Mesenchymal Stromal Cells for Treatment of Acute Steroid-Refractory Graft Versus Host Disease: Clinical Responses and Long-Term Outcome.

Acute graft-versus-host disease (aGvHD) remains a major cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation. Steroid-resistant aGvHD is associated with poor outcome, and no commonly accepted salvage therapy is available for its treatment. Here, we report 58 adult patients treated with mesenchymal stromal cells (MSCs) as salvage therapy for steroid-refractory aGvHD. Third-party MSCs expanded in platelet lysate-containing medium were transfused at a median dose of 0.99 × 10(6) cells per kg b.wt. A median of two MSC infusions were administered to each patient. Median time between the onset of aGvHD and the first infusion of MSCs was 12 days (range, 6-62 days). Most patients (79%) had grade IV aGvHD. Five patients showed complete response, five showed very good partial response, 17 showed partial response, and 31 showed no response. The estimated probability of survival after 1 year was 19%, and median survival was 69 days. Overall survival was not significantly different from that of a historical cohort of patients receiving alternative salvage therapy and no MSC infusions. In conclusion, MSC treatment on top of conventional immunosuppression was associated with an overall response rate of 47% but improved outcome in terms of survival remains to be shown.

ICOS mediates the generation and function of CD4+CD25+Foxp3+ regulatory T cells conveying respiratory tolerance.

Costimulatory molecules like ICOS are crucial in mediating T cell differentiation and function after allergen contact and thereby strongly affect the immunologic decision between tolerance or allergy development. In this study, we show in two independent approaches that interruption of the ICOS signaling pathway by application of a blocking anti-ICOSL mAb in wild-type (WT) mice and in ICOS(-/-) mice inhibited respiratory tolerance development leading to eosinophilic airway inflammation, mucus hypersecretion, and Th2 cytokine production in response to OVA sensitization. Respiratory Ag application almost doubled the number of CD4(+)Foxp3(+) regulatory T cells (Tregs) in the lung of WT mice with 77% of lung-derived Tregs expressing ICOS. In contrast, in ICOS(-/-) mice the number of CD4(+)CD25(+)Foxp3(+) Tregs did not increase after respiratory Ag application, and ICOS(-/-) Tregs produced significantly lower amounts of IL-10 than those of WT Tregs. Most importantly, in contrast to WT Tregs, ICOS(-/-) Tregs did not convey protection when transferred to "asthmatic" recipients demonstrating a strongly impaired Treg function in the absence of ICOS signaling. Our findings demonstrate a crucial role of ICOS for the generation and suppressive function of Tregs conveying respiratory tolerance and support the importance of ICOS as a target for primary prevention strategies.

Differential effect of platelet-rich plasma and fetal calf serum on bone marrow-derived human mesenchymal stromal cells expanded in vitro.

Mesenchymal stromal cells (MSCs) derived from various sources have great potential for use in cell-based therapies. Since the proportion of primary MSCs contained in bone marrow or adipose tissue is low, plastic adherence and in vitro expansion are necessary to expand MSCs prior to clinical application. Human platelet-rich plasma has been introduced as an alternative serum source but functional differences have so far not been described. Here we cultured MSCs derived from human bone marrow in medium supplemented with either 10% fetal calf serum (FCS) or 5% and 10% platelet-rich plasma (PRP) until the first or second passage. Parameters under investigation were cell yield, clonogenicity, phenotype as well as migratory and differentiation potential. In addition, the secretion of SDF-1α and the induced migration of CD34(+) haematopoietic stem cells (HSCs) were investigated with regard to the different serum source. The use of PRP resulted in a significantly higher expansion rate and yield at passages 0 and 1. In addition, the level of secreted SDF-1α was significantly increased in the supernatant of MSCs cultured with FCS instead of human PRP. Consistent with this, the migration capacity of MSCs cultured with 10% FCS as well as their capability to induce the migration of CD34(+) haematopoietic progenitors in a transwell assay was higher. Our results demonstrate that human PRP can be seen as an alternative serum source to FCS for MSC cultivation. However, the requirements of the specific clinical application must be carefully considered before the respective serum source is selected.