Lactic acid and short chain fatty acids (SCFAs) produced by vaginal microbiota have reported antimicrobial and immune modulatory activities indicating their potential as biomarkers of disease and/or disease susceptibility. In asymptomatic women of reproductive-age the vaginal microbiota is comprised of lactic acid-producing bacteria that are primarily responsible for the production of lactic acid present at ~110 mM and acidifying the vaginal milieu to pH ~3.5. In contrast, bacterial vaginosis (BV), a dysbiosis of the vaginal microbiota, is characterized by decreased lactic acid-producing microbiota and increased diverse anaerobic bacteria accompanied by an elevated pH>4.5. BV is also characterized by a dramatic loss of lactic acid and greater concentrations of mixed SCFAs including acetate, propionate, butyrate, and succinate. Notably women with lactic acid-producing microbiota have more favorable reproductive and sexual health outcomes compared to women with BV. Regarding the latter, BV is associated with increased susceptibility to sexually transmitted infections (STIs) including HIV. In vitro studies demonstrate that lactic acid produced by vaginal microbiota has microbicidal and virucidal activities that may protect against STIs and endogenous opportunistic bacteria as well as immune modulatory properties that require further characterization with regard to their effects on the vaginal mucosa. In contrast, BV-associated SCFAs have far less antimicrobial activity with the potential to contribute to a pro-inflammatory vaginal environment. Here we review the composition of lactic acid and SCFAs in respective states of eubiosis (non-BV) or dysbiosis (BV), their effects on susceptibility to bacterial/viral STIs and whether they have inherent microbicidal/virucidal and immune modulatory properties. We also explore their potential as biomarkers for the presence and/or increased susceptibility to STIs.

The spent culture supernatant of the human Lactobacillus acidophilus strain LB produces an antibacterial activity against a wide range of gram-negative and gram-positive pathogens. It decreased the in vitro viability of Staphylococcus aureus, Listeria monocytogenes, Salmonella typhimurium, Shigella flexneri, Escherichia coli, Klebsiella pneumoniae, Bacillus cereus, Pseudomonas aeruginosa, and Enterobacter spp. In contrast, it did not inhibit lactobacilli and bifidobacteria. The activity was heat stable and relatively sensitive to enzymatic treatments and developed under acidic conditions. The antimicrobial activity was independent of lactic acid production. Activity against S. typhimurium SL1344 infecting human cultured intestinal Caco-2 cells was observed as it was in the conventional C3H/He/oujco mouse model with S. typhimurium C5 infection and oral treatment with the LB spent culture supernatant.

BACKGROUND

Irritable bowel syndrome (IBS) is a poorly understood, yet highly prevalent functional gastrointestinal disorder (FGID). The withdrawal, due to adverse events, of a number of pharmacological agents that were approved for the treatment of IBS has left a therapeutic vacuum for patients suffering from the disorder.

OBJECTIVE

To review, summarise and critically evaluate current knowledge of lactic acid bacteria (LAB) used to treat IBS.

METHODS

We assessed a comprehensive range of relevant literature from Pubmed, Medline and online sources based on our definition of LAB which included both typical and atypical species, covering Lactobacilli, Bifidobacteria, Enterococci, Streptococci and Bacilli.

RESULTS

Of the 42 trials evaluated examining the efficacy of LAB in IBS, 34 reported beneficial effects in at least one of the endpoints or symptoms examined, albeit with tremendous variation in both the magnitude of effect and the choice of outcome under consideration. However, numerous concerns have been expressed over deficits of trial design and execution relating to strain selection, optimum dosage, mode of action, safety and long-term tolerability in a disorder that can persist throughout the lifetime of affected individuals.

CONCLUSIONS

Progress in the field will require an improved understanding of how the microbiota impacts on health and disease, adequately powered long-term multicentre trials and the embracing of bench to bedside approaches. Recent incremental advances suggest these areas are being addressed and that the future holds much promise for the use of lactic acid bacteria in the treatment of irritable bowel syndrome.

Increases in bone formation have been demonstrated in mice and rats treated with statins, a group of molecules that increase the production of bone morphogenetic proteins-2 (BMP2) by stimulating its promoter. However, clinical use of statins (e.g., fluvastatin) is limited by the lack of a suitable delivery system to localize and sustain release. To harness the therapeutic effect of statins in orthopedic applications, a fluvastatin-releasing macromer was synthesized. When copolymerized with a dimethacrylated poly(ethylene glycol) solution, this fluvastatin-containing molecule was covalently incorporated into hydrogel networks, and hydrolysis of lactic acid ester bonds resulted in the release of the pendantly tethered fluvastatin from the hydrogel into the surrounding solution. The rate of fluvastatin release was controlled by the length of lactic acid spacer (2-6 repeats), and the dose was controlled by the initial comonomer composition (5-500 microg fluvastatin/gel). Released fluvastatin increased human mesenchymal stem cell (hMSC) gene expression of CBFA1, ALP, and COL I by 34-fold, 2.6-fold, and 1.8-fold, respectively, after 14 days of in vitro culture. In addition, treating hMSCs with the released fluvastatin resulted in an average of 2.0- and 1.5-fold greater BMP2 production whereas mineralization increased an average of 3.0-fold and 2.5-fold for 0.01 and 0.1 microM fluvastatin, respectively, over the 2 week culture period. Therefore, fluvastatin-releasing hydrogels may be useful in bone tissue engineering applications, not only for triggering osteogenic differentiation of hMSCs, but also by modulating their function.

In mineral salts medium under oxygen deprivation, Corynebacterium glutamicum exhibits high productivity of L-lactic acid accompanied with succinic and acetic acids. In taking advantage of this elevated productivity, C. glutamicum was genetically modified to produce D-lactic acid. The modification involved expression of fermentative D-lactate dehydrogenase (D-LDH)-encoding genes from Escherichia coli and Lactobacillus delbrueckii in L-lactate dehydrogenase (L-LDH)-encoding ldhA-null C. glutamicum mutants to yield strains C. glutamicum DeltaldhA/pCRB201 and C. glutamicum DeltaldhA/pCRB204, respectively. The productivity of C. glutamicum DeltaldhA/pCRB204 was fivefold higher than that of C. glutamicum DeltaldhA/pCRB201. By using C. glutamicum DeltaldhA/pCRB204 cells packed to a high density in mineral salts medium, up to 1,336 mM (120 g l(-1)) of D-lactic acid of greater than 99.9% optical purity was produced within 30 h.

Consumption of lactic acid bacteria (LAB) has been suggested to confer a range of health benefits including stimulation of the immune system and increased resistance to malignancy and infectious illness. In the present study, the effects of feeding Lactobacillus rhamnosus (HN001, DR20), Lactobacillus acidophilus (HN017) and Bifidobacterium lactis (HN019, DR10) on in vivo and in vitro indices of natural and acquired immunity in healthy mice were examined. Mice were fed daily with L. rhamnosus, L. acidophilus or B. lactis (10(9) colony forming units) and their immune function was assessed on day 10 or day 28. Supplementation with L. rhamnosus, L. acidophilus or B. lactis resulted in a significant increase in the phagocytic activity of peripheral blood leucocytes and peritoneal macrophages compared with the control mice. The proliferative responses of spleen cells to concanavalin A (a T-cell mitogen) and lipopolysaccharide (a B-cell mitogen) were also significantly enhanced in mice given different LAB. Spleen cells from mice given L. rhamnosus, L. acidophilus or B. lactis also produced significantly higher amounts of interferon-gamma in response to stimulation with concanavalin A than cells from the control mice. LAB feeding had no significant effect on interleukin-4 production by spleen cells or on the percentages of CD4+, CD8+ and CD40+ cells in the blood. The serum antibody responses to orally and systemically administered antigens were also significantly enhanced by supplementation with L. rhamnosus, L. acidophilus or B. lactis. Together, these results suggest that supplementation of the diet with L. rhamnosus (HN001), L. acidophilus (HN017) or B. lactis (HN019) is able to enhance several indices of natural and acquired immunity in healthy mice.

Elafin, a natural protease inhibitor expressed in healthy intestinal mucosa, has pleiotropic anti-inflammatory properties in vitro and in animal models. We found that mucosal expression of Elafin is diminished in patients with inflammatory bowel disease (IBD). This defect is associated with increased elastolytic activity (elastase-like proteolysis) in colon tissue. We engineered two food-grade strains of lactic acid bacteria (LAB) to express and deliver Elafin to the site of inflammation in the colon to assess the potential therapeutic benefits of the Elafin-expressing LAB. In mouse models of acute and chronic colitis, oral administration of Elafin-expressing LAB decreased elastolytic activity and inflammation and restored intestinal homeostasis. Furthermore, when cultures of human intestinal epithelial cells were treated with LAB secreting Elafin, the inflamed epithelium was protected from increased intestinal permeability and from the release of cytokines and chemokines, both of which are characteristic of intestinal dysfunction associated with IBD. Together, these results suggest that oral delivery of LAB secreting Elafin may be useful for treating IBD in humans.

Many elderly subjects are at increased risk of infectious and noninfectious diseases due to an age-related decline in lymphoid cell activity (immunosenescence). Noninvasive means of enhancing cellular immunity are therefore desirable in the elderly. Previous reports have suggested that dietary supplementation could represent an effective means of enhancing the activity of circulating natural killer (NK) cells in the elderly. In the present study, we have conducted a pre-post intervention trial to determine the impact of dietary supplementation with probiotic lactic acid bacteria (LAB) on peripheral blood NK cell activity in healthy elderly subjects. Twenty-seven volunteers consumed low-fat/low-lactose milk supplemented with known immunostimulatory LAB strains (Lactobacillus rhamnosus HN001 or Bifidobacterium lactis HN019) for a period of 3 weeks. A dietary run-in of milk alone was shown to have no significant effect on NK cells. In contrast, the proportion of CD56-positive lymphocytes in peripheral circulation was higher following consumption of either LAB strain, and ex vivo PBMC tumoricidal activity against K562 cells was also increased. Supplementation with HN001 or HN019 increased tumoricidal activity by an average of 101 and 62%, respectively; these increases were significantly correlated with age, with subjects older than 70 years experiencing significantly greater improvements than those under 70 years. These results demonstrate that dietary consumption of probiotic LAB in a milk-based diet may offer benefit to elderly consumers to combat some of the deleterious effects of immunosenescence on cellular immunity.

BACKGROUND

The vaginal microbiota of healthy women consists typically of a diversity of anaerobic and aerobic microorganisms. Lactobacilli are the most prevalent and often numerically dominant microorganisms and are relevant as a barrier to infection. The capacity of lactobacilli to adhere and compete for adhesion sites in the vaginal epithelium and the capacity to produce antimicrobial compounds (hydrogen peroxide, lactic acid, bacteriocin-like substances), are important in the impairment of colonization by pathogens.

OBJECTIVE

This review summarizes the role of lactic acid bacteria in preventing illness of the host, including bacterial vaginosis, yeast vaginitis, urinary tract infection and sexually transmitted diseases.

CONCLUSIONS

The administration of probiotics that colonize the vaginal tract can be important in maintaining a normal urogenital health and also to prevent or treat infections.

Lactococcus lactis is a lactic acid bacterium used in the production of many fermented dairy products. We report the complete genome sequence of L. lactis subsp. lactis KF147, a nondairy strain isolated from mung bean sprouts. The circular chromosome of 2,598,144 bp, the largest among the sequenced lactococcal strains, encodes many properties related to adaptation to the plant environment.

This communication presents our recent results that the activity of photocatalytic H2 production can be significantly enhanced when a small amount of MoS2 is loaded on CdS as cocatalyst. The MoS2/CdS catalysts show high rate of H2 evolution from photocatalytic re-forming of lactic acid under visible light irradiation. The rate of H2 evolution on CdS is increased by up to 36 times when loaded with only 0.2 wt % of MoS2, and the activity of MoS2/CdS is even higher than those of the CdS photocatalysts loaded with different noble metals, such as Pt, Ru, Rh, Pd, and Au. The junction formed between MoS2 and CdS and the excellent H2 activation property of MoS2 are supposed to be responsible for the enhanced photocatalytic activity of MoS2/CdS.

The honey bee is a key pollinator species in decline worldwide. As part of a commercial operation, bee colonies are exposed to a variety of agricultural ecosystems throughout the year and a multitude of environmental variables that may affect the microbial balance of individuals and the hive. While many recent studies support the idea of a core microbiota in guts of younger in-hive bees, it is unknown whether this core is present in forager bees or the pollen they carry back to the hive. Additionally, several studies hypothesize that the foregut (crop), a key interface between the pollination environment and hive food stores, contains a set of 13 lactic acid bacteria (LAB) that inoculate collected pollen and act in synergy to preserve pollen stores. Here, we used a combination of 454 based 16S rRNA gene sequencing of the microbial communities of forager guts, crops, and corbicular pollen and crop plate counts to show that (1) despite a very different diet, forager guts contain a core microbiota similar to that found in younger bees, (2) corbicular pollen contains a diverse community dominated by hive-specific, environmental or phyllosphere bacteria that are not prevalent in the gut or crop, and (3) the 13 LAB found in culture-based studies are not specific to the crop but are a small subset of midgut or hindgut specific bacteria identified in many recent 454 amplicon-based studies. The crop is dominated by Lactobacillus kunkeei, and Alpha 2.2 (Acetobacteraceae), highly osmotolerant and acid resistant bacteria found in stored pollen and honey. Crop taxa at low abundance include core hindgut bacteria in transit to their primary niche, and potential pathogens or food spoilage organisms seemingly vectored from the pollination environment. We conclude that the crop microbial environment is influenced by worker task, and may function in both decontamination and inoculation.

To better estimate how frequently patients with low serum cobalamin (Cbl) levels in current clinical practice are truly deficient in Cbl and to determine the incidence of atypical or nonclassic presentations of Cbl deficiency, we prospectively studied 300 unselected consecutive patients with serum Cbl concentrations less than 200 pg/mL seen at two medical centers over a 2-year period. Baseline hematologic, neuropsychiatric, and biochemical measurements were obtained, followed by a course of parenteral Cbl therapy and reassessment. A response to Cbl therapy was defined as one or more of the following: (1) an increase in hematocrit of 0.05 or more; (2) a decrease in mean cell volume of 5 fL or more; (3) a clearing of hypersegmented neutrophilis and macroovalocytes from the peripheral blood smear; and (4) an unequivocal and prompt improvement of neuropsychiatric abnormalities. Of the 300 patients with serum Cbl levels less than 200 pg/mL, 86 had one or more responses to Cbl therapy and 59 had no response. In 155, insufficient data was available. In the Cbl-responsive patients, normal values were found for the following tests: hematocrit, 44%; mean cell volume less than or equal to 100 fL, 36%; white blood cell count, 84%; platelet count, 79%; serum lactic dehydrogenase, 43%; and serum bilirubin, 83%. Peripheral blood smears were nondiagnostic in 6% when reviewed by the investigators, but 33% as reported by routine laboratories. Serum Cbl levels in the 100 to 199 pg/mL range were present in 38%. Neuropsychiatric abnormalities were noted in 28%, often in the absence of anemia, macrocytosis, or both. Serum levels of methylmalonic acid and/or total homocysteine were elevated greater than 3 SDs above the mean for normal subjects in 94% of the Cbl-responsive patients. We conclude that Cbl deficiency should be considered and investigated in patients with unexplained hematologic or neuropsychiatric abnormalities of the kind seen in Cbl deficiency, even if anemia, an elevated mean cell volume, a marked depression of the serum Cbl, or other classic hematologic or biochemical abnormalities are lacking. Levels of serum methylmalonic acid and total homocysteine are useful as ancillary diagnostic tests in the diagnostis of Cbl deficiency.

Lactobacillus casei strains are lactic acid bacteria (LAB) that colonize diverse ecological niches, and have broad commercial applications. To probe their evolution and phylogeny, 40 L. casei strains were characterized; the strains included isolates from plant materials (n=9), human gastrointestinal tracts (n=7), human blood (n=1), cheeses from different geographical locations (n=22), and one strain of unknown origin. API biochemical testing identified niche-specific carbohydrate fermentation profiles. A multilocus sequence typing (MLST) scheme was developed for L. casei. Partial sequencing of six housekeeping genes (ftsZ, metRS, mutL, nrdD, pgm and polA) revealed between 11 (nrdD) and 20 (mutL) allelic types, as well as 36 sequence types. Phylogenetic analysis of MLST data by Reticulate and split decomposition analysis indicated frequent intra-species recombination. Purifying selection was detected, and is likely to have contributed to the evolution of certain L. casei genes. Pulsed-field gel electrophoresis (PFGE) using SfiI was able to discriminate all the isolates, even those not differentiated by MLST. Phylogenetic trees reconstructed based on the MLST data using minimum evolution algorithm, and the SfiI-PFGE restriction patterns using the unweighted-pair group method with arithmetic mean (UPGMA), revealed consensus clusters of strains specific to cheese and silage. Topological discrepancies between the MLST and PFGE trees were also observed, suggesting that intragenic point mutations have accumulated at a slower rate than indels and genome rearrangements in L. casei. The L. casei population analysed in this study demonstrated both a high level of phenotypic and genotypic diversity, as well as specificity to different ecological niches.

Highly porous poly(L-lactic acid)/apatite composites were prepared through in situ formation of carbonated apatite onto poly(L-lactic acid) foams in a simulated body fluid. The highly porous polymer foams (up to 95% porosity) were prepared from polymer solution by solid-liquid phase separation and subsequent sublimation of the solvent. The foams were then immersed in the simulated body fluid at 37 degrees C to allow the in situ apatite formation. After incubation in the simulated body fluid for a certain period of time, a large number of characteristic microparticles formed on the surfaces of pore walls throughout the polymer foams. The microparticles were characterized with scanning electron microscopy, energy dispersive spectroscopy, Fourier transform IR spectroscopy, and X-ray diffractometry. These porous spherical microparticles were assemblies of microflakes. They were found to be carbonated bonelike apatite. A series of composite foams with varying sizes and concentrations of the apatite particles was obtained by varying incubation time and conditions. These porous composites may be promising scaffolding materials for bone tissue engineering and regeneration because the excellent bone-bonding properties of the apatite may provide a good environment for osteoblast and osteoprogenitor cells' attachment and growth.

1. In barbiturate-anesthetized cats we examined the interaction of lactic acid and static contraction on the discharge of group III muscle afferents. Only afferents whose receptive fields were located in the triceps surae muscles were studied. 2. Twelve of 20 afferents were stimulated by a 60-s static contraction. The majority of firing occurred within the first few seconds of contraction. Thirteen of 20 afferents were stimulated by femoral arterial injections of 24 mM lactic acid (1-4 ml) with the muscle at rest. Repeated injections of lactic acid with the muscle at rest led to tachyphylaxis. Lactic acid was then injected (24 mM; 4 ml) during the last 15 s of static contraction. In eight of nine afferents that were tachyphylactic to lactic acid with the muscle at rest, we noted a restored sensitivity to lactic acid during contraction. 3. In separate experiments we examined the effects of dichloroacetate (DCA) on the responses of group III muscle afferents to static contraction. DCA reduces the production of lactic acid by increasing levels of the active form of the enzyme pyruvate dehydrogenase. 4. DCA lowered arterial and venous lactate concentrations at rest and during contraction. DCA significantly decreased (31%; P < 0.05) the responses of the afferents to contraction. This effect was most prominent within the first 10 s of contraction and was not due to a reduced level of mechanical stimulation after DCA, because peak tension levels were the same during the two bouts of contraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Streptococcus pyogenes, S. equinus, S. bovis, S. salivarius, S. sanguis, S. mutans, S. rattus, S. cricetus, S. lactis, S. raffinolactis and Enterococcus faecalis have been characterized by oligonucleotide cataloguing of their 16S ribosomal RNA. All the organisms form a loose but coherent group that is phylogenetically equivalent to those of lactobacilli, bacilli, the Brochothrix and Listeria group, and related taxa that constitute one of several sublines within the 'Clostridium' branch of Gram-positive eubacteria. Within the Steptococcus-Enterococcus group, organisms fall into three moderately related clusters defined by Enterococcus, the lactic acid streptococci and streptococci of the pyogenic and oral groups, respectively.

During the last few years the studies about the physiology and bioenergetics of lactic acid bacteria during growth and starvation have evolved from a descriptive level to an analysis of the molecular events in the regulation of various processes. Considerable progress has been made in the understanding of the modes of metabolic energy generation, the mechanism of homeostasis of the internal pH, and the mechanism and regulatory processes of transport systems for sugars, amino acids, peptides, and ions. Detailed studies of these transport processes have been performed in cytoplasmic membrane vesicles of these organisms in which a foreign proton pump has been introduced to generate a high proton motive force.

Gene therapy approaches to bone tissue engineering have been widely explored. While localized delivery of plasmid DNA encoding for osteogenic factors is attractive for promoting bone regeneration, the low transfection efficiency inherent with plasmid delivery may limit this approach. We hypothesized that this limitation could be overcome by condensing plasmid DNA with nonviral vectors such as poly(ethylenimine) (PEI), and delivering the plasmid DNA in a sustained and localized manner from poly(lactic-co-glycolic acid) (PLGA) scaffolds. To address this possibility, scaffolds delivering plasmid DNA encoding for bone morphogenetic protein-4 (BMP-4) were implanted into a cranial critical-sized defect for time periods up to 15 weeks. The control conditions included no scaffold (defect left empty), blank scaffolds (no delivered DNA), and scaffolds encapsulating plasmid DNA (non-condensed). Histological and microcomputed tomography analysis of the defect sites over time demonstrated that bone regeneration was significant at the defect edges and within the defect site when scaffolds encapsulating condensed DNA were placed in the defect. In contrast, bone formation was mainly confined to the defect edges within scaffolds encapsulating plasmid DNA, and when blank scaffolds were used to fill the defect. Histomorphometric analysis revealed a significant increase in total bone formation (at least 4.5-fold) within scaffolds incorporating condensed DNA, relative to blank scaffolds and scaffolds incorporating uncondensed DNA at each time point. In addition, there was a significant increase both in osteoid and mineralized tissue density within scaffolds incorporating condensed DNA, when compared with blank scaffolds and scaffolds incorporating uncondensed DNA, suggesting that delivery of condensed DNA led to more complete mineralized tissue regeneration within the defect area. This study demonstrated that the scaffold delivery system encapsulating PEI-condensed DNA encoding for BMP-4 was capable of enhancing bone formation and may find applications in other tissue types.

Biodegradable polymers have been used extensively as scaffolding materials to regenerate new tissues. These scaffolds should possess certain physical characteristics including a three-dimensional structure, high porosity with an interconnected pore structure, and a suitable surface structure for cell attachment, proliferation, and differentiation. To mimic the fibrous architecture of type I collagen, nano-fibrous matrices have been created in our laboratory using a phase-separation technique of poly(L-lactic acid) (PLLA) solutions. In addition, biodegradable scaffolds with controlled interconnected spherical pore networks have been fabricated in our laboratory. In this work, these two techniques were combined to yield scaffolds with highly interconnected spherical macroporous structures and nano-fibrous architectures. Paraffin spheres were first fabricated with a dispersion method, and were thermally bonded to form an interconnected mold. PLLA solutions were cast over the paraffin sphere assembly and were thermally phase-separated to form nano-fibrous matrices. After leaching out the paraffin, synthetic nano-fibrous extracellular matrices with interconnected spherical pores were yielded. By utilizing this fabrication process, we are able to control the architecture of the scaffolds at several different levels, including the macroscopic shape of the scaffold, the spherical pore size, interfiber distance, and the fiber diameter at the nano-size scale. The inter-pore connectivity could be controlled by varying the heat treatment time of the paraffin spheres, and mechanical properties could be controlled by varying the porosity of the scaffolds. With an interconnected macroporous structure that promotes cell seeding throughout the interstices of the scaffold, and a synthetic collagen-like matrix, these novel matrices may be an excellent scaffold for tissue engineering.

To determine if organic anions contribute to the diarrhea of inflammatory bowel disease, we measured osmolality, electrolytes, short-chain fatty acids, lactic acid, and some Krebs cycle anions in 24-hr fecal collections from 18 patients with chronic ulcerative colitis, 20 with Crohn's disease of the colon, and 16 normals. Mean lactic acid concentration was significantly elevated in ulcerative and Crohn's colitis, but values correlated with fecal weight only in the former syndrome. In ulcerative colitis, concentrations of each short-chain fatty acid, especially butyrate, were decreased compared with those from normals or Crohn's disease. Lactate and short-chain fatty acids accounted for nearly half the variability in fecal weight in ulcerative colitis. Crohn's patients had elevated mean fecal water osmolality and osmotic gap not observed in ulcerative colitis. Increased lactic acid and/or deficient short-chain fatty acids may modulate the diarrhea of ulcerative colitis. This mechanism seems less important in Crohn's colitis where an additional osmotic component may be significant.

In engineering a cell-carrier to support cartilage growth, hydrogels provide a unique, largely aqueous environment for 3-dimensional chondrocyte culture that facilitates nutrient transport yet provides an elastic framework dictating tissue shape and supporting external loads. Although the gel environment is often >90% water, we demonstrate that slight variations in hydrogel chemistry control gel degradation, evolving macroscopic properties, and ultimately the secretion and distribution of extracellular matrix molecules. Specifically, biodegradable poly(ethylene glycol)-co-poly(lactic acid) hydrogels were fabricated via photopolymerization. When chondrocytes were photoencapsulated in these gels, changes in the poly(ethylene glycol)-co-poly(lactic acid) repeat unit ratio from 19 to 7 increased total collagen synthesis 2.5-fold after 6 weeks in vitro. Furthermore, the ratio of collagen to glycosaminoglycans varied from glycosaminoglycan-rich, 0.33 +/- 0.13, to collagen-rich, 4.58 +/- 1.21, depending on gel chemistry and in vitro versus in vivo culture environment. By tuning scaffold chemistry, and subsequently, gel structure and degradation behavior, we can better guide tissue evolution and development.

The application of metallic stents for benign stenosis is limited due to long-term complications. We report here the results of the implantation of a novel biodegradable poly-L-lactic acid (PLLA) esophageal stent in two patients with benign esophageal stenosis after endoscopic submucosal dissection (ESD). Case 1 was a 64-year-old man who received ESD for an early squamous esophageal cancer in the middle esophagus. The mucosal defect was seven-eighths of the circumference, and the distal margin of the resection scar formed the stenosis. After balloon dilatation, the PLLA esophageal stent was endoscopically placed; for 6 months, he has not experienced any symptoms of re-stenosis. Case 2 consisted of a 62-year-old man who developed an early squamous esophageal cancer in the middle esophagus. The lesion was resected by ESD, and the mucosal defect was seven-eighths of the circumference. The resection scar formed the stenosis, and the PLLA esophageal stent was endoscopically placed. He also has not experienced any symptoms of re-stenosis for 6 months. In conclusion, the PLLA esophageal stent provides a new possibility for the management of benign esophageal strictures after ESD. Due to the biodegradable features of this stent, longer term studies are necessary to investigate the relationship between the expected disappearance of the stent and the patency of the stricture.

Bone marrow Mesenchymal stem cells capable of differentiating into neuronal cells on engineered nanofibrous scaffolds have great potential for bionanomaterial-cell transplantation therapy of neurodegenerative diseases and injuries of the nervous system. MSCs have been the highlight of many tissue engineering studies mainly because of their multipotential properties. We investigated the potential of human bone marrow derived Mesenchymal stem cells (MSCs) for neuronal differentiation in vitro on poly(L-lactic acid)-co-poly-(3-caprolactone)/Collagen (PLCL/Coll) nanofibrous scaffolds. PLCL and PLCL/Coll nanofibrous scaffolds were fabricated by electrospinning process and their chemical and mechanical characterizations were carried out using SEM, contact angle, FTIR, and tensile instrument. The differentiation of MSCs was carried out using neuronal inducing factors including beta-mercaptoethanol, epidermal growth factor, nerve growth factor and brain derived growth factor in DMEM/F12 media. The proliferations of MSCs evaluated by MTS assay showed that the cells grown on PLCL/Coll nanofibrous scaffolds were comparatively higher (80%) than those on PLCL. Scanning electron microscopy results showed that MSCs differentiated on PLCL/Coll nanofibrous scaffolds showed neuronal morphology, with multipolar elongations and expressed neurofilament and nestin protein by immuno-fluorescent microscopy. Our studies on the differentiation of MSCs to neuronal cells on nanofibrous scaffolds suggest their potential application towards nerve regeneration.