Experimental Study Of The Biological Characteristics Of Granulation Tissue Derived Cells From Skin Wounds Combined With Total Body Irradiation

Radiation injury is a complex and medically challenging disorder and often occurs after nuclear explosives, nuclear accidents, radiological or nuclear terrorism, and radiation therapy in combination with surgery. The radiation induced injury is often coupled with skin wounds and can cause large-scale incidence. Combined radiation and wound injury(CRWI) is very complicated and is much more difficult to heal than single injuries. Wound healing is a complicated process, and exposure to radiation can significantly aggravate the degree of damage and prolong the healing progress. Currently, there is no effective medical countermeasure for the management of CRWI. Emerging stem cell-based therapy in different diseases such as leukemia, immune disease, burn and cancer, holds great promise for the CRWI treatment, but the cell source remains a challenging issue.In recent decades, the study of stem cells has developed a lot. Stem cells are specific cell populations that have the ability of self-renewal and differentiation,and can be found almost in all adult tissues. Among various stem cell populations, embryonic stem cells has negative effect on ethical issues, and the induced pluripotent stem cells show unsafety in application. Then, adult stem cells exhbite feasibility in clincal application. Bone marrow derived mesenchymal stromal cells (BMSCs) are commonly applied in experimental models and clinical trials. However, the lymphohematopoietic system is very sensitive and vulnerable to radiation exposure, which suggests that bone marrow is not a good source for autologous cell therapy in CRWI and there is an urgent need to develop alternative cell sources.Skin is the largest organ in the body and during the past decades, researchers have established the importance of skin dermis as an easily accessible source of stem cell populations and their promising significance in wound repair and other diseases.In 2001, we have successfully isolated and cultured the dermal pluripotent stem cells from rats,and proved that the cells preserved good capabilities of prolifertion and differentiation.Nery recently, the granulation tissue derived cells (GTCs) were further characterized as an abundant cell source for their important therapeutic efficacy in wound healing and tissue repair. Because skin is relatively insensitive to radiation, we hypothesized that the granulation tissue derived cells from CRWI may represent an alternative source of adult stem cells for transplantation.In this study, we aim to explore the biological features of the granulation tissue derived cells from the skin wounds combined with total body irradiation (C-GTCs). Multiple biological characteristics involving radiation sensitivity of C-GTCs were investigated as compared to BMSCs, neonatal dermal stem cells (DSCs) and GTCs of skin wound without irradiation. The main results and conclusions of this study are summarized below:1. Radiation can significantly prolong the progress of wound healing, and the comparision of the numbers of Ki67+ cells and new vessels in the granulation tissues of CRWI and skin injury (SI) demonstrated that the retardation time is about 2?3 days.2. Investigating the capability of in vitro culture ability and self-renewal with BMSCs of CRWI as control, we found that BMSCs got high sensitivity to radiation exposure, and the senescene increased significantly than GTCs. However, GTCs from CRWI can preserve relatively higher proliferation, which suggested that GTCs of CRWI exhibited significant superiority in the in vitro culture capability over BMSCs.3. Comparing the isolated GTCs from CRWI and SI, and neonatal dermal mesenchymal stem cells, we found that GTCs from CRWI showed comparable ability in cell proliferation,migration and adhesion. Although there was a reduction in CFU-F and differentiation, the GTCs from CRWI can still retain the important features defined for stem cells.4. After the GTCs were injected locally into the wound injury, the wound healing of CRWI were accelerated, which confirmed that GTCs from CRWI have a therapeutic efficacy for wound repair.In addition, detecting the influence of the conditioned media confected with GTCS culture supernatant on cell growth, we verified that GTCs can promote proliferation.