Fibroblast growth on a porous collagen sponge containing hyaluronic acid and fibronectin

Therapeutic Efficacy of Polymeric Biomaterials in Treating Diabetic Wounds-An Upcoming Wound Healing Technology

Diabetic wounds are one of the serious, non-healing, chronic health issues faced by individuals suffering from diabetic mellitus. The distinct phases of wound healing are either prolonged or obstructed, resulting in the improper healing of diabetic wounds. These injuries require persistent wound care and appropriate treatment to prevent deleterious effects such as lower limb amputation. Although there are several treatment strategies, diabetic wounds continue to be a major threat for healthcare professionals and patients. The different types of diabetic wound dressings that are currently used differ in their properties of absorbing wound exudates and may also cause maceration to surrounding tissues. Current research is focused on developing novel wound dressings incorporated with biological agents that aid in a faster rate of wound closure. An ideal wound dressing material must absorb wound exudates, aid in the appropriate exchange of gas, and protect from microbial infections. It must support the synthesis of biochemical mediators such as cytokines, and growth factors that are crucial for faster healing of wounds. This review highlights the recent advances in polymeric biomaterial-based wound dressings, novel therapeutic regimes, and their efficacy in treating diabetic wounds. The role of polymeric wound dressings loaded with bioactive compounds, and their in vitro and in vivo performance in diabetic wound treatment are also reviewed.

Novel Bacterial Cellulose-Poly (Acrylic Acid) Hybrid Hydrogels with Controllable Antimicrobial Ability as Dressings for Chronic Wounds

This investigation examines the combination of poly (acrylic acid) (PAA) and bacterial cellulose (BC) nanofibers to synthesize hydrogel hybrid composites used for wound dressing application. Amoxicillin (AM) was also grafted onto the composites for drug release. Fourier transform infrared analysis and scanning electron microscopy conducted revealed the structure and porosity of the composite being developed, as well as the successful fabrication of BC-PAA composites. The results of mechanical testing and hygroscopicity revealed that the composite shows higher stability than hydrogels which are currently used worldwide, albeit with a slight reduction in swelling capabilities. However, the composite was revealed to be responsive to a rise in pH values with an increase in composite swelling and drug release. These results together with their morphological characteristics suggest that BC-PAA hydrogel hybrid composite is a promising candidate for wound dressing application.

Collagen matrix as a tool in studying fibroblastic cell behavior

Type I collagen is a fibrillar protein, a member of a large family of collagen proteins. It is present in most body tissues, usually in combination with other collagens and other components of extracellular matrix. Its synthesis is increased in various pathological situations, in healing wounds, in fibrotic tissues and in many tumors. After extraction from collagen-rich tissues it is widely used in studies of cell behavior, especially those of fibroblasts and myofibroblasts. Cells cultured in a classical way, on planar plastic dishes, lack the third dimension that is characteristic of body tissues. Collagen I forms gel at neutral pH and may become a basis of a 3D matrix that better mimics conditions in tissue than plastic dishes.

Collagen-glycosaminoglycan matrix implantation promotes angiogenesis following surgical brain trauma

Surgical brain injury (SBI) is unavoidable during many neurosurgical procedures intrinsically linked to postoperative neurological deficits. We have previously demonstrated that implantation of collagen glycosaminoglycan (CG) following surgical brain injury could significantly promote functional recovery and neurogenesis. In this study we further hypothesized that this scaffold may provide a microenvironment by promoting angiogenesis to favor neurogenesis and subsequent functional recovery. Using the rodent model of surgical brain injury as we previously established, we divided Sprague-Dawley male rats (weighting 300-350 g) into three groups: (1) sham (2) surgical injury with a lesion (L), and (3) L with CG matrix implantation (L + CG). Our results demonstrated that L + CG group showed a statistically significant increase in the density of vascular endothelial cells and blood vessels over time. In addition, tissue concentrations of angiogenic growth factors (such as VEGF, FGF2, and PDGF) significantly increased in L + CG group. These results suggest that implantation of a CG scaffold can promote vascularization accompanied by neurogenesis. This opens prospects for use of CG scaffolds in conditions such as brain injury including trauma and ischemia.

Monodisperse collagen-gelatin beads as potential platforms for 3D cell culturing

A droplet-based microfluidics technique is used to produce monodisperse, 80 μm collagen-gelatin beads with tunable mechanical properties in the range of 1-10 kPa after photo-crosslinking. The gel beads are porous, mechanically robust and stable in buffer, but can be degraded enzymatically. Encapsulated fibroblast cells maintain 70% viability after one-week encapsulation and preliminary results show that the degree of spreading of cells in gels is correlated with the stiffness of the material.

Biopolymer-based nanoparticles for drug/gene delivery and tissue engineering

There has been a great interest in application of nanoparticles as biomaterials for delivery of therapeutic molecules such as drugs and genes, and for tissue engineering. In particular, biopolymers are suitable materials as nanoparticles for clinical application due to their versatile traits, including biocompatibility, biodegradability and low immunogenicity. Biopolymers are polymers that are produced from living organisms, which are classified in three groups: polysaccharides, proteins and nucleic acids. It is important to control particle size, charge, morphology of surface and release rate of loaded molecules to use biopolymer-based nanoparticles as drug/gene delivery carriers. To obtain a nano-carrier for therapeutic purposes, a variety of materials and preparation process has been attempted. This review focuses on fabrication of biocompatible nanoparticles consisting of biopolymers such as protein (silk, collagen, gelatin, β-casein, zein and albumin), protein-mimicked polypeptides and polysaccharides (chitosan, alginate, pullulan, starch and heparin). The effects of the nature of the materials and the fabrication process on the characteristics of the nanoparticles are described. In addition, their application as delivery carriers of therapeutic drugs and genes and biomaterials for tissue engineering are also reviewed.

Evaluation of functions and tissue compatibility of poly (D,L-lactic-co-glycolic acid) seeded with human dermal fibroblasts

In tissue engineering and wound-healing applications, dermal substitutes are used to provide fibroblasts with the mechanical support for their growth and then to facilitate the skin formation. In this study, three-dimensional porous poly(lactic-co-glycolic acid) (PLGA) 65/35 scaffolds were prepared and then the composites of the scaffolds and human fetal dermal fibroblasts were fabricated as a tissue-engineered dermal substitute. The function and tissue compatibility of the artificial dermal substitute were evaluated at the levels of gene expression (by RT-PCR) and protein expression (total collagen quantities), as well as by histological and immunohistochemical analysis. The PCR products indicated that the mRNA of type-I collagen, mainly secreted by the fibroblasts onto the PLGA scaffolds, was clearly expressed after 4 weeks. The amount of total collagen synthesized from the cells was shown to increase gradually during the initial culture period and slightly decreased afterwards. After 8 weeks of culture, the fibroblasts were well attached and migrated entirely throughout the pores of the PLGA scaffold with normal function. Furthermore, the positively stained type-I collagen was intensively detected throughout the pores. These results suggest that the function and tissue compatibility may be important criteria in evaluating an artificial tissue-engineered skin.

A Collagen/DBP Sponge System Designed for in Vitro Analysis of Chondroinduction

In response to subcutaneous implants of demineralized bone powder (DBP), cells are attracted to the DBP, are converted to chondroblasts, and produce a cartilage matrix that is resorbed and replaced by bone. In order to define the cellular mechanisms of this induction, we developed a collagen sponge model for simulating the in vivo environment and for promoting the ingrowth and viability of cells cultured in them in vitro. Reconstituted pepsin–digested type I collagen from bovine hide was neutralized. Rat DBP (75–250 εm) was added into the collagen mixture (20 mg/ml). In order to simulate the connective tissue environment, modified chondroitin sulfate, heparan sulfate, or hyaluronic acid was added into the mixture. Aliquots (0.2 ml) were placed in 3/8 inch diameter molds and freeze-dried. Human dermal fibroblasts were cultured from minced fresh tissue and inoculated at 1.5 × 105 cells/sponge. Fifteen hours later, some sponges were transferred to medium which contained growth factors (PDGF or TGF-β). At intervals, samples were examined histologically. The inoculated cells attached to the collagen fibers and migrated into the sponge. Eventually the sponges contracted and acquired an oval shape. Cells on or near DBP were ovoid or stellate in shape. Cell morphology was modulated by glycosaminoglycan composition of the sponge. Increasing doses of PDGF or TGF-β promoted cellularity within the sponges. In conclusion, this system simulates the in vivo environment but allows accessibility for analysis. This three-dimensional matrix culture system will enable investigation of mechanisms of chondroinduction by morphogenic material.

Collagenous Biocomposites for the Repair of Soft Tissue Injury

Results of implantation studies in a variety of animal tissue models demonstrate that the rate of biogradation of a collagen scaffold should parallel the rate of wound healing observed in particular anatomic sites. This rapid degradation maximizes tissue regeneration and minimizes encapsulation of the implant. The following paper reviews the effects of crosslinking on the rate of tissue ingrowth and regeneration. In addition, preliminary mechanical data on newly developed soluble type I collagen fibers is presented as a possible advance in the production of high strength collagen based tissue scaffolds.

Changes in skin physiology and clinical appearance after microdroplet placement of hyaluronic acid in aging hands

BACKGROUND

Up to now rejuvenating treatment of the hands has been challenging and results often disappointing.

AIMS

To determine whether hyaluronic acid (HA) microdroplet placement into the dorsal hands has an impact on skin physiology and clinical appearance and whether there is any difference between stabilized HA (S-HA) and nonstabilized HA (NS-HA).

PATIENTS/METHODS

The intra-individual comparison in 15 volunteers involved injection sessions at week 0, 4, and 8 with random assignment of left and right hand to either S-HA or NS-HA. Skin physiology parameters cutaneous elasticity, surface roughness, hydration, and transepidermal water loss (TEWL) were measured in vivo at weeks 0 (before treatment), 4 (before subsequent treatment), 12, and 24. Clinical hand assessment was carried out at weeks 0 and 12 by a blinded dermatologist.

RESULTS

Intradermal injection of S-HA generated significant improvement in skin elasticity and surface roughness at week 12 compared to baseline. On the hands treated with NS-HA, there was a trend for improvement (not significant). While there was no significant difference in hydration and TEWL between both hands before treatment, at week 12 hands treated with S-HA displayed a significantly higher hydration level and lower TEWL compared to NS-HA treatment. Clinically S-HA proved to be significantly superior to NS-HA. At week 24 the observed effects started to return back toward baseline, with S-HA treatment still offering better results compared to the NS-HA.

CONCLUSIONS

Skin revitalization with injectable HA can improve clinical appearance and skin physiology parameters on the back of the hands. It has been shown that S-HA has better effects when compared with NS-HA.

In vitro integration of human skin dermis with porous cationic hydrogels

Porous poly(DMAA-co-AMTAC) hydrogels, fabricated using the inverted colloid crystal method, were used to observe their integration with human skin. Full thickness human breast skin explants discarded from surgeries were cultured for up to 10days at the air-liquid interface using a Transwell culture system. Cylindrical, disk- or other shaped hydrogels were placed inside the skin explants fitting punctures produced by punch biopsies or scalpels and full section histological analysis of the skin explants with the inserted hydrogel was then performed. In addition, separated hydrogels were cultured up to 7days with human fibroblasts. The results indicate that poly(DMAA-co-AMTAC) hydrogels induce substantial extracellular matrix material deposition, maintain dermal integrity in the contact areas with the skin and permit dermal fibers to integrate into the hydrogel pores. Different types of cells remaining in the explants migrated into the hydrogels pores, including red blood cells. Fibroblasts adhered to and colonized separately cultured hydrogels. We plan to use this type of soft material as an interface to permit skin integration with percutaneous devices in contact with skin.

Effect of hyaluronan-enriched transfer medium on implantation and pregnancy rates after day 3 and day 5 embryo transfers: a prospective randomized study

OBJECTIVE

To analyze whether the use of a hyaluronan-enriched transfer medium (HETM) increases rates of implantation (IRs) and clinical pregnancy (CPRs), compared with the use of a conventional transfer medium after day 3 and day 5 embryo transfers.

DESIGN

Prospective randomized controlled trial.

SETTING

An assisted reproduction program in a private tertiary-care hospital in Turkey.

PATIENT(S)

A total of 1,282 consecutive fresh embryo transfer cycles (825 day 3 and 457 day 5) were randomly allocated into two groups. In 639 women, ET was effected with HETM, and in 643, it was effected with a conventional embryo transfer medium.

INTERVENTION(S)

Embryo transfer using HETM or conventional embryo transfer medium.

MAIN OUTCOME MEASURE(S)

Clinical pregnancy rates and IRs were compared with regard to day of embryo transfer, women's age, quality of the transferred embryos, and presence of previous implantation failures.

RESULT(S)

Overall CPRs and IRs significantly increased with the use of HETM (CPR: 54.6% vs. 48.5%, odds ratio: 1.28, 95% confidence interval: 1.03-1.59; IR: 32% vs. 25%, odds ratio: 1.43, 95% confidence interval: 1.23-1.66, for HETM and control groups, respectively). The number needed to treat (NNT) for one additional pregnancy with routine use of HETM was 17. The beneficial effect was more prominent in women who were >35 years of age (NNT = 7), in women who had previous failed cycles (NNT = 7), and in women who had poor-quality embryos (NNT = 8).

CONCLUSION(S)

The enrichment of transfer medium with hyaluronan increases CPRs and IRs, both for day 3 and day 5 embryo transfers. The beneficial effect was most evident in women who were >35 years of age, in women who had only poor-quality embryos available for transfer, and in women who had previous implantation failures.

Biocompatible nanofiber matrices for the engineering of a dermal substitute for skin regeneration

Natural and synthetic biodegradable nanofibers are extensively used for biomedical applications and tissue engineering. Biocompatibility and a well-established safety profile for polycaprolactone (PCL) and collagen represent a favorable matrix for preparing a dermal substitute for engineering skin. Collagen synthesized by fibroblasts is a good surface active agent and demonstrates its ability to penetrate a lipid-free interface. During granulation tissue formation, fibronectin provides a temporary substratum for migration and proliferation of cells and provides a template for collagen deposition, which increases stiffness and tensile strength of this healing tissues. The objective of this study was to fabricate nanofiber matrices from novel biodegradable PCL and collagen to mimic natural extracellular matrix (ECM) and to examine the cell behavior, cell attachment, and interaction between cells and nanofiber matrices. Collagen nanofiber matrices show a significant (p < 0.001) level of fibroblast proliferation and increase up to 54% compared with control tissue culture plate (TCP) after 72 h. The present investigation shows that PCL-coated collagen matrices are suitable for fibroblast growth, proliferation, and migration inside the matrices. This novel biodegradable PCL and collagen nanofiber matrices support the attachment and proliferation of human dermal fibroblasts and might have potential in tissue engineering as a dermal substitute for skin regeneration.

Adhesion strength of human tenocytes to extracellular matrix component-modified poly(DL-lactide-co-glycolide) substrates

We report a direct measurement of the adhesion strength of human embryonic tenocytes (HETCs) and transformed human embryonic tenocytes (THETCs) to fibronectin (FN)- and type I collagen (CNI)- modified poly(DL-lactide-co-glycolide) (PLGA) substrates with a micropipette aspiration technique. PLGA substrates were first coated with poly-D-lysine (PDL), and then with various concentrations (1 microg/ml, 2 microg/ml, 5 microg/ml, and 10 microg/ml) of FN and CNI in serum-free F12 media. Anti-FN and Anti-CNI antibodies were used to inhibit attachment of tenocytes to FN- and CNI- modified substrates in a dilution range of 1:5000-1:500 and 1:1500-1:250, respectively. The substrates were employed for incubation of HETCs and THETCs for 30 min at 37 degrees C before the adhesion strength measurements. We found that the adhesion strengths showed a strong dependence on the seeding time and FN or CNI concentrations. Anti-FN and Anti-CNI antibodies significantly compromised adhesion of HETCs and THETCs to the corresponding modified substrates (P < 0.05). These findings show that FN- or CNI-modified polymer substrates offer significant advantages for tissue engineering tendon scaffolds concerning tenocyte adhesion. In addition, HETCs and THETCs bear similar biological behaviors in terms of adhesion, indicating the possibility of using THETCs in place of HETCs in tissue engineering construction of human tendons.

Quantitative measurement of collagen methylation by capillary electrophoresis

Collagen methylation has been exploited in various applications involving living cells. We have observed correlation between the collagen methylation with the rate of cell proliferation in three-dimensional (3-D) microenvironment. To quantify the degree of collagen methylation, we have developed a capillary zone electrophoresis method. Using a polyvinyl alcohol-coated fused-silica capillary and UV detection at 200 nm, we have optimized pH and separated the native collagen into three major bands in phosphate buffer (50 mM, pH 2.5) with 0.05% hydroxypropylmethylcellulose. Under these conditions, the methylated collagens were separated into four major bands, which changed with different methylation reaction conditions. We propose an index to quantify the degree of collagen methylation that also correlates with their effects on cell proliferation.

Composite cell support membranes based on collagen and polycaprolactone for tissue engineering of skin

The preparation and characterisation of collagen:PCL composites for manufacture of tissue engineered skin substitutes and models are reported. Films having collagen:PCL (w/w) ratios of 1:4, 1:8 and 1:20 were prepared by impregnation of lyophilised collagen mats by PCL solutions followed by solvent evaporation. In vitro assays of collagen release and residual collagen content revealed an expected inverse relationship between the collagen release rate and the content of synthetic polymer in the composite that may be exploited for controlled presentation and release of biopharmaceuticals such as growth factors. DSC analysis revealed the characteristic melting point of PCL at around 60 degrees C and a tendency for the collagen component, at high loading, to impede crystallinity development within the PCL phase. The preparation of fibroblast/composite constructs was investigated using cell culture as a first stage in mimicking the dermal/epidermal structure of skin. Fibroblasts were found to attach and proliferate on all the composites investigated reaching a maximum of 2 x 10(5)/cm(2) on 1:20 collagen:PCL materials at day 8 with cell numbers declining thereafter. Keratinocyte growth rates were similar on all types of collagen:PCL materials investigated reaching a maximum of 6.6 x 10(4)/cm(2) at day 6. The results revealed that composite films of collagen and PCL are favourable substrates for growth of fibroblasts and keratinocytes and may find utility for skin repair.

A collagen-based scaffold for a tissue engineered human cornea: physical and physiological properties

Stabilized collagen-glycosaminoglycan scaffolds for tissue engineered human corneas were characterized. Hydrated matrices were constructed by blending type I collagen with chondroitin sulphates (CS), with glutaraldehyde crosslinking. A corneal keratocyte cell line was added to the scaffolds with or without corneal epithelial and endothelial cells. Constructs were grown with or without ascorbic acid. Wound-healing was evaluated in chemical-treated constructs. Native, noncrosslinked gels were soft with limited longevity. Crosslinking strengthened the matrix yet permitted cell growth. CS addition increased transparency. Keratocytes grown within the matrix had higher frequencies of K+ channel expression than keratocytes grown on plastic. Ascorbic acid increased uncrosslinked matrix degradation in the presence of keratocytes, while it enhanced keratocyte growth and endogenous collagen synthesis in crosslinked matrices. Wounded constructs showed recovery from exposure to chemical irritants. In conclusion, this study demonstrates that our engineered, stabilized matrix is well-suited to function as an in vitro corneal stroma.

Osteoblastic differentiation of cultured rat bone marrow cells on hydroxyapatite with different surface topography

Hydroxyapatite (HA) has been used in orthopedic, dental, and maxillofacial surgery as a bone substitute.

OBJECTIVE

The aim of this investigation was to study the effect of surface topography produced by the presence of microporosity on the response of the rat bone marrow cells, evaluating: cell attachment, proliferation, total protein content, alkaline phosphatase (ALP) activity, and bone-like nodule formation.

METHODS

Cells were cultured on HA discs manufactured by a combination of uniaxial powder pressing and different sintering conditions, with different percentage of microporosity (<5%-HA5, 15%-HA15, and 30%-HA30). For attachment evaluation, cells were cultured for 2 h. Proliferation was evaluated after 7 and 14 days. After 14 days, total protein content and ALP activity were measured. For bone-like nodule formation, cells were cultured for 21 days. Data were compared by ANOVA and Duncan's multiple range test when appropriate.

RESULTS

Cell attachment was not affected by surface topography (p=0.37). Proliferation (p=0.001), total protein content (p=0.039), ALP activity (p=0.050), and bone-like nodule formation (p=0.00001) were all significantly decreased by the most irregular surface (HA30). SIGNIFICANCE. These results suggest that initial cell events were not affected by the surface topography of the HA. However, intermediary and final events such as proliferation, protein synthesis, ALP activity, and bone-like nodule formation favored surfaces with a more regular topography, such as that presents in HA with 15% or less of microporosity.

Dural cell culture. A new approach to study duraplasty

Fistulas of the cerebrospinal fluid are often repaired by insertion of grafts of various kinds. However, current knowledge of wound healing after graft insertion is limited, and only a few animal studies are available. The objective of this study is to test whether an in vitro model is suited to analyze cellular healing aspects after duraplasty and to assess dura substitutes in such conditions in regard to their surface attractiveness for cellular migration from the dura margins. Harvested dura pieces from minipigs were perforated to mimic central dura lesions, placed on various coated surfaces (collagen, laminin, poly-L-lysine) or grafts, and investigated in a cell culture for cellular closure of the perforation. Cellular migration from the dura into the central perforation was noted on collagen-coated surfaces and when defects were filled with collagen gels, but there was no cell growth on surfaces with poly-L-lysine or laminin coating. Immunocytochemistry identified the migrating cells mainly as fibroblasts with some intermingled epithelial cells. Scanning electron microscopy proved cellular closure of defects after dura placement on allogenic non-crosslinked collagen transplants. Less cellular migration was observed on poly-P-dioxanon sheets, while no cells migrated into the central dura perforation after placement on a cartilage substitute. Cell counting indicated enhanced cellular closure of the dura opening after introduction of insulin or fibroblast growth factor (sign test for both: 0.031). Our study succeeded in establishing a cell culture model for duraplasty and indicated cellular migration from the dura borders at the site of the defect during the wound healing process. The cell culture model presented in this report shows that collagen grafts are best suited for duraplasty. In accordance with the immunocytological finding of fibroblast migration from the dura borders additional application of fibroblast-stimulating growth factors accelerated cellular defect closure.

TAK-778 enhances osteoblast differentiation of human bone marrow cells

TAK-778 has been shown to induce bone growth in in vitro and in vivo models. However, there are no studies evaluating the effect of TAK-778 on human cells. Thus, the aim of this study was to investigate osteogenesis induced by TAK-778 on human bone marrow cells. Cells were cultured in 24-well culture plates at a cell density of 2 x 10(4) cells/well in culture medium containing TAK-778 (10(-7), 10(-6), and 10(-5) M, each) or vehicle. During the culture period, cells were incubated at 37 degrees C in a humidified atmosphere of 5% CO(2) and 95% air. For attachment evaluation, cells were cultured for 4 and 24 h. After 7, 14, and 21 days, cell proliferation, cell viability, total protein content, alkaline phosphatase (ALP) activity, and bone-like formation were evaluated. Data were compared by ANOVA and Duncan's multiple range test. TAK-778 did not affect cell attachment and viability. Cell number was reduced by TAK-778 in all time period evaluated in a dose-dependent way. The effect of TAK-778 on total protein content, ALP activity and bone-like formation was a dose-dependent increase. The present results suggest that initial cell events such as cell attachment are not affected by TAK-778 while events that indicate osteoblast differentiation including reduced cell proliferation, and increased both ALP activity and bone-like formation are enhanced by TAK-778 in a time and dose-dependent way. It means that TAK-778 could be a useful drug to enhance new bone formation in clinical situations that require rapid restoration of physiologic function, such as orthopedic and maxillofacial surgery.

TAK-778 enhances osteoblast differentiation of human bone marrow cells cultured on titanium

TAK-778 induces bone growth in in vitro and in vivo models. The aim of this study was to evaluate the osteogenic potential of TAK-778 on human bone marrow cells cultured on commercially pure titanium (cpTi). Cells were cultured either in absence or in presence of TAK-778 (10(-5)M) on cpTi in supplemented alpha-MEM. For attachment evaluation, cells were cultured for 4 and 24h. After 7, 14, and 21 days, cell proliferation, cell viability, total protein content, alkaline phosphatase (ALP) activity, and bone-like formation were evaluated. TAK-778 did not affect cell attachment and viability. Cell number was reduced by TAK-778. ALP activity, total protein content, and bone-like formation were increased by TAK-778. These results suggest that initial cell events such as cell attachment are not affected by TAK-778 while events that indicate osteoblast differentiation including reduced cell proliferation, and increased both ALP activity and bone-like formation are enhanced by TAK-778 in presence of cpTi. It means that TAK-778 could be a useful drug to improve the osseointegration of implants by both enhancing and accelerating bone formation on Ti surface.

Effect of cpTi surface roughness on human bone marrow cell attachment, proliferation, and differentiation

There is general agreement that rough surfaces improve both biologic and biomechanical responses to titanium (Ti) implants. The aim of this investigation was to study the effect of Ti surface roughness on the response of human bone marrow cell culture evaluating: cell attachment, cell proliferation, total protein content, alkaline phosphatase (ALP) activity, and bone-like nodule formation. Cells were cultured on commercially pure titanium (cpTi) discs with fourdifferent average roughnesses (Ra). For attachment evaluation, cells were cultured for 4 h. After 21 days, cell proliferation, total protein content, and ALP activity were evaluated. For bone-like nodule formation, cells were cultured for 28 days. Data were compared by ANOVA and Duncan's multiple range test. Cell attachment was not affected by surface roughness. For cells cultured on Ti with Ra ranging from 0.80 microm to 1.90 microm, proliferation was reduced while total protein content, and ALP activity were increased. There was a non-statistically significant increase of bone-like nodule formation on a surface with Ra near 0.80 microm. These results suggest that for Ti an Ra ranging from 0.80 microm to 1.90 microm would optimize both intermediary and final cellular responses but not affect the initial response, and a smoother surface would not favor any evaluated response.

Bio-artificial skin composed of gelatin and (1-->3), (1-->6)-beta-glucan

Porous scaffolds composed of gelatin and beta-glucan were prepared using the freeze-drying method. The scaffold had an inter-connected pore structure with average pore size of 90-150 microm. Results for the contact angle and cell attachment revealed that a high gelatin content was suitable for cellular attachment and distribution in two- or three-dimensional fibroblast cultures, because the gelatin had acidic residues, and arginine-glycine-aspartic acid groups. To prepare a stratified wound dressing to mimic the normal human skin, fibroblasts and keratinocyte cells were isolated from a child's foreskin, and were co-cultured in gelatin/beta-glucan scaffolds were cross-linked using 1-ethyl-(3-3-dimethylaminopropyl) carbodiimide hydrochloride. An in vivo study showed that after 1 week, the artificial dermis containing the fibroblasts enhanced the re-epithelialization of a full-thickness skin defect rather than the acellular scaffold.

Response of rat bone marrow cells to commercially pure titanium submitted to different surface treatments

OBJECTIVES

Alterations in the commercially pure titanium (cpTi) surface may be undertaken to improve its biological properties. The aim of this study is to investigate the biocompatibility of cpTi submitted to different surface treatments.

METHODS

The cpTi surfaces were prepared so that machined and blasted surfaces, either acid etched or not, were compared using rat bone marrow cells cultured to differentiated into osteoblast. For attachment evaluation, cells were cultured for 4 and 24h. Cell morphology was evaluated after 3 days. After 7, 14, and 21 days cell proliferation was evaluated. Total protein content and alkaline phosphatase (ALP) activity were evaluated after 14 and 21 days. For bone-like nodule formation, cells were cultured for 21 days. Data were compared by analysis of variance.

RESULTS

Cell attachment, cell morphology, cell proliferation, and ALP activity were not affected by surface treatments. Total protein content was reduced by blasted and acid etched surface. Bone-like nodule formation was significantly reduced by blasted, acid etched, and a combination of both blasted and acid etched surfaces.

CONCLUSIONS

Based on these results, it can be suggested that cpTi surfaces that were submitted only to machining treatment favor the final event of osteoblastic differentiation of the rat bone marrow cells, evidenced by increased bone-like nodule formation.

Rat bone marrow cell response to titanium and titanium alloy with different surface roughness

In general, cell response is affected by both chemical composition and surface roughness of implant materials. The aim of this study was to evaluate the effect of titanium (Ti) chemical composition and surface roughness on the response of rat bone marrow cells, examining cell attachment, cell proliferation, total protein content, alkaline phosphatase (ALP) activity, and bone-like nodule formation. Cells were cultured on both commercially pure titanium (cpTi) and titanium-6-aluminum-4-vanadium alloy (Ti-A) discs with four different average roughnesses (Ra). For attachment evaluation, cells were cultured for 2 h. After 14 days, cell proliferation, total protein content, and ALP activity were evaluated. Bone-like nodule formation was evaluated after 21 days. Data were compared by anova and Duncan's multiple range test when appropriate. Cell attachment and total protein content were affected by neither Ti chemical composition (P = 0.201, and P = 0.639, respectively) or surface roughness (P = 0.972, and P = 0.660, respectively). Proliferation, ALP activity, and bone-like nodule formation were affected only by Ti chemical composition (P = 0.0001, P = 0.064, and P = 0.0001, respectively). These results suggest that cpTi would optimize osteoblastic differentiation by rat bone marrow cells, including reduced cell proliferation, and increased ALP activity and bone-like nodule formation, while surface roughness, within the Ra parameters used, would not affect significantly the rat bone marrow cell response.

Surface topography of hydroxyapatite affects ROS17/2.8 cells response

Hydroxyapatite (HA) has been used in orthopedic, dental, and maxillofacial surgery as a bone substitute. The aim of this investigation was to study the effect of surface topography produced by the presence of microporosity on cell response, evaluating: cell attachment, cell morphology, cell proliferation, total protein content, and alkaline phosphatase (ALP) activity. HA discs with different percentages of microporosity (< 5%, 15%, and 30%) were confected by means of the combination of uniaxial powder pressing and different sintering conditions. ROS17/2.8 cells were cultured on HA discs. For the evaluation of attachment, cells were cultured for two hours. Cell morphology was evaluated after seven days. After seven and fourteen days, cell proliferation, total protein content, and ALP activity were measured. Data were compared by means of ANOVA and Duncan's multiple range test, when appropriate. Cell attachment (p = 0.11) and total protein content (p = 0.31) were not affected by surface topography. Proliferation after 7 and 14 days (p = 0.0007 and p = 0.003, respectively), and ALP activity (p = 0.0007) were both significantly decreased by the most irregular surface (HA30). These results suggest that initial cell events were not affected by surface topography, while surfaces with more regular topography, as those present in HA with 15% or less of microporosity, favored intermediary and final events such as cell proliferation and ALP activity.

Manipulation of selective cell adhesion and growth by surface charges of electrically polarized hydroxyapatite

Adherence of cells to a surface, such as a biomaterial surface, can be significantly influenced by the surface charge on that material. The applicability of electrically charged hydroxyapatite ceramics to selective cell adhesion was examined, and we show that polarized hydroxyapatite has significant effects on cell growth and adhesion. The surface charge applied to polarized hydroxyapatite promotes (i) enhanced colony formation of osteoblast-like cells, (ii) activation of gap junctions, and (iii) specific orienting of neuroblastoma cells. These findings will be of great utility and have significance in applications of tissue engineering, for example, in potential treatments for osteoporosis.

Functional human corneal equivalents constructed from cell lines

Human corneal equivalents comprising the three main layers of the cornea (epithelium, stroma, and endothelium) were constructed. Each cellular layer was fabricated from immortalized human corneal cells that were screened for use on the basis of morphological, biochemical, and electrophysiological similarity to their natural counterparts. The resulting corneal equivalents mimicked human corneas in key physical and physiological functions, including morphology, biochemical marker expression, transparency, ion and fluid transport, and gene expression. Morphological and functional equivalents to human corneas that can be produced in vitro have immediate applications in toxicity and drug efficacy testing, and form the basis for future development of implantable tissues.

Effect of surface roughness and composition on costochondral chondrocytes is dependent on cell maturation state

During endochondral bone formation, as occurs in fracture healing, chondrocytes are one of the first cells to see an implant surface. We tested the hypothesis that chemical composition and surface roughness affect chondrocyte differentiation, matrix synthesis, and local factor production and that the nature of the response is dependent on the state of maturation of the cells. To do this, we harvested rat growth zone and resting zone chondrocytes and examined their response to smooth and rough disk surfaces manufactured from either commercially pure titanium or titanium alloy. Profilometry, scanning electron microscopy, Auger spectroscopy, and Fourier transform infrared spectroscopy were used to characterize the surfaces. Average roughness values were 0.22 microm for smooth titanium surfaces, 0.23 microm for smooth titanium alloy surfaces, 4.24 microm for rough titanium surfaces, and 3.20 microm for rough titanium alloy surfaces. Cells were grown on the different disk surfaces until the cultures had reached confluence on plastic. The effect of the surfaces was determined by assaying cell number and [3H]thymidine incorporation as measures of cell proliferation, cell layer and cell alkaline phosphatase specific activity as markers of differentiation, and collagen production and [35S]sulfate incorporation as indicators of extracellular matrix production. In addition, the synthesis of prostaglandin E2 and transforming growth factor-beta were examined to measure changes in local factor synthesis. In growth zone and resting zone cultures, cell number and [3H]thymidine incorporation were decreased on rough surfaces; however, this effect was greater on commercially pure titanium surfaces. Cell layer and cell alkaline phosphatase specific activity were decreased in resting zone cells grown on rough surfaces. Cell alkaline phosphatase specific activity in growth zone cells was decreased on rough surfaces, whereas cell layer alkaline phosphatase specific activity was increased only in growth zone cells grown on rough commercially pure titanium surfaces. Resting zone cell collagen production was decreased only on rough commercially pure titanium, whereas in growth zone cells, collagen production was increased. Increased prostaglandin E2 release into the media was found for growth zone and resting zone cell cultures on the disks with rough surfaces. The observed effect was greater on rough commercially pure titanium. Production of transforming growth factor-beta by resting zones was similarly affected, whereas an increase in its production by growth zone cells was measured only on rough commercially pure titanium. These results indicate that surface roughness affects chondrocyte proliferation, differentiation, matrix synthesis, and local factor production and that these parameters are also affected by chemical composition. Furthermore, the nature and extent of the cell response is dependent on cell maturation. The overriding variable in response to an implant material, however, appears to be roughness of the surface.

Studies on the desamidation of bovine collagen

The most important reactive groups in collagen are amino, amido, guanidino, and carboxyl, all of which are present in comparatively large numbers. It is possible to modify amide groups present in the collagen of achilles tendons and hide trimmings by desamidation (DAM). DAM causes progressive hydrolysis of the amide groups of asparagine and glutamine side chains of collagen, thereby resulting in the reduction of the amide content of collagen. Loss of amide brings about an increase in the number of free carboxyl groups in the desamidated collagen, shown by reduction in its isoionic pH. The new modified collagen, like type I bovine collagen, has high viscosity and high hydroxyproline content. The fibril formation of the modified collagen showed slight variation, and polyacrylamide gel electrophoretic analysis indicated largely alpha components, indicating destruction of inter- and intramolecular crosslinks. The swelling behavior of the modified collagen is significantly higher compared to type I bovine collagen.

Regeneration of rat calvarial defects using a bioabsorbable membrane technique: influence of collagen cross-linking

The aim of the present study was to examine the influence of cross-linking on collagen membranes used for guided bone regeneration of calvarial defects in rats. In 48 Wistar rats, divided equally into 4 groups, 1 control and 3 experimental, standardized transosseous circular calvarial defects were made midparietally. In the control group, the defect was only covered by the soft tissue flap while in the 3 experimental groups, 3 differently cross-linked collagen membranes were interposed between the osseous defect and the overlying flap before suturing. The healing was assessed at 10, 20, and 30 days after surgery. The results showed that augmenting the degree of collagen cross-linking diminished the membrane resorption rate. Compared to the sham-operated sites, the membrane protected defects showed significantly more bone regeneration (on average 4 times more) as attested by histology and measured by histomorphometric analysis. Although the bone gain seemed to augment with increasing degrees of cross-linking, the results within the 3 experimental groups were not statistically different. Since longer healing periods might have been necessary to substantiate results within experimental groups, a study is currently undertaken to evaluate this aspect. This study demonstrated the efficacy of collagen membranes in guiding bone regeneration, as well as the importance of the type and degree of cross-linking.

Deposition of collagen fibril bundles by long-term culture of fibroblasts in a collagen sponge

Human fibroblasts cultured for 10 days in a collagen sponge migrated through the pores of the sponge and expressed a moderate mitotic activity, which stabilized after 10 days, and a high collagen and protein synthesis. Between 10 and 27 days, the newly synthesized collagen filled the pores of the sponge. This matrix accumulation induced a delayed decrease of collagen and protein synthesis. Finally, after 27 days of culture, the fibroblasts expressed low biosynthetic activities similar to the ones exhibited in vivo. The newly synthesized matrix was highly differentiated, as shown by the presence of a dense network of quarter-staggered collagen fibrils (42 nm +/- 6 nm in diameter) surrounding the cells. The size and the shape of these fibrils demonstrated that the newly synthesized procollagen was fully processed in collagen by removal of their N- and C-terminal propeptides. Moreover, these fibrils were packed in bundles organized into an interwoven network that mimics the pattern of the papillary dermis. These findings show that fibroblasts cultured for one month in a collagen sponge construct large amounts of a highly differentiated connective tissue.

Three-dimensional composite of demineralized bone powder and collagen for in vitro analysis of chondroinduction of human dermal fibroblasts

Implantation of demineralized bone powder (DBP) in muscle or connective tissue stimulates chondrogenesis followed by ectopic bone formation, in this way inducing the differentiation of endochondral bone. A new 3-dimensional in vitro composite sponge was designed to duplicate the packing density of in vivo DBP implants. The composite device, which consists of DBP packed between two layers of a porous collagen lattice, was used to assess the chondroblastic differentiation of human dermal fibroblasts. Important design considerations for this device were biocompatibility, rigidity and ability of cells to penetrate. In this study, collagen concentration and source, irradiation, and lyophilization conditions were varied in fabrication. Human dermal fibroblasts were seeded onto the composite sponge, migrated through the collagen lattice into the packet of DBP, and deposited a metachromatic extracellular matrix amongst the particles of DBP. In contrast, cells cultured in collagen sponges or in composite sponges with inactivated guanidine-extracted DBP did not secrete metachromatic matrix. This new in vitro system will be valuable in defining the mechanism of differentiation by osteoinductive materials and in evaluating the influence of other extracellular components and soluble factors on skeletal differentiation.

Chondroitin-6-sulphate incorporated into collagen gels for the growth of human keratinocytes: the effect of cross-linking agents and diamines

This study demonstrates the effect of the glycosaminoglycans, hyaluronic acid and chondroitin-6-sulphate (Ch6SO4), diamines and a carbodiimide cross-linking agent on the growth of human epidermal cells on collagen gels. Ch6SO4 incorporated into collagen gels stimulated cell growth rate, but the effect was found to be inconsistent. We found that approximately 50% of the incorporated Ch6SO4 in the gels leached out into the growth medium after the first 3 d in culture, and this is thought to lead to the inconsistent cell growth response. In order to minimize the elution of Ch6SO4 from the gels and thereby maximize its effect on the growth of the keratinocytes, 1-100 micrograms ml-1 Ch6SO4 was added in the medium. The results showed that Ch6SO4 at these concentrations in the medium did not stimulate the cell growth on either plain collagen gels or gels containing 20% Ch6SO4. As an alternative strategy, 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide and diamines (putrescine or diaminohexane) were used to immobilize Ch6SO4 onto the collagen gels and to cross-link the gels. The cross-linking process partially prevented the elution of Ch6SO4 from the gels. Interestingly, only putrescine, not diaminohexane, promoted the growth of keratinocytes on the cross-linked plain collagen gels. We proposed to develop an artificial skin substitute containing putrescine as a growth factor for the human epidermal cells.

Confocal laser-scanning microscopy for determining the structure of and keratinocyte infiltration through collagen sponges

The development of artificial skin substitutes based on cultured cells and biomaterials such as collagen requires an understanding of cellular interactions with the substrate. In this study, human keratinocytes were cultured on the surface of collagen sponges, and confocal laser-scanning microscopy (CLSM) was used to assess both the microstructure of the sponge, and the cell morphology and distribution throughout the sponge. It was found that the pore size increased with increasing depth into the sponge. Both pore size and fiber thickness increased during incubation for up to 10 days at 37 degrees C in culture medium in the absence of cells. This latter effect was not observed when the sponges were incubated in distilled water. Keratinocytes penetrated into the sponge even after only 3 days in culture. By 10 days in culture, the cells had penetrated to the maximum depth that could be examined (120 microns from the sponge surface). In the presence of cells, the inner structure of the collagen sponge had altered after 10 days in culture, with the collagen fibers becoming thicker, and pore geometry less regular. The mechanism responsible for this is unknown at present. Although the presence of the keratinocytes increases distortion of the sponge structure, factors from the medium itself also contribute to this effect. CLSM is a powerful tool for assessing cellular interactions with bioimplants, providing both qualitative and quantitative information. It offers many advantages over scanning electron microscopy (SEM) and histological techniques. CLSM minimizes the time-consuming, extensive preparation of samples required with the latter two methods, and allows noninvasive serial optical sectioning of intact samples.

Development of a skin model based on insoluble fibrillar collagen

A biocompatible, 3-dimensional, noncontracting, crosslinked collagen matrix was adapted to promote differentiation of epidermal keratinocytes. To produce the matrix, a 3% wt/wt dispersion of insoluble bovine collagen containing 5 mg polylysine/g collagen in 0.001 N HCl was blended, lyophilized, and crosslinked using a dehydrothermal technique. Matrices 4 cm2 and 3 mm thick were seeded with human dermal fibroblasts (1 x 10(5)/cm2). After 5 days in culture, the matrices were seeded with human epidermal keratinocytes (1 x 10(5)/cm2). The cultures were grown submerged for 1 week and raised to the liquid/air interface for 3 weeks to promote epidermal differentiation. Based on morphology and immunological staining with antibodies for human involucrin, keratin 1 (k1), filaggrin, and loricrin, the state of differentiation of the epidermal layer was nearly equivalent to that seen with cultures grown on contracted collagen lattices produced according to the methodology described in the literature and similar to the pattern produced in normal neonatal foreskin. These results demonstrate the usefulness of an in vitro skin model employing a crosslinked collagen matrix that permits the incorporation of additional covalently linked bioactive molecules during matrix formation.

Effect of titanium surface roughness on chondrocyte proliferation, matrix production, and differentiation depends on the state of cell maturation

Although it is well accepted that implant success is dependent on various surface properties, little is known about the effect of surface roughness on cell metabolism or differentiation, or whether the effects vary with the maturational state of the cells interacting with the implant. In the current study, we examined the effect of titanium (Ti) surface roughness on chondrocyte proliferation, differentiation, and matrix synthesis using cells derived from known stages of endochondral development. Chondrocytes derived from the resting zone (RCs) and growth zone (GCs) of rat costochondral cartilage were cultured on Ti disks that were prepared as follows: HF-HNO3-treated and washed (PT); PT-treated and electropolished (EP); fine sand-blasted, HCl-H2SO4-etched, and washed (FA); coarse sand-blasted, HCl-H2SO4-etched, and washed (CA); or Ti plasma-sprayed (TPS). Based on surface analysis, the Ti surfaces were ranked from smoothest to roughest: EP, PT, FA, CA, and TPS. Cell proliferation was assessed by cell number and [3H]-thymidine incorporation, and RNA synthesis was assessed by [3H]-uridine incorporation. Differentiation was determined by alkaline phosphatase specific activity (AL-Pase). Matrix production was measured by [3H]-proline incorporation into collagenase-digestible (CDP) and noncollagenase-digestible (NCP) protein and by [35S]-sulfate incorporation into proteoglycan. GCs required two trypsinizations for complete removal from the culture disks; the number of cells released by the first trypsinization was generally decreased with increasing surface roughness while that released by the second trypsinization was increased. In RC cultures, cell number was similarly decreased on the rougher surfaces; only minimal numbers of RCs were released by a second trypsinization. [3H]-thymidine incorporation by RCs decreased with increasing surface roughness while that by GCs was increased. [3H]-Uridine incorporation by both GCs and RCs was greater on rough surfaces. Conversely, ALPase in the cell layer and isolated cells of both cell types was significantly decreased. GC CDP and NCP production was significantly decreased on rough surfaces while CDP production by RC cells was significantly decreased on smooth surfaces. [35S]-sulfate incorporation by RCs and GCs was decreased on all surfaces compared to tissue culture plastic. The results of this study indicate that surface roughness affects chondrocyte proliferation, differentiation, and matrix synthesis, and that this regulation is cell maturation dependent.

Effect of titanium surface roughness on chondrocyte proliferation, matrix production, and differentiation depends on the state of cell maturation

Although it is well accepted that implant success is dependent on various surface properties, little is known about the effect of surface roughness on cell metabolism or differentiation, or whether the effects vary with the maturational state of the cells interacting with the implant. In the current study, we examined the effect of titanium (Ti) surface roughness on chondrocyte proliferation, differentiation, and matrix synthesis using cells derived from known stages of endochondral development. Chondrocytes derived from the resting zone (RCs) and growth zone (GCs) of rat costochondral cartilage were cultured on Ti disks that were prepared as follows: HF-HNO3-treated and washed (PT); PT-treated and electropolished (EP); fine sand-blasted, HCl-H2SO4-etched, and washed (FA); coarse sand-blasted, HCl-H2SO4-etched, and washed (CA); or Ti plasma-sprayed (TPS). Based on surface analysis, the Ti surfaces were ranked from smoothest to roughest: EP, PT, FA, CA, and TPS. Cell proliferation was assessed by cell number and [3H]-thymidine incorporation, and RNA synthesis was assessed by [3H]-uridine incorporation. Differentiation was determined by alkaline phosphatase specific activity (AL-Pase). Matrix production was measured by [3H]-proline incorporation into collagenase-digestible (CDP) and noncollagenase-digestible (NCP) protein and by [35S]-sulfate incorporation into proteoglycan. GCs required two trypsinizations for complete removal from the culture disks; the number of cells released by the first trypsinization was generally decreased with increasing surface roughness while that released by the second trypsinization was increased. In RC cultures, cell number was similarly decreased on the rougher surfaces; only minimal numbers of RCs were released by a second trypsinization. [3H]-thymidine incorporation by RCs decreased with increasing surface roughness while that by GCs was increased. [3H]-Uridine incorporation by both GCs and RCs was greater on rough surfaces. Conversely, ALPase in the cell layer and isolated cells of both cell types was significantly decreased. GC CDP and NCP production was significantly decreased on rough surfaces while CDP production by RC cells was significantly decreased on smooth surfaces. [35S]-sulfate incorporation by RCs and GCs was decreased on all surfaces compared to tissue culture plastic. The results of this study indicate that surface roughness affects chondrocyte proliferation, differentiation, and matrix synthesis, and that this regulation is cell maturation dependent.

Adherence, proliferation and collagen turnover by human fibroblasts seeded into different types of collagen sponges

We describe an in vitro model that we have used to evaluate dermal substitutes and to obtain data on cell proliferation, the rate of degradation of the dermal equivalent, contractibility and de novo synthesis of collagen. We tested three classes of collagenous materials: (1) reconstituted non-crosslinked collagen, (2) reconstituted collagen that was chemically crosslinked with either glutaraldehyde, aluminium alginate or acetate, and (3) native collagen fibres, with or without other extracellular matrix molecules (elastin hydrolysate, hyaluronic acid or fibronectin). The non-crosslinked reconstituted collagen was degraded rapidly by human fibroblasts. The chemically crosslinked materials proved to be cytotoxic. Native collagen fibres were stable. In the absence of ascorbic acid, the addition of elastin hydrolysate to this type of matrix reduced the rate of collagen degradation. Both elastin hydrolysate and fibronectin partially prevented fibroblast-mediated contraction. Hyaluronic acid was only slightly effective in reducing the collagen degradation rate and more fibroblast-mediated contraction of the material was found than for the native collagen fibres with elastin hydrolysate and fibronectin. In the presence of ascorbate, collagen synthesis was enhanced in the native collagen matrix without additions and in the material containing elastin hydrolysate, but not in the material with hyaluronic acid. These results are indicative of the suitability of tissue substitutes for in vivo application.