Assessment of mesh shrinkage using fibroblast-populated collagen matrices: a proof of concept for in vitro hernia mesh testing

PURPOSE

This study uses free-floating contractile fibroblast-populated collagen matrices (FPCMs) to test the shrinkage of different hernia mesh products. We hope to present this model as a proof of concept for the development of in vitro hernia mesh testing-a novel technology with interesting potential.

METHODS

FPCMs were formed by seeding Human Dermal Fibroblasts into collagen gels. FPCMs were seeded with three different cell densities and cast at a volume of 500 μl into 24-well plates. Five different mesh products were embedded within the collagen constructs. Gels were left to float freely within culture media and contract over 5 days. Photographs were taken daily and the area of the collagen gel and mesh were measured. Media samples were taken at days 2 and 4 for the purposes of measuring MMP-9 release. After 5 days, dehydrated FPCMs were also examined under light and fluorescence microscopy to assess cell morphology.

RESULTS

Two mesh products-the mosquito net and large pore lightweight mesh were found to shrink notably more than others. This pattern persisted across all three cell densities. There were no appreciable differences observed in MMP-9 release between products.

CONCLUSIONS

This study has successfully demonstrated that commercial mesh products can be successfully integrated into free-floating contractile FPCMs. Not only this, but FPCMs are capable of applying a contractile force upon those mesh products-eliciting different levels of contraction between mesh products. Such findings demonstrate this technique as a useful proof of concept for future development of in vitro hernia mesh testing.

P-001 FORMING A LIVING TISSUE MODEL OF THE POSTERIOIR RECTUS SHEATH

Aim

To develop an in-vitro model of the posterior rectus sheath. The model should be formed of living cells and aligned collagen that is of a similar thickness and tensile strength to the posterior rectus sheath.

Materials and Methods

Rectangular Fibroblast populated Colagen matrices (FPCMs) were formed using rat-tail collagen and seeded with an immortal cell line of human fibroblasts. FPCMs were formed into 3D-printed tethered gel moulds where they were tethered at opposing ends to induce the formation of an aligned construct. FPCMs were cultured for 10 days. After 10 days, excess fluid was removed and the constructs were plastic compressed under custom made compression blocks. Constructs were fixed in 4% paraformaldehyde. Constructs underwent flouresence icroscopy, second harmonic generation microscopy and uniaxial tensile strength analysis.

Results

6 constructs were developed. Lateral alignment of both fibroblatss and collagen were confirmed on flouresence and second harmonic generation microscopy respectively. Median construct thickness after compression was 0.57mm. Tensile strength analysis still awaited.

Conclusion

- here we present one of the first ever in-vitro models of the posterioir rectus sheath made with living human fibroblasts. It represents a novel potential development of a “living mesh” or rectus shetah transplant. Our model will be further optimised in the coming months by introducing human rectus sheath fibroblasts.

OC-023 USING FIBROBLAST MEDIATED MATRIX CONTRACTION TO TEST MESH SHRINKAGE - A PROTOTYPE FOR IN VITRO MESH TESTING

Background/Aim

Measuring how hernia meshes shrink after implantation is a commonly used parameter in in vivo mesh testing. We aim to use fibroblast populated collagen matrices (FPCMs) and their contraction to assess how different meshes shrink.

Methods/Materials

1 millilitre circular FPCMs were formed in 24 well plates. Different hernia meshes were placed halfway through the FPCMs so that they were embedded. Matrices were seeded with immortalised human fibroblasts, allowed to set and then separated form the well plate using a sterile needle. Gels were cultured in fibroblast media at 37 degrees 5% CO2 for seven days and were allowed to contract naturally. Each day, photographs were taken and the area of the collagen and the mesh were calculated.

Results

When comparing collagen contraction with/without hernia mesh, It was noted that significantly greater contraction was observed without mesh - which hampered collagen contraction. When comparing meshes, It was noted that a lightweight mesh with larger pores lead to greater collagen contraction (54% Vs 45%) and greater mesh shrinkage (55% Vs 20%) compared to heavyweight mesh with smaller pores.

Conclusion

We present a cheap, standardised and unique technique for measuring mesh contraction in vitro.

Application of Demirjian's and Cameriere's Method in Dental Age Estimation of 8-16 Year Old Adolescents from Hunan Han Nationality

Abstract

Objective To apply Demirjian's and Cameriere's method for dental age estimation of adolescents from Hunan Han nationality, and compare the accuracy of the two methods. Methods A total of 480 orthopantomograms of?8-16 year?old adolescents from Hunan Han nationality?with no special diseases and good nutritional status were collected?by Xiangya Stomatological Hospital of Central South University from January, 2016 to July, 2017, among them 236 males and 244 females. The dental age of each adolescent was determined by Demirjian's method and Cameriere's method, respectively, and the paired t-test of the estimated dental age and the chronological age determined by the two methods was conducted by SPSS 20.0 software to compare the difference between estimated dental age and chronological age. Results Mean chronological age of males and females was 11.91 and 11.88 years, respectively. The estimated dental age determined by Demirjian's method showed an underestimate of chronological age by an average of 0.11 years （males） and 0.15 years （females）, while the estimated dental age determined by Cameriere's method showed an underestimate of chronological age by an average of 0.83 years （males） and 0.72 years （females）. Conclusion Demirjian's method is more accurate than Cameriere's method in dental age estimation of adolescents from Hunan Han nationality, therefore more suitable for dental age estimation of adolescents in this region.