Nitric-Oxide-Releasing Biomaterial Regulation of the Stem Cell Microenvironment in Regenerative Medicine.

Stem cell therapy has proven to be an attractive solution for the treatment of degenerative diseases or injury. However, poor cell engraftment and survival within injured tissues limits the successful use of stem cell therapy within the clinical setting. Nitric oxide (NO) is an important signaling molecule involved in various physiological processes. Emerging evidence supports NO's diverse roles in modulating stem cell behavior, including survival, migration, differentiation, and paracrine secretion of proregenerative factors. Thus, there has been a shift in research focus to concentrate efforts on the delivery of therapeutic concentration ranges of NO to the target tissue sites. Combinatory therapies utilizing biomaterials that control NO generation and support stem cell delivery can be holistic and synergistic approaches to significantly improve tissue regeneration. Here, the focus is on recent developments of various therapeutic platforms, engineered to both transport NO and to enhance stem-cell-mediated regeneration of damaged tissues. New and emerging revelations of how the stem cell microenvironment can be regulated by NO-releasing biomaterials are also highlighted.

A HPLC fingerprint study on Chaenomelis Fructus.

BACKGROUND: Chaenomelis Fructus is a type of traditional medicine used in China. At present, the quality standard of Chaenomelis Fructus is mainly based on the content of each component as a control index, lacking overall control. To improve the rapid identification of chemical ingredients for Chaenomelis Fructus, a new approach to the construction for Chaenomelis Fructus is presented in this paper. METHODS: The precision, repeatability and stability of the proposed HPLC method were validated in the study. Twenty batches of Chaenomelis Fructus samples from their geographical origin were analyzed by the HPLC method. Common peaks in the chromatograms were adopted to calculate their relative retention time and relative peak area. The chromatographic data were processed by the Similarity Evaluation System for Chromatographic Fingerprint of Traditional Chinese Medicine software (Version 2004 A) for similarity analysis. RESULTS: The HPLC method demonstrated satisfactory precision, repeatability and stability. The similarities of the 20 Chaenomelis Fructus samples were 0.967, 0.979, 0.965, 0.992, 0.994, 0.988, 0.974, 0.909, 0.993, 0.894, 0.983, 0.976, 0.992, 0.960, 0.990, 0.992, 0.901, 0.815, 0.947, and 0.504, indicating that the similarities of 19 samples showed a similar pattern with the exception of sample 20. Sample S20 could be considered adulterated. This was further confirmed by principal component analysis and hierarchical clustering analysis. The HPLC fingerprints of different Chaenomelis Fructus had obvious differences in area of common peaks, but less differences in the number of common peaks. CONCLUSIONS: The chromatographic fingerprint of Chaenomelis Fructus with high characteristics and specificity can be used as a reference to control its quality, providing a fast quality evaluation tool for distinguishing between the authentic Chaenomelis Fructus and the adulterated products.

Synthesis, biodistribution, and imaging of PEGylated-acetylated polyamidoamine dendrimers.

Polyamidoamine (PAMAM) dendrimers have been widely used as drug carriers, non-viral gene vectors and imaging agents. However, the use of dendrimers in biological system is constrained because of inherent toxicity and organ accumulation. In this study, the strategy of acetylation and PEGylation-acetylation was used to minimize PAMAM dendrimers toxicities and to improve their biodistribution and pharmacokinetics for medical application. PEGylated-acetylated PAMAM (G4-Ac-PEG) dendrimers were synthesized by PEGylation of acetylated PAMAM dendrimer of generation 4 (G4) with acetic anhydride and polyethylene glycol (PEG) 3.4 k. To investigate the cytotoxicity and in vivo biodistribution of the conjugates, in vitro cell viability analysis, Iodine-125 (125I) imaging, tissue distribution and hematoxylin-eosin (HE) staining were performed. We find that acetylation and PEGylation-acetylation essentially eliminates the inherent dendrimer cytotoxicity in vitro. Planar gamma (gamma) camera imaging revealed that all the conjugates were slowly eliminated from the body, and higher abdominal accumulation of acetylation PAMAM dendrimer was observed. Tissue distribution analysis showed that PEGylated-acetylated dendrimers have longer blood retention and lower accumulation in organs such as the kidney and liver than the non-PEGylated-acetylated dendrimers, but acetylation only can significantly increase the accumulation of G4 in the kidney and decrease the concentration in blood. Histology results reveal that no obvious damage was observed in all groups after high dose administration. This study indicates that PEGylation-acetylation could improve the blood retention, decrease organ accumulation, and improve pharmacokinetic profile, which suggests that PEGylation-acetylation provides an alternative method for PAMAM dendrimers modification.

Improved mesenchymal stem cell survival in ischemic heart through electroacupuncture.

OBJECTIVE: To investigate whether electroacupuncture (EA) can promote cell survival and enhance heart function of mesenchymal stem cells (MSCs) therapy. METHODS: MSCs were isolated from bone marrow and expanded in Minimum Essential Medium Alpha (α-MEM). MI was induced in 72 Sprague-Dawley (S-D) rats by ligation of the left anterior descending coronary artery (LAD) for 30 min and reperfusion. MI rats randomly received injection of 1×10(6) DiI-labeled MSCs alone (n =24, MSC group), or plus electroacupuncture (EA) at Neiguan (PC6, n=24, EA+MSC group), or saline (n =24, saline group). EA treatment was performed for 4 days. Another 24 rats were subjected to chest-open surgery without LAD occlusion and treatment (sham group). Three time points, 4, 14 and 28 days (n =8 for each group) were included in this study. The survival of transplanted MSCs and the protective gene expression were analyzed by reverse transcriptase polymerase chain reaction (RT-PCR) and Western blot at day 4 and 14. Left ventricular remodeling, cardiac function, infarction area, fibrosis and capillary density were analyzed at day 28. RESULTS: EA can enhance MSC survival (2.6-fold up) at day 4. Big capillary density was 53% higher in EA+MSC treated group than MSC alone group. Furthermore, the rats treated by EA reduced the fibrosis and had 36% smaller infarct size comparing to MSC alone. EA also attenuated left ventricular remodeling and enhanced the functional recovery of infarcted hearts at week 4. CONCLUSION: EA at Neiguan acupoint can promote the stem cell survival and improve ischemic heart function. EA could become a useful approach in stem cell therapy for ischemia heart diseases.