Digit regeneration in mice is stimulated by sequential treatment with FGF2 and BMP2

Nature Communications · 2026-04-17

Epimorphic regeneration in mice is stimulated at a non-regenerative digit amputation by sequential treatment with FGF2 and BMP2 (FGF2→BMP2). FGF2 stimulates digit amputation wound cells to form a blastema and BMP2 induces blastema differentiation to regenerate the amputated distal phalangeal element, albeit imperfectly. The formation of a phalangeal growth plate suggests that the induced regenerate recapitulates embryonic development and cell lineage studies show that wound cells that enter the blastema cells are positionally re-specified during regeneration. FGF2→BMP2 treatment also stimulates a blastema-independent response that regenerates a synovial joint complex containing stump-derived tendon, ligament and a sesamoid-like bone. Together the blastema-dependent and blastema-independent responses can result in the regeneration of all skeletal structures removed by amputation. The induced regeneration response demonstrates the availability of regeneration competent cells at a non-regenerating wound, and that FGF and BMP signaling is sufficient to trigger a regenerative outcome at wounds that heal by fibrosis. Wound fibrosis after amputation in mammals is replaced with regeneration of amputated structural elements by sequential FGF2/BMP2 treatment. Regenerated tissues include phalangeal/sesamoid bones, tendon/ligament, synovial joint, articular cartilage.

Altered digit tip blastema differentiation and bone regeneration in skeletally mature Ts65Dn Down syndrome mice

Bone · 2025-09-01

Down syndrome (DS), the result of Trisomy 21 (T21), is associated with accelerated aging and impacts many organ systems across the lifespan, including the musculoskeletal system. Skeletal deficits such as low bone mineral density predispose the T21 population to skeletal injuries, especially as they age, and likely reduce their capacity to repair bone. Previous studies have demonstrated impaired secondary fracture healing in 4-month-old DS mice and diminished bone regeneration in young (2-months-old) DS mice. To investigate how bone regeneration is further impacted in skeletally mature (6-months-old) mice, terminal phalanx (P3) digit tip amputations were performed in a murine model of DS, Ts65Dn mice. The P3 regeneration cascade is characterized by an initial phase of bone degradation followed by intramembranous ossification to restore the amputated bone. These studies demonstrate that the bone regeneration anomalies observed in young Ts65Dn mice are exacerbated in skeletally mature mice, characterized by a complex dysregulation of bone resorption and formation genes. Collectively, skeletally mature Ts65Dn mice show fundamental in vivo deficits in progenitor cell differentiation, cell activity, cell proliferation, and alterations in gene expression associated with diminished regenerative outcomes. Importantly, these deficiencies in bone regeneration in skeletally mature Ts65Dn mice have implications to the adult T21 population as the last several decades have seen substantial increases in the average life span of T21 individuals. If the regenerative defects in Ts65Dn mice are recapitulated during bone healing in the T21 population, this could have profound consequences for this growing population.

Digit regeneration in mice is stimulated by sequential treatment with FGF2 and BMP2

Research Square · 2025-06-11 · 1 citations

145. Lymphatic Ablation Accelerates Murine Digit Tip Regeneration Through Enhanced Osteoclast Activity

Plastic & Reconstructive Surgery Global Open · 2025-04-24

Neda Vishlaghi, Trisha Ghotra, Monisha Mittal, Ji Hae Choi, Sneha Korlakunta, Mingquan Yan, Janna L. Crossley, Danielle Griswold-Wheeler, Conan Juan, Shiri Gur-Cohen, Babak Mehrara, Robert Tower, Michael Dellinger, Lindsay A. Dawson, Benjamin Levi INTRODUCTION: In the United States, over 2 million individuals suffer from limb loss, resulting in chronic pain and limited form and function. Current treatments are inadequate in supporting tissue regeneration, emphasizing the need to understand post-traumatic endogenous regeneration for devising effective treatment strategies. P3 regeneration parallels a similar response in humans, and is characterized by the phases of inflammation, osteolysis, skin closure, blastema formation, bone differentiation, and matrix deposition. The lymphatic vasculature has been essentially ignored in bone tissue research as prior studies have failed to identify lymphatics in cortical bone during quiescence. In this study, we utilized different transgenic mouse models to elucidate the function of lymphatic vessels and lymphatic signaling during P3 regeneration. MATERIALS AND METHODS: Mice aged between 10-12 weeks underwent a P3 amputation on hind limb digits 2 and 4 of each paw. Samples were harvested on day 5-8 (inflammatory phase and osteolysis), day 10-14 (skin closure and blastema phase), day 16-21 (P3 bone mineralization), and day 28-42 (P3 late-stage bone regeneration). Prox1-eGFP mice were used for the temporal and spatial localization of lymphatic vessels. FLT4CreERT2;iDTR mice were employed for the selective ablation of both capillary and collecting lymphatic vessels. Vegfr3mut/wt mice were utilized to assess the impact of lymphatic hypoplasia on regeneration. Pharmacological inhibition of lymphangiogenesis was achieved using a VEGFR3 inhibitor diet. Surgical removal of the popliteal and inguinal lymph nodes were performed to surgically manipulate lymphatics during the regeneration process. RESULTS: Using a lymphatic-specific reporter line, we discovered that lymphatic vessels are restricted to the ventral side of the digit both during quiescence and following digit amputation throughout the phases of digit tip regeneration. These native and regenerating lymphatics closely surround—but do not invade—the native or regenerated bone. Unexpectedly, genetic, pharmacological, and surgical interventions that reduced lymphangiogenesis accelerated the early osteolysis phase of P3 regeneration. This enhanced regeneration occurred via the transition of myeloid cells to osteoclasts, resulting in faster and more robust digit tip regeneration. The increased myeloid-to-osteoclast transition was due to decreased myeloid cell egress and an elevated transition of myeloid cells to osteoclasts. CONCLUSION: Overall, these findings suggest that therapeutic manipulation of lymphatic vessel dynamics could enhance regenerative mechanisms, offering new insights into the complex interplay between lymphatic vessels, myeloid-to-osteoclast transitions, and tissue regeneration) Lymphangiogenesis patterns during digit tip regeneration) MicroCT images and analysis of VEGFR3 inhibition showing increased bone volume formation) scRNA-seq data confirming lower lymphatic marker expression and higher osteoclast activity. J-L) Histolysis is enhanced after VEGFR3 inhibition during regeneration.

FGF8 induces bone and joint regeneration at digit amputation wounds in neonate mice

Bone · 2025-10-04 · 1 citations

Due to increases in vascular diseases, the incidence of limb loss is predicted to more than double in the next quarter century. Therefore, developing a greater understanding of the latent regenerative capacity in mammals is a significant and growing goal. Mammals, including humans and mice, have limited regenerative capacity following limb amputation, with regenerative responses restricted to amputations transecting the distal digit tip (P3). Unlike P3, amputations of the adjacent skeletal segment, the middle phalanx, P2, are non-regenerative and result in bone truncation and soft tissue scar formation. As such, P2 amputation is a simple yet powerful model to test strategies for inducing mammalian musculoskeletal regeneration from an otherwise non-regenerative amputation plane. Here, we report that Fibroblast Growth Factor 8 (FGF8) drives synovial joint regeneration at P2 amputation wounds in neonate mice. This response is characterized by the regeneration of a synovial cavity, a skeletal nodule lined with articular cartilage, and tendon and ligament regeneration. FGF8 also induces cartilage formation on the P2 stump that serves as a template for partial P2 bone regeneration, thus FGF8 drives the composite regeneration of stump and joint tissues. FGF8-induced joint regeneration is associated with the upregulation of several, but not all, genes that characterize joint development, and is morphologically distinct from digit joint development. Lineage tracing studies demonstrate that cells at the amputation wound contribute to the regenerated joint structures. These studies provide evidence that the otherwise non-regenerative P2 amputation wound possesses tremendous regenerative capacity that is dormant under normal circumstances.

Male Down syndrome Ts65Dn mice have impaired bone regeneration

Bone · 2024-12-13 · 1 citations

Trisomy of human chromosome 21 (Ts21) individuals present with a spectrum of low bone mineral density (BMD) that predisposes this vulnerable group to skeletal injuries. To determine the bone regenerative capacity of Down syndrome (DS) mice, male and female Dp16 and Ts65Dn DS mice underwent amputation of the digit tip (the terminal phalanx (P3)). This is a well-established mammalian model of bone regeneration that restores the amputated skeletal segment and all associated soft tissues. P3 amputation was performed in 8-week-old male and female DS mice and WT controls and followed by in vivo μCT, histology and immunofluorescence. Following P3 amputation, the bone degradation phase was attenuated in both Dp16 and Ts65Dn males. In Dp16 males, P3 regeneration was delayed but complete by 63 days post amputation (DPA); however, male Ts65Dn exhibited attenuated regeneration by 63 DPA. In both Dp16 and Ts65Dn female DS mice, P3 regenerates were indistinguishable from WT by 42 DPA. In Ts65Dn males, osteoclasts and eroded bone surface were significantly reduced, and osteoblast number significantly decreased in the regenerating digit. In Ts65Dn females, no significant differences were observed in any osteoclast or osteoblast parameter. Like Ts21 individuals and DS mice with sex differences in bone mass, these data expand the characteristic sexually dimorphism to include bone resorption and regeneration in response to skeletal injury in Ts65Dn mice. These observations suggest that sex differences contribute to the poor bone healing of DS and compound the increased risk of bone injury in the Ts21 population.

JAMA Internal Medicine

JAMA Internal Medicine · 2023-08-01 · 1 citations

Mission Statement: To promote the art and science of medicine and the betterment of public health by publishing manuscripts of interest and relevance to internists practicing as generalists or as medical subspecialists.

Fluid Optimisation in Emergency Laparotomy (FLO-ELA) Trial: study protocol for a multi-centre randomised trial of cardiac output-guided fluid therapy compared to usual care in patients undergoing major emergency gastrointestinal surgery

Trials · 2023 · 10 citations

• Medicine
• Emergency medicine
• Intensive care medicine

INTRODUCTION: Postoperative morbidity and mortality in patients undergoing major emergency gastrointestinal surgery are a major burden on healthcare systems. Optimal management of perioperative intravenous fluids may reduce mortality rates and improve outcomes from surgery. Previous small trials of cardiac-output guided haemodynamic therapy algorithms in patients undergoing gastrointestinal surgery have suggested this intervention results in reduced complications and a modest reduction in mortality. However, this existing evidence is based mainly on elective (planned) surgery, with little evaluation in the emergency setting. There are fundamental clinical and pathophysiological differences between the planned and emergency surgical setting which may influence the effects of this intervention. A large definitive trial in emergency surgery is needed to confirm or refute the potential benefits observed in elective surgery and to inform widespread clinical practice. METHODS: The FLO-ELA trial is a multi-centre, parallel-group, open, randomised controlled trial. 3138 patients aged 50 and over undergoing major emergency gastrointestinal surgery will be randomly allocated in a 1:1 ratio using minimisation to minimally invasive cardiac output monitoring to guide protocolised administration of intra-venous fluid, or usual care without cardiac output monitoring. The trial intervention will be carried out during surgery and for up to 6 h postoperatively. The trial is funded through an efficient design call by the National Institute for Health and Care Research Health Technology Assessment (NIHR HTA) programme and uses existing routinely collected datasets for the majority of data collection. The primary outcome is the number of days alive and out of hospital within 90 days of randomisation. Participants and those delivering the intervention will not be blinded to treatment allocation. Participant recruitment started in September 2017 with a 1-year internal pilot phase and is ongoing at the time of publication. DISCUSSION: This will be the largest contemporary randomised trial examining the effectiveness of perioperative cardiac output-guided haemodynamic therapy in patients undergoing major emergency gastrointestinal surgery. The multi-centre design and broad inclusion criteria support the external validity of the trial. Although the clinical teams delivering the trial interventions will not be blinded, significant trial outcome measures are objective and not subject to detection bias. TRIAL REGISTRATION: ISRCTN 14729158. Registered on 02 May 2017.

Contextual Information

2023-01-01

Induced regeneration of articular cartilage – identification of a dormant regeneration program for a non-regenerative tissue

Development · 2023-10-26 · 4 citations

A mouse organoid culture model was developed to regenerate articular cartilage by sequential treatment with BMP2 and BMP9 (or GDF2) that parallels induced joint regeneration at digit amputation wounds in vivo. BMP9-induced chondrogenesis was used to identify clonal cell lines for articular chondrocyte and hypertrophic chondrocyte progenitor cells from digit fibroblasts. A protocol that includes cell aggregation enhanced by BMP2 followed by BMP9-induced chondrogenesis resulted in the differentiation of organized layers of articular chondrocytes, similar to the organization of middle and deep zones of articular cartilage in situ, and retained a differentiated phenotype following transplantation. In addition, the differentiation of a non-chondrogenic connective tissue layer containing articular chondrocyte progenitor cells demonstrated that progenitor cell sequestration is coupled with articular cartilage differentiation at a clonal level. The studies identify a dormant endogenous regenerative program for a non-regenerative tissue in which fibroblast-derived progenitor cells can be induced to initiate morphogenetic and differentiative programs that include progenitor cell sequestration. The identification of dormant regenerative programs in non-regenerative tissues such as articular cartilage represents a novel strategy that integrates regeneration biology with regenerative medicine.