Osteolytic and mixed cancer metastasis modulates collagen and mineral parameters within rat vertebral bone matrix

Abstract

Metastatic involvement in vertebral bone diminishes the mechanical integrity of the spine; however minimal data exist on the potential impact of metastases on the intrinsic material characteristics of the bone matrix. Thirty-four (34) female athymic rats were inoculated with HeLa (N = 17) or Ace-1 (N = 17) cancer cells lines producing osteolytic or mixed (osteolytic and osteoblastic) metastases, respectively. A maximum of 21 days was allowed between inoculation and rat sacrifice for vertebrae extraction. High performance liquid chromatography (HPLC) was utilized to determine modifications in collagen-I parameters such as proline hydroxylation and the formation of specific enzymatic and non-enzymatic (pentosidine) cross-links. Raman spectroscopy was used to determine relative changes in mineral crystallinity, mineral carbonation, mineral/collagen matrix ratio, collagen quality ratio, and proline hydroxylation. HPLC results showed significant increase in the formation of pentosidine and decrease in the formation of the enzymatic cross-link deoxy-pryridinoline within osteolytic bone compared to mixed bone. Raman results showed decreased crystallinity, increased carbonation, and collagen quality (aka 1660/1690 sub-band) ratio with osteolytic bone compared to mixed bone and healthy controls along with an observed increase in proline hydroxylation with metastatic involvement. The mineral/matrix ratio decreased in both osteolytic and mixed bone compared to healthy controls. Quantifying modifications within the intrinsic characteristics of bone tissue will provide a foundation to assess the impact of current therapies on the material behavior of bone tissue in the metastatic spine and highlight targets for the development of new therapeutics and approaches for treatment. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:2126-2136, 2016.

Mechanical behavior of metastatic vertebrae are influenced by tissue architecture, mineral content, and organic feature alterations

“…This is further motivated as while studies have shown a negative relationship between pen concentration and bone strength, other works have found a negative, positive, or no relationship between bone stiffness and pen concentration. The observed increase in pen levels and decrease in dpyr levels in the osteolytic vertebral bone seen in previous work may be indicative of diminished vertebral mechanical behavior independent of its compromised architecture.…”

Label-free Raman spectroscopy provides early determination and precise localization of breast cancer-colonized bone alterations

“… 21 , 23 , 25 , 26 The mineral component is often calcium-deficient, and possesses carbonate substitutions with respect to stoichiometric hydroxyapatite. Recent investigations have extended the assessments of bone fragility and metastatic lesions using Raman spectroscopy to include in-depth evaluations of collagen integrity 16 , 18 , 24 along with the contributions of proteoglycans, tissue water, and lipids 17 as well as oxidative damage. 39 …”

“…The degree of bone remodeling was estimated as the carbonate ν 1 /amide I ratio (since the carbonate-to-matrix ratio has been associated with increased risk of fracture), and mineral crystallinity as the reciprocal of full-width at half maximum (FWHM) of phosphate ν 1 peak. 16 , 21 , 23 , 26 …”

“…Label-free vibrational spectroscopy's unique attributes can address these unmet needs as it provides objective biomarkers of bone composition for diagnoses 16 , 18 and may provide patient stratifications for more effective therapy. 17 The exquisite molecular specificity of this approach enables multiplexed biomolecular analyses without necessitating exposure to radiation or addition of exogenous contrast agents.…”

“… 22 – 24 Important insights can also be gained from the emerging evidence on Raman spectral changes in metastatic bone primed by prostate and breast cancer. 16 , 25 , 26 …”