Human mesenchymal stem cells are tolerized by mice and improve skin and spinal cord injuries.

P686 Aims: To use Human Mesenchymal Stem Cells (HMSC) for skin and spinal cord repairment in mice. Methods: Human bone marrow was obtained from a young healthy donor in order to separate and culture HMSC. These cells were CD44+ and after their expansion in vitro were cryopreserved and used in all the experiments. 40 female Spargue Dawley mice, one month of age were used and mantained under controlled conditions. 20 mice were included in Group 1 (Skin repairment), 20 in Group 2 (Spinal Cord repairment); 5 mice in each Group were controls. Mice in Group 1 underwent a surgical large dorsal skin defect of 20 cm2 deeply to the fascia level. Mice in Group 2 were surgically sectioned at the lower dorsal level of their spinal cord. 5 Mice of each group received an infusion of a 2 ml solution with 2 x 106 HMSC over one minute through the dorsal tail vein (Groups 1a and 2a). 5 Mice of each Group received an implant of a human fibrinogen biopolymer with 106 HMSC/ml that polymerized at the level of the skin or the spinal cord injuries respectively (Groups 1b and 2b). 5 Mice in each Group received both HMSC infusion and local implant with HMSC in the lesions simultaneously (Groups 1c and 2c). Control animals not received either the cell infusion or the polymer with cells. All mice were strictly controlled until death or over a period of three month by two different observers with daily evolution of their general performance status, and weekly measurement and evaluation of the rate and quality of wound healing and scar formation as well as neurological status. Results: All implants and IV infusions of HMSC where well accepted by mice without any local or general, acute or delay, adverse reaction. No animal treated by these methods died during the observation period. 2 mice died in the skin control group and 4 in the spinal cord one. All skin defects healed without scar or retraction in a median time of 14 days when HMSC were locally administered with the fibrin polymer. IV treated animals closed their wounds with lesser scar formation than controls, in the same median time of 30 days. When infusion of cells was combined with the local treatment the median time to complete healing was also 14 days. 4 control mice in the spinal cord injury experiments died and 1 perpetuated its paralysis worsening its muscular atrophy with increasing propensity to skin damage. 2 animals treated with IV infusion and polymer with HMSC simultaneously had an outstanding improvement of their neurological activities after the first week. They were able to walk with difficulties but with full reflexes after one month of evolution. 3 other animals of this group as well as 2 of Group 2b, improved their reflexes and some movements of the back legs. The rest of the animals treated in both ways did not had excessive muscular atrophy or skin lesions. Conclusions: HMSC can differenciate into other cells types when cultured or placed in the best environment. We corroborate the idea that HMSC are not immunologically reactives and can traspass species defense barriers. We also show that these human cells do not cause any haemodynamic disturbance when infused into inferior vertebrates. We also found that animals treated with these cells repair injuries better than controls and no one has died during the experiments, perhaps giving them a surviving advantage over the controls. It is also surprising the improvement in the neurological activities after spinal cord injuries. In this way we propose that universal HMSC from living or cadaveric donors can be cultured, expanded and cryopreserved to be ready to use in human organ or tissue regeneration.