Mucopolysaccharidase activity during human deciduous root resorption

Comparative analysis of secretory factors from permanent- and deciduous-teeth periodontal ligament cells

OBJECTIVE

Studies of regenerative therapies have focused on the paracrine effects of mesenchymal stem cells, but little has been revealed about the humoral factors of periodontal ligament (PDL) stem cells. The aim of this study was to identify and compare the secretory factors of human permanent- and deciduous-teeth PDL cells (P-PDL and D-PDL cells, respectively) in order to understand the characteristics of these cells and their potential applications in regenerative therapies.

DESIGN

Conditioned media were collected from P-PDL and D-PDL cells (P-PDL-CM and D-PDL-CM, respectively). These media were analyzed with high-performance liquid-chromatography-coupled electrospray ionization tandem mass spectrometry and a cytokine membrane assay. In addition, Western blot analysis was performed to verify the differences between the two media.

RESULTS

Cytokines related to neurogenesis (NT-3 and NT-4) and angiogenesis-related cytokines (EGF and IGF-1) were identified in P-PDL-CM. The expression levels of immune-response-related cytokines (interleukins I, II, and IV) and secreted proteins related to tissue degradation and catalytic activities (matrix metallopeptidase 1 (MMP1), Proteasome subunit, alpha type, 1 (PSMA1), and cullin 7 (CUL7)) were higher in D-PDL-CM. Vasorin (VASN) was expressed more strongly in P-PDL-CM, but tudor domain containing 7 (TDRD7) was expressed more strongly in D-PDL-CM in Western blot analysis.

CONCLUSION

The cytokine expressions of the two cell types showed different patterns, especially in neurogenesis and immune responses. P-PDL cells are more suitable candidates for applications in regenerative therapies.

Comparative gene expression analysis of the human periodontal ligament in deciduous and permanent teeth

There are histological and functional differences between human deciduous and permanent periodontal ligament (PDL) tissues. The aim of this study was to determine the differences between these two types of tissue at the molecular level by comparing their gene expression patterns. PDL samples were obtained from permanent premolars (n = 38) and anterior deciduous teeth (n = 31) extracted from 40 healthy persons. Comparative cDNA microarray analysis revealed several differences in gene expression between the deciduous and permanent PDL tissues. These findings were verified by qRT-PCR (quantitative reverse-transcription-polymerase chain reaction) analysis, and the areas where genes are expressed were revealed by immunohistochemical staining. The expressions of 21 genes were up-regulated in deciduous relative to PDL tissues, and those of 30 genes were up-regulated in permanent relative to deciduous PDL tissues. The genes that were up-regulated in deciduous PDL tissues were those involved in the formation of the extracellular matrix (LAMC2, LAMB3, and COMP), tissue development (IGF2BP, MAB21L2, and PAX3), and inflammatory or immune reactions leading to tissue degradation (IL1A, CCL21, and CCL18). The up-regulated genes in permanent PDL tissues were related to tissue degradation (IL6 and ADAMTS18), myocontraction (PDE3B, CASQ2, and MYH10), and neurological responses (FOS, NCAM2, SYT1, SLC22A3, DOCK3, LRRTM1, LRRTM3, PRSS12, and ARPP21). The analysis of differential gene expressions between deciduous and permanent PDL tissues aids our understanding of histological and functional differences between them at the molecular level.

Developmental growth and degeneration of pulpal axons in feline primary incisors

The life history of pulpal axons in primary mandibular incisors was examined by light and electron microscopy in 56 kittens aged from 25 days postconception to 120 days after birth. Cells resembling Schwann cells preceded the first arrival of pulpal axons, 1 week postnatally. myelination was initiated during the second week. Two months after birth the incisors were fully grown and each pulp contained about 100 axons. Between 10 and 20% of these were myelinated and ranged in size from 1 to 5 micrometer. The relation between number of myelin lamellae and axon size appeared nonlinear and differed markedly from that in similarly sized inferior alveolar nerve axons. During the third month many unmyelinated axons showed signs of degeneration. With progress of root resorption an increasing proportion of both unmyelinated and myelinated axons degenerated. In highly resorbed incisors necrotic Schwann cells were associated with degenerating axons and there was a generalized pulpal tissue reaction. In some teeth with advanced root resorption pulpal axons were lacking. A progressive derangement of all pulpal tissue elements continued until shedding during the second half of the fourth month. In incisor nerve branches below the incisor teeth axon degeneration was very limited.

Dental pulp mucopolysaccharidase: identification and role in tooth resorption

The presence of mucopolysaccharidase activity within the pulps of resorbing deciduous teeth was investigated using histochemical techniques. The loss of toluidine blue metachromasia within glycosaminoglycan film subtrates indicated the presence of enzyme activity. This was related to physiologic resorption.

Mucopolysaccharidase activity and glycosaminoglycan content in traumatized resorbing deciduous teeth

The periodontal ligaments from traumatized deciduous teeth, while undergoing rapid resorption, were analyzed biochemically for mucopolysaccharidase activity and for total glycosaminoglycan content of dentin and cementum. Enzyme activity was present only in resorbing teeth. A concomitant 65 percent decrease in glycosaminoglycans from these teeth occurred as well.

Mucopolysaccharidase activity in traumatized human deciduous teeth undergoing accelerated resorption: isolation and characterization

Mucopolysaccharidase activity was observed in traumatized human decidous teeth. Histochemical analysis of the periodontal ligaments from these teeth revealed a loss of film substrate metachromasia during incubation, indicating enzyme activity. Routine histology of these ligaments showed the presence of an inflammatory infiltrate throughout this tissue. Biochemical analysis of the ligaments revealed a 10-fold increase of enzyme activity when incubation time was increased from 1 to 8 h. When compared to the enzyme activity measured during physiologic resorption, activity was increased. This suggests that the presence of an inflammatory infiltrate not observed in the tissues undergoing physiologic resorption may be responsible for the rapid resorption seen in traumatized deciduous teeth.