Pathophysiological characteristics and gene transcriptional profiling of bone microstructure in a low calcium diet fed laying hens

• Published in: Poultry science 2019-10, Vol.98 (10), p.4359-4368
• Main Authors: Jiang, S, Wu, X.L., Jin, M.L., Wang, X.Z., Tang, Q, Sun, Y.X., Cheng, H.W.
• Format: Article
• Language: English
• Subjects: Animals; Bone and Bones - physiopathology; bone remodeling; Bone Remodeling - genetics; Calcification, Physiologic - genetics; Calcium, Dietary - metabolism; Chickens - genetics; Chickens - physiology; Female; Femur - physiology; hen; low calcium diet; Random Allocation; skeletal damage; Tibia - physiology; Transcription, Genetic - physiology; transcriptional profiling
• ISSN: 0032-5791; 1525-3171
• DOI: 10.3382/ps/pez271

Calcium depletion is a valuable non-invasive tool for studying skeletal system disorders. A low calcium diet (LCD) was used to examine the pathophysiological characteristics and molecular mechanisms of osteoporotic damage in caged laying hens. Sixty 64-wk-old laying hens were randomly housed in single-bird cages, and the cages were divided into 2 treatments: fed a regular calcium diet (RCD, 3.69%) or a LCD (1.56%) for 8 wk. The diet-induced changes of serum bone remodeling indicators, bone strength, microstructure of the distal femur, and the gene expression profiling of keel bone were measured. Compared to RCD hens, LCD hens had higher activity of serum alkaline phosphatase and tartrate resistant acid phosphatase but lower serum calcium concentrations with reduced tibial and femoral mass, width, and strength (P < 0.05). In addition, LCD hens had greater densities of osteoclasts, osteoblasts, connective tissue cells, and osteoid in the trabecular bone (P < 0.05). The transcriptome analysis revealed that 563 unigenes were differentially expressed in keel bone between LCD and RCD hens. The Kyoto Encyclopedia of Genes and Genomes pathway analyses revealed that these differentially expressed genes were mainly associated with the osteoporosis-related signaling pathways involved in the biological functions of the bone cellular and extracellular structural modulations. The real-time PCR analysis further confirmed that the LCD enhanced the mRNA expression of collagen type 1 alpha 2, integrin-binding sialoprotein and periostin, but inhibited sclerostin expression. These findings indicate that LCD hens have a higher bone turnover and micro-architectural damage compared to RCD hens. The results further evidence dietary supplement of calcium is a critical nutrient strategy for improving hen skeletal health.