Objective The potential of stem cells to repair compromised cartilage tissues such as in osteoarthritis (OA) depends strongly on how transplanted cells respond to factors secreted from the residing OA chondrocytes. This study determines the effect of morphogenetic signals from OA chondrocytes on chondrogenic differentiation of human mesenchymal stem cells (hMSCs). Methods Effect of OA chondrocyte secreted morphogens on chondrogenic differentiation of hMSCs was evaluated using a co-culture system involving both primary and passaged OA chondrocytes. The findings were compared against hMSCs cultured in OA chondrocytes conditioned medium. Gene expression, biochemical assays, and immunofluorescent staining were used to characterize the chondrogenic differentiation of hMSCs. Mass spectrometry analysis was used to identify the soluble factors. Numerical analysis was carried out to model the concentration profile of soluble factors within the hMSC-laden hydrogels. Results The hMSCs co-cultured with primary OA chondrocytes underwent chondrogenic differentiation even in the absence of growth factors; however the same effect could not be mimicked using OA chondrocytes conditioned medium or expanded cells. Additionally, the co-cultured environment down-regulated hypertrophic differentiation of hMSCs. Mass spectrometry analysis demonstrates cell-cell communication and chondrocyte phenotype-dependent effects on cell-secreted morphogens. Conclusion The experimental findings along with the numerical analysis suggest a crucial role of soluble morphogens and their local concentrations on the differentiation pattern of hMSCs in a three-dimensional environment. This concept of utilizing a small number of chondrocytes to promote chondrogenic differentiation of hMSCs while preventing their hypertrophic differentiation could be of great of importance in formulating effective stem cell-based cartilage repair.

The length of survival of 149 patients harboring primary brain tumors was retrospectively correlated with the presence and location of lymphocytic infiltration. Mononuclear invasion of malignant gliomas confined to the perivascular spaces was the only histolgical finding that correlated significantly with survival. Patients with malignant gliomas containing perivascular infiltration live up to four months longer than those with no lymphocyte infiltration. The survival of patients with brain tumors who had lymphocyte invasion associated with areas of hemorrhage and necrosis beyond and separate from perivascular spaces was the same as far as for those with no lymphocyte involvement.

Cytosolic guanylyl cyclases (GTP pyrophosphate-lyase [cyclizing; EC 4.6.1.2]), primary receptors for nitric oxide (NO) generated by NO synthases, are obligate heterodimers consisting of an ␣ and a ␤ subunit. The ␣ 1/ ␤ 1 form of guanylyl cyclase has the greatest activity and is considered the universal form. An isomer of the ␤ 1 subunit, i.e., ␤ 2, has been detected in the liver and kidney, however, its role is not known. In this study, we investigated the function of ␤ 2. Immunoprecipitation experiments showed that the ␤ 2 subunit forms a heterodimer with the ␣ 1 subunit. NO-stimulated cGMP formation in COS 7 cells cotransfected with the ␣ 1 and ␤ 2 subunits was ‫ف‬ 1/3 of that when ␣ 1 and ␤ 1 subunits were cotransfected. The ␤ 2 subunit inhibited NO-stimulated activity of the ␣ 1/ ␤ 1 form of guanylyl cyclase and NOstimulated cGMP formation in cultured smooth muscle cells. Our results provide the first evidence that the ␤ 2 subunit can regulate NO sensitivity of the ␣ 1/ ␤ 1 form of guanylyl cyclase. Northern analysis for guanylyl cyclase subunits was performed on RNA from kidneys of Dahl salt-sensitive rats, which have been shown to have decreased renal sensitivity to NO. Compared to the Dahl salt-resistant rat, message for ␤ 2 was increased, ␤ 1 was decreased, and ␣ 1 was unchanged. These results suggest a molecular basis for decreased renal guanylyl cyclase activity, i.e., an increase in the ␣ 1/ ␤ 2 heterodimer, and decrease in the ␣ 1/ ␤ 1 heterodimer. (

Resonance Raman spectra of the alpha 1 beta 1 isoform of bovine lung soluble guanylate cyclase expressed from baculovirus have been measured. The spectra show that the ferric heme is five-coordinate high spin whereas the ferrous heme in the absence of added exogenous ligands is a mixture of six-coordinate low spin and five-coordinate high spin. In the Fe-CO-derivative, the correlation between the Fe-CO frequency (497 cm-1) and the C-O frequency (1959 cm-1) demonstrates that the proximal ligand in our preparation is histidine. The Fe-NO stretching frequency (found at 520 cm-1) and other spectral features of the ferrous Fe-NO-bound sGC are similar to those reported by Deinum et al. (1) and Yu et al. (2). These data indicate that although large preparation-dependent differences in the occupancy of the distal pocket exist, all the preparations have the same proximal histidine ligation and share the same mechanism of activation by NO.