Use of canine sourced platelet-rich plasma in a feline contaminated cutaneous wound

Abstract

A 4-year-old neutered female domestic shorthaired cat was treated with canine sourced platelet-rich plasma at the Veterinary Hospital at University of Padua for a large skin defect on the left lateral neck region. The wound healed completely within 20 days and no adverse reaction was observed during the healing process.

In both animal and human patients, proper wound healing depends on several variables including blood supply, defect size, tension and mobility of wound margins, susceptibility to infection, and type and condition of underlying tissue (1–3). Skin healing is a dynamic event that involves different phases and cellular interactions coordinated by cytokines and growth factors (4). Several clinical studies on the restoration of tissue integrity have shown the positive role of platelets in natural wound healing (2,5). According to the “pull theory” (6), wound contraction is mediated by fibroblasts and myofibroblasts generated in response to platelet derived growth factors and macrophage derived growth factors. Platelet-rich plasma (PRP) is defined as a portion of the plasma fraction of blood having a high number of platelets and growth factors concentrated in a limited volume of plasma (1,7,8). Platelet-rich plasma is a recent therapeutic component of regenerative and human sport medicine; attractive features of PRP therapy include being minimally invasive, rapid, inexpensive, and relatively easy to prepare (9). Platelet-rich plasma is known to enhance hemostasis, wound healing, re-epithelialization, and tissue regeneration (1,3–5,10–12). To achieve these effects, the platelet concentration must be more than 4 to 5 times the baseline intravascular platelet count (9,13), which is considered the minimal concentration for accelerated epithelialization and granulation (7). Autologous PRP is increasingly used in therapeutic tissue regeneration, as evidenced by several published clinical and experimental reports in human medicine in both non-healing and healing wounds (1,5,14). The use of platelet concentrate for therapeutic purposes is a recent technology in veterinary medicine, particularly in equine and canine medicine (2,7,8,10,11,15–18). To the best of our knowledge, there are no published reports that describe the use of autologous or heterologous PRP in wound healing in cats, although canine serum has been used in feline patients for the treatment of corneal ulcers with encouraging clinical experiences, without literature support (19). This report describes the successful application of canine PRP on a large skin defect in a cat.

Case description

A 4-year-old neutered female domestic shorthaired cat weighing 3.0 kg was presented to the Veterinary Hospital at the University of Padua for a traumatic large, contaminated wound in the jugular region (Figure 1). The owner reported that the cat had been injured by a dog bite 2 d earlier. On presentation no abnormalities were found on general physical examination; body temperature, mucous membranes, and capillary refill time were all within normal limits. Routine hematology and biochemistry were unremarkable. Serological tests for feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) were negative. The wound bed appeared to be covered by an avascular sheet of necrotic tissue without effusion. Neither foreign bodies nor bone fragments were found inside the wound. The skin surrounding the wound was warm and swollen. Based on the case history and clinical examination, the wound was classified as a full-thickness contaminated wound. Hair was clipped from the area around the wound and all debris was removed. The wound was then cleaned with a sterile saline solution administered under pressure by an 18-gauge needle attached to a 35-mL syringe to generate 7 to 8 psi. Following lavage the wound measured 23 mm × 46 mm (Figure 2A).

Figure 1.

First presentation of the wound. This figure shows a traumatic large contaminated skin wound over the jugular region in a 4-year-old neutered female domestic shorthaired cat.

Figure 2.

Wound healing process. The panel shows the wound healing process. A — appearance of the wound after debridement: the wound measured 23 × 46 mm and the total wound area was 743.01 mm²; B — wound 8 d after the PRP application (total wound area: 198.79 mm², percentage of wound contraction: 73%, percentage of re-epithelialization: 68%); C — wound 13 d after the PRP application (total wound area: 64.01 mm², percentage of wound contraction: 91%, percentage of re-epithelialization: 84%); D — wound 20 d after the PRP application; complete wound healing with slight scar formation in the center of the area.

Due to the dimensions and contamination of the defect, the wound was left to heal by second intention since simple apposition of the edges of the wound created significant tension. Furthermore, it was decided to not close the wound using reconstructive plastic surgery because this would have required general anesthesia for the patient and a greater economic investment by the owner. Instead, the wound was treated with the application of PRP to stimulate the healing process. Given the need to use a large volume of whole blood for the preparation of the required PRP, with the agreement of the cat’s owner, it was decided to obtain PRP from a blood sample from a single healthy adult dog. The donor dog was kept in an individual kennel with water and food ad libitum and a complete cell count of blood from the donor was conducted (Table 1). The initial platelet count of the donor indicated that sample was satisfactory for the preparation of PRP. The PRP was prepared by the tube method described by Perazzi et al (15). A 16-mL volume of blood was collected from the donor’s jugular vein with commercially designed platelet sequestration tubes containing sodium citrate (Vacutainer CPT; Becton, Dickinson and Company, Franklin Lakes, New Jersey, USA) and then centrifuged to obtain 2 mL of PRP. The final 2 mL of PRP contained a mean concentration of 1513 × 10³ platelets/μL (Table 1).

Table 1.

Concentration of cells in donor’s whole blood and platelet-rich plasma

Cells	Whole blood	Platelet rich plasma
Red blood cells	5.78 × 106/μL	0.20 × 106/μL
Lymphocytes	3.44 × 103/μL	6.41 × 103/μL
White blood cells	11.90 × 103/μL	7.14 × 103/μL
Platelets	322 × 103/μL	1513 × 103/μL

The PRP solution was gently applied directly to the surface of the lesion with a sterile syringe. After the application of PRP, the wound generally remains moist and the granulation tissue that forms does not usually dry out. For this reason, a light wet-to-dry protective bandage was applied to reduce the risk of wound contamination. To monitor for possible adverse reactions, the patient was hospitalized for 5 d. During the postoperative period, clavulanic acid-potentiated amoxicillin (Synulox; Pfizer Animal Health, Latina, Italy), 20 mg/kg body weight (BW), was administered q12h for 5 d. During the recovery, no non-steroidal anti-inflammatory drugs (NSAIDS) were given. The bandage was changed every 2 d to allow for inspection of the wound, collection of data relating to the healing process, and to avoid leaving dirty gauze on the wound. The area was cleaned using a sterile isotonic saline solution without scrubbing the lesion.

There were no signs of inflammation, necrosis, infectious complications or adverse immune reaction during the healing process. The cat had neither hyperthermia, anorexia, lethargy, nor excitement. To measure the dimensions of the wound and the progression of healing, digital pictures that included a 2-dimensional calibration scale next to the wound were obtained. Using commercial software (Autocad, 2005), the total area of the wound, the percentage of wound contraction, and the percentage of re-epithelialization were calculated as described by Bohling (20) (Figures 2B–C). Macroscopic observation of wound healing was the basis for recording the quality and color of granulation tissue. With day 0 as the day of PRP application, the wound showed significant clinical improvement beginning on day 1. On day 4, there was a reduction of 50% in the wound area. On day 10, the percentage of contraction was 90%, after which complete healing was observed in another 10 d. Following wound contraction, the percentage of re-epithelialization was calculated. On day 6, we observed more than 50% of re-epithelialization, which increased to 80% at day 10. Granulation tissue was first observed at the center of the lesion on day 2. On day 4, this had covered at least 50% of the lesion and on day 6 almost 90%. The granulation bed completely filled the lesion on day 8. On day 10, the granulation tissue appeared more pale and irregular at the center of the lesion and more abundant at the edges. Wound healing was complete 20 d after treatment, with slight scar formation (Figure 2D). There was hair re-growth 25 d after the treatment, except in the area of scar tissue. At a 3-month follow-up, the patient appeared to be in good health with an excellent cosmetic result.

Discussion

Despite the proven efficacy of autologous platelet rich plasma in several studies (1,2,5,7,8,10,16), heterologous PRP could be a safe alternative to autologous PRP when the condition of the patient prevents use of its own blood. In a recent study, Abegao et al (4) used heterologous blood for the production of PRP to treat experimentally induced dermal wounds in rabbits. The positive results of this study confirmed the data reported in a previous study that described successful use of heterologous blood for the production of PRP because of the difficulties in obtaining blood from small animals (21). Beneficial effects have been also demonstrated with heterologous PRP in joint cartilage lesions (22), and corneal ulcer healing was achieved in rabbits using a heterologous blood component associated with PRP (23). Kaffashi et al (23) reported that topical application of heterologous platelet jelly and blood serum may shorten the healing period of corneal ulcerated areas leading to a better quality of healing. In our case the patient was too small to allow a sufficient volume of blood to be taken for preparation of the required autologous PRP. A similar study was recently published by Chung et al (3) who described a large skin defect in a very small dog treated with topical homologous PRP obtained from a donor of the same species (3). In that case the patient was too small to provide sufficient blood for autologous PRP. Supported by evidence of the literature and having the owners’ consent it was decided to use heterologous instead of homologous PRP to have a donor with a higher blood volume and to reduce the risk of transmission of infectious diseases.

We noticed early granulation tissue at the center of the lesion, which could explain the rapid wound contraction. Wound contraction is more effective in areas where the skin is loosely attached to the underlying tissue, but our case progressed more rapidly than normal wound contraction during healing by second intention without treatment (20,24). Bohling et al (20) described the macroscopic features of second intention induced cutaneous wound healing in the cat: the authors reported the percentages of epithelialization (13.0% at day 14 and 34.4% at day 21), wound contraction (53.0% at day 14 and 75.8% at day 21), and total healing (59.0% at day 14 and 83.9% at day 21). With regard to the percentage of contraction in our case, after 1 wk the wound contraction was 90% and complete healing was observed 20 d after the treatment. No delayed healing or exuberant granulation tissue was noted. The use of heterologous PRP was not associated with signs suggestive of infection, similar to that reported by de Rezende et al (22) and Abegao et al (4), who used heterologous PRP sources. This absence of infection, either after the PRP application or during the healing process, may be attributed to the high concentration of leucocytes with antimicrobial activity present in PRP (4).

The present report describes the safe use of heterologous platelet-rich plasma in second intention healing in a cat. Notably, there were no local or systemic adverse effects. Our findings suggest that heterologous PRP, as a topical low cost therapy, may stimulate early and good granulation tissue formation without any adverse reaction in cats. These findings could open a new field of wound therapy, particularly in patients with a small body mass or blood volume. Further investigation of the efficacy of canine PRP in large clinical trials in cats is recommended to confirm the successful results seen in this case report and to identify possible adverse effects of using PRP for this application. CVJ