doi:10.1016/j.bjps.2004.12.012
Copyright © 2005 The British Association of Plastic Surgeons Published by Elsevier Ltd.
Histological evaluation of Permacol™ as a subcutaneous implant over a 20-week period in the rat model
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T.M. Macleoda, 
, 
, G. Williamsb, R. Sandersa and C.J. Greenb
aRestoration of Appearance and Function Trust, Mount Vernon Hospital, Northwood, Middlesex, London, UK
bNorthwick Park Institute of Medical Research, Northwick Park Hospital, Harrow, London, UK
Received 12 January 2004;
accepted 15 December 2004.
Available online 1 April 2005.
Summary
This study assessed the suitability of Permacol™ (a porcine derived, isocyanate cross linked collagen based biomaterial) as an alternative to autologous tissue in soft tissue reconstruction. The Sprague–Dawley rat was used as a model for subcutaneous implantation over a 20 week period and comparison made with two other porcine biomaterials (small intestinal submucosa and glycerol treated-ethylene oxide sterilised porcine dermis). Implants were scored histometrically on the degree of acute inflammation, chronic inflammation, fibrosis and stromal response. The vascularity and percentage composition of collagen within Permacol™ were assessed by stereology and seescan image analysis, respectively. In general terms, Permacol™ was well tolerated as a subcutaneous implant, with only a minor chronic inflammatory response remaining after a 20 week period of implantation. There was evidence of collagen degradation during this period and vascular ingrowth into Permacol™ was limited. Permacol™ has the potential for a broad range of applications in plastic surgery, but may benefit from modification to promote a more rapid degree of vascularisation.
Keywords: Biomaterials; Subcutaneous implant; Porcine; Histological response; Biocompatibility
Figure 1. (A) Macroscopic appearance of Permacol™. (B) Histological section stained with Masson's trichrome showing the microscopic appearance of Permacol™ with typical dermal collagen architecture (original magnification ×40).
Figure 2. (A) Macroscopic appearance of small intestinal submucosa. (B) Histological section stained with H&E showing the microscopic appearance of SIS (original magnification×40).
Figure 3. (A) Macroscopic appearance of glycerol treated-ethylene oxide sterilised porcine ADM. (B) Histological section stained with Masson's trichrome showing the microscopic appearance of Gly-EO dermis (original magnification×40).
Figure 4. Subcutaneous placement of Permacol™ implant between panniculus layer of the skin and the underlying rectus abdominus muscle layer. (A) Macroscopic view. (B) Histological section stained with Masson's trichrome showing a Permacol™ implant between the panniculus layer of the skin and the underlying rectus abdominus muscle layer (Masson's Trichrome) (original magnification×20).
Figure 5. Histological section stained with H&E showing acute neutrophilic inflammation graded as moderate (original magnification×10).
Figure 6. Histological section stained with H&E showing chronic lymphocytic inflammation with some admixed eosinophils graded as moderate–severe (original magnification×20).
Figure 7. Histological section stained with H&E showing eosinophilic infiltration graded as minimal (original magnification×40).
Figure 8. Histological section stained with H&E showing stromal fibroblastic reaction graded as mild (original magnification×10).
Figure 9. Histological section stained with Masson's trichrome demonstrating fibrosis graded as moderate (original magnification×10).
Figure 10. Histological section stained with H&E showing surrounding vascularity graded as mild (original magnification×10) at the periphery of the implant.
Figure 11. A line graph showing the change in the mean thickness of 0.75 mm thickness Permacol™ implants over a 20 week period of subcutaneous implantation as assessed by Seescan image analysis. Results shown are means±standard error of the mean for n=8 implants at each time point. *P<0.05 vs. implant thickness prior to implantation.
Figure 12. A line graph showing the mean collagen density of 0.75 mm thickness standard Permacol™ implants over a 20 week period of implantation as assessed by Seescan image analysis. Results are means±standard error of the mean for n=8 implants at each time point. *P<0.05; **P<0.01 vs collagen density prior to implantation.
Figure 13. A frequency distribution histogram showing the thicknesses of 25 pieces of Permacol™ cut from the same sheet of standard 0.75 mm Permacol™. Measurements have been taken with spring-loaded callipers to assess both the hydrated thickness (black blocks) and nonhydrated thickness (white blocks) of each piece. Results shown are frequencies grouped to the nearest 0.05 mm.
Figure 14. The mean percentage vascularity±standard error of the mean for n=8 implants of 1.5, 0.75 and 0.4 mm thickness Permacol™ 1 week (black bars) and 2 weeks (white bars) after subcutaneous implantation. No difference in the percentage vascularity of the three different thicknesses of standard Permacol™ implants after 1 week and 2 weeks of subcutaneous implantation. In addition, there is no significant increase in the percentage vascularity of any of the three thicknesses of Permacol™ from week 1 to week 2 of subcutaneous implantation.
Table 1.
Histometric scoring system used to grade acute inflammation, chronic inflammation, eosinophilic infiltration, fibrosis, stromal reaction and vascularity in the tissues surrounding subcutaneous implants
Table 2.
Histometric scores for the degree of chronic inflammation seen around Permacol™ (P™), glycerol treated-ethylene oxide sterilised (Gly-EO) dermis and small intestinal submucosa (SIS) implants 1, 2, 4, 10 and 20 weeks after subcutaneous implantation
Statistical comparison between all three groups at each time interval is reflected in the overall P-value, and individual comparisons between Permacol™ and each of the other two matrices are represented in the two right hand columns of the table. Results shown are medians (and range) of a maximum of n=8 implants at each time interval.
Table 3.
Histometric scores for the degree of eosinophilic infiltration seen around Permacol™ (P™), glycerol treated-ethylene oxide sterilised (Gly-EO) dermis and small intestinal submucosa (SIS) implants 1, 2, 4, 10 and 20 weeks after subcutaneous implantation
Statistical comparison between all three groups at each time interval is reflected in the overall P-value, and individual comparisons between Permacol™ and each of the other two matrices are represented in the two right hand columns of the table. Results shown are medians (and range) of a maximum of n=8 implants at each time interval.
Table 4.
Histometric scores for the degree of stromal reaction seen around Permacol™ (P™), glycerol treated-ethylene oxide sterilised (Gly-EO) dermis and small intestinal submucosa (SIS) implants 1, 2, 4, 10 and 20 weeks after subcutaneous implantation
Statistical comparison between all three groups at each time interval is reflected in the overall P-value, and individual comparisons between Permacol™ and each of the other two matrices are represented in the two right hand columns of the table. Results shown are median (and range) of a maximum of n=8 implants at each time interval.
Table 5.
Histometric scores for the degree of fibrosis seen around Permacol™ (P™), glycerol treated-ethylene oxide sterilised (Gly-EO) dermis and small intestinal submucosa (SIS) implants 1, 2, 4, 10 and 20 weeks after subcutaneous implantation
Statistical comparison between all three groups at each time interval is reflected in the overall P-value, and individual comparisons between Permacol™ and each of the other two matrices are represented in the two right hand columns of the table. Results shown are median (and range) of a maximum of n=8 implants at each time interval.
Table 6.
Histometric scores for the degree of vascularity seen around Permacol™ (P™), glycerol treated-ethylene oxide sterilised (Gly-EO) dermis and small intestinal submucosa (SIS) implants 1, 2, 4, 10 and 20 weeks after subcutaneous implantation
Statistical comparison between all three groups at each time interval is reflected in the overall P-value, and individual comparisons between Permacol™ and each of the other two matrices are represented in the two right hand columns of the table. Results shown are median (and range) of a maximum of n=8 implants at each time interval.
Table 7.
Summary of the histometric scores for Permacol™ (bold type), glycerol treated-ethylene oxide sterilised (Gly-EO) dermis (italic type) and small intestinal submucosa (SIS) (regular type) implants following 1, 2, 4, 10 and 20 weeks of subcutaneous implantation
Results shown are median (and range) of a maximum of n=8 implants at each time interval.
Corresponding author. Address: Department of Plastic Surgery, Nottingham City Hospital, Hucknall Road, Nottingham NG 5 1PB, UK. Tel.: +44 116 969 1169; fax: +44 115 962 7706.
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