Date of Completion

Spring 5-1-2025

Thesis Advisor(s)

Archana Sanjay; J. Peter Gogarten

Honors Major

Molecular and Cell Biology

Disciplines

Medical Pathology

Abstract

Bones function as living organs through their mineralized matrix and specialized cell populations, which provide structural support and enable movement, while storing minerals and creating a space for blood cell production in the marrow1. As individuals age, hormonal changes reduce osteoblast activity while osteoclast-mediated bone resorption persists, resulting in lower mineral density and heightened fracture risk2. We examined how aging impacts young and old murine femurs because these models display bone structure and cellular organization that closely resemble human long bones. This research study used six distinct histological stains to observe essential features of bone tissue3. The Safranin-O/Fast Green staining shows the cartilage matrix produced by chondrocytes as red/orange and the bone matrix produced by osteoblasts as green/blue-green, which allows the visualization of the growth plate and newly formed bone surfaces4. The Toluidine Blue stain reveals sulfated glycosaminoglycans in cartilage and connective tissues, helping identify chondrocyte distribution5. Von Kossa’s silver-nitrate–based technique highlights mineralized areas, staining calcium deposits black or brown to show the extent of calcification in both young and old samples6. The Osterix stain identifies cells expressing a transcription factor responsible for osteoblast differentiation and bone formation7. Alkaline phosphatase staining serves as a marker of early osteoblast activity and mineralization potential8. The SOX9 stain marks chondroprogenitor and chondrocyte lineage cells, indicating the activity and spatial localization of cartilage-forming cells9. These methods together illustrate the progressive decline in bone matrix production and mineralization in aged murine samples.

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