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Up-regulation of site-specific remodeling without accumulation of microcracking and loss of osteocytes.
Abstract: Functional adaptation of bone normally protects the skeleton from fracture during daily activity. Accumulation of microcracking and loss of osteocytes have been implicated in the regulation and initiation of targeted (reparative) remodeling of bone and, in certain situations, the development of fatigue or stress fracture. We performed a histologic study of the dorsal cortex of the mid-diaphysis of the third metacarpal (Mc-III) bone of Thoroughbred racehorses after bones were bulk-stained in basic fuchsin and transverse calcified sections were prepared. The Thoroughbred racehorse is an extreme athlete whose Mc-III bone experiences particularly high cyclic strains during training and racing. A group of non-athletic horses was also included in the experiment. The following variables were quantified: activation frequency (Ac.f); bone formation rate (BFR); resorption space density (Rs.N/T.Ar); microcrack density (Cr.Dn); microcrack mean length (Cr.Le); microcrack surface density (Cr.S.Dn); osteocyte density (Ot.N/T.Ar; Ot.N/B.Ar); and bone volume fraction (B.Ar/T.Ar). Ac.f and BFR were estimated using a mathematical algorithm. Using confocal microscopy, bones were examined for fine microcracks, diffuse matrix injury, and disruption of the osteocyte syncytium. Low values for Cr.Dn (#/mm2) were found in both groups (0.022+/-0.008 and 0.013+/-0.006 for racing Thoroughbreds and non-athletic horses, respectively). There was no significant relationship between Cr.Dn and Ot.N/T.Ar; Ot.N/B.Ar, B.Ar/T.Ar, and Ot.N/T.Ar; Ot.N/B.Ar, and remodeling (Ac.f, Rs.N/T.Ar) and Ot.N/T.Ar; Ot.N/B.Ar. Intense remodeling of the Mc-III dorsal cortex was found in the racing Thoroughbreds (Ac.f 12.8+/-7.4 #/mm2/year; BFR 31.5+/-15.6%; Rs.N/T.Ar 0.19+/-0.09 #/mm2) and was significantly increased compared with non-athletic horses. Overall, remodeling was weakly correlated with Cr.Dn (r2=0.15, P<0.05). Subtle matrix injury, not detectable by bright-field microscopy, was particularly evident adjacent to resorption spaces in Thoroughbred bone. In non-athletic horses, disruption of the dendritic cell processes of osteocytes associated with cement lines and interstitial fragments was more evident. Taken together, these findings suggest that site-specific (targeted) induction of remodeling during functional adaptation of bone in a high-strain skeletal site is not dependent on accumulation of microcracking or loss of osteocytes. We hypothesize that athleticism can directly influence bone turnover in this extreme athlete through pathways that do not involve classical linear microcracks.
Publication Date: 2005-05-24 PubMed ID: 15908291DOI: 10.1016/j.bone.2004.12.016Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
The study investigates the ability of bone to adapt and repair itself under stress, particularly focusing on racehorses who experience high strain on their bones during training and racing. The results suggest that stress-induced bone remodeling and repair do not necessarily depend on accumulated microcracking or loss of osteocytes, suggesting alternate pathways for bone repair in highly athletic organisms.
Research Method
- The researchers conducted a histological study of the dorsal cortex in a specific part (mid-diaphysis) of the third metacarpal bone in Thoroughbred racehorses. This bone tends to experience high stress during training and racing.
- The bones were stained and sectioned, and variables related to bone health and stability were quantified. These variables include activation frequency, bone formation rate, resorption space density, microcrack density, osteocyte density, and bone volume fraction.
- The study also included a group of non-athletic horses for comparison.
- Confocal microscopy was used to examine fine microcracks, diffuse matrix injury, and disruption of the osteocyte syncytium.
Findings
- The study found low levels of microcrack density in both groups of horses. There was no significant relationship found between microcrack density and several measured variables, including osteocyte and bone volume fraction, or between microcrack density and remodeling activity.
- Intense remodeling of the dorsal cortex was observed in the racing Thoroughbreds, which was significantly increased when compared with non-athletic horses.
- Remodeling was weakly correlated with microcrack density.
- In Thoroughbred horses, subtle matrix injury adjacent to resorption spaces was observed, while disruption of osteocyte processes was more evident in non-athletic horses.
Conclusion
- The research suggests that site-specific bone remodeling in response to functional adaptation at high-strain skeletal sites is not dependent on the accumulation of microcracks or the loss of osteocytes. This suggests other pathways might be responsible for stress-induced bone repair and remodeling.
- Overall, this research suggests that athleticism might directly influence bone turnover in athletes via pathways that do not involve accumulation of classical linear microcracks.
Cite This Article
APA
Da Costa Gómez TM, Barrett JG, Sample SJ, Radtke CL, Kalscheur VL, Lu Y, Markel MD, Santschi EM, Scollay MC, Muir P.
(2005).
Up-regulation of site-specific remodeling without accumulation of microcracking and loss of osteocytes.
Bone, 37(1), 16-24.
https://doi.org/10.1016/j.bone.2004.12.016 Publication
Researcher Affiliations
- Comparative Orthopaedic Research Laboratory, School of Veterinary Medicine, University of Wisconsin-Madison, 2015 Linden Drive, Madison, WI 53706, USA.
MeSH Terms
- Age Factors
- Animals
- Bone Matrix / pathology
- Bone Remodeling
- Cell Count
- Haversian System / pathology
- Horses
- Metacarpus / metabolism
- Metacarpus / pathology
- Metacarpus / physiopathology
- Microscopy, Confocal
- Osteocytes / pathology
- Physical Conditioning, Animal
- Up-Regulation
Citations
This article has been cited 10 times.- Crawford KL, Finnane A, Greer RM, Barnes TS, Phillips CJC, Woldeyohannes SM, Bishop EL, Perkins NR, Ahern BJ. Survival Analysis of Training Methodologies and Other Risk Factors for Musculoskeletal Injury in 2-Year-Old Thoroughbred Racehorses in Queensland, Australia. Front Vet Sci 2021;8:698298.
- Crawford KL, Finnane A, Phillips CJC, Greer RM, Woldeyohannes SM, Perkins NR, Kidd LJ, Ahern BJ. The Risk Factors for Musculoskeletal Injuries in Thoroughbred Racehorses in Queensland, Australia: How These Vary for Two-Year-Old and Older Horses and with Type of Injury. Animals (Basel) 2021 Jan 21;11(2).
- Taguchi T, Lopez MJ. An overview of de novo bone generation in animal models. J Orthop Res 2021 Jan;39(1):7-21.
- Hopper N, Singer E, Henson F. Increased sclerostin associated with stress fracture of the third metacarpal bone in the Thoroughbred racehorse. Bone Joint Res 2018 Jan;7(1):94-102.
- Rumpler M, Würger T, Roschger P, Zwettler E, Peterlik H, Fratzl P, Klaushofer K. Microcracks and osteoclast resorption activity in vitro. Calcif Tissue Int 2012 Mar;90(3):230-8.
- Skedros JG, Sybrowsky CL, Anderson WE, Chow F. Relationships between in vivo microdamage and the remarkable regional material and strain heterogeneity of cortical bone of adult deer, elk, sheep and horse calcanei. J Anat 2011 Dec;219(6):722-33.
- Skedros JG, Clark GC, Sorenson SM, Taylor KW, Qiu S. Analysis of the effect of osteon diameter on the potential relationship of osteocyte lacuna density and osteon wall thickness. Anat Rec (Hoboken) 2011 Sep;294(9):1472-85.
- Muir P, Peterson AL, Sample SJ, Scollay MC, Markel MD, Kalscheur VL. Exercise-induced metacarpophalangeal joint adaptation in the Thoroughbred racehorse. J Anat 2008 Dec;213(6):706-17.
- Dai R, Ma Y, Sheng Z, Jin Y, Zhang Y, Fang L, Fan H, Liao E. Effects of genistein on vertebral trabecular bone microstructure, bone mineral density, microcracks, osteocyte density, and bone strength in ovariectomized rats. J Bone Miner Metab 2008;26(4):342-9.
- Bentley VA, Sample SJ, Livesey MA, Scollay MC, Radtke CL, Frank JD, Kalscheur VL, Muir P. Morphologic changes associated with functional adaptation of the navicular bone of horses. J Anat 2007 Nov;211(5):662-72.
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