A new biometric: In utero growth curves for metacarpal and phalangeal lengths reveal an embryonic patterning ratio.

OBJECTIVES: The objectives of this study are to develop gestational age-specific growth curves for fetal third metacarpal and phalangeal lengths and to determine if fetal hand proportion is established in utero. METHODS: This prospective cross-sectional study used 2D ultrasound across gestational ages 12 to 39 weeks to evaluate the third fetal metacarpal and phalangeal measurements. Gestational age-specific reference growth curves were developed. Associations between continuous variables were assessed using Spearman correlations (rs ) and restricted cubic splines. A nonlinear biologic regression model was used to predict metacarpal and phalangeal lengths as a function of gestational age. Measurements derived from five cases of thanatophoric dysplasia were used to determine if brachydactyly could be objectified. RESULTS: Fetal metacarpal and phalangeal lengths are highly correlated across gestational age (rs  = 0.96, P < 0.001). The mean fetal metacarpal to phalangeal ratio is constant from gestational age 15 to 39 weeks (rs  = -0.07, P = 0.49). Third-digit metacarpal and phalangeal lengths in thanatophoric dysplasia showed brachydactyly in all cases (5/5), and none of the cases (0/5) demonstrated a normal metacarpal to phalangeal ratio of 0.49. CONCLUSION: We present gestational age-specific reference growth curves for fetal third metacarpal and phalangeal lengths, which may be used to detect brachydactyly. We demonstrate a prenatal metacarpal to phalangeal ratio of 1:2.

The missing segment of the autopod 1st ray: new insights from a morphometric study of the human hand.

Whether the 1st segment of the human autopod 1st ray is a 'true' metapodial with loss of the proximal or mid phalanx or the original basal phalanx with loss of the metacarpal has been a long-lasting discussion. The actual knowledge of the developmental pattern of upper autopod segments at a fetal age of 20-22 weeks, combined with X-ray morphometry of normal long bones of the hand in the growing ages, was used for analysis of the parameters, percentage length, position of epiphyseal ossification centers and proximal/distal growth rate. The symmetric growth pattern in the fetal anlagen changed to unidirectional in the postnatal development in relation to epiphyseal ossification formation. The percentage length assessment, the distribution of the epiphyseal ossification centers, and differential proximal/distal growth rate among the growing hand segments supported homology of most proximal segment of the thumb with the 2nd-5th proximal phalanges and that of the proximal phalanx of the thumb with the 2nd-5th mid phalanges in the same hand. Published case reports of either metanalysis of 'triphalangeal thumb' and 'proximal/distal epiphyseal ossification centers' were used to support the applied morphometric methodology; in particular, the latter did not give evidence of growth pattern inversion of the proximal segment of the thumb. The presented data support the hypothesis that during evolution, the lost segment of the autopod 1st ray is the metacarpal.

Growth and shaping of metacarpal and carpal cartilage anlagen: application of morphometry to the development of short and long bone. A study of human hand anlagen in the fetal period.

A histological and morphometric analysis of human metacarpal and carpal anlagen between the 16th and 22nd embryonic weeks was carried out with the aim of studying the establishment of the respective anlage architecture. No differences in the pattern of growth were documented between the peripheral and central zones of the metacarpal epiphyses and those of the carpals. The regulation of longitudinal growth in long bone anlagen occurred in the transition zone between the epiphysis and the diaphysis (homologous to the metaphyseal growth plate cartilage in more advanced developmental stage of the bone). Comparative zonal analysis was conducted to assess the chondrocyte density, the mean chondrocyte lacunar area, the paired chondrocyte polarity in the orthogonal longitudinal and transverse planes, and the lacunar shape transformation in the metacarpal. In transition from epiphysis to diaphysis chondrocyte density decreased and mean lacunar area increased. No significant differences in the chondrocyte maturation cycle were observed between proximal/distal metacarpal epiphyses and the carpal anlagen. The number of paired chondrocyte oriented along the growth vector was significantly higher in both proximal/distal transition zones between epiphysis and diaphysis. Human metacarpals shared with experimental models (like mice and nonmammal tetrapods) an early common chondrocyte maturation cycle but with a different timing due to the slower embryonic and fetal developmental rate of human anlagen.

Carpal Coalitions and Metacarpal Synostoses: A Review.

Background: Carpal coalition and metacarpal synostosis are uncommon congenital anomalies of the carpus and hand. Methods: A comprehensive review of the literature was performed to help guide surgical and non-surgical treatment of carpal coalition and metacarpal synostosis. Results: The embryology, epidemiology, medical and surgical management, and associated outcomes are detailed. Conclusions: Most patients with these disorders will likely benefit from conservative measures. Surgery should be considered in patients with pain and limitations in wrist and hand function.

Dynamic imaging of the growth plate cartilage reveals multiple contributors to skeletal morphogenesis.

The diverse morphology of vertebrate skeletal system is genetically controlled, yet the means by which cells shape the skeleton remains to be fully illuminated. Here we perform quantitative analyses of cell behaviours in the growth plate cartilage, the template for long bone formation, to gain insights into this process. Using a robust avian embryonic organ culture, we employ time-lapse two-photon laser scanning microscopy to observe proliferative cells' behaviours during cartilage growth, resulting in cellular trajectories with a spreading displacement mainly along the tissue elongation axis. We build a novel software toolkit of quantitative methods to segregate the contributions of various cellular processes to the cellular trajectories. We find that convergent-extension, mitotic cell division, and daughter cell rearrangement do not contribute significantly to the observed growth process; instead, extracellular matrix deposition and cell volume enlargement are the key contributors to embryonic cartilage elongation.

Regulation of cell polarity in the cartilage growth plate and perichondrium of metacarpal elements by HOXD13 and WNT5A.

The morphology of bones is genetically determined, but the molecular mechanisms that control shape, size and the overall gestalt of bones remain unclear. We previously showed that metacarpals in the synpolydactyly homolog (spdh) mouse, which carries a mutation in Hoxd13 similar to the human condition synpolydactyly (SPD), were transformed to carpal-like bones with cuboid shape that lack cortical bone and a perichondrium and are surrounded by a joint surface. Here we provide evidence that spdh metacarpal growth plates have a defect in cell polarization with a random instead of linear orientation. In parallel prospective perichondral cells failed to adopt the characteristic flattened cell shape. We observed a similar cell polarity defect in metacarpals of Wnt5a(-/-) mice. Wnt5a and the closely related Wnt5b were downregulated in spdh handplates, and HOXD13 induced expression of both genes in vitro. Concomitant we observed mislocalization of core planar cell polarity (PCP) components DVL2 and PRICKLE1 in spdh metacarpals indicating a defect in the WNT/PCP pathway. Conversely the WNT/ß-CATENIN pathway, a hallmark of joint cells lining carpal bones, was upregulated in the perichondral region. Finally, providing spdh limb explant cultures with cells expressing either HOXD13 or WNT5A led to a non-cell autonomous partial rescue of cell polarity the perichondral region and restored the expression of perichondral markers. This study provides a so far unrecognized link between HOX proteins and cell polarity in the perichondrium and the growth plate, a failure of which leads to transformation of metacarpals to carpal-like structures.

How is digit identity determined during limb development?

Digit identity has been studied using the chick embryo as a model system for more than 40 years. Using this model system, several milestone findings have been reported, such as the apical ectodermal ridge (AER), the zone of polarizing activity (ZPA), the Shh gene, and the theory of morphogen and positional information. These experimental results and models provided context for understanding pattern formation in developmental biology. The focus of this review is on the determination of digit identity during limb development. First, the history of studies on digit identity determination is described, followed by descriptions of the molecular mechanisms and current models for determination of digit identity. Finally, future questions and remarkable points will be discussed.

Development of the deep flexor tendons and lumbricalis muscle in the hand and foot: a histological study using human mid-term foetuses.

To revisit foetal development of the deep flexor tendons of the hand and foot, we examined the paraffin-embedded histology of 20 mid-term foetuses at 8-15 weeks of estimated gestational age (35-118 mm crown-rump length or CRL). At 8-9 weeks, in front of the metacarpal bones, the flexor pollicis longus and flexor digitorum profundus (FDP) muscles provided a plate-like, common tendon from which the lumbricalis muscles originated. However, in the foot, we had no evidence of such a common tendon. The flexor pollicis tendon was separated from the common tendon at 9-10 weeks possibly due to mechanical stress from the laterally growing thumb. Notably, at the lumbricalis muscle origins at 10-12 weeks, the FDP and flexor digitorum longus tendons remained undifferentiated and the primitive tenocytes were dispersed from them. The dispersed cells seemed to develop into an interface tissue between the lumbricalis muscle fibre and the deep tendon. In 3 of 5 specimens at 15 weeks, we found an excess number of the FDP tendons (5-7) in the proximal side of the lumbricalis muscle origin. However, the excess tendons dispersed in the lumbricalis muscle origin. The development of the lumbricalis muscle origin might follow the tendon splitting for four fingers. However, conversely, we hypothesised that the developing lumbricalis muscles re-arranged the deep flexor tendons to provide a configuration of one deep tendon per one finger (or toe). The quadrates plantae muscle seemed not to contribute on the re-arrangement.

Morphogenesis of the human palma arch using three-dimensional geometric modeling.

The hand goes through complex morphological modifications during embryogenesis. The goal of this study was to use geometric modeling to study the morphometric modifications of the palmar arch. Five embryos were used for the study (sizes: 15, 17, 23, 30, and 44 mm). After digitalization of histologic sections (Sony DXC-930P 3CCD camera, Leica Qwin) and segmentation of the metacarpal cartilaginous matrices (Winsurf 4.3 software), geometric modeling and calculations were performed using MSC.Patran 2005r2 software. Correlations (r > 0.99) were found between embryo size and metacarpal volume, metacarpal surface, and the surface of the modeled palmar arch. The growth of the palmar arch is nonhomothetic. Significant reduction (P = 0.05) in the divergence of the 2nd, 3rd, 4th, and 5th metacarpals was observed. Deepening of the palmar arch is correlated with embryo size and age (r > 0.99). Geometric modeling allows 3D rendering of histologic sections and thus quantitative description of the morphogenesis. The results of this study support the hypothesis that opposition of the thumb in correlation with deepening of the palmar arch appears early in embryological development. It constitutes a specific morphological characteristic that appears very early in the human phylum. The fact that the human thumb is naturally in opposition in the resting position is a consequence of this morphogenesis. The thumb's resting position has received little attention in clinical settings and should be considered as the reference position for biomechanical analysis of the thumb column.

[Effect of sustained increasing fibroblast growth factor signal on development of epiphyseal plate cultured in vitro].

OBJECTIVE: The biological effects of fibroblast growth factor (FGF) may be different under different intensities and durations. To investigate the impact of sustained increasing FGF signal upon the development of epiphyseal plate. METHODS: Epiphyseal plates cultured in vitro were obtained from embryonic C57BL/6J mice, and were divided into control group (0.1% DMSO), basic FGF (bFGF) group (100 microg/L bFGF and 0.1% DMSO), and PD98059 group (100 microg/L bFGF and 50 micromol/L PD98059 with 0.1% DMSO). The total length (TL) and ossified tissue length (OSL) of the cultured bones were measured with Calcein staining 6 days after culture. The expressions of Indian hedgehog (Ihh), collagen type II (Col II), and Col X genes were detected by real-time fluorescent quantitative PCR 7 days after culture. RESULTS: The embryonic bones cultured in vitro continued growth. At 6 days after culture, there was no significant difference in increased percentage of TL between bFGF group and control group (P > 0.05), the increased percentage of OSL in bFGF group was significantly less than that in control group (P < 0.05). There was no significant difference in the increased percentage of TL and OSL between PD98059 group and control group (P > 0.05), but they were significantly higher than those of bFGF group (P < 0.05). At 7 days after culture, the gene expressions of Ihh, Col II, and Col X in bFGF group significantly decreased when compared with those in control group (P < 0.05). There was no significant difference in the gene expressions of Col II and Col X between PD98059 group and control group (P > 0.05), but the gene expressions were significantly higher than those of bFGF group (P < 0.05); the expression of Ihh in PD98059 group was significantly higher than that in control group and bFGF group (P < 0.05). CONCLUSION: Sustained increasing FGF signal may affect the Col II and Col X expressions by down-regulating Ihh, which may lead to the development retardation of epiphyseal plate cultured in vitro. The external signal regulated kinase pathway may play an important role in the process.

Leukemia inhibitory factor inhibits osteoclastic resorption, growth, mineralization, and alkaline phosphatase activity in fetal mouse metacarpal bones in culture.

Leukemia inhibitory factor (LIF) has been reported to affect bone metabolism, but results are variable. We examined the effect of mouse recombinant LIF on osteoclastic resorption in fetal bone explants representing different stages of osteoclast development. In cultures of 17-day-old fetal mouse metacarpals in which only osteoclast progenitors and precursors are present, resorption (measured as 45Ca release) was significantly inhibited to 29.2% and to 96.6% in the presence of LIF 100 and 1000 U/ml, respectively. Histologic examination of the explants treated with 1000 U/ml of LIF confirmed the biochemical findings and showed that osteoclast progenitors and precursors remained in the periosteum and did not invade the mineralized matrix. In metacarpals of older fetuses (18- and 19-day-old) in which the mineralized cartilage has been invaded by mature osteoclasts, the inhibition of resorption by LIF (1000 U/ml) was 87.9 and 74.7%, respectively, the latter being significantly less than the inhibition observed in 17-day-old metacarpal cultures. The inhibitory effect of LIF was absent during concurrent administration of PTH or 1,25-(OH)2D3 and could be reversed by PTH. In addition, LIF was found to inhibit growth, mineralization, and alkaline phosphatase activity in metacarpals independently of osteoclastic resorption. These results suggest that LIF affects the development rather than the activity of osteoclasts, probably through an effect on the osteogenic cells. LIF may be an important endogenous regulator of bone metabolism.