Vascularization of methl-methacrylate modified polymerized 2-hydroxyethyl methacryate hydrogel orbital implant

Dongfang YIN; Yifei HUANG; Qinghua HE

ABSTRACT

BACKGROUND:

The application of polymerized 2-hydroxyethyl methacryate (PHEMA) in many organs of living body shows good biocompatibility.

OBJECTIVE:

To observe the biocompatibility and fibrovascular condition of methl-methacrylate (MMA) modified PHEMA hydrogel orbital implant.

DESIGN:

Single sample observation.

SETTING:

Department of Ophthalmology, the General Hospital of Chinese PLA; Institute of Polymer Science,Department of Chemical Engineering, Tinghua university.MATERIALS Twenty-five New Zealand rabbits of either gender and clean grade, weighing 2.0 to 2.5 kg, were provided by the Animal Experimental Center, General Hospital of Chinese PLA. The animals were observed at postoperative 2, 4,8, 12 and 24 weeks, 5 at each time point. The experiment was permitted by ethics committee. MMA modified PHEMA hydrogel orbital implant was provided by Institute of Polymer Research, Department of Chemical Engineering, Tinghua University. The experiment was permitted by ethics committee.

METHODS:

This experiment was carried out in the laboratory of Department of Ophthalmology, the General Hospital of Chinese PLA from March to October 2003. The right eye served as operation eye. When the rabbits were anesthetized,their eyelids were open with eyelid retractor. Bulbar conjunctiva was open along the edge of limbus of cornea for isolating fascia. Oculorotatory muscle was isolated and pre-set suture line was made, then muscle was cut off. When optical nerve was cut off, eyeball was completely excised. A MMA modified PHEMA hydrogel orbital implant with the diameter of 14 mm was implanted into the fossa orbitalis of rabbits. Single photon emission computed tomography (SPECT) was performed at postoperative 2, 4, 8, 12 and 24 weeks. The hydrogel orbital implant was taken out at postoperative 2, 4, 8,12 and 24 weeks for light microscope, immunohistochemical and electron microscope examinations.MAIN OUTCOME

MEASURES:

Vascularization of hydrogel orbital implant was observed in vivo by isotope tracing observation at different time points. Vascularization of hydrogel orbital implant was observed ex vivo by light microscope,immunohistochemical and electron microscope observations.

RESULTS:

All 25 New Zealand rabbits were involved in the final analysis. ①SPECT examination showed that isotope increased around the implants at week 2, and extended gradually at weeks 4 and 8. The radiotracer accumulated evenly in the implants from surrounding to the center at week 12. ②Light microscopic examination of the prostheses revealed fiber vessels grew from the surrounding to the center. At week 2,fibrovascular tissue grew in the hole of implant. Long or round cells with deeply dyed nucleuses were found in the hole, being fibroblasts. The vascular structure in the hole of the implant was clear, and vascular wall and blood cells were found. The inflammatory cells were mainly neutrophils and lymphocytes, and occasionally large macrophages. ③Scanning electron microscope showed that fibrovascular tissue grew in the hole of the implant, and was dense and intercrossed at week 12. ④ Conjunctiva split appeared postoperatively in 1 of 25 cases, and healed well after two times of operation. Conjunctival congestion lessened and conjunctiva healed within postoperative 7 days in the remaining 24 animals.

CONCLUSION:

MMA modified PHEMA hydrogel orbital implant has good histocompatibility and fast vascularization process, and is easy to be operated with fewer complications. So, it is a safe and practicable new type orbital implant.