Transplant of the Abdominal Rectus Fascia in rats, first report of a novel experimental technique

Abstract

Background: After intestinal or multivisceral transplant, closing the abdominal wall can be challenging, as negative pressure dressing or synthetic meshes pose risks like infections and fistulas. Clinical practice has evolved from vascularized abdominal wall transplants to non-vascularized Abdominal Rectus Fascia (TxARF). Although it was successful, many immunological aspects remain unknown, highlighting the need for further research.

Methods: The technique was developed by reproducing the technical aspects of the procedure described for humans in rats (Wistar and Sprague Dawley). Twenty-six Isogenic and Allogeneic TxARF procedures were performed and followed until 30 and 120 post-transplant days (PTD). The non-implanted fascias served as a control group. Rats were then re-assessed for engraftment on 7, 11, 30 and 120 PTD. Fascia samples were taken to assess neovascularization by quantifying cell composition and blood vessels using H&E and Orcein staining.

Results: All animals (N=26) survived at 30 and 120 PTD, with 4 (15.4 %) developed subcutaneous serum collection. Upon reoperation, grafts showed neovascularization. No adhesions were observed between the intestines and the grafts. The principal cell compound of the fascia was represented by Fibroblasts (18.35 cells/field) and Myocytes (6.57 cells/field). A significant increment of the number of blood vessels were observed during the period studied (p=0.046).

Conclusions: Our report on TxARF in rats, proves the feasibility of this experimental and translational model, showing similar results to those published in the clinical field. Further studies are required to evaluate the immunogenicity as well as the changes in ARF overtime.

Keywords: ARF; Non-vascularized; Tissue; Transplant and intestine.

Fig. 1

A and B- Dissection and fixation of the External Abdominal Rectus Fascia (EARF) and the Internal Abdominal Rectus Fascia (IARF) with Peritoneum. C- Final state of the tissue to implant in the recipient rat.

Fig. 2

A- The white lines induce the cut directions of the skin in the donor rat. B- The white lines induce the cut directions of the abdominal wall in the donor rat. C- Abdominal muscle wall ready for dissection.

Fig. 3

A and B- Appear of Abdominal muscle wall without dissection. C and D- External Abdominal Rectus Fascia (EARF) and Internal Abdominal Rectus Fascia (IARF) with Peritoneum.

Fig. 4

A- Extraction of a portion of the native abdominal wall (white line), (External Abdominal Fascia, Internal Abdominal Fascia and Peritoneum) ready to implant. B- Graft implantation in the recipient ARF.

Fig. 5

A- Appearance of the isogenic TxARF at 7 PTD. B- Appearance of the isogenic TxARF at 11 PTD (with presence of seroma). C- Appearance of the allogeneic TxARF on 7 PTD. D- Appearance of the allogeneic TxARF on 11 PTD.

Fig. 6

A- Isogenic TxARF on day 30. B- Isogenic TxARF at 120 PTD. C- Macroscopic appearance of the fascia and abdominal visceras in isogenic TxARF. D- Allogeneic TxARF at 30 PTD. E- Allogeneic TxARF at 120 PTD. F- Macroscopic appearance of the fascia and abdominal visceras in allogeneic TxARF. The arrows indicate the non-adhesions between the graft and the intestine.

Fig. 7

A- Appearance of the graft at 7 PTD (Isogenic TxARF). B- Appearance of the graft at 11 PTD (Allogeneic TxARF). C- Appearance of the graft at 30 PTD (Allogeneic TxARF). Skin (*). Native Abdominal muscle wall (**). The arrows indicate neo-vascularization in the graft.

Fig. 8

A- Number of cells per 40x field in the control fascia: Fb (Fibroblast), My (Myocytes), Nt (Neutrophils), Mn (Monocytes), Mt (Mast cells), Lf (Lymphocytes), Eo (Eosinophils); B- Presence of arteries in the fascia: * (p ≤ 0.0466), ** (p ≤ 0.0091); C- Presence of veins in the fascia: * (p = 0.0191), ** (p ≤ 0.0061); D- Representative images of blood vessels identified by Orcein: D.1: Small blood vessels, D.2: Big blood vessels, + (Venous wall), * (Arterial wall).