Effect of Transplantation of Human Mesenchymal Stem Cells and Dermal Fibroblasts on the Angiogenesis in Rats

Han, Seung Kyu; Chun, Kyung Wook; Kye, Min Seok; Kim, Woo Kyung

Abstract

It has been established that the graft of cryopreserved dermal fibroblast is able to improve wound healing. Transplantation of mesenchymal stem cells has the ability to undergo site-specific differentiation and participates in wound healing process. The wound healing process requires angiogenesis and the formation of a vascular network throughout the newly formed tissue. In this study we examined the effect of xeno- transplantation of fresh human mesenchymal stem cells and dermal fibroblasts on the angiogenesis. Human mesenchymal stem cells and human fibroblasts were isolated from bone marrow and dermis of the same patients and were grown in culture respectively. We have developed a porous polyethylene disc as an experimental model system for angiogenesis. Single block of polyethylene was cut into discs which were 5 mm in diameter and 3 mm in thickness. Four discs were soaked in a solution containing 4 106 cells and 1 ml thrombin. After porous polyethylene discs were loaded with the cell-thrombin composite, they then were coated with fibrinogen. After the discs were cleaned from surrounding fibrin, they were implanted in the back of Sprague-Dawley rats. In group I, the discs were filled with fibrin alone without cells. In group II and III, the discs were loaded with fibroblasts and mesenchymal stem cells respectively. Eight rats and 16 discs per group(total 48 discs) were used in this study. After creating 6 pockets in the back of a rat, 6 discs(2 discs per group) were implanted. At three different time intervals from 1 to 3 weeks, the implanted discs were harvested and processed for histological study. A longitudinal section was cut with a thickness of 6 micrometers in the very middle of a disc. Histological study was carried out to examine the formation of microvessels in the implants. Microvascular density was measured by counting the number of microvessels in the very middle of a biopsy specimen under 100 magnification field. Only fibrinoid materials and inflammatory cells were detected in most of specimens in the first week under 100 magnification field of the very middle. There was no significant differences in microvascular density among the three groups. In the second week, extracellular matrices including microvessels were detected in all the 3 groups. The microvascular density of group III(17.75/ 100 magnification field) was significantly higher than that of group II(10.50/100 magnification field) and group I (10.25/100 magnification field). The third week specimens showed that most of the pores of the implants contained extracellular matrices. Significantly greater differences were seen in the microvascular density. The microvascular densities averaged 52.88, 26.12, and 17.50 per 100 magnification field for group III, II, and I respectively. The results indicate that transplantation of mesenchymal stem cells and dermal fibroblasts can significantly improve the angiogenesis in the wound healing process and mesenchymal stem cells are superior to dermal fibroblasts.