Preparation and In Vitro Behavior of a Poly(lactic acid)-Fiber/Hydroxyapatite Composite Sheet

This paper describes the processing and in vitro behavior of a poly(lactic acid) (PLA)-fiber/hydroxyapatite (HA) composite sheet consisting of a knitted PLA-fiber sheet and HA powder for bone tissue engineering. Type I collagen was used as a binding agent to combine the PLA fibers and the HA powder. Precipitate formation in Hanks' balanced salt (HBS) solution was monitored to evaluate the in vitro apatite formation ability of the PLA-fiber/HA composite sheet. Precipitate formation was observed on the surface of the PLA-fiber/HA composite sheet after immersion in HBS solution for only 1 day, while no precipitate formation was observed on the PLA-fiber sheet without HA as a control. In conclusion, a PLA-fiber/HA composite sheet for use as a scaffold was successfully prepared. Within the limitations of this investigation, we confirmed that the PLA-fiber/HA composite sheet has a high apatite formation activity compared with the PLA-fiber sheet and represents a promising material for use as a scaffold

Novel cryptic exons identified in introns 2 and 3 of the human dystrophin gene with duplication of exons 8-11

The dystrophin gene, which is mutated in Duchenne muscular dystrophy, is thelargest known human gene and characterized by the huge size of its introns. Intron 2has been shown to include cryptic exons termed exons 2a and 2b, while intron 3 hasbeen shown to include a cryptic exon designated exon 3a. In the present study, weidentified 2 and 1 additional cryptic exons in introns 2 and 3, respectively. A previouslyunknown 157-bp insertion was identified between exons 2 and 3 of a dystrophin mRNAisolated from the lymphocytes of a dystrophinopathy patient with duplication of exons8-11. Since this sequence exhibited the typical characteristics of a genomic exon, wedesignated it 'exon 2c-l'. A more detailed examination revealed that a position 4 bpdownstream from the 5' end of exon 2c-l was also used as a splice acceptor site, and thisexon was designated 'exon 2c-s'. In the same patient, a 357-bp insertion was identifiedbetween exons 3 and 4. Since this sequence also showed the typical characteristics of anexon, and its 3' end was the same as the splice donor site of exon 3a, we designated thenovel cryptic exon 'exon 3a-l', and changed the name of the previously reported exon3a to 'exon 3a-s'. Among these novel cryptic exons, exon 3a-l was also incorporatedinto the dystrophin mRNA from normal lymphocytes, whereas exons 2c-l and 2c-s werenot. The physiological or pathophysiological roles of these novel cryptic exons remainto be clarified