Amnion-derived multipotent progenitor cells increase gain of incisional breaking strength and decrease incidence and severity of acute wound failure

Abstract

Objective: Acute wound failure is a common complication following surgical procedures and trauma. Laparotomy wound failure leads to abdominal dehiscence and incisional hernia formation. Delayed recovery of wound-breaking strength is one mechanism for laparotomy wound failure. Early fascial wounds are relatively acellular, and there is a delay in the appearance of acute wound growth factors and cytokines. The objective of this study was to accelerate and improve laparotomy wound healing using amnion-derived multipotent cells (AMPs). AMPs' nonimmunogenic phenotype and relative abundance support its role as a cell therapy.

Methods: AMPs were injected into the load-bearing layer of rat abdominal walls prior to laparotomy, and cell viability was confirmed. Wound mechanical properties were measured over 28 days. The incidence and severity of laparotomy wound failure was measured in an incisional hernia model.

Results: AMP cells were viable in laparotomy wounds for at least 28 days and did not migrate to other tissues. Laparotomy wound-breaking strength was increased by postoperative day 7 following AMP therapy. AMP therapy reduced the incidence of hernia formation and the size of hernia defects. Histology suggested stimulated wound fibroplasia and angiogenesis.

Conclusions: AMP cell therapy reduces the incidence of laparotomy wound failure by accelerating the recovery of wound-breaking strength. This results in fewer incisional hernias and smaller hernia defects.

Figure 1

Delivery of NS or AMP suspension in NS into linea alba. 200 μ L NS or AMP NS suspension was injected along 5 cm of the linea alba using a 22G needle (0.7 mm × 38 mm). Even tissue distribution was achieved.

Figure 2

Measurement of hernia size. Digital pictures were taken with a ruler as reference for every sample. Software Spot was employed to measure the calibrated hernia sizes. A digital perimeter was drawn along the hernia ring to measure the hernia size in square centimeters.

Figure 3

Cultured GFP labeled human AMP (AMP-GFP).

Figure 4

Viability of human AMP-GFP in laparotomy wounds. AMP-GFP were injected in rat linea alba and tissue harvested over 7, 14, and 28 days. Frozen tissue sections of abdominal wall collected at these three time points were examined under a fluorescent microscope. A: POD 7; B: POD 14; C: POD 28. D: Frozen skin tissue section adjacent to injection site collected on POD 7.

Figure 5

Tensiometric measurements and histology examination on early postoperative incisions. Fascial mechanical breaking characteristics were measured with an Instron tensiometer on POD 7 (A to F). Values are the mean ± SEM of 6 wound biopsies each from the NS-S control and the AMP-S groups. t-Test was employed to compare the difference between the 2 groups. *: P < 0.05, **: P < 0.01. Morphology of fascial incisional wound at POD 7 from NS-S (G) and AMP-S (H) groups. H&E staining was performed for histology.

Figure 6

Time course of mechanical wound breaking property recovery. Fascial mechanical breaking characteristics were measured with an Instron tensiometer on 3 time points, POD 7, POD 14, and POD 28. Values are the mean ± SEM of 6 wound biopsies each from the NS-S control and the AMP-S groups.

Figure 7

Effect of AMP on hernia healing. Hernia or wound defect size was measured on POD 28. Values are the mean ± SEM of 11 hernia biopsies each from the NS-H control and the AMP-H groups. **: compared with NS-H, P < 0.01. Morphology of hernia ring from NS-S (B) and AMP-S (C) groups. H&E staining was performed on tissue sections.