groups (1, 2, 4, 8, and 12 weeks). After initial decrease of biomechanical properties at week 2, these were increased over the next 10 weeks reaching similar values to week 1.(i) Pronounced inflammatory response 1 to 4 weeks after implantation for SIS compared with porcine dermis, but falling to similar negligible values for both after 12 weeks.
(ii) Large neovascularization and collagen deposition, which was higher for SIS group.
(iii) SIS implants degraded more quickly and were almost totally replaced by organized collagenous tissues.
(iv) Contraction at the first weeks leading to significant lower surface area in both materials.

Jenkins et al., 2011 [53]Abdominal wall defect repaired with porcine dermal matrix in 24 Yucatan minipigs randomized into 2 survival groups (1 and 6 months). Significantly greater incorporation strengths after 6 months compared with 1 month.(i) Moderate cell infiltration.
(ii) Moderate extracellular matrix deposition.
(iii) Moderate neovascularisation.
(iv) Partial degradation and from widely to mild fibrous encapsulation.

Kolb et al., 2012 [40]Cross-linked porcine dermis (Permacol) implanted subcutaneously in 5 pigs randomized into 4 survival groups (7, 21, 90, and 180 days).(i) Mild inflammatory response decreased to minimal from day 7 to day 180 after implantation.
(ii) None to minimal neovascularization after 180 days.
(iii) Small amount of residual SIS remained surrounded by mild to moderate chronic inflammation.
(iv) Moderate levels of encapsulation.

Daly et al., 2012 [66]Abdominal wall defect repaired with porcine dermis in rats randomized into 3 survival groups (1, 3, and 35 days).(i) Cell infiltrates into all grafts by day 35.
(ii) Degradation of the scaffold most pronounced at the periphery with fibrous tissue, angiogenesis, and foreign body giant cells noted.
(iii) Grafts surrounded by a dense and circumferentially organized connective tissue.
(iv) Mononuclear cells decreased in number compared with earlier time points.