Delayed healing remains a major clinical problem and here we have sought to develop an improved dressing film comprising 1.95% w/v fibroin and 0.05% w/v aloe gel extract. The tensile strength of dry film was 21.1 ± 0.5 MPa and broke at 1.1 ± 0.2% elongation; corresponding values for wet film were 18.3 ± 1.3 MPa and 1.9 ± 0.1%. The film maintained its shape upon water immersion and the swelling ratio of the dry film was 0.8 ± 0.1 while the water uptake was 43.7 ± 2.6%. After 28 days of incubation in phosphate buffered saline (1 M, pH 7.4, 37 °C), the weight of film was reduced by 6.7 ± 1.1% and the tensile strength and elongation at breaking point (dry state) were 15.4 ± 0.6 MPa and 1.5 ± 0.2%, respectively. Compared to aloe-free fibroin film (2.0% fibroin extract only), the blended film enhanced the attachment and proliferation of skin fibroblasts. The bFGF immunofluorescence of fibroblasts cultured on the blended film appeared greater than those cultured on tissue culture plate or on aloe-free fibroin film while α-smooth muscle actin was maintained. In streptozotocin-induced diabetic rats, the wounds dressed with the blended film were smaller (p <0.05) by day 7 after wounding, compared to untreated diabetic wounds. Histology of repaired diabetic wounds showed the fibroblast distribution and collagen fiber organization to be similar to wounds in normal rats, and this was matched by enhanced hydroxyproline content. Thus, such accelerated wound healing by the blended fibroin/aloe gel films may find application in treatment of diabetic non-healing skin ulcers.

Dexamethasone (Dex) is used widely to induce differentiation in human mesenchymal stem cells (hMSCs); however, using a pharmaceutical agent to stimulate hMSC differentiation is not the best choice for engineered tissue transplantation due to potential side-effects. The goal of the present study was to investigate the effects of dynamic compressive loading on differentiation and mineralized matrix production of hMSCs in 3D polyurethane scaffolds, using a loading regimen previously shown to stimulate mineralised matrix production of mature bone cells (MLO-A5). hMSCs were seeded in polyurethane scaffolds and cultured in standard culture media with or without Dex. Cell-seeded scaffolds were compressed at 5% global strain for 2 h on day 9 and then every 5 days in a media-filled sterile chamber. Samples were tested for mRNA expression of alkaline phosphatase (ALP), osteopontin (OPN), collagen type 1 (col 1) and runt-related transcription factor-2 (RUNX-212 h) after the first loading, cell viability by MTS assay and alkaline phosphatase activity at day 12 of culture and cell viability, collagen content by Sirius red and calcium content by alizarin red at day 24 of culture. Neither Dex nor loading had significant effects on cell viability. Collagen content was significantly higher (p<0.01) in the loaded group compared with the non-loaded group in all conditions. There was no difference in ALP activity or the amount of collagen and calcium produced between the non-loaded group supplemented with Dex and the loaded group without Dex. We conclude that dynamic loading has the ability to stimulate osteogenic differentiation of hMSC in the absence of glucocorticoids.

Bone turnover in vivo is regulated by mechanical forces such as shear stress originating from interstitial oscillatory fluid flow (OFF), and bone cells in vitro respond to mechanical loading. However, the mechanisms by which bone cells sense mechanical forces, resulting in increased mineral deposition, are not well understood. The aim of this study was to investigate the role of the primary cilium in mechanosensing by osteoblasts. MLO-A5 murine osteoblasts were cultured in monolayer and subjected to two different OFF regimens: 5 short (2 h daily) bouts of OFF followed by morphological analysis of primary cilia; or exposure to chloral hydrate to damage or remove primary cilia and 2 short bouts (2 h on consecutive days) of OFF. Primary cilia were shorter and there were fewer cilia per cell after exposure to periods of OFF compared with static controls. Damage or removal of primary cilia inhibited OFF-induced PGE2 release into the medium and mineral deposition, assayed by Alizarin red staining. We conclude that primary cilia are important mediators of OFF-induced mineral deposition, which has relevance for the design of bone tissue engineering strategies and may inform clinical treatments of bone disorders causes by load-deficiency.—Delaine-Smith, R. M., Sittichokechaiwut, A., Reilly, G. C. Primary cilia respond to fluid shear stress and mediate flow-induced calcium deposition in osteoblasts.

The physicochemical and biological properties of the blended fibroin/aloe gel film as a wound dressing were investigated to support the wound healing efficacy of the film described in our previous study. In the current study, protein content, molecular weight pattern, and chemical characteristics of the silk fibroin and the aloe gel extracts were analyzed. The two extracts were then dissolved in lactic acid solution and casted to obtain the blended fibroin/aloe gel film. We found that gamma irradiation did not affect any physicochemical properties of the film, i.e., the irradiated and the non-sterilized films had similar physical appearance, surface morphology, mechanical properties, and chemical characteristics. On normal human fibroblast cultures, the film induced non-cytotoxicity and stimulated the expression of vascular epidermal growth factor. The film-treated cells were shown to proliferate by shifting from G 0 /G 1 phase (76.26 ± 0.72%) to S phase (7.19 ± 0.23%) and G 2 /M phase (16.09 ± 0.58%) which are higher than the untreated cells. The film-treated cells provided a completely healed scratch at 36 h after scratch creation, while the created scratch of the untreated cells was not healed, indicating that the biological activity of the film enhanced the proliferation and the migration of fibroblast cells. We speculated that the prepared film might be able to use as wound dressing for the diabetic foot ulcer.

In diabetic patients, the process of wound healing is usually delayed or impaired. A diabetic environment could be associated with dermal fibroblast dysfunction, reduced angiogenesis, the release of excessive proinflammatory cytokines, and senescence features. Alternative therapeutic treatments using natural products are highly demanded for their high potential of bioactive activity in skin repair. Two natural extracts were combined to develop fibroin/aloe gel wound dressing. Our previous studies revealed that the prepared film enhances the healing rate of diabetic foot ulcers (DFUs). Moreover, we aimed to explore its biological effects and underlying biomolecular mechanisms on normal dermal, diabetic dermal, and diabetic wound fibroblasts. Cell culture experiments showed that the γirradiated blended fibroin/aloe gel extract film promotes skin wound healing by enhancing cell proliferation and migration, vascular epidermal growth factor (VEGF) secretion, and cell senescence prevention. Its action was mainly linked to the activation of the mitogen-activated protein kinases/extracellular signal-regulated kinase (MAPK/ERK) signaling pathway known to regulate various cellular activities, including proliferation. Therefore, the findings of this study confirm and support our previous data. The blended fibroin/aloe gel extract film displays a biological behavior with favorable properties for delayed wound healing and can be considered as a promising therapeutic approach in the treatment of diabetic nonhealing ulcers.