EVALUATION OF PLATELET–DERIVED AND EPIDERMAL GROWTH FACTORS ON SURGICALLY-INDUCED WOUNDS IN NEW ZEALAND WHITE RABBITS TREATED WITH METHYLPREDNISOLONE

ABSTRACT

The study was designed to evaluate the influence of platelet-derived growth factor (PDGF-AB) and epidermal growth factor (EGF-AB) on modulating wound healing of rabbits. A total of twenty four (24) New Zealand White rabbits of nine months to one year old from both sexes were used for the study.

The rabbits weigh between 1.5–2.0 kg body weights. The rabbits were randomly grouped into two major groups (1 and 2) of twelve rabbits each. The rabbits were treated parenterally with methylprednisolone (methylP), and compared with the control treated parenterally with normal saline (NS). They were subsequently placed randomly, into four sub-groups each 1A (methylP + EGF), 1B (methylP + PDGF), 1C (methylP + NS) and 1D (methylP + EGF + PDGF); 2A (NS + EGF), 2B (NS + PDGF), 2C (NS + NS) and 2D (NS + EGF + PDGF) of three rabbits each.

The animals were pre-anaesthetised with atropine sulphate and chlorpromazine. Ketamine hydrochloride was used for anaesthesia. An area of wound that is 2 cm × 1 cm dimension on rabbit dorsum, was created on each site of the dorsum. Group 1 were treated parenterally with methylP 0.5 mg/kg and the sub-groups were treated topically with 1A (EGF), 1B (PDGF), 1C (Normal saline) and 1D (EGF + PDGF).

Group 2 were parenterally treated with normal saline and topically with 2A (EGF), 2B (PDGF), 2C (Normal saline) and 2D (EGF + PDGF). Each wound designated for PDGF, EGF and NS were smeared with 2.92 µg of PDGF, 20.8 µg of EGF, and 0.2 mL of normal saline, respectively. The wounds were monitored until complete healing.

Doppler ultrasound of the scar tissue was carried out at the frequency of 5 Hz using C5 sonostar laptop ultrasound. Blood, serum and wound biopsy were taken. Wound retraction was recorded in all the groups with highest peak in NS + PDGF (3.13 cm2) at day 3 and 3.11 cm2 in NS + NS at day 5. Onset of epithelialisation was recorded at day 7 except for groups treated with EGF + PDGF the recorded epithelialisation at day 5 post-wounding.

Inflammatory cells influx were diffused in the NS + NS and NS + EGF + PDGF groups. However, synergy in anti-inflammatory activity was not recorded with the use of methylP + PDGF but was observed on methylP + EGF. The PDGF group showed superior anti-inflammatory activity compared to the EGF treated rabbits. Ultrasonography of NS + NS scar line showed hyper-echogenicity with least vascular perfusion but small scar lines in the EGF and PDGF treated rabbits.

The methylP + PDGF and methylP + EGF rabbits had the strongest scar strength as recorded by the tensile strength of 76.8 N/cm2 and 71.25 N/cm2, respectively. In conclusion, the overall healing time of methylprednisolone-treated rabbits was delayed; however the scar had the best connective tissue fibre arrangement.

Reduced period of wound retraction was achieved with the use methylprednisolone, EGF or PDGF, thus, reduced wound surface area for contamination and reduced chances of wound infection. Smallest scar size was achieved with the use of PDGF and methylP + PDGF, thus, maybe important in cosmetic surgeries.

The administration of methylprednisolone at 0.5mg/kg in wound management to enhance collagen fibre arrangements in scar tissue. Tensile strength was best observed in methylP + PDF and methylP + EGF, thus, are relevant in management of wounds in a weight carrying regions like the ventral aspects of the abdomen. The place of proper wound dressing in wound healing management cannot be replaced.

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