The cryopreservation of a tissue engineered dermal replacement by programmed freezing

Long-term storag of engineered bio-artificial tissues is required to ensure the off-the-shelf availability to clinicians due to their long production cycle. Cryopreservation is likely the choice for long-term preservation. This study investigated the effects of dimethyl sulfoxide (DMSO) concentrations, cooling rates, cryoprotectant medium treatment methods and seeding on the cell viability of a tissue-engineered dermal substitute. The dermal fibroblast was cultured on a polyglycolic acid (PGA) scaffolding at 37degree C and a 5% CO<inf>2</inf>atmosphere for 14 days, and dermal slices (10&#215;3&#215;1.5mm) were used in the experimental group. The freezing was carried out in a computer-controlled programmable freezer at 0.5degree C/min, 1degree C/min and 2degree C/min in1.4M, 2.1M and 2.8M DMSO from 4degree C to -60degree C and then plunged into the liquid nitrogen tank immediately. After 24th of cryopreservation, the samples wereped in removed from liquid nitrogen and placed at room temperature in air for 0.5-1min, prior to submergence in a water bath at 37 degree C. viability of fresh control and cryopreserved dermal slices were determined with our modification of the MTT (3-[4,5-Dimethythiazol-2-yl] -2,5-diphenyltetrazolium bromide) assay. The effects of two cryoprotectant medium treatment methods and seeding (at -7degree C)on cell viability were also assessed. A cryopreservation protocol of 1degree C/min in 1.4M DMSO from 4degree C to -60degree C, and seeding at -7degree C proved optimal for this tissue-engineered dermal replacement, provided the dermal slice was transferred into the cryopreservation bag containing 1mL 1.4M DMSO bag and hold for 15min at 4degree C prior to freezing.

Experimental study on sludge reduction by ultrasound

In recent years, considerable impetus emerges to develop strategies for reducing excess sludge produced in biological wastewater treatment (BWT) systems. In this study, an experiment on sludge reduction by ultrasound treatment was conducted. The influences of sonication on observed yield, sludge reduction, effluent quality, sludge settleability and stability were extensively evaluated. It was found that ultrasound had an impressive potential to reduce sludge production. Moreover, it was also concluded that a treatment time of 10 minutes was more cost-effective for sludge reduction, and a reduction by 44% was reached with an ultrasonic intensity of 0.25 w/ml. The reduction could be mainly attributed to disintegration of bio-flocs and cryptic growth. In addition, sonication time seemed to be more effective to reduce sludge production compared with ultrasonic intensity. Slight deterioration of the effluent quality and some variations of the sludge settleability and stability were observed after ultrasound treatment.

TGF-beta: a fibrotic factor in wound scarring and a potential target for anti-scarring gene therapy

Hypertrophic scar and keloid are common and difficult to treat diseases in plastic surgery. Results of wound healing research over the past decades have demonstrated that transforming growth factor-beta (TGF-beta) plays an essential role in cutaneous scar formation. In contrast, fetal wounds, which heal without scarring, contain a lower level of TGF-beta than adult wounds. How to translate the discovery of basic scientific research into the clinical treatment of wound scarring has become an important issue to both clinicians and basic researchers. The development of gene therapy techniques offers the potential to genetically modify adult wound healing to a healing process similar to fetal wounds, and thus reduces wound scarring. This article intends to review the roles of TGF-beta in the formation of wound scarring, the possible strategies of antagonizing wound TGF-beta, and our preliminary results of scar gene therapy, which show that wound scarring can be significantly reduced by targeting wound TGF-beta.

Preparation and use of thermosensitive polymers

Restoration of organ structure and function, utilizing tissue engineering technologies, often requires the use of a temporary porous scaffold. The function of the scaffold is to direct the growth of cells migrating from the surrounding tissue (tissue conduction), or of cells seeded within the porous structure of the scaffold. The scaffold must therefore provide a suitable substrate for cell attachment, differentiated function, and, in certain cases, cell proliferation (1-3). These critical requirements may be met by the choice of an appropriate material from which to construct the scaffold, although the suitability of the scaffold may also be affected by the processing technique. There are many biocompatible materials that could potentially be used to construct scaffolds, however, a biodegradable material is normally desirable, since the role of the scaffold is usually only a temporary one. Many natural and synthetic biodegradable polymers, such as collagen, poly(α-hydroxyesters), and poly(anhydrides), have been widely and successfully used as scaffolding materials because of their versatility and ease of processing. Many researchers have used poly(α-hydroxyesters) as starting materials from which to fabricate scaffolds, using a wide variety of processing techniques. These polymers have proven successful as temporary substrates for a number of cell types, allowing cell attachment, proliferation, and maintenance of differentiated function (10). Poly(α-hydroxyesters) such as the polyoxamers are a family of more than 30 different nontoxic, nonionic surface active agents. These compounds are made at elevated temperature and pressure by the sequential additi on of propylene oxide and then ethylene oxide to neutralize the salt that is generally retained in the final product.

[Experimental study for repair of cranial defects with bone marrow stromal cells and modified alginate]

OBJECTIVE

The primary aim of this investigation was to determine whether expanded BMSCs in vitro mixed with modified alginate gelatin could repair critical defects in rats without the addition of exogenous growth or bone morphogenetic factors.

METHODS

Bone marrow stem cells from syngeneic rats cultured in vitro and mixed with modified alginate gel to paint the cranial critical size defect. A full-thickness cranial plate defect was created without damage of dura mater. Modified alginate gelatin with or without BMSCs were painted over the cranial defects. Animals being made cranial defect but received no implant served as sham-operated controls. Craniotomy defects were divided into three groups, which included defects left unpainted (group I, n=6), defects painted with modified alginate gelatin alone (group II, n=6), and defects painted with a modified alginate mixed with BMSCs (group III, n=6). A total of 18 implant experiments were carried out, with postsurgical radiographic and histological analysis completed at 12 week.

RESULTS

None of the implants exhibited extrusion or infection. Radiographs showed a likely increased calcification in group III, without finally new calcification in group I and in group II. Histology showed that group I and group II were featured by thinning of the bone at the edges of the defect margins with minimal bone growth inward and dense fibrous tissue with rudimentary alginate material spanning the intervenient gap. The results demonstrated that a great amount of new bone in growth took place in BMSCs-alginate group, stemming from cranial defect edges and proceeding inward.

CONCLUSION

Transplantation of syngeneic BMSCs with alginate gel can serve as an example of a cell-based treatment for skeletal reformation and would be especially useful for augmenting or regenerating bone in skeletal defects. So syngeneic BMSCs with alginate gel demonstrate a potential technique to regenerate a variety of skeletal defects that occur in different clinical scenaries.

[Autologous tissue engineered skin for full thickness skin replacement]

OBJECTIVE

To evaluate the feasibility of regenerating or repairing damaged skin utilizing tissue engineering techniques.

MATERIALS AND METHODS

Yorkshire pigs were used in the study. A critical size defect of six, full thickness, 4 cm in diameter round wounds, which were marked on the paravertebral region of the animal were excised. The skin defects were randomly divided into three groups. Group I as control group received no cells or polymer. Group II as a second control group received pluronic hydrogel with no cells. Group III as the experimental group received a mixture of cells (keratinocytes and fibroblasts) and pluronic hydrogel. All specimens were harvested at 4 and 6 weeks in vivo, and underwent gross, histological, and transmission electron microscope evaluation.

RESULTS

Histologically, the skin in the experimental group was similar to normal skin with stratified epidermis overlying a moderately thick collageneous dermis. The interface of the tissue was apparently demarcated by epidermal ridges and dermal papillae. The control groups showed no skin formation except for granulation with infiltrating inflammatory cells in the wound. Transmission electron microscopy showed that the basal lamina of the experimental group was well developed and attached to the extracellular matrix.

CONCLUSION

This finding demonstrates the successful use of tissue engineered skin with Pluronic F-127 as a cell carrier.

[Shear bond test of HF acid etching porcelain bonded to enamel with different concentration and disposing time]

OBJECTIVE:Understand the effect of shear bond test of HF acid etching porcelain bonded to enamel with different concentration and disposing time. METHODS:After HF acid etching under 30 groups composed of 5 different HF concentrations and 6 exposing times,shear bonding strength of porcelain to enamel was tested under imitating occlusion and debonding types of the composite were examined by microscope.RESULTS:The favorable concentration-time groups for clinics were 2.5%-5min;5.0%-2.5min;10%-30s;7.5%,15%-5min.The debonding type of porcelain resin enamel composite body was mixed one.CONCLUSION:The results showed HF acid etching technique had a positive influence on the bonding strength of porcelain to enamel.

[The experimental study on optimal cell density and formation time of tissue engineered autologous cartilage]

OBJECTIVE

This paper aims to investigate the suitable cell density and the best formation time of tissue engineered autologous cartilage and to provide theoretical basis and parameters for clinical application.

METHODS

The chondrocytes isolated from mini swines' ears were mixed with injectable biocompatible matrix (Pluronic), and the density of cell suspensions were 10, 20, 30, 40, 50, 60, 70 x 10(4)/ml. The chondrocyte-polymer constructs were subcutaneously injected into the abdomen of autologous swine. The specimens were observed grossly and histologically after 6 weeks, and investigated the suitable cell density. Then the chondrocyte-polymer constructs with suitable cell density were transplanted into the abdomen of autologous swine and evaluated grossly and histologically in 1, 3, 6, 9, 15 weeks after transplantation to investigate the best formation time of tissue engineered cartilage.

RESULTS

The experiments demonstrated that the tissue engineered autologous cartilage was similar to the natural cartilage on animals with normal immune system in histological characteristics. The optimal chondrocyte density is 50 x 10(6)/ml, and the proper harvest time is the sixth week.

CONCLUSION

With tissue engineering skills, we have identified the optimal chondrocyte density and the proper harvest time.

Characteristics of cartilage engineered from human pediatric auricular cartilage

In the repair of cartilage defects, autologous tissue offers the advantage of lasting biocompatibility. The ability of bovine chondrocytes isolated from hyaline cartilage to generate tissue-engineered cartilage in a predetermined shape, such as a human ear, has been demonstrated; however, the potential of chondrocytes isolated from human elastic cartilage remains unknown. In this study, the authors examined the multiplication characteristics of human auricular chondrocytes and the ability of these cells to generate new elastic cartilage as a function of the length of time they are maintained in vitro. Human auricular cartilage, harvested from patients 5 to 17 years of age, was digested in collagenase, and the chondrocytes were isolated and cultured in vitro for up to 12 weeks. Cells were trypsinized, counted, and passaged every 2 weeks. Chondrocyte-polymer (polyglycolic acid) constructs were created at each passage and then implanted into athymic mice for 8 weeks. The ability of the cells to multiply in vitro and their ability to generate new cartilage as a function of the time they had been maintained in vitro were studied. A total of 31 experimental constructs from 12 patients were implanted and compared with a control group of constructs without chondrocytes. In parallel, a representative sample of cells was evaluated to determine the presence of collagen. The doubling rate of human auricular chondrocytes in vitro remained constant within the population studied. New tissue developed in 22 of 31 experimental implants. This tissue demonstrated the physical characteristics of auricular cartilage on gross inspection. Histologically, specimens exhibited dense cellularity and lacunae-containing cells embedded in a basophilic matrix. The specimens resembled immature cartilage and were partially devoid of the synthetic material of which the construct had been composed. Analyses for collagen, proteoglycans, and elastin were consistent with elastic cartilage. No cartilage was detected in the control implants. Human auricular chondrocytes multiply well in vitro and possess the ability to form new cartilage when seeded onto a three-dimensional scaffold. These growth characteristics might some day enable chondrocytes isolated from a small auricular biopsy to be expanded in vitro to generate a large, custom-shaped, autologous graft for clinical reconstruction of a cartilage defect, such as for congenital microtia.

Tissue-engineered nipple reconstruction

We describe a simple, effective approach to the creation of autologous tissue-engineered cartilage in the shape of a human nipple by injecting a reverse thermosensitive polymer seeded with autologous chondrocytes in an immunocompetent porcine animal model. A biodegradable, biocompatible copolymer of polyethylene oxide and polypropylene oxide (Pluronic F-127), which exists as a liquid below 4 degrees C and polymerizes to a thick gel when it is exposed to physiologic temperatures (body temperatures), was used as a vehicle for chondrocyte delivery and as a scaffold to guide growth. Autologous chondrocytes isolated from porcine auricular elastic cartilage and suspended in 30% (weight/volume) Pluronic F-127 were injected on the ventral surface of the pigs from which the cells had been isolated. A circumferential subdermal suture was used to support the contour of the implant and assist in its projection in the form of a human nipple. After 3 weeks, the skin over and surrounding the implant was tattooed to create the appearance of a human nipple-areolar complex. As controls, an equal number of injections were made using either cells alone (not suspended in hydrogel), or hydrogel alone. After 10 weeks, all specimens were excised and examined both grossly and histologically. Before harvesting, visual inspection of the tattooed chondrocyte-Pluronic F-127 hydrogel implant sites revealed that they closely resembled a human female nipple-areolar complex. Nodules were similar in size, shape, and texture to a human nipple at each injection site. Glistening opalescent tissue was surgically isolated from each implant site. Hematoxylin and eosin, safranine o, trichrome blue, and Verhoeff's stains of the experimental implants showed nodules with the characteristic histologic signs of elastic cartilage. Control injections of copolymer hydrogel alone exhibited no evidence of cartilage formation. Control injections of chondrocytes alone showed evidence of dissociated microscopic nodules of elastic cartilage.

Tissue engineered neocartilage using plasma derived polymer substrates and chondrocytes

This study demonstrates that fibrin monomers can be polymerized into moldable gels and used for the encapsulation of isolated chondrocytes. This biologically derived scaffold will maintain three-dimensional spatial support, allowing new tissue development in a subcutaneous space. Chondrocytes isolated from the glenohumeral and humeroradioulnar joints of a calf were combined with cyroprecipitate and polymerized with bovine thrombin to create a fibrin glue gel with a final cell density of 12.5 x 10(6) cells/ml. The polymer-chondrocyte constructs were implanted subcutaneously in 12 nude mice and incubated for 6 and 12 weeks in vivo. Histologic and biochemical analysis including deoxyribonucleic acid (DNA) and glycosaminoglycan quantitation confirmed the presence of actively proliferating chondrocytes with production of a well-formed cartilaginous matrix in the transplanted samples. Control specimens from 12 implantation sites consisting of chondrocytes alone or fibrin glue substrates did not demonstrate any gross or histologic evidence of neocartilage formation. Moldable autogenous fibrin glue polymer systems have a potential to serve as alternatives to current proprietary polymer systems used for tissue engineering cartilage as well as autogenous grafts and alloplastic materials used for facial skeletal and soft-tissue augmentation.

Microsurgical replantation of the avulsed scalp: report of six cases

This article reports the successful microsurgical replantation of six scalps avulsed for over 3 to 11 hr, after trauma and before repair, including five total and one partial avulsion. The authors believe that one key to successful replantation is effective vessel anastomoses. In the reported series, three scalps were reconstructed with two superficial temporal vessels and in five cases, with a 1:1 ratio between arteries and veins. The partially avulsed scalp was replanted successfully with only one artery and one vein. The management of postoperative complications is discussed.

Synthesis and application of Fmoc-hydrazine for the quantitative determination of saccharides by reversed-phase high-performance liquid chromatography in the low and subpicomole range

A new derivatization reagent, Fmoc-hydrazine, has been synthesized from the reaction of Fmoc-chloroformate with hydrazine as a precolumn fluorometric labeling reagent for reducing sugars such as glucose, galactose, mannose, fructose, fucose, ribose, xylose, arabinose, lactose, and maltose. The optimization of derivatization conditions was examined in detail. Using a reversed-phase high-performance C-8 column and a mobile phase consisting of acetonitrile-aqueous acetic acid, seven sugar derivatives were separated under either isocratic or gradient conditions within 20 min. The Fmoc-hydrazine and sugar Fmoc-hydrazone derivatives exhibit excellent stability. The extent of the hydrazone formation was 77 and 82% for mannose and fucose as assessed by Dionex high-performance anion-exchange chromatography with pulsed amperometric detection. Linear calibration graphs were established in the range from 0.5 to 2 pmol and 12 to 110 pmol for individual sugar derivatives. The determination limits were 0.05-0.09 pmol for mannose, galactose, and ribose; 0.1 pmol for maltose, xylose, and glucose; 0.2 pmol for fucose and lactose; 0.3 pmol for arabinose; and 0.4 pmol for fructose. The component monosaccharides of ultramicroquantities of two glycoproteins (e.g., from 7 ng fetuin and ovalbumin) were determined in the subpicomole range.

Clinical application of the free flap based on the cutaneous branch of the acromiothoracic artery

The nasal reconstruction in 8 patients and cheek reconstruction in 1 using a free flap from the deltoid region has been successfully undertaken in our department since August 1987. The flap has a direct cutaneous artery--the acromial artery--as its vascular axis. The experiences and a brief anatomical review of the donor site are reported.