Research Skeletal Biology

Tyler Ingersoll, Texas Biomedical Research Institute

In the summer of 2016 I conducted an Internship at the Texas Biomedical Research Institute in San Antonio, TX. The Institute works on projects throughout the year in three major departments: Virology, Immunology and Genetics. My internship was within the Genetics department. Along with my mentor Dr. Ellen Quillen and her lab assistant’s Anne Sheldrake and Jaydee Foster I looked at the osteoporosis and osteoarthritis in baboons and the impact that sex age and diet had on these diseases. The following report gives an overview of the Institute and its history, my activities during the course of the internship and what we found.

 

Saving Lives with the Power of Scientific Discovery

The main aim of the Texas Biomedical Research Institute is to “Unravel the mysteries of chronic and infectious diseases through innovative thinking, creative problem solving and cutting edge technologies.” The Foundation of Applied Research, or FAR, was founded on December 16th, 1941 by Thomas Baker Slick Jr. It would later be known as The Texas Biomedical Research Institute.

 

A little about Thomas Baker Slick Jr.

He was a successful inventor, businessman, oilman, rancher, engineer, philanthropist, peacemaker and adventurer. When he graduated he made the decision to “realize in bricks and mortar the nonprofit approach to scientific research” that he always envisioned. In 1940 he had acquired approximately 1600 acres of land from Leon Creek to Potranco.  This section of land was the site of Essar Ranch; it was here that the Brangus was conceived, a cattle hybrid of the Brahman and the Angus.

In 1942 Tom Slick volunteered in the U.S. Navy as a lieutenant. During his time in the South Pacific he came across an article from Dr. Vagtborg. In that article Dr. Vagtborg was misquoted when he said “Anything can be improved” but nethertheless Tom Slick made the monumental decision to recruit him to aid in developing his research institutes.

Slick met many skeptics along the way; but he never wavered. He was determined to succeed, and his family stood by his side. His mother would always donate to the major projects and his younger brother was a trustee from the start of the institution. Tom’s sister Betty wanted to have a permanent support base for the research programs; so they purchased The Argyle, a southern mansion that they turned into a private club with 1400 members that was devoted to supporting its research. His brother-in-law, like Tom himself, believed in using scientific research to “better man-kind” and served as the chairman of the Institute for over a decade. Family members and descendants are still involved even today.

Tom Slick’s determination and enthusiasm infected his friends, family and even those he briefly met. They joined in his mission to “build a ‘city of science’ that would benefit all of humanity through advances in research.”

 

Overview of Genetics

What is Genetics?

The broad definition is the study of heredity and the variation of inherited characteristics. Why is the study of heritability important? With having a fundamental understanding of genetics we have been able to do things such as alter our food (for example the development of maize from teosinte), develop different breeds of dogs, and even finding cures and vaccines for diseases.

 

How is this important to Anthropology?

Anthropology has always been about understanding who we are and how we got here; but it is also about where we are going. One way to do that is through studying our genetics as well as those of other primates. By doing this we can learn more about ourselves and work towards alleviating diseases that plague us. One such disease is osteoporosis and osteoarthritis.

 

So what was the project?

We were looking at the impact that age, sex and diet had on crack propagation, or movement, through bone. We used still microscopic images from baboons between 15-26 years old (and a few outside of that range), that were both male and females, and were on two different diets: Chow vs. High Fat (animals were put on the HF diet for between 18 mos – 2 years).

 

Grant Proposal

In her grant proposal Dr. Quillen said

Significant gaps in our knowledge remain as to how complex bone traits work in concert to confer robust bone strength and fracture resistance. As a consequence, variables representing a combination of these traits must be considered if we are to significantly advance our knowledge in this area.

The hypothesis is

That bone traits functionally co-vary in a complex multivariate manner at multiple hierarchical physical length scales to produce sufficient structural integrity for routine daily loading. These combinations of traits can result in morphological and tissue level variability in bone structures that confer adequate functional structural integrity, but some of the resulting bone structures will perform poorly under non-habitual loading conditions such as those encountered in a fall.

Whew! That is a lot of big words! Another way to say that is we don’t know a whole lot about how complex bone traits work when it comes to bone strength. Bones are strong, they have to be; with the amount of load bearing they do day in and day out. However, there are circumstances when our bones experience more than just normal load bearing. This is when bone strength traits come in; when we do something like fall that force is not normal for our bones, it is sudden and painful. What we were wanting to look at is whether there is a difference in how the crack moves through the osteons using the variables of age, sex and diet. Before we understand how the crack moves we need to understand how bones work.

 

Bone morphology and function

Bone is multifunctional, its major role is in mechanical support and protection but it also plays a role in mineral homeostasis and hematopoiesis (or blood forming). There are two different types of bone: trabecular (cancellous) bone and cortical bone.

Trabecular bone is the inner spongy portion of bone; it’s most important function is redirecting stresses to the stronger cortical bone. It is found primarily in the metaphyses, or ends, of long bones, vertebrae, ribs and the iliac crest.

Cortical bone are the thicker plates that surround the spongy bone, takes up the majority of bone mass and takes on most of the role for load bearing. It is the primary component of the shafts, or diaphyses, of the bones of the extremities.

One of the things that is so impressive about bone is that it has become highly adapted to avoid fractures due to repetitive loading. In areas where trauma would be fatal (ie. the torso and cranium) the bones also serve a protective function. When it comes to these areas the organization of bone is different than it is in others; the organization is designed to absorb maximum energy with minimum trauma to the bone itself.

 

How do bones form?

Bones form in two different ways: Intramembranous ossification and Endochondral ossification.

Intramembranous ossification occurs “in-between” membranes. Bones that serve protective functions like the flat bones of the skull, ribs and the diaphyses of the clavicle form in part by this type of ossification.

Endochondral ossification occurs when the bone develops within cartilage; these types of bones include our long bones (arms and legs) as well as our knee.

 

Bone as a hematopoietic organ

What is hematopoiesis?

Hematopoiesis just means the formation and development of blood cells. When we are children the marrow cavity is an important site for red marrow during growth and development. As we grow older the red marrow is replaced by yellow fat marrow. Even though, as adults, the majority of the red marrow we had as children has been replaced we still have a few areas that are good sources of red blood cells. These areas are composed primarily of trabecular bone and are located in the iliac crest, vertebrae and the proximal femur.

 

Bone composition

65% of bone by weight is mineral, mostly carbonated apatite.

20-25% is made up of type I collagen (the organic component)

The remaining ~10% is made up of water that is both bound to the composite as well as unbound that free flows through the canalicular and vascular channels in bone.

Bone composition is a balancing act; water is exchanged on a nearly 1:1 basis with mineral. As bone becomes more mineralized water content lowers and vice versa. The higher the mineralization of bone, the stiffer the bone becomes, but the dryer the bone becomes as well. Having highly mineralized bone is not a good thing because the dryer bone tends to become more brittle and breaks more easily.

 

Bone cells

There are three types of bone cells: osteoclasts, osteoblasts and osteocytes

Osteoclasts are the primary cells in bone resorption. Bone resorption is when bone is broken down; this allows for a transfer of calcium and other minerals from the bone to the bloodstream. At the same time that the osteoclasts are breaking down bone osteoblasts come in and lay down new bone. The activities performed by these cells are important in bone development and maintaining the integrity of adult skeletons. Last but not least are osteocytes. Osteocytes are former osteoblasts that become entombed during bone deposition. They show up regularly in the bone matrix and they are the most abundant cells in bone.

 

Internship Activities

At the beginning of the internship I was asked to go through and identify the features found in microscopic bone. This was to ensure that 1) I was correctly identifying features such as Haversian sets, osteon sets, pores and undefined canals as well as others and 2) To ensure that I was yielding similar results to what they had already found. In order to do this I was required to learn and use a program called Bioquant.

I opened up a practice folder and began going through and identifying features in both the inferior and superior bone sample images. First thing that had to be done was to select and measure the sample area. After that then I was able to get to work identifying the remaining features.

After I had completed those practice images and were receiving accurate results I began to work on the main project and determine and label the osteons along the main crack as deflected, penetrated or ambiguous.

Osteons are either deflected or penetrated (ambiguous was only used if you could NOT tell what to label it). When an osteon deflects the fracture it means that the fracture moves around the outer cement line of the osteon. Penetration is when the fracture cuts through the osteon altogether. Once completed it was time to work on the porosity levels for the crack images. This was done exactly as I had done my practice images.

Finally the last thing I had to do was go through the data and prepare a spreadsheet so we could run a T-test to determine if age, sex or diet impacted the percentage of osteons that were penetrated.

Dr. Quillen and I ran the T-test and found that there was no significant difference when it came to age, sex or diet. This meant that we had to run another test to see if there was a large heritability percentage that led to a greater possibility of osteon penetration.

The reason that we were looking for heritability is because if the heritability is high the easier (in theory) it is to find the genes that might be attributed to the development of osteoporosis and osteoarthritis. In order to determine the heritability percentage the data was run through a stats program called R. The equation that was used was (normally you would also subtract out the other variables of age and sex but since the original T-test ruled that out we did not have to). This equation gives us the percentage to show how much of what we were seeing was based on genes. Because we didn’t have to subtract out age and sex we had the potential of having a higher heritability percentage. If we found that the percentage for heritability was high enough then that would be strong evidence that osteoporosis and osteoarthritis could possibly be labeled a metabolic syndrome issue.

This list includes issues such as:

Heart Disease

Diabetes

Obesity

High Blood Pressure as well as many others.

Unfortunately once the test was completed and our results came back the percentage we got for heritability was 0.000000000%.

So all in all the project that I was working on yielded negative results. But in science, negative results are still results and we learned that we need to find something new to test in order to gain a better understanding of osteoporosis and osteoarthritis. When we do that maybe, just maybe, we will be able to work towards a cure; or at the very least work towards prevention of these chronic and debilitating diseases.

 

References:

Burr, D. B., & Allen, M. R. (2014). Basic and applied bone biology. Amsterdam: Elsevier/Academic Press.

Quillen, Ellen PhD. (2010). BSI_R01_Havillella_02_02_2010_FinalDraft. Unpublished Grant Proposal.

About the author

The Internship Coordinator

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