Corticosteroids For Bone Repair & Regeneration

Corticosteroids For Bone Repair & Regeneration

Posted on April 30th, 2013

This post was originally posted in Nutricula Magazine on April 27th, 2013

Part 1- A discussion about the use of cortisol to heal a bone fracture in a canine patient; a veterinary perspective.

Part 2- Corticosteroids can not only stop bone loss but can aid in cortical bone healing, repair and regeneration.

When we think of corticosteroid use, we usually think of it causing bone weakening, thinning, and loss of bone density. But there are specific cases where the use of corticosteroids has been shown to be extremely beneficial for the repair and healing of bone as well…

Part 1 - by Al Plechner, DVM

The word osteoporosis apparently comes from the Greek word “porous bone”.

Osteoporosis seems to be more commonly found in humans than in animals. However, there are many conditions in both humans and animals that can lead to “porous bones”.

Dr. Plechner: “In my clinical veterinary experience, I have found that a lack of calcium in the diet may lead to osteoporosis. Osteoporosis can also come from a pancreatic trypsin deficiency that may be either genetic or acquired.”

When a trypsin deficiency is present in animals, fat soluble vitamins like A, D, and E will also bind calcium and disallow its required absorption for normal bone growth as well as for bone maintenance. In this case, a plant-based digestive enzyme can be added to each meal to alleviate this problem.

Kidney disease can also cause osteoporosis merely by creating excess phosphorus in the body. The body tries to maintain a 1-to-1 or a 1 part calcium-to-2 parts phosphorus ratio for proper homeostasis, but improper kidney function and/or disease can cause it to signal the removal of calcium from the bones…thus, again…causing osteoporosis.

Elevated estrogen is also a culprit for causing bone loss.

Dr. Plechner : “I measure total estrogen in my animal patients, but do you realize that for woman, only ovarian estrogen is measured…which includes estradiol, estrone and estriol. If elevated estrogen seems to be so important, yet only partial estrogen is measured, hopefully you can see why cancer and autoimmune diseases…as well as osteoporosis… may keep on occurring at such an alarming rate.”

Human males are thought to have only estradiol-which is absolutely wrong!

Dr. Plechner: “In my animal patients I have found that measuring total estrogen is very important. If this is not done, this may be why cancer, heart attacks, strokes, and autoimmune compromises occur. The MD’s I have worked with have also found this same problem with humans.”

Why does elevated total estrogen lead to osteoporosis, (if it is even measured)?

Elevated total estrogen, that includes the estrogen from the inner layer adrenal cortex, causes the B-lymphocytes to decrease their production of antibodies (i.e., immunoglobulins), and when the mucous membrane antibody, IgA, drops below a certain level, malabsorption occurs, not only with certain oral supplements, but with calcium as well…which can, and most probably will, lead to osteoporosis.

Disorders of the parathyroid gland can also lead to the mobilization of calcium from the patient’s bones, but this occurs less frequently.

To get back to the subject of why proper cortisol administration may help an animal heal a fractured bone, please go to www.drplechner.com and read about “Plechner’s Syndrome” to see if you or your animal just may have the imbalances that can lead to osteoporosis.

The medical profession has always believed that the use of a steroid would definitely slow down the healing of a damaged tissue. This also includes bone damage and the healing/repair of bone as well. What the world [so far] does not realize is that there needs to be a daily amount of natural cortisol produced from the middle layer adrenal cortex for the proper control of the immune system, while simultaneously, allowing for the maximum absorption of calcium.

Identification of any of these imbalances may be important for your overall bone health and that of your pet’s health as well.

Dr. Plechner: “I would like to share with you an interesting case of a spayed female Maltese [canine] that had my syndrome, (See, Plechner’s Syndrome at www.drplechner.com), and was on a replacement steroid and thyroid hormone for over 2 years. She was doing very well until she fractured her femur (thigh bone). I had no idea that the surgeon she went to was in the same hospital where I practiced, and neither the surgeon nor the owner contacted me at the time of the incident. The canine patient presented a cortisol imbalance that led to an elevated body total estrogen. This in turn caused the binding up of her thyroid receptor sites. Due to this, a lack of bone healing and calcium malabsorption incurred. “

The surgeon said to stop the steroids because it would slow and stop the healing even though blood test results indicated a steroid imbalance was present. The owner did oblige to this. After 3 more surgeries for a non-healing fracture, I finally heard from the owner as to what was happening.

Dr. Plechner: “I immediately had the owner begin a steroid and thyroid regimen, and within 8 weeks the fracture had completely healed.”

This is a prime example of why normal steroid production is vital to bone fracture healing. If the normal production of cortisol is deficient or defective this healing will be hampered.

FYI: Mother Nature has created a unique type of living clay called calcium montmorillinite, that when taken orally enhances calcium absorption; I use this with all my patients. “I do have an article in the magazine, Pet Age, (November, 1985 Issue), which discusses the values of trace minerals. Please refer to my website on this where I have the facts which show that this type of natural product was even researched at Cal Tech. From what I have read, calcium montmorillinite has been used by the astronauts as they walk in space.” Testing has revealed that test subjects who utilize calcium montmorillinite and are exposed to negative gravity, (i.e., walking in space), do not develop bone loss.

Dr. Plechner: “I also use a plant based digestive enzyme with each meal in my affected patients for optimal absorption. Make sure that you and your pet are ruled out for food allergies. In allergy conditions of this kind, the endocrine-immune imbalances that cause a low IgA will just about guarantee malabsorption.In these situations there will be greater risks for the development of osteoporosis/porous bone disease”.

Part 2- by Bob Berger, MS, MVSc, PhD

In specific medical events, corticosteroid administration is not only a major factor responsible for the healing of bone and bone fractures, but is also responsible for reversing bone loss as well. This is highly important for the healing of supporting structures and for the regeneration of bones which play important roles in the protection and function of vital organs.

From the Dept. of Medicine/Dept. of Cell Biology & Physiology, the UNC McAllister Heart Institute and the Lineberger Comprehensive Cancer Center,University of North Carolina, Chapel Hill, in a comprehensive study by Duan, J. and Lee, Y., et al. (2013) Rib Fractures and Death from Deletion of Osteoblast β-catenin in Adult Mice is Rescued by Corticosteroids. PLos One, 8, e55757 ¹, investigators showed howglucocorticoid administration regenerates rib/rib cage cortical bone and increases survival (as well as the rescue from death), in a [transgenic] murine model. Results from this investigation are significant, especially for clinicians and scientists, as the general thought has historically been that the prolonged use of steroidal drugs induces bone loss and does not re-build it. The traditional “train of thought” is (obviously) still valid, but supportive scientific evidence from this and other studies show that the therapeutic use of steroids for bone loss/bone fractures of specific etiology is also valid. In the UNCCH study, steroid administration was found to repair and regenerate cortical bone of the ribs/rib cage and to also suppress bone density loss of these structures in a specific transgenic mouse model.

In vertebrates, the ribs protect the chest wall and allow for the proper expansion of the lungs. The breakdown and/or fractures of the ribs/rib cage, which can occur via traumatic or by non-traumatic events (such as when bone density decreases in the elderly or when breast cancer has metastasized to the rib cage), can result in a flail chest, and this condition could become essentially life-threatening. It is vital that the ribs/rib cage be in sound and stable physical condition for normal respiration to occur.

We normally emphasize that the pelvis and spinal column are structures which become fragile as aging, injury, and diseases occur, but at times we neglect the importance of the ribs and rib cage. When the ribs lose bone density, due to their relative “diminutive” thickness, (as compared to other bones), the ability to re-build, as well as to maintain their cortical density, is vital for the protection of the lungs. The inability to repair and maintain rib/ rib cage density would definitely be considered a high mortality risk.

Osteoclastogenesis, or the development of osteoclasts, (specific bone cells that demineralize the matrix, cause bone resorption, and decrease bone density), perform opposing tasks of what osteoblasts (fibroblasts that form bone/increase density), do. As bone is in a dynamic state, the osteoclasts and osteoblasts must perform their “duties” in proper balance.

A full description of the UNCCH study is beyond the scope of this article. The goal was to create an investigative [in vivo] situation where a genetically-modified mouse would be produced that could be manipulated as a working model. Using a Cre-Loxsystem, (Feil and Brocard, et al. 1996¹), [specifically,aCreERT/LoxP-mediated DNA recombination], which utilizes a site-specific DNA recombinase targeting DNA sequences for insertion, a transgenic mouse was produced.(CreERT is a mouse lineage where Cre recombinase is fused to a ligand-binding domain of the human estrogen receptor (ER), resulting in a CreERT that is “activated” by tamoxifen (T), having the ability totrigger tissue specific expression in genetically-modified animals.^2,3) By creating a transgenic mouse lineage known as Col1a2CreERT/β-catenin ^fl/fl,when the gene for β-catenin, (a signaling protein that controls the cell-to-cell communication during embryonic development and the healing processes), was deleted from fibroblasts inCre-expressing cells of the adult mice, the deletion resulted in osteoclastogenesis, rapid bone resorption, and bone fracture, (most notably of the ribs/rib cage). The deletion of β-catenin initiates aggressive osteoclastogenesis by the Receptor Activation of Nuclear Factor Kappa-β ligand (RANKL), also known as Tumor Necrosis Factor (TNF)-related activity-induced cytokine.

In order to delete (conditionally knock-out, orCKO), β-catenin in the Cre-expressing cells, tamoxifen was administered intra-peritoneally on a daily basis for 11 days in 8 week old Col1a2CreERT/β-catenin ^fl/fl mice. Due to this deletion, these mice no longer expressed the β-catenin (protein) gene, and the results showed that within several days of the last tamoxifen dose, theβ-catenin-CKO mice developed labored breathing, presented medium group survival of only 11 days, and all died by day 25. In contrast to the β-catenin-CKO group, the Col1a2CreERT/β-catenin ^fl/fl control group (where a corn oil vehicle was used in place of tamoxifen), as well as in other murine groups, (i,e, tamoxifen-injected β-catenin ^fl/fl and Col1a2CreERT:R26R^LacZmice), no deaths were reported.

Upon necropsy of the β-catenin-CKO group, all organs (where β-catenin is normally expressed), still presented normal to unremarkable appearances. Upon further analysis, it was determined that these animals expired due to lung collapse, (although lung tissue from this group was also assessed as normal). It was further determined (via CT scan), that the animals had experienced multiple and spontaneous fractures, (labeled as flail chests), of a great number of the ribs. It appeared that the ribs/rib cages of the β-catenin-CKO group had up to 70% less bone when compared to the rib/rib cages of normal mice.

It was concluded that because the cortical ribs and rib cage had such extensive bone loss, the chest wall was unable to support proper breathing, respiratory failure rapidly ensued, and the animals expired.

To reiterate two main points:1. The β-catenin-CKO mice died within days of β-catenin deletion. This deletion caused rib and rib cage massive cortical bone thinning and destruction. What ensued was respiratory insufficiency, impaired ventilation, and finally respiratory failure which was caused by lung collapse due to the “non-support” of the lung physiology.

2. Although the β-catenin-CKO mice exhibited extensive rib/rib cage resorption due to osteoclastogenesis, the data suggests that the rib/rib cage destruction was secondary to osteoclast recruitment which followed β-catenin deletion in the rib osteoblasts.

The UNCCH investigators showed that when osteoclast activity was inhibited, this prevented bone resorption in the β-catenin-CKO mice, and it rescued these mice from death. When compared to a bisphosphonate (via administration of Pamidronate @ 5 mg/kg), when administered along with tamoxifen, (as this protocol delayed but did not prevent death in the majority of the mice, as only 20% of this group survived for 65 days after the final tamoxifen dose),in the mice administered dexamethasone phosphate [equiv. to 1 mg dexamethasone/kg], 75%of the dexamethasone treated β-catenin-CKO mice were still alive at 65 days. (This was compared to the 0% survival at day 25 in the “tamoxifen only” group). It is suggested that the osteoclastogenesis that resulted from β-catenin deletion in the rib osteoblasts was far more aggressive than that of the bone density loss which is more commonly found in “bisphosphonate-stabilized” osteoporosis.

These results showed that the corticosteroid, (dexamethasone), improved survival and preserved rib/rib cage structures by suppressing/down-regulating RANKL expression; (i.e., RANKL expression initiated osteoclastogenesis in β-catenin-CKO mice). The deletion of β-catenin initiates osteoclastogenesis/osteoclast recruitment, which was the result of the up-regulation of RANKL. Since RANKL expression has been shown to be a controlling factor for the deletion of β-catenin protein [expression], the suppression of RANKL by corticosteroid administration allowed for the repair, restoration, and regeneration of rib/rib cage cortical bone and the increased survival (rescue) of these animals.

The UNCCH investigators showed that 75% of the β-catenin-CKO mice administered dexamethasone survived, and after 80 days, their ribs and rib cages presented evidence of significant repair and even showed new cortical bone formation. The utilization of CT lung scans also showed an increase in lung expansion along with a significant decrease in the number of osteoclasts present in the ribs and rib cages of these animals.

Mode Of Action (MOA)

The RANKL molecule is the surface-bound, TNF-cytokine, osteoclast activator for expression of osteoclastogenesis and osteoclast recruitment of the osteoblastic cell. In the UNCCH study, RANKL expression was shown to be suppressed (down-regulated), by the glucocorticoid, dexamethasone, to quite a physiologically significant degree. This MOA [effect] was shown to reduce the RANKL concentration levels in the β-catenin-CKO mice back to those [concentrations] comparable to the levels of normal mice. This enabled the restoration, repair, and regeneration of cortical rib bone as well as increased the survival times back to those of normal mice.

Significance

This research presents not only a method to treat fractures that might be caused by rapid, severe, and/or highly aggressive bone loss, but also a possible, (and very affordable, as the cost of most steroidal medications are comparably inexpensive), method to treat the type of bone loss that patients who suffer with cancers that metastasize to bones also experience on a world-wide basis.

In many late-stage cancers, such as those of the breast, uterus, cervix, lung, prostate, etc., metastasized cancer cells spread to proximal and distal bone structures, many times at aggressive and alarming rates. Some structures, such as those of the bones of the pelvis and femur, can absorb stress for long periods of time before they eventually wear down, diminish, and even break, while others, such as those of the rib cage, because of their lower bone density, are more apt to crack, splinter, and break much more rapidly.

In many cases involving breast cancer metastases, the bones that are usually invaded first and most significantly are those of the ribs/rib cage, due to their close proximity to the primary tumor or mass. Because the rib/rib cage density is relatively low, if left untreated, structural damage is eminent. The potential damage to the ribs is comparable to major “trauma-type” fractures, which can even be acutely life-threatening.

Cathepsin K Expression & Metastasis to Bone

There area large family of proteases which play a vital role in mammalian cellular turnover called Cathepsins. One of these proteases, Cathepsin K, is specific for catabolizing substances that are integral parts of bone and bone function, (i.e., elastin, collagen, etc.), and has the ability to break down bone and cartilage. Cathepsin K expression may be stimulated by other inflammatory cytokines which are released post-damage to many types of malignancies and metastases. For instance, in cancers of the breast, metastasis of solid neoplasm and malignant cells commonly spread to a proximal bone site such as the ribs. The ability of cancer cells to penetrate the matrix of rib/rib cage bone could be attributed to Cathepsin K which may be released by cancer cells as they invade cortical bone tissue of the rib/rib cage.

As malignant breast cancer cells advance towards the ribs, they may possess the ability, via the action of Cathepsin K, to “bore” into and/or penetrate the cortical bone matrices. (It is widely recognized that the rib/rib cage is a frequent metastatic site for cancers such as those of the breast.⁴) The control of bone metastasis is clinically important, as cancers, such as those of the breast, when spreading (to the proximal rib/rib cage), are frequently associated with pathological fracture.⁵ Although bisphosphonates have been commonly used against bone metastasis, RANKL- targeted drugs and Cathepsin K inhibitors show great promise.⁵

One of the concepts we must remember, (and that we are constantly reminded of), is that many cancers are most probably initiated and allowed to propagate due to both systemic inflammation and a compromised immune system, which both thrive on the synergy of each other.

Bone destruction and inflammation are linked together. Cytokines, which upregulate the receptor activator of nuclear factor-κB (NF-κB) ligand (RANKL), play a major role in inflammatory bone destruction processes.⁶ It can be observed and supported through the research and multiple studies and analyses, that RANKL and cytokine activity, (such as that of Cathepsin K), are best modulated/controlled by a non-compromised, well-functioning immune system which can recognize and control systemic inflammation.^6-8 We know that both inflammation and a compromised, weakened immune system are harbingers for the onset of many cancers, and this is a specific area where the use of RANKL-targeted drugsand Cathepsin K inhibitors have shown so much promise.

The traditional paradigm, which historically has shown that steroidal compounds cause and even further advance bone loss when administered chronically, still stands. Yet, in cases of rapid bone loss, which are due to aggressive osteoclastogenesis and/or osteoclast activity, (as seen in later stage, advanced metastatic cancers that tenaciously invade bone matrices), the administration of specific steroidal compounds may be able to inhibit bone loss of these supporting structures and initiate bone regeneration and repair.This would be a great step in reducing mortality and prolonging life.

…fin…

References (for Part 2)

1. Duan, J. and Lee, Y., et al. (2013) Rib Fractures and Death from Deletion of Osteoblast β-catenin in Adult Mice is Rescued by Corticosteroids. PLos One, 8, e55757.

2. Feil, R. and Brocard, J., et al. (1996) Ligand-activated site-specific recombination in mice. Proc. Natl. Acad. Sci., 93, 10887.

3. Hameyer, D. and Loonstra, A., et al. (2007) Toxicity of ligand-dependentCre recombinases and generation of a conditional Cre deleter mouse allowing mosaic recombination in peripheral tissues. Physiol. Genomics, 31, 32.

4. Papachristou, D.J., Basdra, E.K. and Papach, A.G. (2012) Bone Metastasis: Molecular mechanics and novel therapeutic interventions. Med. Res. Rev., 32, 611.

5. Hayashi, S. and Hanamura, T. (2011) Encounter of cancer cells with bone. Development of bone metastasis-specific targeting therapy. Clin. Calcium, 21, 389.

6. Moon, S.J. and Ahn, I.E., et al. (2013) Temporal differential effects of proinflammatory cytokines on osteoclastogenesis. Int. J. Mol. Med., 31, 769.

7. Naidu, V.G. and Dinesh, K.R., et al. (2013) RANKL targeted peptides inhibit osteoclastogenesis and attenuate adjuvant induced arthritis by inhibiting NF-κB activation and down regulating inflammatory cytokines. Chem. Biol. Interact., 203, 467.

8. Nanjundaiah, S.M., Stains, J.P., and Moudgil, K.D. (2013) Kinetics and interplay of mediators of inflammation-induced bone damage in the course of adjuvant arthritis. Int. J. Immunopathol. Pharmacol., 26, 37.