OKAYAMA, Japan, December 26, 2018 /PRNewswire/ --

Researchers at Okayama University report in the journal Molecules that commensal microbiota - microorganisms present in the human body - may play a key role in human-bone remodeling by enhancing the activity of both cells breaking down bone tissue and cells synthesizing bone.

     (Photo: https://mma.prnewswire.com/media/802369/Okayama_University.jpg )

Humans are host to several types of microorganisms like bacteria, fungi and viruses. Those residing in the human body without harming it are collectively called commensal microbiota.  While it has been established that commensal microbiota play an important role in the body's energy management and the development of its immune system, recent findings have suggested that they affect the regulation of human bone formation too.  Now, by performing comparative experiments on mice, Professor Manabu Morita, Yoko Uchida (D.D.S.) and colleagues from Okayama University confirmed the link between commensal microbiota and bone cell regulation.  Specifically, they found that the presence of the microorganisms enhances the activity of both osteoclasts (cells that break down bone tissue) and osteoblasts (cells that synthesize bone).

Professor Morita and colleagues worked with two types of mouse: germ-free (GF) mice, free of any microorganisms, and specific-pathogen-free (SPF) mice, which are guaranteed to be free of certain pathogens but at the same time host to commensal microbiota.

The researchers investigated the activity of osteoclasts and osteoblasts in 8-week-old GF and SPF mice.  They first looked at body weight and size.  The SPF mice were found to have larger body size but lower bone mineral density in alveolar bones (the bones that contain the tooth sockets on the jaw bones), an observation attributed to the presence of commensal microbiota.  In addition, by analyzing blood serum of the mice for substances that are associated with osteoclast activity, Professor Morita and colleagues were able to conclude that commensal microbiota cause greater development and activity of osteoclasts.

The scientists also discovered that the expression of osteocalcin messenger RNA- a maker of bone mineralization - is significantly higher in SPF mice, providing a further link between commensal microbiota and bone-remodeling processes.

While the precise mechanism of commensal microbiota affecting the expression of osteo-blast-specific genes such as osteocalcin needs to be further investigated in order to be completely understood, quoting Professor Morita and colleagues, "[these results] suggest that the commensal microbiota prevents excessive mineralization possibly by stimulating osteocalcin expression in osteoblasts, and enhances both osteoblast and osteoclast activity by regulating specific transcription factors."

Background 

Commensal microbiota 

The term microbiota refers to the collective of bacteria and other microorganisms in an animal's body. The term commensal is used when the presence of the microbiota is not harmful for the animal host. Professor Manabu Morita, Yoko Uchida (D.D.S.) and colleagues from Okayama University have now studied the influence of commensal microbiota on bone remodeling in mice. Their findings show that commensal microbiota have a regulatory effect on bone formation, as shown by differences in body weight and size between mice with and without commensal microbiota.

Osteocalcin.  Bone density 

Osteocalcin is a protein occurring in bone, produced by osteoblasts (bone-synthesizing cells). It is known to play a role in bone mineralization.  As such, osteocalcin is often used as a biochemical marker for bone-formation activity. Professor Morita and colleagues were able to show that in specific-pathogen-free (SPF) mice, the expression of osteocalcin is related to the presence of commensal microbiota.

The study also involved measurements of bone density, or bone mineral density - the amount of bone mineral in bone tissue. While the SPF mice exhibited a larger body size, their bone density was found to be lower.

Reference 

Yoko Uchida, Koichiro Irie, Daiki Fukuhara, Kota Kataoka, Takako Hattori, Mitsuaki Ono, Daisuke Ekuni, Satoshi Kubota, Manabu Morita. Commensal microbiota enhance both osteoclast and osteoblast activities. Molecules, 2018 Jun 23;23(7). pii: E1517.
DOI: 10.3390/molecules23071517.  
https://www.mdpi.com/1420-3049/23/7/1517

Reference (Okayama University OU-MRU) : Professor Morita's team 

OU-MRU Vol.59：Role of commensal flora in periodontal immune response investigated

Okayama University Medical Research Updates （OU-MRU） 

The whole volume : OU-MRU (1- )

Vol.1：Innovative non-invasive 'liquid biopsy' method to capture circulating tumor cells from blood samples for genetic testing

Vol.2：Ensuring a cool recovery from cardiac arrest

Vol.3：Organ regeneration research leaps forward

Vol.4：Cardiac mechanosensitive integrator

Vol.5：Cell injections get to the heart of congenital defects

Vol.6：Fourth key molecule identified in bone development

Vol.7：Anticancer virus solution provides an alternative to surgery

Vol.8：Light-responsive dye stimulates sight in genetically blind patients

Vol.9：Diabetes drug helps towards immunity against cancer

Vol.10：Enzyme-inhibitors treat drug-resistant epilepsy

Vol.11：Compound-protein combination shows promise for arthritis treatment

Vol.12：Molecular features of the circadian clock system in fruit flies

Vol.13：Peptide directs artificial tissue growth

Vol.14：Simplified boron compound may treat brain tumours

Vol.15：Metamaterial absorbers for infrared inspection technologies

Vol.16：Epigenetics research traces how crickets restore lost limbs

Vol.17：Cell research shows pathway for suppressing hepatitis B virus

Vol.18：Therapeutic protein targets liver disease

Vol.19：Study links signalling protein to osteoarthritis

Vol.20：Lack of enzyme promotes fatty liver disease in thin patients

Vol.21：Combined gene transduction and light therapy targets gastric cancer

Vol.22：Medical supportive device for hemodialysis catheter puncture

Vol.23：Development of low cost oral inactivated vaccines for dysentery

Vol.24：Sticky molecules to tackle obesity and diabetes

Vol.25：Self-administered aroma foot massage may reduce symptoms of anxiety

Vol.26：Protein for preventing heart failure

Vol.27：Keeping cells in shape to fight sepsis

Vol.28：Viral-based therapy for bone cancer

Vol.29：Photoreactive compound allows protein synthesis control with light

Vol.30：Cancer stem cells' role in tumor growth revealed

Vol.31：Prevention of RNA virus replication

Vol.32：Enzyme target for slowing bladder cancer invasion

Vol.33：Attacking tumors from the inside

Vol.34：Novel mouse model for studying pancreatic cancer

Vol.35：Potential cause of Lafora disease revealed

Vol.36：Overloading of protein localization triggers cellular defects

Vol.37：Protein dosage compensation mechanism unravelled

Vol.38：Bioengineered tooth restoration in a large mammal

Vol.39：Successful test of retinal prosthesis implanted in rats

Vol.40：Antibodies prolong seizure latency in epileptic mice

Vol.41：Inorganic biomaterials for soft-tissue adhesion

Vol.42：Potential drug for treating chronic pain with few side effects

Vol.43：Potential origin of cancer-associated cells revealed

Vol.44：Protection from plant extracts

Vol.45：Link between biological-clock disturbance and brain dysfunction uncovered

Vol.46：New method for suppressing lung cancer oncogene

Vol.47：Candidate genes for eye misalignment identified

Vol.48：Nanotechnology-based approach to cancer virotherapy

Vol.49：Cell membrane as material for bone formation

Vol.50：Iron removal as a potential cancer therapy

Vol.51：Potential of 3D nanoenvironments for experimental cancer

Vol.52：A protein found on the surface of cells plays an integral role in tumor growth and sustenance

Vol.53：Successful implantation and testing of retinal prosthesis in monkey eyes with retinal degeneration

Vol.54：Measuring ion concentration in solutions for clinical and environmental research

Vol.55：Diabetic kidney disease: new biomarkers improve the prediction of the renal prognosis

Vol.56：New device for assisting accurate hemodialysis catheter placement

Vol.57：Possible link between excess chewing muscle activity and dental disease

Vol.58：Insights into mechanisms governing the resistance to the anti-cancer medication cetuximab

Vol.59：Role of commensal flora in periodontal immune response investigated

About Okayama University 

Okayama University is one of the largest comprehensive universities in Japan with roots going back to the Medical Training Place sponsored by the Lord of Okayama and established in 1870. Now with 1,300 faculty and 13,000 students, the University offers courses in specialties ranging from medicine and pharmacy to humanities and physical sciences. Okayama University is located in the heart of Japan approximately 3 hours west of Tokyo by Shinkansen.

Website: http://www.okayama-u.ac.jp/index_e.html

Correspondence to 

Professor Manabu Morita, D.D.S., Ph.D.
Department of Preventive Dentistry,
OkayamaUniversity Graduate School of Medicine, Dentistry and
Pharmaceutical Sciences, 2-5-1 Shikata-cho, Kita-ku, Okayama,
700-8558, Japan.
E-mail: mmorita@md.okayama-u.ac.jp

Further information  

Okayama University
1-1-1 Tsushima-naka , Kita-ku , Okayama 700-8530, Japan

Public Relations and Information Strategy
E-mail: www-adm@adm.okayama-u.ac.jp
Website: http://www.okayama-u.ac.jp/index_e.html
Okayama Univ. e-Bulletin: http://www.okayama-u.ac.jp/user/kouhou/ebulletin/

About Okayama University (YouTube):
https://www.youtube.com/watch?v=iDL1coqPRYI

Okayama University Image Movie (YouTube):
https://www.youtube.com/watch?v=KU3hOIXS5kk 

SOURCE Okayama University