Mesenchymal stem cells (MSCs) are considered as emergent "universal" cells and various tissue repair programs using MSCs are in development. In vitro expansion of MSCs is conventionally achieved in medium containing fetal calf serum (FCS) and is increased by addition of growth factors. However, for widespread clinical applications, contact of MSCs with FCS must be minimized since it is a putative source of prion or virus transmission. Therefore, because platelets are a natural source of growth factors, we sought to investigate in vitro MSC expansion in response to platelet lysates (PL) obtained from platelet-rich plasma. Human MSCs were expanded in FCS (+/-bFGF)- or PL-supplemented medium through a process of subculture. We demonstrated that PL-containing medium is enriched by growth factors (platelet-derived growth factors (PDGFs), basic fibroblast growth factor (bFGF), transforming growth factor (TGF-beta), insulin-like growth factor-1 (IGF-1) ...) and showed that PL is able to promote MSC expansion, to decrease the time required to reach confluence, and to increase CFU-F size, as compared to the FCS medium. Furthermore, we demonstrated that MSCs cultured in the presence of PL maintain their osteogenic, chondrogenic, and adipogenic differentiation properties and retain their immunosuppressive activity. Therefore, we propose that PL may be a powerful and safe substitute for FCS in development of tissue- and cellular-engineered products in clinical settings using MSCs.

No abstract

The therapeutic management of severe radiation burns remains a challenging issue. Conventional surgical treatment (excision and skin autograft or rotation flap) often fails to prevent unpredictable and uncontrolled extension of the radiation necrotic process. We report here an innovative therapeutic strategy applied to the victim of a radiation accident (December 15, 2005) with an iridium gammagraphy radioactive source (192Ir, 3.3 TBq). The approach combined numerical dosimetry-guided surgery with cellular therapy using mesenchymal stem cells. A very severe buttock radiation burn (2000 Gy at the center of the skin surface lesion) of a 27-year-old Chilean victim was widely excised (10 cm in diameter) using a physical and anatomical dose reconstruction in order to better define the limit of the surgical excision in apparently healthy tissues. A secondary extension of the radiation necrosis led to a new excision of fibronecrotic tissues associated with a local cellular therapy using autologous expanded mesenchymal stem cells as a source of trophic factors to promote tissue regeneration. Bone marrow-derived mesenchymal stem cells were expanded according to a clinical-grade technique using closed culture devices and serum-free medium enriched in human platelet lysate. The clinical evolution (radiation pain and healing progression) was favorable and no recurrence of radiation inflammatory waves was observed during the 11 month patient's follow-up. This novel multidisciplinary therapeutic approach combining physical techniques, surgical procedures and cellular therapy with adult stem cells may be of clinical relevance for improving the medical management of severe localized irradiations. It may open new prospects in the field of radiotherapy complications.

Subepithelial fibrosis in the bronchi of asthmatics is the result of an irreversible lung fibroblast activation, triggered by cytokines secreted by IL-4- and IL-5-activated inflammatory cells. Here, we provide evidence that human lung fibroblasts (ICIG7 cells) express a single class of high-affinity IL-4 receptor (IL-4R). This receptor is functional and composed of at least the IL-4Ralpha and IL-13Ralpha1 chains in the absence of the IL-2Rgamma chain. The IL-4Ralpha is efficiently internalized at 37 degrees C within 15 min in the presence of IL-4, whereas this process is slower with IL-13. In ICIG7 cells, IL-4 triggers the tyrosine phosphorylation of at least two proteins (110 and 180 kDa), and up-regulates the transcription of c-fos, c-jun and c-myc proto-oncogenes. In addition, the secretion of several cytokines [IL-6, granulocyte colony stimulating factor and granulocyte macrophage colony stimulating factor (GM-CSF)] as well as the expression of beta1 integrin and VCAM-1 adhesion molecules are augmented by IL-4. IL-13 displays similar biological activities, but less effectively than IL-4. On the other hand, ICIG7 cells could constitute a lung fibroblast population defined by the spontaneous release of several pro-inflammatory cytokines (IL-6, IL-11 and GM-CSF) and cell surface phenotype (CD4 and Thy-1). Through this peculiar cytokine pattern and the IL-4/IL-13-dependent activities, these cells could act as effector cells in the pathogenesis of asthma, triggering and maintaining the recruitment, homing and activation of bone marrow-derived inflammatory cells, and playing a role in the remodeling process of the airways.