Anatomy and age estimation of an early blue whale (Balaenoptera musculus) fetus.

The external anatomy of a 130-mm blue whale fetus (Balaenoptera musculus) is described, and its internal anatomy is reconstructed noninvasively from microCT scans. The specimen lies developmentally at the junction of the embryonic and fetal periods. Similarly to the embryos of many odontocetes, it lacks a caudal fluke and dorsal fin, but it also exhibits an elongated rostrum, resorbed umbilical hernia, partially exposed cornea, and spatial separation of the anus and genitalia seen in early odontocete fetuses. Dermal ossification of the cranial bones has begun, but the endochondral skeleton is completely cartilaginous. The shape and position of the maxilla suggest that the earliest stages of anterior skull telescoping have begun, but there is no indication of occipital overlap posteriorly. The nasopharynx, larynx, and heart already display the distinctive morphology characteristic of Balaenoptera. This study develops a model of body length changes during blue whale development by integrating the large International Whaling Statistics (IWS) database, historical observations of blue whale migration and reproduction, and descriptions of fetal growth trends in other mammals. The model predicts an age of 65 days postconception for the specimen. The early developmental milestones of Balaenoptera mirror those of the odontocete Stenella to a remarkable extent, but the first appearance of the caudal fluke and dorsal fin are delayed relative to other morphological transitions. The accelerated prenatal growth characteristic of Balaenoptera occurs during fetal, not embryonic, development.

Human umbilical cord perivascular cells (HUCPVC): A mesenchymal cell source for dermal wound healing.

Human bone marrow mesenchymal stem cells (hBM-MSC) have recently been employed in the clinical treatment of challenging skin defects. We have described an MSC population that can be easily harvested from human umbilical cord perivascular tissue, human umbilical cord perivascular cells (HUCPVC), which exhibit a higher proliferative rate and frequency than hBM-MSC. Our objective was to establish whether HUCPVC could promote healing of full thickness murine skin defects, and thus find utility as a cell source for dermal repair. To this end, bilateral full thickness defects were created on the dorsum of Balb/c nude mice. Fibrin was used as a delivery vehicle for 1 x 106 PKH-67 labeled HUCPVC with contralateral controls receiving fibrin only. Epifluorescent and brightfield microscopic evaluation of the wound site was carried out at 3 and 7 days while mechanical testing of wounds was carried out at 3, 7, and 10 days. Our results show that by 3 days, marked contraction of the wound was observed in the fibrin controls whilst the HUCPVC samples exhibited neither collapse nor contraction of the defect, and the dermal repair tissue was considerably thicker and more organized. By 7 days, complete re-epithelialization of the HUCPVC wounds was observed whilst in the controls re-epithelialization was limited to the wound margins. Wound strength was significantly increased in the HUCPVC treatment group by 3 and 7 days but no statistical difference was seen at 10 days. We conclude that HUCPVCs accelerate early wound healing in full thickness skin defects and thus represent a putative source of human MSCs for use in dermal tissue engineering.

Human umbilical cord perivascular (HUCPV) cells: a source of mesenchymal progenitors.

We describe the isolation of a nonhematopoietic (CD45-, CD34-, SH2+, SH3+, Thy-1+, CD44+) human umbilical cord perivascular (HUCPV) cell population. Each HUCPV cell harvest (2-5 x 10(6), depending on the length of cord available) gave rise to a morphologically homogeneous fibroblastic cell population, which expressed alpha-actin, desmin, vimentin, and 3G5 (a pericyte marker) in culture. We determined the colony-forming unit-fibro-blast (CFU-F) frequency of primary HUCPV cells to be 1:333 and the doubling time, which was 60 hours at passage 0 (P0), decreased to 20 hours at P2. This resulted in a significant cell expansion, producing over 10(10) HUCPV cells within 30 days of culture. Furthermore, HUCPV cells cultured in nonosteogenic conditions contained a subpopulation that exhibited a functional osteogenic phenotype and elaborated bone nodules. The frequency of this CFU-osteogenic subpopulation at P1 was 2.6/10(5) CFU-F, which increased to 7.5/10(5) CFU-F at P2. Addition of osteogenic supplements to the culture medium resulted in these frequencies increasing to 1.2/10(4) and 1.3/10(4) CFU-F, respectively, for P1 and P2. CFU-O were not seen at P0 in either osteogenic or non-osteogenic culture conditions, but P0 HUCPV cells did contain a 20% subpopulation that presented neither class I nor class II cell-surface major histocompatibility complexes (MHC-/-). This population increased to 95% following passage and cryopreservation (P5). We conclude that, due to their rapid doubling time, high frequencies of CFU-F and CFU-O, and high MHC-/- phenotype, HUCPV cells represent a significant source of cells for allogeneic mesenchymal cell-based therapies.

Bone marrow genesis after subcutaneous delivery of rat osteogenic cell-seeded biodegradable scaffolds into nude mice.

This study describes the generation of an active hematopoietic marrow within the confines of a biodegradable, macroporous polyester scaffold, seeded with rat osteogenic cells, after subcutaneous implantation in nude mice. A macroporous, poly(DL-lactide-co-glycolide) polymer scaffold, into which resorbable calcium phosphate particles were incorporated, was seeded with rat bone marrow-derived cells. Scanning electron microscopy of the cell-seeded scaffold demonstrated confluent cell colonization. Scaffolds seeded with cells were implanted under the dorsum of immunocompromised mice for 5 weeks. Histological analysis revealed bone formation along the scaffold pores creating bony cavities within which a host-derived, hematopoietic marrow was observed which included hematopoietic precursors, megakaryocytes, fat cells, and numerous marrow sinusoids. In those areas where bone was not elaborated on the scaffold surface, no marrow genesis was observed and the scaffold interstices were filled with fibrous tissue. These results demonstrate the utility of this biodegradable scaffold in delivery of a phenotypically functional cell population for bone tissue and bone marrow engineering applications. Moreover, the recapitulation of hematopoietic marrow tissue within the engineered bony cavities also provides a new experimental environment with which to further investigate the interactions of hematopoietic and nonhematopoietic compartments of the marrow microenvironment.

Collagen-hydroxyapatite composite prepared by biomimetic process.

A novel bone graft substitute comprising a porous, collagenous scaffold was biomimetically coated with hydroxyapatite using a simulated body fluid solution chemistry method. The scaffold had a porosity of approximately 85%, with pore sizes between 30 microm and 100 microm. Glutaraldehyde vapor was used to stabilize the collagenous scaffold, giving a significantly increased thermal stability over an unstabilized scaffold, as shown by differential scanning calorimetry. A thin layer (<10 microm) of crystalline hydroxyapatite was deposited onto the stabilized collagenous scaffold by soaking the collagenous construct in simulated body fluid in the presence of calcium silicate glass. The presence of crystalline hydroxyapatite was confirmed by X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy. In vitro cytotoxicity testing of the composite construct using L-929 fibroblasts (ISO 10993-5) and rabbit periosteal cells revealed a cytocompatible material that supported cellular attachment and proliferation.