An in vitro and in vivo study on the properties of hollow polycaprolactone cell-delivery particles

Biomimetic immunomodulation strategies for effective tissue repair and restoration

Inflammation plays a central role in wound healing following injury or disease and is mediated by a precise cascade of cellular and molecular events. Unresolved inflammatory processes lead to chronic inflammation and fibrosis, which can result in prolonged wound healing lasting months or years that hampers tissue function. Therapeutic interventions mediated by immunomodulatory drugs, cells, or biomaterials, are therefore most effective during the inflammatory phase of wound healing when a pro-regenerative environment is essential. In this review, we discuss the advantages of exploiting knowledge of the native tissue microenvironment to develop therapeutics capable of modulating the immune response and promoting functional tissue repair. In particular, we provide examples of the most recent biomimetic platforms proposed to accomplish this goal, with an emphasis on those able to induce macrophage polarization towards a pro-regenerative phenotype.

Comparison of polycaprolactone and calcium hydroxylapatite dermal fillers in a rat model

Polycaprolactone (PCL) and calcium hydroxylapatite (CaHA) are semipermanent dermal fillers that are frequently preferred in the last decade. This study aims to compare the effects of these two fillers in the rat skin. A total of 30 female rats were divided into; control, PCL, and CaHA group. Tissue samples taken at the second and fourth month were stained with hematoxylin-eosin, Masson trichrome, collagen type 1, and 3 immunohistochemical antibodies. Collagen density was quantitatively compared using the Image J computer program. At 2 and 4 months, the density of collagen increased in both filler groups compared to the control group. There was no significant difference between collagen density or type 1 and type 3 collagen H scores in the filler groups. The number of fibroblast nuclei was significantly higher in the PCL group at 4 months compared to the other two groups. Dermis thickness was found to be superior in both filler groups compared to the control group at the fourth month, there was no significant difference between the filler groups. We compared the effect of CaHA and PCL filler on collagenization histologically and immunohistochemically. We found that PCL and CaHA fillers are effective in increasing dermal collagen density, type 1 and type 3 collagen amount, and preventing dermis atrophy and showed that they have no advantage over each other in this respect. We have shown that PCL filler provides more fibroblast increase compared to CaHA filler and the effect of stimulating fibroblast proliferation takes longer.

Endothelin increases the proliferation of rat olfactory mucosa cells

The olfactory mucosa holds olfactory sensory neurons directly in contact with an aggressive environment. In order to maintain its integrity, it is one of the few neural zones which are continuously renewed during the whole animal life. Among several factors regulating this renewal, endothelin acts as an anti-apoptotic factor in the rat olfactory epithelium. In the present study, we explored whether endothelin could also act as a proliferative factor. Using primary culture of the olfactory mucosa, we found that an early treatment with endothelin increased its growth. Consistently, a treatment with a mixture of BQ₁₂₃ and BQ₇₈₈ (endothelin receptor antagonists) decreased the primary culture growth without affecting the cellular death level. We then used combined approaches of calcium imaging, reverse transcriptase-quantitative polymerase chain reaction and protein level measurements to show that endothelin was locally synthetized by the primary culture until it reached confluency. Furthermore, in vivo intranasal instillation of endothelin receptor antagonists led to a decrease of olfactory mucosa cell expressing proliferating cell nuclear antigen (PCNA), a marker of proliferation. Only short-term treatment reduced the PCNA level in the olfactory mucosa cells. When the treatment was prolonged, the PCNA level was not statistically affected but the expression level of endothelin was increased. Overall, our results show that endothelin plays a proliferative role in the olfactory mucosa and that its level is dynamically regulated. This study was approved by the Comité d’éthique en expérimentation animale COMETHEA (COMETHEA C2EA -45; protocol approval #12-058) on November 28, 2012.

Toxicity and Safety Study of D-PLEX100 in a Sternal Surgical Defect in New Zealand White Rabbits

Bacterial infections are a common complication after surgical procedures. Therefore, local delivery of antibiotics has been developed, including the use of biodegradable polymers. A newly developed product for prevention of surgical site infections is a polymer-lipid encapsulation matrix loaded with doxycycline, named D-PLEX₁₀₀ (D-PLEX). We evaluated the toxicity and safety of D-PLEX using a sternal surgical defect model in rabbits. D-PLEX was tested with three different concentrations of doxycycline in comparison to sham-operated control after administration into the sternal surgical defect and on the ventral side of the sternum in New Zealand White (NZW) rabbits, following 15 months of exposure. No mortality or abnormal clinical findings were attributed to D-PLEX, and clinical pathology assays were normal. Histological examinations revealed no treatment-related adverse findings in any of the examined tissues, including the osseous and surrounding soft tissues. It has been shown that D-PLEX gradually degraded until complete disappearance after 9 months, and mainly during the first 3 months, in parallel to normal bone formation. In addition, the administration of D-PLEX did not affect sternal bone strength. This study adds to the growing data on preclinical safety studies utilizing biodegradable materials and provides information on the expected normal reaction to biodegradable materials in the sternum of NZW rabbits.