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Shortcomings of Current Biomaterials
Studies on Collagen
Studies on Collagen

Local reaction of pigs to the intradermal implantation of porcine and human
collagens:

Porcine type I collagen extracted from pig hides and Human type I and type I+III collagens extracted from human placentas were all prepared by the same technique published by Tiollier et al (1990). These highly purified collagens, of the same quality, were implanted in the dermis of the same pigs. Biopsies at 7 days, 1 month and 3 months were analysed by histology. These studies were carried out in collaboration with Biomatech, in Chasse sur Rhône – France.  

The purpose of the study was to analyse the influence of the homologous or heterologous character of the collagen source. Porcine collagen was homologous for the pigs. Human collagen was heterologous for the pigs.

At 7 days, no difference was observed between porcine and human collagens. No inflammation was observed for both implants, demonstrating the excellent short term tolerance of both implants and the absence of any visible short term immune reaction.

At 1 month and 3 months, a major difference was observed between porcine and human collagens.

Intradermal implantation in a pig - Porcine Collagen at 1 month Intradermal implantation in a pig - Human Collagen at 1 month

High magnification showing the fibroblasts migration at 1 month in the intradermal porcine collagen implant (homologous).

High magnification

A massive and persistent inflammation of the dermis was induced by the human collagen with many lymphocytes, monocytes and granulocytes showing a long term local immune reaction of the pig. The local environment of proteases, induced by a heterologous collagen negatively interferes against fibroblasts in their neo-collagen synthesis.

No inflammation was induced by the homologous porcine collagen showing an excellent tolerance of the dermis and no immune response of the pig. There is an early and important migration of active fibroblasts starting their local collagen synthesis, in a quiet environment (no digestion by proteases).

Intradermal implantation in a pig -
 Porcine Collagen at 3 months
Intradermal implantation in a pig -
Human Collagen at 3 months

From these experiments in pigs we propose the following conclusions, which may be applicable for human patients:

  • A heterologous collagen implant does induce a persistent local immune response in the dermis, which negatively interferes against the neo-collagen synthesis by fibroblasts;
  • Any re-injection of heterologous collagens would increase the local dermis reaction and would not improve the persistence of the correction;
  • The cosmetic result of a heterologous collagen implantation could be due to the local oedema produced by the local inflammation;
  • A homologous collagen implant does not induce any local inflammation and is quickly colonized by many fibroblasts which actively synthesize new collagen fibrils;
  • Any re-injection of homologous collagens would increase the local collagen synthesis and could improve the quality and the persistence of the correction;
  • The cosmetic result of a homologous collagen implantation is only dependent upon a local neo-collagen synthesis.