Hydrostatic pressure-generated reactive oxygen species induce osteoarthritic conditions in cartilage pellet cultures.

Osteoarthritis (OA) is one of the most common causes of disability and represents a major socio-economic burden. Despite intensive research, the molecular mechanisms responsible for the initiation and progression of OA remain inconclusive. In recent years experimental findings revealed elevated levels of reactive oxygen species (ROS) as a major factor contributing to the onset and progression of OA. Hence, we designed a hydrostatic pressure bioreactor system that is capable of stimulating cartilage cell cultures with elevated ROS levels. Increased ROS levels in the media did not only lead to an inhibition of glycosaminoglycans and collagen II formation but also to a reduction of already formed glycosaminoglycans and collagen II in chondrogenic mesenchymal stem cell pellet cultures. These effects were associated with the elevated activity of matrix metalloproteinases as well as the increased expression of several inflammatory cytokines. ROS activated different signaling pathways including PI3K/Akt and MAPK/ERK which are known to be involved in OA initiation and progression. Utilizing the presented bioreactor system, an OA in vitro model based on the generation of ROS was developed that enables the further investigation of ROS effects on cartilage degradation but can also be used as a versatile tool for anti-oxidative drug testing.

Perfusion Enhances Hypertrophic Chondrocyte Matrix Deposition, But Not the Bone Formation.

Perfusion bioreactors have been an effective tool in bone tissue engineering. Improved nutrient delivery and the application of shear forces have stimulated osteoblast differentiation and matrix production, allowing for generation of large, clinically sized constructs. Differentiation of hypertrophic chondrocytes has been considered an alternative strategy for bone tissue engineering. We studied the effects of perfusion on hypertrophic chondrocyte differentiation, matrix production, and subsequent bone formation. Hypertrophic constructs were created by differentiation in chondrogenic medium (2 weeks) and maturation in hypertrophic medium (3 weeks). Bioreactors were customized to study a range of flow rates (0-1200 µm/s). During chondrogenic differentiation, increased flow rates correlated with cartilage matrix deposition and the presence of collagen type X. During induced hypertrophic maturation, increased flow rates correlated with bone template deposition and the increased secretion of chondroprotective cytokines. Following an 8-week implantation into the critical-size femoral defect in nude rats, nonperfused constructs displayed larger bone volume, more compact mineralized matrix, and better integration with the adjacent native bone. Therefore, although medium perfusion stimulated the formation of bone template in vitro, it failed to enhance bone regeneration in vivo. However, the promising results of the less developed template in the critical-sized defect warrant further investigation, beyond interstitial flow, into the specific environment needed to optimize hypertrophic chondrocyte-based constructs for bone repair.

Consumer exposure to certain ingredients of cosmetic products: The case for tea tree oil.

Reliable exposure data are essential to evaluate the safety of ingredients in cosmetics. The study reported here was carried out on behalf of the Australian Tea Tree Industry Association in order to support safety assessment of TTO in consumer cosmetic products. Data regarding the use of TTO-containing cosmetic products were collected through a web-survey among 2535 qualified users of validated TTO-containing cosmetics in 5 European countries. Data regarding the percentage of TTO present in the individual products (TTO-inclusion) were collected from the suppliers of those products. Beyond TTO exposure-measures there were several significant findings: One is a special "TTO-effect" for several categories of TTO-containing cosmetic products showing a positive correlation between consumers' strength of TTO-orientation and frequency of product use, combined with a negative correlation between frequency of product use and amount of product used per application. Another is significant differences regarding the intensity of product use between TTO-containing cosmetics and respective types of products in general. Thus it seems not to be appropriate to evaluate the toxicological safety of certain ingredients of cosmetic products from exposure data on "generic" types of cosmetic products.

Tissue-engineered hypertrophic chondrocyte grafts enhanced long bone repair.

Bone has innate ability to regenerate following injury. However, large and complex fractures exceed bone's natural repair capacity and result in non-unions, requiring external intervention to facilitate regeneration. One potential treatment solution, tissue-engineered bone grafts, has been dominated by recapitulating intramembranous ossification (bone formation by osteoblasts), although most serious bone injuries heal by endochondral ossification (bone formation by remodeling of hypertrophic cartilaginous anlage). The field has demonstrated that using endochondral ossification-based strategies can lead to bone deposition. However, stem cell differentiated hypertrophic chondrocytes, the key cell type in endochondral ossification, have not been studied for long bone defect repair. With translation in mind, we created tissue-engineered grafts using human adipose stem cells (ASC), a clinically relevant stem cell source, differentiated into hypertrophic chondrocytes in decellularized bone scaffolds, and implanted these grafts into critical-size femoral defects in athymic rats. Over 12 weeks of implantation, these grafts were compared to acellular scaffolds and grafts engineered using ASC-derived osteoblasts. Grafts engineered using hypertrophic chnodrocytes recapitulated endochondral ossification, as evidenced by the expression of genes and proteins associated with bone formation. Markedly enhanced bone deposition was associated with extensive bone remodeling and the formation of bone marrow, and with the presence of pro-regenerative M2 macrophages within the hypertrophic grafts. As a result, hypertrophic chondrocyte grafts bridged 7/8 defects, as compared to only 1/8 for osteoblast grafts and 3/8 acellular scaffolds. These data suggest that ASC-derived hypertrophic chondrocytes in osteogenic scaffolds can improve long bone repair.

Endoscopic pancreatic sphincterotomy and stenting for preoperative prophylaxis of pancreatic fistula after distal pancreatectomy.

BACKGROUND: Pancreatic fistula (PF) is the most common postoperative complication after distal pancreatectomy (DP). Endoscopic pancreatic sphincterotomy and drainage have been shown to be an effective treatment for PF. Recently, preoperative endoscopic pancreatic stenting was proposed to prevent PF, but there are no controlled trials so far. OBJECTIVE: We investigated whether preoperative pancreatic sphincterotomy and stenting could prevent the development of PF in patients with DP. DESIGN: Nonrandomized cohort study with a prospective endoscopic intervention group and a retrospective control group. SETTING: Single-center academic teaching hospital. PATIENTS: Preoperative endoscopic pancreatic sphincterotomy and stenting were intended to prevent PF after DP in 25 patients between July 2004 and October 2008. The incidence of PF was compared with that in a control group of 23 patients who underwent DP between January 2001 and March 2004 without preoperative endoscopic intervention. INTERVENTIONS: Pancreatic sphincterotomy and stenting. MAIN OUTCOME MEASUREMENT: PF rate. RESULTS: Overall, a cohort of 48 patients underwent DP between January 2001 and October 2008. In all 25 patients who underwent preoperative endoscopic pancreatic intervention, sphincterotomy was successfully performed, and stenting of the pancreatic duct was successful in 23 patients. PF developed in none of the 25 patients in the endoscopic intervention group. In the 23 patients without preoperative endoscopic intervention, a PF developed in 5 patients (22%) (P = .02). LIMITATIONS: Nonrandomized design, retrospective control group. CONCLUSIONS: Preoperative pancreatic sphincterotomy and stenting were a feasible and safe procedure in this series. Prophylactic preoperative endoscopic intervention may decrease PF rates after DP.