A finite element analysis on the biomechanical performance of implant-retained finger prostheses designed for Asians.

This study aims to explore the biomechanical performance of implant-retained finger prostheses of different lengths and diameters designed specifically for Asians under external loads from different directions by the finite element method. According to the metacarpophalangeal stumps (length: 4, 7, 10 mm, diameter: 3.5, 4.5 mm) retained in Asian patients with finger defects, six implant-retained finger prosthesis models of different lengths and diameters were designed in Solid Works 3D, transported to Abaqus, and constructed based on computerized tomography (CT). The finite element simulation of the finger prosthesis structure was performed using HyperMesh. The strain and stress distribution of the finger prosthesis models under three loads were calculated: axial force, lateral force, and lateral force with bending moments. As the load increased, the cancellous bone yielded first, while the dense bone and implant could withstand much higher loads than the cancellous bone. As the implant depth increased, the maximum strain of the cancellous bone increased significantly, but the effect of the implant diameter remained unclear. In addition, the structure could withstand large axial loads but was much less able to withstand both lateral forces and bending moments. The yielding and destruction of the implant-retained finger prostheses designed specifically for Asians are mainly attributed to cancellous bone. As the depth of the implants increases, the maximum strain of cancellous bone rises significantly. In addition, in the treatment of patients with finger defects, this method may be used to analyze and select which implant can withstand stronger stress according to the finger stumps of the patients with finger defects so that the most suitable implant and individual surgical plan for the patient can be designed.

Muscle Synergy Alteration of Human During Walking With Lower Limb Exoskeleton.

Muscle synergy reflects inherent coordination patterns of muscle groups as the human body finishes required movements. It may be still unknown whether the original muscle synergy of subjects may alter or not when exoskeletons are put on during their normal walking activities. This paper reports experimental results and presents analysis on muscle synergy from 17 able-bodied subjects with and without lower-limb exoskeletons when they performed normal walking tasks. The electromyography (EMG) signals of the tibialis anterior (TA), soleus (SOL), lateral gastrocnemius (GAS), vastus medialis oblique (VMO), vastus lateralis oblique (VLO), biceps femoris (BICE), semitendinosus (SEMI), and rectus femoris (RECT) muscles were extracted to obtain the muscle synergy. The quantitative results show that, when the subjects wore exoskeletons to walk normally, their mean muscle synergy changed from when they walked without exoskeletons. When the subjects walked with and without exoskeletons, statistically significant differences on sub-patterns of the muscles' synergies between the corresponding two groups could be found.

Investigation of Microsurgical Technique Combined With Skin Flap Expansion for Ear Reconstruction in Treating Hunter Type III Congenital Microtia.

OBJECTIVE: This study aims to observe the efficacies of microsurgical technique combined with the Zhuang's skin soft tissue expander in treating Hunter type III congenital microtia. METHODS: Fifty-eight patients (61 ears) were enrolled from 2003 to 2012; the skin tissue expander was embedded subepidermally in the first stage via the intrahairline longitudinal incision in the postauricular mastoid area, the diseased-side rib cartilage was then taken for preparing the ear bracket in the second stage, and the tragus was surgically reconstructed in the third stage. RESULTS: The mean follow-up lasted 6 months to 10 years, the results were satisfactory for 54 ears and acceptable for 5 ears, and 2 ears (in two patients) appeared with complications, including 1 case of ear flap expansion rupture and 1 case of postoperative lateral helix flap necrosis. CONCLUSIONS: The combination of microsurgical technique, Zhuang's skin soft tissue expander, and autogenous rib cartilage graft could achieve satisfactory results in treating Hunter type III congenital microtia, and the complications were less, so it was worthy of clinical applications.

Short-term memory of danger signals or environmental stimuli in mesenchymal stem cells: implications for therapeutic potential.

Mesenchymal stem/stromal cells (MSCs) possess some characteristics of immune cells, including a pro-inflammatory phenotype, an immunosuppressive phenotype, antibacterial properties and the expression of Toll-like receptor proteins. Here we show that, similar to immune cells, MSCs retain information from danger signals or environmental stimuli for a period of time. When treated with the pro-inflammatory factors lipopolysaccharide (LPS) or tumor necrosis factor-α (TNF-α), MSCs display increased expression of IL-6, IL-8 and MCP-1. Following re-plating and several rounds of cell division in the absence of stimulating factors, the expression of IL-6, IL-8 and MCP-1 remained higher than in untreated cells for over 7 days. A spike in cytokine secretion occurred when cells were exposed to a second round of stimulation. We primed MSCs with LPS and LPS-primed MSCs had better therapeutic efficacy at promoting skin flap survival in a diabetic rat model than did unprimed MSCs. Finally, we found that several microRNAs, including miR146a, miR150 and miR155, along with the modification of DNA by 5-hydroxymethylcytosine (5hmC), mediate the MSC response to LPS and TNF-α stimulation. Collectively, our data suggest that MSCs have a short-term memory of environmental signals, which may impact their therapeutic potential.

A New Modified S-plasty for Skin Defect Closure.

BACKGROUND: Dog-ear, or standing cone deformity, is a common problem during surgical procedures. Multiple methods have been reported to correct the deformity but most create long scars or excessive normal skin loss. METHODS: We designed a simple and convenient procedure to remove small- and medium-sized skin defects. Based on mathematical calculations, the procedure is an easily designed surgical technique. RESULTS: All of our patients healed uneventfully with no significant complications. The procedure not only resulted in a shortened surgical incision and preserved a greater amount of healthy skin, but also left a simple "S-shaped" curvilinear scar with favorable esthetic outcomes. CONCLUSION: This novel modified S-plasty is a simple tool to successfully remove skin defects, with a low deformity risk.

Chondrogenesis by co-culture of adipose-derived stromal cells and chondrocytes in vitro.

Adipose-derived stromal cells (ADSCs) could be induced to differentiate into chondrocytes in the presence of cellular factors. In this study, we explored the feasibility of inducing the differentiation of ADSCs into chondrocytes in the presence of chondrocytes. Human ADSCs and porcine auricular chondrocytes were expanded in vitro and then were mixed at the ratio of 7:3. 5.0 × 10(7) mixed cells were seeded onto a polyglycolic acid/polylactic acid scaffold as co-culture group. Chondrocytes and ADSCs with the same cell number were seeded onto the scaffold as positive control group and negative control group. A total of 1.5 × 10(7) chondrocytes were seeded as low-concentration chondrocyte group. After culturing for 8 weeks, gross observation, wet weight, histology, glycosaminoglycan quantification, and collagen II expression were evaluated. Cells in all groups well adhered to the scaffold and could secrete extracellular matrices. In the co-culture group and positive control group, cell-scaffold constructs could maintain the original size and shape during the culture. At the 8th week, cartilage-like tissues were formed, and abundant type II collagen could be detected by immunohistochemistry and reverse transcription-polymerase chain reaction in co-culture and positive control groups. Wet weights and glycosaminoglycan contents of tissues in co-culture group were approximately onefold of those in the negative control group. In the negative control group, constructs shrunk gradually without mature cartilage lacuna formation. In low-concentration chondrocyte group, constructs also shrunk obviously with small amount of cartilage formation. Chondrocytes can provide chondrogenic microenvironment to induce chondrogenic differentiation of ADSCs and thus promote the chondrogenesis of ADSCs in vitro.

[Preliminary study of in vitro chondrogenesis by co-culture of chondrocytes and adipose-derived stromal cells].

OBJECTIVE: To explore the feasibility of in vitro chondrogenesis by co-culture of chondrocytes and adipose-derived stromal cells (ADSCs) so as to confirm the hypothesis that chondrocytes can provide chondrogenic microenvironment to induce chondrogenic differentiation of ADSCs. METHODS: Human ADSCs and porcine auricular chondrocytes were in vitro expanded respectively and then were mixed at the ratio of 7:3 (ADSCs: chondrocytes). 200 microl mixed cells (5.0 x 10(7)/ml) were seeded onto a polyglycolic acid/polylactic acid (PGA/PLA) scaffold, 8 mm in diameter and 2 mm in thickness, as co-culture group. Chondrocytes and ADSCs with the same cell number were seeded respectively onto the scaffold as positive control group and negative control group. 200 microl chondrocytes (1.5 x 10(7)/ml) were seeded as low concentration chondrocyte group. There were 6 specimens in each group. All specimens were harvested after in vitro culture for 8 weeks in DMEM plus 10% FBS. Gross observation, histology, immunohistochemistry, wet weight measurement and glycosaminoglycan (GAG) quantification were used to evaluate the results. Multiple-sample t-test statistics analysis was done to compare the difference of wet weight and glycosaminoglycan(GAG) content between the groups. RESULTS: Cells in all groups had fine adhesion to the scaffold and could secrete extracellular matrix. In co-culture group and positive control group, cell-scaffold constructs could maintain the original size and shape during in vitro culture. At 8 weeks, cartilage-like tissue formed in gross appearance and histological features, and abundant type II collagen could be detected by immunohistochemistry. Wet weight and glycosaminoglycan(GAG) content of co-culture group were respectively (174 +/- 12) mg and (7.6 +/- 0.4) mg. There were respectively 75% (P < 0.01) and 79% (P<0.01) of those of positive control group. In negative control group, however, constructs shrunk gradually without mature cartilage lacuna in histology. In low concentration chondrocyte group, constructs also shrunk obviously with small amount of cartilage formation at the edge area of the construct, and wet weight was (85 +/- 5) mg, which was 37% (P<0.01) of that of positive control group. CONCLUSIONS: Chondrocytes can provide chondrogenic microenvironment to induce chondrogenic differentiation of ADSCs and thus promote the in vitro chondrogenesis of ADSCs.

[Preliminary study on the phenomenon of epidermal stem cell ectopy in expanded skin].

OBJECTIVE: To observe the differentiation and distribution of epidermal stem cell (ESC) after skin soft tissue expansion, and to initially probe into the growth mechanism of expanded skin tissue. METHODS: Samples of normal skin and expanded skin (mean effusion period 45 days) were harvested from head and cervical region in 15 patients who underwent II stage surgery after skin expansion. Samples were divided into scalp adjacent to the center of expander group (expanded scalp, 3 cm from the vertical axis of the expander), scalp from lateral part of the expander group (expanded scalp, 5 - 7 cm lateral to the vertical axis of the expander), cervical skin expansion group, un-expanded scalp control group, and un-expanded cervical skin control group, according to the position of skin harvested. The tissue structure of skin in each group was observed with HE staining, and the differentiation and distribution characteristics of cytokeratin 19 (CK19) positive cells were observed with immunohistochemical staining. RESULTS: Compared with those in the un-expanded control groups, uneven, relatively thickened and obviously folded epidermis with more cell layers and cells with obvious aggregation close to the basal layer were observed in the expanded groups, but those cells were not well-arranged and the transition of polarity was not obvious. The continuity of CK19 positive cells in the basal layer of skin was observed in each of the expanded group with immunohistochemical staining, and positive cells increased obviously and arranged in multilayer in certain parts of basal layer. Clustered or dispersed CK19 positive cells were also observed outside the basal layer. No above-mentioned phenomenon was observed in the un-expanded control group. CONCLUSIONS: The proliferation and differentiation of ESC with ectopic distribution may enhance the repair process after skin soft tissue expansion.

[Preliminary investigation on the dynamic change in epidermal stem cells under mechanical stress in vivo].

OBJECTIVE: To observe the distribution of epidermal stem cell (ESC) after soft tissue expansion, and to explore dynamic change in ESC under mechanical stress and kinetic mechanism of skin expansion. METHODS: Skin samples were collected from patients after expansion of the scalp. They were divided into three groups: A group (scalp harvested 3 cm away from the center of dilator), B group (scalp tissues at the edge of dilator), and control group (scalp without dilatation). The tissue structures were observed with optical microscope with HE staining. The distribution and differentiation characteristics of cell keratin 19 (CK19) positive cells were observed with inverted phase contrast microscope after immunohistochemistry staining. RESULTS: HE staining showed that the epidermis was thickened and distributed densely with uneven, rugged and increased layers in A, B groups. With immunohistochemistry staining, CK19 positive cells appeared in multilayers in basal membrane, a few of them were in cluster or dispersed , with" hollowing" structure formation. These phenomena were not seen in control group. CONCLUSION: ESC can proliferate with abnormal distribution and "hollowing" structure formation after mechanical dilatation, which may be related to dynamic changes in basal layer cells.

Progress of cellular dedifferentiation research.

Differentiation, the stepwise specialization of cells, and transdifferentiation, the apparent switching of one cell type into another, capture much of the stem cell spotlight. But dedifferentiation, the developmental reversal of a cell before it reinvents itself, is an important process too. In multicellular organisms, cellular dedifferentiation is the major process underlying totipotency, regeneration and formation of new stem cell lineages. In humans, dedifferentiation is often associated with carcinogenesis. The study of cellular dedifferentiation in animals, particularly early events related to cell fate-switch and determination, is limited by the lack of a suitable, convenient experimental system. The classic example of dedifferentiation is limb and tail regeneration in urodele amphibians, such as salamanders. Recently, several investigators have shown that certain mammalian cell types can be induced to dedifferentiate to progenitor cells when stimulated with the appropriate signals or materials. These discoveries open the possibility that researchers might enhance the endogenous regenerative capacity of mammals by inducing cellular dedifferentiation in vivo.

[Isolation, culture and identification of adult epidermal stem cell].

OBJECTIVE: To explore and establish a new method of isolation, culture, and identification of adult epidermal stem cell in vitro for the provision of seed-cells in tissue engineering of skin. METHODS: Epidermis was obtained by digesting human foreskin with protease and it was dissociated into single cells with trypsin and ethylenediaminetetraacetic acid (EDTA). These single epidermis cells were inoculated onto human collagen IV coated flasks and cultured at 37 degrees C in a humidified atmosphere containing 5% CO(2). The nonadherent cells were rinsed off 10-15 minutes after inoculation. The adherent cells were observed under phase contrast microscope and electron microscope, and they were identified with immunocytochemical methods. Cell cycles of the adherent cells were determined with flow cytometry. RESULTS: With phase contrast microscope, the rapidly adherent cells were observed to form colonies 24 hours after inoculation. Immunocytochemistry showed the rapidly adherent cells were positive for beta1-integrin and keratin 19. Cell cycles showed that about 86.83% cells were in resting state/pre-DNA-synthetic gap (G0/G1 phase). Electron microscopy revealed that the rapidly adherent cells were immature. CONCLUSION: This study shows that adult epidermal stem cells could be isolated and cultured in vitro successfully.