Transforming growth factor‐beta 3(Tgf‐β3) in a collagen gel delays fusion of the rat posterior interfrontal suture in vivo

Abstract

Postnatal expansion of the intramembranous bones of the craniofacial skeleton occurs as bone growth at sutures. Loss of the bone growth site occurs when the suture fails to form, or when the newly formed sutures become ossified, resulting in premature obliteration. Previous experiments demonstrated that removal of dura mater from fetal rat coronal sutures, or neutralizing transforming growth factor-beta 2 (Tgf-␤2) activity using antibodies resulted in premature obliteration of the suture in vitro. Conversely, addition of Tgf-␤3 to coronal sutures in vitro rescued them from osseous obliteration. To examine whether Tgf-␤3 rescues sutures from obliteration in vivo, a collagen gel was used as a vehicle to deliver Tgf-␤3 to the normally fusing rat posterior interfrontal (IF) suture. Surgery was done on postnatal day 9 (P9) rats, in which collagen gels containing 0, 3, or 30 ng Tgf-␤3 were placed above the IF suture, underneath the periosteum for 2 weeks. By P24, 75-100% of animals in control unoperated, sham-operated, and collagen gel-only groups had fused IF sutures. In contrast, 40% of sutures exposed to 3 ng Tgf-␤3 remained open, while sutures exposed to 30 ng Tgf-␤ were similar to controls. By immunohistochemistry, sutures rescued from obliteration by Tgf-␤3 had the same Tgf-␤ receptor type II (T␤r-II) distribution as controls. However, Tgf-␤3-treated sutures had altered Tgf-␤2 and T␤r-I distribution compared to controls. Anat Rec 267: 120 -130, 2002.

Changes in Biomechanical Strain and Morphology of Rat Calvarial Sutures and Bone After Tgf‐β3 Inhibition of Posterior Interfrontal Suture Fusion

“…All other cranial sutures remained patent. Previous research showed that Tgf‐β3 delayed IFS closure in rats, at least until P24 (Opperman et al, 2002), and that Tgf‐β3‐treatment of a rabbit model of delayed onset suture fusion, allowed continued bone growth up to 84 days (Chong et al, 2003). This study showed a complex but patent IFS morphology in Tgf‐β3 treated rat IFS by P70, indicating that Tgf‐β3 treatment not only delays but also inhibits normal IFS fusion for extended periods of time, possibly by preventing the loss of the suture mesenchyme as described by Holmes et al (2009).…”

“…The first author conducted all surgeries, using methods reported previously (Opperman et al, 2002). Nine days after birth (P9), rat pups were anesthetized using 3.25% isofluorane (Butler, Dallas, TX) and 900 cc/min O 2 inhalant anesthetic delivered by a Foregger F500 anesthesia system via a nose cone.…”

“…Tgf‐β2 added to fetal rat calvariae in culture induced the normally patent coronal sutures to fuse, while Tgf‐β3 rescued these sutures from fusion. Furthermore, IFS obliteration was delayed in the short term by Tgf‐β3 in vivo (Opperman et al, 2002; Chong et al, 2003). It is possible that Tgf‐β3 prevented the loss of the suture mesenchyme as described in cases of craniosynostosis by Holmes et al (2009).…”

Nasal capsular cartilage is required for rat transpalatal suture morphogenesis

“…Evidence that they do play a role in developing sutures is provided by experiments where obliteration of coronal sutures was induced when calvaria were cultured in the presence of neutralizing antibodies to Tgf‐β3 (Opperman et al, 1998) or in the presence of Tgf‐β2 (Opperman et al, 2000). In addition, sutures can be rescued from obliteration with Tgf‐β3, both in vitro (Opperman et al, 2000) and in vivo (Chong et al, 2003; Opperman et al, 2002).…”

“…A variety of growth factors have also been identified that regulate cranial suture morphogenesis. To date, in vitro experiments have identified Bmp2, Bmp4, Fgf2, Fgf4, Tgf‐β2, and Tgf‐β3 (Jabs et al, 1993; Roth et al, 1997; Kim et al, 1998; Opperman et al, 1999, 2000; Moursi et al, 2002; Ignelzi et al, 2003), and in vivo experiments have identified Fgf2, Tgf‐β2, and Tgf‐β3 (Chong et al, 2003; Opperman et al, 2002).…”