Leaving the abdomen open (also laparotomy) has been widely used in a variety of surgical emergencies for its potential benefit to severely injured patients, involving abdominal compartment syndrome, intra-abdominal sepsis, trauma, and combat casualties [
The healing process of open abdominal wounds involves a complex and dynamic series of overlapping phases [
In this study, we used rapidly
Forty-eight adult male Sprague-Dawley rats (180–250 g, Jinling Hospital, Nanjing, China) were used for the present experiments. The animals were maintained in a controlled environment (21 ± 2°C, 50–60% humidity, 12-hour light-dark cycle, and lights on at 6 am) and allowed free access to food and water. All the animal care and experimental protocols were reviewed and approved by Animal Investigation Ethics Committee of Jinling Hospital.
PRP was prepared by enriching whole blood platelet concentration using a two-step centrifugation procedure. Ten milliliters of whole blood was drawn from healthy rat through cardiac puncture into prechilled tubes containing ACD-A at a blood/ACD-A ratio of 9 : 1. Subsequently, each blood sample was centrifuged at 400 ×g for 10 min to obtain the three typical layers: red blood cells at the bottom, a “buffy coat” layer in between, and acellular plasma in the supernatant. Using a sterile pipette, the upper layer was transferred to another neutral tube along with the buffy coat and recentrifuged at 800 ×g for 10 min. About 2 mL of PRP was omitted from the bottom of the tube and about 2 mL of PPP was collected in the supernatant to yield the final PRP and PPP product, respectively. The final platelet concentrations in whole blood, PPP, and PRP were analyzed in an automatic counter. Samples of PRP and PPP were frozen at −80°C and then thawed in cold water in order to lyse the platelets. The concentrations of VEGF, TGF
All rats were fasted overnight and anesthetized by intraperitoneal injections of a ketamine (50 mg/kg body weight) and xylazine (5 mg/kg body weight) mixture. Under aseptic conditions, the colon ascendens stent peritonitis (CASP) procedure was performed to create a continuous intra-abdominal sepsis [
After that, the animals were randomly divided into three groups: the PRP group, the PPP group, and the control group, with eight rats in each group. PRP or PPP gel was administered as a two-component system: the prepared PRP or PPP as one component and a thrombin/Ca+2 composition as the other. The system used a double-syringe arrangement wherein the two components were mixed
(a) A double-syringe arrangement for dispensing PRP gel and (b) topical application of PRP gel to the open abdominal wound.
The granulation tissue together with underlying bowel loops was collected at day 7 and fixed with 10% neutral formaldehyde, followed by dehydration in graded ethanol (70% to 100%), embedding in paraffin, serially section using a microtome (5
Blood perfusion in wound areas was measured with a laser speckle contrast imaging (LSCI, PeriCam PSI System, Perimed, Sweden) for 2 min, to ensure temporal stability between measurements. The system uses a divergent laser beam with a wavelength of 785 nm. The spatial resolution of the perfusion image is 0.2 mm/pixel at a measurement distance of 12 cm. The image size was set to correspond to 2 cm × 3 cm and the image acquisition rate was set to 3 images/s. Data were digitized and stored in a computer, and mean perfusion levels in regions of the image were analyzed offline with signal processing software (PimSoft 1.4, Perimed AB, Sweden). All LSCI blood perfusion measurements are presented in laser speckle perfusion units (LSPU).
Data are presented as means ± SEM unless otherwise noted. All measurements were preformed from at least six different slides or rats, with multiple readings for each data point. Continuous variables were analyzed by one-way ANOVA as appropriate. A repeated measure of analysis of variance with a post hoc LSD test was used when comparing more than two variables. All statistical analyses were performed with IBM SPSS Statistics 18 (SPSS Inc., Chicago, IL, USA) and
The platelet count in the whole blood, PPP, and PRP had a mean value of
As shown in Figure
Quantification of growth factors (pg/mL) in PRP and PPP. All samples were freeze-thawed to lyse the platelets prior to measurement.
Histological analysis revealed that, compared to control group, PRP gel yielded improved healing response, which showed a much more rapid cellular accumulation and matrix deposition. To accurately quantitate the amount of new tissue, we chose three other independent measures of tissue formation—granulation tissue thickness, myofibroblasts count, and vessel numbers and diameter.
PRP gel treatments induced significant 1.4- and 2.5-fold increase, respectively, in granulation tissue thickness compared with the PPP and control group (Figure
Thickness of the granulation tissue at one week after treatment in control (a), PPP (b), and PRP (c) group. (d) The statistical analysis of the granulation thickness in the three groups. Scale bar indicates 100
CD31 immunostaining analysis of granulation tissue capillaries at one week after treatment in control (a), PPP (b), and PRP (c) group. (d) The statistical analysis of the percentage of CD31 positive area in the three groups. Scale bar indicates 100
To better determine the functionality of the developing vasculature, we analyzed wounds on day 7, using laser Doppler to assess blood perfusion in the wound area. We found that PRP gel induced more blood flow to the wound area than did the PPP scaffold and the wound covered with only mesh (Figure
Laser speckle contrast imaging of open abdominal wound at one week after treatment in control (a), PPP (b), and PRP (c) group. (d) The statistical analysis of blood perfusion in the three groups. Scale bar indicates 100
In this study, we have demonstrated the benefits of topical platelet-rich plasma gel for the treatment of open abdominal wounds. We have shown that wounds treated with PRP gel exhibited faster healing rates and adequate granulation tissue formation when compared to wounds treated with mesh alone, subsequently reducing the time it takes to undergo skin graft. In addition, topical use of PRP gel has been shown to enhance angiogenesis in the early stage of the repair process after open abdomen and subsequently to promote wound healing.
Appreciation for the potential complications of open abdominal wound has continued to evolve. Accordingly, various surgical techniques and nonanatomic coverage alternatives for early restoration of abdominal domain after OA have been proposed. Generally, the optimal goal of early management is to facilitate early closure (within the first 7 days) and prevent delayed complications. However, in some cases, especially in an infected abdomen, primary abdominal fascial closure is not possible secondary to ongoing visceral edema and depleted fascia edges due to inflammation and lateral retraction. In these cases, the patient is left with an “open abdomen” until sufficient granulation. Thus, promoting early granulation tissue formation is necessary to prevent complications.
The use of blood-derived biomaterials to seal wounds and accelerate healing began with the use of fibrin glues in the early 1970s, which comprised a highly concentrated fibrinogen (polymerization induced by thrombin and calcium) [
In general, wound healing has three classic stages: the inflammatory, proliferative, and remodeling stages [
Furthermore, platelet concentrates contain many powerful mitogenic and chemotactic growth factors, which regulate key processes involved in tissue repair, including cell proliferation, chemotaxis, migration, cellular differentiation, and extracellular matrix synthesis [
In addition, the observed effect may be partially due to its antimicrobial activity. The roles that platelets in PRP play in host defense mechanism at the wound site have been demonstrated by previous studies [
We propose PRP gel for use in clinical practice. It can be accessible to most physicians, whether in metropolitan areas or in those areas with hospital facilities. PRP gel is easy to prepare from only 20–40 mL autologous blood of the patient and is of relatively low cost. All available PRP techniques share common principles: blood is collected with an anticoagulant just before use and is immediately centrifuged twice. This time is variable but is always completed within no more than an hour. Also, application of autologous PRP gel to the wound site is technically easy and could be used as a conventional nonoperative therapy. The obtained platelet concentrate, together with thrombin and calcium chloride, is placed separately in a double-syringe system with a distal mixing device.
A variety of techniques, with the goal of either achieving definitive primary fascial closure (DPC) or restoring abdominal domain, are now available after open abdomen, including Bogota bag, the Wittmann Patch, synthetic mesh, VAC device, or combinations of various approaches [
As a preliminary study, several limitations need to be addressed. First, a potential weakness of our approach is that allogeneic instead of autologous PRP was used. Originally, PRP is defined as an autologous concentration of platelets in a small volume of plasma [
In conclusion, rapidly
The authors declare no conflict of interests.
This study was supported by the National Natural Science Foundation of China (Grant no. 81270478) and the Climbing Program in Natural Science Foundation of Jiangsu Province for Distinguished Scholars (Grants no. BK2010017). The authors thank Professors Xiaomei Shao and Jianqiao Fang for helping to teach the use of PeriCam PSI System.