Affecting osteoblastic responses with in vivo engineered potato pectin fragments.

Pectins, complex plant-derived polysaccharides, are novel candidates for biomaterial nanocoatings. Pectic rhamnogalacturonan-I regions (RG-I) can be enzymatically treated to so-called modified hairy regions (MHR). We surveyed the growth and differentiation of murine preosteoblastic MC3T3-E1 cells on Petri dishes coated with RG-Is from native or genetically engineered potato tubers. Uncoated tissue culture polystyrene (TCPS) and aminated (AMI) dishes served as controls. MHRPTR_GAL sample was depleted of galactose (9 mol % galactose; 23 mol % arabinose) and MHRPTR_ARA of arabinose (61 mol % galactose; 6 mol % arabinose). Wild-type (modified hairy region from potato pectin (MHRP)_WT) fragment contained default amounts (58 mol % galactose; 13 mol % arabinose) of both sugars. Focal adhesions (FAs) indicating cellular attachment were quantified. Reverse transcriptase polymerase chain reaction (RT-PCR) of alkaline phosphatase and osteocalcin genes indicating osteoblastic differentiation was performed along with staining the produced calcium with tetracycline as an indicator of osteoblastic differentiation. Osteoblasts proliferated on all the samples to some extent. The control surfaces performed better than any of the pectin samples, of which the MHRP_WT seemed to function best. FA length was greater on MHRPTR_GAL than on other pectin samples, otherwise the mutants did not significantly deviate. RT-PCR results indicate that differences between the samples at the gene expression level might be even subtler. However, tetracycline-stained calcium-containing mineral was detected merely only on uncoated TCPS. These results indicate the possibility to affect bone cell growth with in vivo-modified pectin fragments, consecutively providing information on the significance of certain monosaccharides on the biocompatibility of these polysaccharides.

Pectin-coated titanium implants are well-tolerated in vivo.

Multiform coated titanium implants are widely used in orthopedic and dental surgery. In this study, we have investigated the reactivity of pectin-coated titanium samples implanted under the latissimus dorsi-muscle fascia of rats. Samples were coated with two enzyme treated apple pectins; modified hairy regions (MHR-A and MHR-B) that differed in chemical structure. Aminated (AMI) and uncoated titanium (Ti) served as controls. The thicknesses of the peri-implant fibrous tissue capsules formed 1 or 3 weeks after implantation were measured as indicative of possible inflammatory reactions toward the biomaterials. After 1 week, the MHR-B implant was surrounded by a thicker fibrous capsule (42.9 microm) than any of the other sample types: MHR-A (33.2 microm), AMI (32.5 microm), and Ti (32.3 microm), the last one being the only statistically significant difference. After 3 weeks, however, this difference disappeared; the capsule thicknesses around MHR-B and Ti implants had decreased to the values found for AMI and MHR-A. Additionally, the capsule formation represents merely a stromal rather than an inflammatory reaction, as indicated by the absence of activated macrophages or foreign body giant cells in the capsules. These results indicate for the first time the in vivo tolerability of covalently linked pectins, and suggest the feasibility of pectin-coated bone and dental implants for clinical use.

Effect of modified pectin molecules on the growth of bone cells.

The aim of this study was to investigate molecular candidates for bone implant nanocoatings, which could improve biocompatibility of implant materials. Primary rat bone cells and murine preosteoblastic MC3T3-E1 cells were cultured on enzymatically modified hairy regions (MHR-A and MHR-B) of apple pectins. MHRs were covalently attached to tissue culture polystyrene (TCPS) or glass. Uncoated substrata or bone slices were used as controls. Cell attachment, proliferation, and differentiation were investigated with fluorescence and confocal microscopy. Bone cells seem to prefer MHR-B coating to MHR-A coating. On MHR-A samples, the overall numbers as well as proportions of active osteoclasts were diminished compared to those on MHR-B, TCPS, or bone. Focal adhesions indicating attachment of the osteoblastic cells were detected on MHR-B and uncoated controls but not on MHR-A. These results demonstrate the possibility to modify surfaces with pectin nanocoatings.