Aberrant Collagen Fibril Morphology in Periodontal Ligament of SPARC-null mice

OBJECTIVE: To determine whether the absence of SPARC expression in mice affects collagen fibril morphology in the periodontal ligament (PDL).

METHODS: Heads from age-matched wild-type (WT) and SPARC-null mice at 1m, 3m, 6m, and >18m of age were fixed, decalcified, embedded in paraffin, and sectioned. At least 3 mice per genotype at each time point contributed to the evaluation. Haemotoxylin and eosin were to evaluate cellular structures and picrosirius red was used to stain collagen fibrils in each section. Images captured under polarized light were used to evaluate the birefringence of collagen fibrils in the PDL of each section stained with picrosirius red.

RESULTS: Significant differences in collagen fibril morphology were evident in SPARC-null PDL at each age examined in comparison to WT mice. The collagen fibrils were more disorganized and appeared smaller and more immature in the absence of SPARC expression. In addition, cellular organization within and bordering the PDL in SPARC-null mice was compromised. Aberrations in PDL structure became more significant with increasing age.

CONCLUSIONS: We conclude that SPARC plays an essential role in collagen fibril organization in the PDL.

Support from NIDCR South Carolina COBRE for oral health: P20 2P20RR017696-06 and a Veteran's Administration Research Career Development Award (VISN7).