Osteogenic differentiation of rat bone mesenchymal stem cells cultured on poly (hydroxybutyrate-co-hydroxyvalerate), poly (ε-caprolactone) scaffolds

Bioresorbable biomaterials can fill bone defects and act as temporary scaffold to recruit MSCs to stimulate their differentiation. Among the different bioresorbable polymers studied, this work focuses on poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) and poly(ε-caprolactone) (PCL). Were prepared blends of PHBV and PCL to obtain PHBV based biomaterials with good tenacity, important for bone tissue repair, associated with biocompatible properties of PCL. This study assesses the viability of Vero cells on scaffolds of PHBV, PCL, and their blends and the osteogenic differentiation of mesenchymal stem cells (MSCs). Materials were characterized in surface morphology, DSC and Impact Strength (IS). Vero cells and MSCs were assessed by MTT assay, cytochemical and SEM analysis. MSC osteogenic differentiation was evaluated through alizarin red staining and ALP activity. We found some roughness onto surface materials. DSC showed that the blends presented two distinct melting peaks, characteristic of immiscible blends. IS test confirmed that PHBV-PCL blends is an alternative for increase the tenacity of PHBV. MTT assay showed cells with high metabolic activities on extract toxicity test, but with low activity in the direct contact test. SEM analysis showed spreading cells with irregular and flattened morphology on different substrates. Cytochemical study revealed that MSCs maintained their morphology, although in smaller number for MSCs. The development of nodules of mineralized organic matrix in MSC cultures was identified by alizarin red staining and osteogenic differentiation was confirmed by the quantification of ALP activity. Thus, our scaffolds did not interfere on viability of Vero cells or the osteogenic differentiation of MSCs.

Mechanical and morphological evaluation of osteochondral implants in dogs

The mechanical behavior of osteochondral defects was evaluated in this study with the intention of developing alternative procedures. Cylindrical pins (5.00 mm in diameter and in height) made of pHEMA hydrogel covered ultra-high molecular weight polyethylene (UHMWPE) or beta-tricalcium phosphate (beta-TCP) matrix were used. Ostoechondral defects were caused in the knees of adult dogs and the evaluation was carried out after a 9-month follow-up period. The mechanical behavior of the implants was evaluated by means of an indentation creep test that showed that the UHMWPE matrix maintained its viscoelastic behavior even after follow-up time, while the beta-TCP matrix osteochondral implants presented significant alterations. It is believed that the beta-TCP osteochondral implants were unable to withstand the load applied, causing an increase of complacency when compared to the UHMWPE osteochondral implants. Based on micro and macroscopic analysis, no significant wear was observed in either of the osteochondral implants when compared to the controls. However, morphological alterations, with fragmentation indices in the patella, were observed either due to friction with the hydrogel in the first postoperative months or due to forming of a dense conjunctive tissue. This wear mechanism caused on the counterface of the implant (patella) was observed, notwithstanding the osteochondral implant studied.

[The preceptor in medical residencies in Pediatrics: main attributes]

OBJECTIVE: To analyze the profile of the preceptors and the attributes they consider important for the exercise of that activity, in two medical residency programs in Pediatrics in Rio de Janeiro METHODS: Through a questionnaire answered by each of the preceptors in two medical residency programs in Pediatrics in Rio de Janeiro, one of them connected to a university and the other one not, information was obtained on gender, age, time since graduation, how long they have been acting as preceptors, graduation titles, specific teaching training, and the listing of up to five attributes believed to be necessary to a good preceptor. The results were consolidated and discussed in the text. RESULTS: Of the 90 participants, 70% were woman, 74% were between 30 and 49 years old, 87% graduated between 10 and 29 years ago. Half of them said they did not have any specific teaching training and the other half had attended courses on Medical Pedagogy and Special Didactics during their respective graduate studies. The attribute categories most frequently mentioned were the exercise of tutorship, Ethics and Humanism, mastery of the subject area, capacity of permanent education, and didactic abilities. CONCLUSION: The preceptors pointed to the challenge of exercising preceptorship based on a medical practice where professional responsibilities, human relationship, organizational skills, evaluation techniques, and mastery of the subject area make the main guiding axes of the practice itself. To these axes they added the ethical and humanistic aspects and their permanent education capacities. They feel, however, the need for a didactic qualification in order to accomplish their duties.