ABS 084: Characterization and Analysis of Osseous Changes in Murine Jaws Induced by Chronic Metabolic Acidosis

Emily Shadron (1), Laura Doherty (2), Mikayla Moody (2), Alix C. Deymier (2)|

¹ Dept. of Biology, Tufts University, Medford, MA, USA
² Dept. of Biomedical Engineering, UConn Health Center, Farmington, CT, USA

Van Wickle (2025) Volume 1, ABS 084

Introduction: Chronic metabolic acidosis (MA), defined by sustained reductions in systemic pH, frequently accompanies chronic kidney disease (CKD), affecting a significant proportion of patients with moderate to late-stage CKD. This acidic state disrupts physiological processes, particularly skeletal homeostasis, where bones serve as a major buffering system to neutralize pH disruptions. Resulting consequences include decreased bone mineral density, altered ion homeostasis, and increased fracture risk. While these impacts are well-characterized in long bones, fewer studies have evaluated craniofacial bone responses—especially those formed by intramembranous ossification, such as the maxilla, and hybrid bones like the mandible. These bones are developmentally and functionally distinct, highly vascularized, and critical for feeding and speech. Because pH disruption alters osteoblast and osteoclast activity, and thereby bone remodeling, understanding craniofacial responses to acidosis is essential for translational applications in dental and craniofacial health. Moreover, given documented sexual dimorphism in skeletal biology, the influence of sex on acidosis-mediated bone alterations remains a critical gap. This study investigates the compositional and structural changes in murine mandibles and maxillae under experimentally induced MA to identify the time-dependent, sex-dependent, and bone-specific effects of acidotic conditions. By combining Raman spectroscopy and micro-computed tomography (µCT), we evaluate the effects of MA over 7- and 14-day intervals on mineral content, crystallinity, and bone structure, providing insight into how metabolic stress differentially impacts craniofacial bone integrity.

Methods: To model chronic MA, CD-1 mice (3–5 months, n=32) were administered increasing concentrations of NH₄Cl in drinking water over 7 or 14 days. Following euthanasia, mandibles and maxillae were dissected and preserved in ethanol. MicroCT imaging at 8μm resolution was used to quantify bone structure in defined regions of interest. Raman spectroscopy was conducted at five cortical regions per bone to measure compositional parameters including mineral:matrix ratio, crystallinity, and carbonate content. Differences by treatment, time point, sex, and bone type were statistically analyzed using two-way ANOVA with a significance threshold of p<0.05.

Results: Raman spectroscopy revealed that acidotic male maxillae exhibited decreased mineral:matrix ratio and increased crystallinity over 14 days, a trend not mirrored in mandibles. Female maxillae also showed significant reductions in mineral content and total protein, as well as increased carbonate substitution. Structural µCT analysis supported compositional changes, with acidotic groups showing reduced bone volume and trabecular thickness. Notably, compositional differences were more pronounced in the maxillae than the mandibles, and in males compared to females.

Discussion: This study demonstrates that chronic metabolic acidosis induces significant compositional changes in craniofacial bone, particularly in the maxilla, with sex-dependent variation in response magnitude. The increased crystallinity and decreased mineralization in acidotic male maxillae suggest impaired remodeling and altered mechanical properties. These findings underline the need to consider developmental bone origin and sex in evaluating acidosis-induced skeletal effects. By focusing on craniofacial structures, this research enhances our understanding of how systemic pH disruptions impact oral and maxillofacial health, with implications for improving clinical interventions in CKD and acid-base disorders.