Micro-Growth Plates by LSJL

It's unlikely that LSJL can re-establish a whole entire new growth plate.  It's far more probable that LSJL can produce smaller growth plates that can each contribute a little to longitudinal bone growth.  Here I present a study that provides evidence of the microgrowth plate theory.

The Interplay between Chondrocyte Redifferentiation Pellet Size and Oxygen Concentration.

"Chondrocytes dedifferentiate{in endochondral ossification chondrocytes die out rather than transdifferentiate into bone type cells so it's unlikely that there's any remnants of dedifferentiated or transdifferentiated chondrocytes that retain some chondrocyte epigenetic material, for LSJL we have to rely on regular mesenchymal stem cells} during ex vivo expansion on 2-dimensional surfaces. Aggregation of the expanded cells into 3-dimensional pellets, in the presence of induction factors, facilitates their redifferentiation and restoration of the chondrogenic phenotype. Typically 1×10(5)-5×10(5) chondrocytes are aggregated, resulting in "macro" pellets having diameters ranging from 1-2 mm. These macropellets are commonly used to study redifferentiation, and recently macropellets of autologous chondrocytes have been implanted directly into articular cartilage defects to facilitate their repair. However, diffusion of metabolites over the 1-2 mm pellet length-scales is inefficient, resulting in radial tissue heterogeneity. The aggregation of 2×10(5) human chondrocytes into micropellets of 166 cells each{it's probable to be able to induce an aggregate of 166 cells with LSJL stimuli, likely more cells are needed as we are dealing with MSCs rather than dedifferentiated chondrocytes}, rather than into larger single macropellets, enhances chondrogenic redifferentiation. The thousands of micropellets were manufactured using the microwell platform, which is an array of 360×360 µm microwells cast into polydimethylsiloxane (PDMS), that has been surface modified with an electrostatic multilayer of hyaluronic acid and chitosan to enhance micropellet formation{Both chitosan and hyaluronic acid are supplements, whether they can help create some kind of basement membrane or scaffold for growth is unclear}. Such surface modification was essential to prevent chondrocyte spreading on the PDMS. Sulfated glycosaminoglycan (sGAG) production and collagen II gene expression in chondrocyte micropellets increased significantly relative to macropellet controls, and redifferentiation was enhanced in both macro and micropellets with the provision of a hypoxic atmosphere (2% O2). Once micropellet formation had been optimized, micropellets could be assembled into larger cartilage tissues{so micro-growth plates can combine to become larger growth plates}."

"The reduced diameter of the micropellets[100 micrometers each] mitigated diffusion gradients, enhanced MSC chondrogenic differentiation and generated a more uniform cell product"


"Hypoxic micropellets assembled into macrotissues.  Alcian blue staining for hypoxic micropellets assembled at different time points (indicated days). The total culture duration was 21 days. Scale bars: 100 µm."

Key Differences between this study and LSJL:
*Articular Cartilage was used and not Growth Plate cartilage
*Dedifferentiated Chondrocytes were used and not mesenchymal stem cells.
*The micro-cartilage was uniform here.  In LSJL, the microgrowth plates would not be uniform.

Regardless it still provides evidence that MSCs could potentially form microgrowth plates and those growth plates could combine to form larger growth plates.  It seems that the higher oxygen concentration was of a more endochondral rather than chondral environment which is good considering that adult bone is vascularized.

Here's some evidence that micro growth plates can undergo endochondral ossification:

Delayed endochondral ossification in early medial coronoid disease (MCD): A morphological and immunohistochemical evaluation in growing Labrador retrievers.

"Early micromorphological changes [occur] in articular cartilage and to describe the postnatal development of the medial coronoid process (MCP) before MCD develops. Three litters of MCD-prone young Labrador retrievers were purpose-bred from a dam and two sires with MCD. Comparisons of the micromorphological appearance of the MCP in MCD-negative and MCD-positive joints demonstrated that MCD was initially associated with a disturbance of endochondral ossification, namely a delay in the calcification of the calcifying zone, without concurrent abnormalities in the superficial layers of the joint cartilage. Cartilage canals containing patent blood vessels were only detected in dogs <12weeks old. Retained hyaline cartilage might ossify as the disease progresses, but weak areas can develop into cracks between the retained cartilage and the subchondral bone, leading to cleft formation and fragmentation of the MCP."

That scattered growth plates could undergo endochondral ossification bodes well that micro growth plates could undergo endochondral ossification.

"Osteochondrosis is characterized by a disturbance of endochondral ossification that leads to an area of retained cartilage"<-osteochondrosis could be key to our understanding of microgrowth plates.

The arrows are pointing to cartilage canals

Cartilage canals dissappeared at 12 weeks of age.

Pathogenesis of epiphyseal osteochondrosis.

"Osteochondrosis (OC) of the articular epiphyseal cartilage complex (AECC) is a developmental disease that is present in the first weeks of life. It is characterized by focal chondronecrosis and retention of growth cartilage due to failure of endochondral ossification. Fissures may extend from the lesion through the overlying articular cartilage to create a cartilage flap and an osteochondral fragment. This articular form is known as osteochondritis dissecans (OCD). There have been many hypotheses about the etiopathogenesis of OC of the AECC including, amongst others, ischemia of growth cartilage or altered cartilage type II collagen metabolism. The ischemia theory proposes that necrosis of the vessels in the cartilage canals of the sub-articular growth cartilage leads to necrosis of chondrocytes and retention of necrotic cartilage{so re-establishing these vessels in the cartilage canals could be critical to forming new growth plates}. Several studies have measured biomarkers in serum and synovial fluid to demonstrate a consistent increase in type II collagen synthesis in young animals of different species. Although these changes could represent lesion reparative events, there is no comparable increase in the synthesis of cartilage matrix proteoglycan molecule. It is therefore speculated that an altered type II collagen metabolism may be involved in the early changes associated with OC. Further studies of OC susceptible animals in utero and the first weeks of life are required to elucidate the cause of vessel necrosis and the exact role of type II collagen structure and metabolism in OC."

"The bones of diarthrodial joints develop from mesenchymal cells that condense and differentiate into chondrocytes to form a cartilage template. Following formation of the primary ossification center in the diaphysis, the chondrocytes of the central area of the epiphysis proliferate, hypertrophy and undergo cell death. A complex sequence of molecular signals orchestrates these events. The hypertrophic chondrocytes themselves secrete type X collagen and alkaline phosphatase that contribute to calcification of the adjacent matrix. The mineralized cartilaginous septae, between the cell lacunae, undergo proteolytic digestion by septoclasts . Proteinases, such as matrix metalloproteinases (MMPs), cathepsins and gelatinases, degrade the mineralized type II-collagen-rich network to allow blood vessel invasion. The invading vessels are a source of mesenchymal stem cells and bone progenitors that differentiate into osteoblasts, secrete osteoid and promote ossification of the secondary center of ossification in the epiphysis" <-Our goal is to induce the mimicing of these events via LSJL to form new growth plates.

Osteochondrosis of the proximal phalanx of the hallux in adolescent footballers.

"We report two cases with radiographic appearances of osteochondrosis in the proximal phalanx of the big toe in adolescent footballers. The radiological findings were those of initial fragmentation with subsequent healing of the epiphysis. This is the first report of osteochondrosis at this site. Local pain was accompanied by swelling with restriction of dorsiflexion of the metatarsophalangeal joint of the big toe. The condition was self-healing over a 2-4-year period. It needs to be included in the differential diagnosis of painful hallux in adolescent footballers."

Unfortunately I could not get this full study.  It'd be interesting to see the healing of the epiphysis.