Aging Study

Introduction

It is no surprise that, with the new technological advances in the medical world, that people are living longer than ever. Coupled with this fact is the need for more and better implants whether it be a pacemaker or mesh scaffolding for surgical repair. An important aspect of these body implants is how the body, particularly the immune system, responds to foreign material.

As part of the Brown Lab at the McGowan Institute for Regenerative Medicine, I worked on the "Aging Project". Previous research conducted by the lab had previously determined that, when comparing 8 week and 18 month old mice, the older mice had a slower transition from M1 macrophages, which shows a more inflammatory response, to M2 macrophages, which showed a more regenerative response. Minimizing the transition time from M1 to M2 is believed to result in better integration of biomaterials into the body.

Objective

This project has two focus objectives. The first of which is focused on characterizing the immune response to implanted biomaterial as affected by age. The previous research conducted by the lab has only looked at 8 week and 18 month mice. This first objective specifically looks at whether there is any additional significant change in response in mice past 18 months. Mice past 18 months old typically have a greater chance of developing tumors which would render them unfit for this study. If there is no additional affect for mice older than 18 months, then 18 month mice can be continued can be used as the oldest age group for future studies. This was done by comparing 18, 21, and 24 month old mice. This objective is known as the In-Housed Aged mice.

The second objective of this specific study is to determine whether the it is the microenvironment or the cells themselves that have the greater impact on the immune response. To accomplish this, chimeric mice were create by transferring bone marrow progenitor cells from old mice transplanted into young mice and vice versa(denoted as OTY for old mice into young mice and YTO for young mice into old mice).

Methodology

To carry out this study, mice were taken, as described in both objectives, and given a small abdominal muscle deformation along with a polypropylene implant. The mice were given some time to recover( 1 week for the first objective mice and varied amounts for the chimeric mice) before being sacrificed. Explants of the abdominal tissue with the mesh were taken out from the mice and cut in several slices to be mounted on slides for analysis.

My role in this project was to stain, in H & E (Hemotoxylin and Eosin) and Masson's Trichrome, image and analyze cells. After staining the slides through their respective staining protocol, the slides were imaged using a microscope with a focus on individual mesh fibers. The goal was four images of four different fibers per mouse. H & E staining was used for cell counting, which I did manually. Masson's Trichrome staining was used for collagen content analysis. This was accomplished using the program ImageJ.

Preliminary Results

We have begun Immunofluorescence staining to inspect certain proteins but are still testing which antibodies to use. Testing is still ongoing so no results are finalized as of now. Additionally, the data from the slides already analyzed has to be put through a statistical test to determine significance.

*First Image obtained from the following source:

Brown, B. N., Haschak, M. J., Lopresti, S. T., & Stahl, E. C. (2017). Effects of age -related shifts in cellular function and local microenvironment upon the innate immune response to implants. Seminars in immunology, 29, 24-32. https://doi.org/10.1016/j.smim.2017.05.001

Aging Study

Introduction

Objective

Methodology

Methodology

Preliminary Results

Preliminary Results

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