Search

The activation status of platelets in Immune Thrombocytopenia (ITP) patients--which is still somewhat controversial--is of potential interest, because activated platelets tend to aggregate (leading to excessive clotting or thromboembolic events) but cannot do so when platelet numbers are low, as in ITP. Although corticosteroids are the first line of therapy in ITP, the effect of steroids on activation of platelets has not been evaluated so far. We examined the status of platelet activation (with and without stimulation with ADP) in ITP patients, at the start of therapy (pre-steroid treatment, naive) and post-steroid treatment (classified on the basis of steroid responsiveness). We used flow cytometry to evaluate the levels of expression of P-selectin, and PAC-1 binding to platelets of 55 ITP patients and a similar number of healthy controls, treated with and without ADP. We found that platelets in ITP patients exist in an activated state. In patients who are responsive to steroids, the treatment reverses this situation. Also, the fold activation of platelets upon treatment with ADP is more in healthy controls than in ITP patients; treatment with steroids causes platelets in steroid-responsive patients to become more responsive to ADP-activation, similar to healthy controls. Thus steroids may cause changes in the ability of platelets to get activated with an agonist like ADP. Our results provide new insights into how, and why, steroid therapy helps in the treatment of ITP.

Retinal pigment epithelia (RPE) and retinal neurons (RN) arise from the same underlying precursor cell population. It is worthwhile to explore the transdifferentiation potential of RPE cells, given the benefits that could accrue from turning RPE into neural retina containing all its normal cellular subpopulations. Factors such as retinoic acid (RA, acting as an inducer of transdifferentiation) and epidermal growth factor (EGF) and basic fibroblast growth factor (bFGF) (E+F, acting as stem cell maintenance and predifferentiating factors) have been known to stimulate the conversion of RPE into observably neuron-like cells. However, since such treatment does not actually transform RPE into neurons, there is a need to rationally explore the efficacy of other factors as well. In this paper, we have compared the effects of RA, a known transdifferentiating factor in optical and other tissues, with the effects of cadaver vitreous on D407 RPE cells, using a combination of light microscopy, immunofluorescent microimaging and flow cytometry. We show that cadaver-derived vitreous (CV) is comparable to, or better than, RA as a transdifferentiation factor in an EGF + bFGF maintenance background. The vitreous humor could thus be an important stimulator of the differentiation of dedifferentiated RPE cells into neurons. This finding assumes significance in light of the fact that vitreous humor is a factor naturally present in the environment of the developing retina.

The etiology of idiopathic thrombocytopenic purpura (ITP), characterized by destruction of platelets, is still poorly understood. Although genetic as well as immunological factors are thought to play a role in the disease pathogenesis, genetic association studies in terms of major histocompatibility complex (MHC) polymorphisms are scarce and discrepant. Results from previous studies suggest that different populations show varying associations with MHC alleles. Since i) there are inconsistencies in HLA associations, and ii) such an association study does not exist for the Indian subcontinent, we carried out sequence specific priming (SSP)-based genotyping of HLA DRB1 alleles in the North Indian population. Data for such studies is available for two East Asian countries, Japan and China, and the association in both cases is different. Further, among the Japanese population too, there are discrepant results. It was therefore important to analyze such an association in the Indian population, belonging to Southern Asia. Our data shows that none of the alleles have any significant association with ITP. Moreover, in contrast to other studies, comparison made between patients who were responsive to steroid therapy against those who were refractory to steroids, also did not show any association of the HLA DRB1 alleles with steroid responsiveness.

Purpose: Granulocyte colony stimulating factor (GCSF) is a potent hematopoietic factor that stimulates the growth of neutrophil granulocyte precursors, and also regulates the differentiation and survival of neutrophils by inhibiting apoptosis. Incidentally, GCSF is also known to act as an endogenous ligand for brain cells, counteracting acute neuronal degeneration and contributing to long-term plasticity of progenitor cells after cerebral ischemia. Since GCSF was recently reported to be present in retinal ganglions, we examined its expression in retinal pigment epithelial (RPE) cells, which, together with retinal neurons, arise from the same underlying precursor cells., Methods: We used reverse transcriptase polymerase chain reaction (PCR) to assay expression of GCSF and GCSF receptor (GCSFR) genes; immunostaining and flow cytometry to assay the presence of GCSFR on cell surfaces; bromodeoxyuridine (BrdU) incorporation measurement to monitor DNA synthesis; and 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay to monitor cell proliferation. The effect of GCSF on differentiation of RPE cells was assessed by immunocytochemistry to detect the presence of various marker proteins., Results: The D407 RPE cells, as well as RPE derived from cadaver eyes, were found to express both GCSF and GCSFR. Despite the presence of the GCSF receptor, exogenously added GCSF did not result in any proliferation of these cells. We found that GCSF acts like a de-differentiating factor, maintaining RPE cells in the rounded form, and in a transdifferentiation-competent state., Conclusions: The expression of GCSF and GCSFR by D407 RPE may be an important factor in RPE cell maintenance.