Location
Philadelphia, PA
Start Date
17-4-2026 1:30 PM
End Date
17-4-2026 2:30 PM
Description
Introduction: Longitudinal bone growth occurs at specialized cartilaginous structures called growth plates. It is composed of spatially organized reserve, columnar and hypertrophic zones, that coordinate cartilage proliferation, differentiation and subsequent replacement by bone. The growth plate is surrounded by the perichondrium that regulates chondrocyte proliferation and differentiation.
The metatarsal (MT) bones form a single growth plate, located proximally in digit 1 and distally in digits 2–5. Previously, we used RNA sequencing of the MT1 and MT3 to compare growth plate forming and non-forming ends to identify differentially expressed genes (DEGs) associated with growth plate formation. DEGs shared between MT1 and MT3 were analyzed at postnatal days (P) 0, P4, and P9, revealing two genes consistently associated with the growth plate across MTs and ages: Tenascin-N (Tnn) and Paired Box 1 (Pax1).
Tnn and Pax1 are genes implicated in diverse developmental and regulatory pathways that govern tissue differentiation and structural organization. Pax1 is a paired-box transcription factor expressed in the sclerotome and developing skeletal mesenchyme, where it contributes to vertebral column formation and skeletal patterning. Tnn encodes Tenascin-N, an extracellular matrix glycoprotein produced by mesenchymal cells that contains EGF-like and fibronectin type III domains that mediate cell matrix signaling. It is expressed in developing bone and periosteum, where it modulates osteoblast adhesion and stimulates integrin-dependent cell migration.
Objective: To further define the role of Pax1 and Tnn during bone formation, we perform in situ hybridization to compare their spatial expression patterns in the growth plate forming and non-forming ends of neonatal mouse MTs.
Methods: Histological specimens consisted of hind limbs collected at P0, P4, and P9 from FVB/NJ mice. Samples were prepared using fixation in an RNase-free preparation of 4% paraformaldehyde and, decalcified in an RNase-free preparation of Morse’s solution (22.5% formic acid and 10% sodium citrate) for 24 hours. They were then embedded in paraffin following standard procedures. We performed in situ hybridization (ISH) on paraffin-embedded sections using RNAscope™ 2.5 HD Assay-RED (ACD Bio) for Pax1 and Tnn following RNAscope™ standard protocol, except replacing standard antigen retrieval processes with the use of an RNAscope™ proprietary antigen retrieval enzyme for bone and cartilage tissue.
Results: Tnn is strongly expressed in the perichondrium and periosteum along the length of all MTs at all three time points. The signal was particularly intense in the bone collar, a ring of perichondrium that surrounds the columnar zone of the growth plate, particularly at the later time points. This expression pattern matches the RNA-seq data which detected an increase in Tnn expression between the MT ends from P0 to P9. Pax1 expression was not consistently detected by RNAscope, likely reflecting low transcript levels consistent with RNA sequencing data.
Conclusion: Tnn expression is highly localized to the perichondrium and periosteum during bone development. Its intensity of expression corresponds with a region known to regulate gene interactions between the bone collar and the growth plate suggesting a potential role in growth plate biology and early bone formation.
Embargo Period
6-3-2027
Tnn expression is associated with growth plate formation in the metatarsal
Philadelphia, PA
Introduction: Longitudinal bone growth occurs at specialized cartilaginous structures called growth plates. It is composed of spatially organized reserve, columnar and hypertrophic zones, that coordinate cartilage proliferation, differentiation and subsequent replacement by bone. The growth plate is surrounded by the perichondrium that regulates chondrocyte proliferation and differentiation.
The metatarsal (MT) bones form a single growth plate, located proximally in digit 1 and distally in digits 2–5. Previously, we used RNA sequencing of the MT1 and MT3 to compare growth plate forming and non-forming ends to identify differentially expressed genes (DEGs) associated with growth plate formation. DEGs shared between MT1 and MT3 were analyzed at postnatal days (P) 0, P4, and P9, revealing two genes consistently associated with the growth plate across MTs and ages: Tenascin-N (Tnn) and Paired Box 1 (Pax1).
Tnn and Pax1 are genes implicated in diverse developmental and regulatory pathways that govern tissue differentiation and structural organization. Pax1 is a paired-box transcription factor expressed in the sclerotome and developing skeletal mesenchyme, where it contributes to vertebral column formation and skeletal patterning. Tnn encodes Tenascin-N, an extracellular matrix glycoprotein produced by mesenchymal cells that contains EGF-like and fibronectin type III domains that mediate cell matrix signaling. It is expressed in developing bone and periosteum, where it modulates osteoblast adhesion and stimulates integrin-dependent cell migration.
Objective: To further define the role of Pax1 and Tnn during bone formation, we perform in situ hybridization to compare their spatial expression patterns in the growth plate forming and non-forming ends of neonatal mouse MTs.
Methods: Histological specimens consisted of hind limbs collected at P0, P4, and P9 from FVB/NJ mice. Samples were prepared using fixation in an RNase-free preparation of 4% paraformaldehyde and, decalcified in an RNase-free preparation of Morse’s solution (22.5% formic acid and 10% sodium citrate) for 24 hours. They were then embedded in paraffin following standard procedures. We performed in situ hybridization (ISH) on paraffin-embedded sections using RNAscope™ 2.5 HD Assay-RED (ACD Bio) for Pax1 and Tnn following RNAscope™ standard protocol, except replacing standard antigen retrieval processes with the use of an RNAscope™ proprietary antigen retrieval enzyme for bone and cartilage tissue.
Results: Tnn is strongly expressed in the perichondrium and periosteum along the length of all MTs at all three time points. The signal was particularly intense in the bone collar, a ring of perichondrium that surrounds the columnar zone of the growth plate, particularly at the later time points. This expression pattern matches the RNA-seq data which detected an increase in Tnn expression between the MT ends from P0 to P9. Pax1 expression was not consistently detected by RNAscope, likely reflecting low transcript levels consistent with RNA sequencing data.
Conclusion: Tnn expression is highly localized to the perichondrium and periosteum during bone development. Its intensity of expression corresponds with a region known to regulate gene interactions between the bone collar and the growth plate suggesting a potential role in growth plate biology and early bone formation.