# Reversing Skeletal Aging by Restoring Functional Skeletal Stem Cell Diversity

> **NIH NIH K99** · STANFORD UNIVERSITY · 2021 · $113,696

## Abstract

PROJECT SUMMARY
Advancing age and obesity are tightly linked to the increasing global incidence of skeletal diseases. Osteoporosis
in particular poses a major public health threat for over 54 million Americans as it is interrelated with high fracture
rates. Osteoporosis-related hip fractures are invariably associated with significant morbidity and strikingly, a 58%
mortality rate in the elderly within the first year of injury. This problem is compounded by a lack of efficient
preventive and medical therapies for age-related bone disease free of major side effects. Recent studies have
revealed adult stem cell populations within bone that could be potentially targeted as a regenerative source to
maintain and restore skeletal health. However, breakthroughs in stem cell based-regenerative strategies have
been hampered by the inability to isolate bona fide stem cell populations which could serve as starting points for
targeted approaches. Our group has helped delineate highly purified skeletal stem cell (SSC) lineages crucial
for maintaining normal bone homeostasis and regeneration following injury. My latest results suggest that aging
shifts lineage determination of stem cells thereby contributing to a decline of regenerative capacity and providing
a rationale that skeletal aging is caused by SSC dysfunction. My preliminary data further provides evidence for
the existence of multiple SSC subtypes (SSC diversity) present in limb long bones. Transcriptomic analysis at
the single-cell level shows that SSCs undergo aging-induced molecular and compositional changes coinciding
with functional heterogeneity. I have identified Wnt1 Inducible Signaling Pathway Protein 2 (Wisp2) that is
specifically upregulated in the aged SSC lineage. Wisp2 significantly impairs bone formation when applied to
SSC in vitro or fractures of young mice in vivo. Thus, Aim1 of this proposal is to determine the role of age-related
changes in SSC diversity including the relative proportion of SSC subtypes and their functional heterogeneity to
skeletal integrity using a variety of methods for spatio-temporal single-cell analysis. In Aim2 I will examine the
mechanism of stem cell-based skeletal aging through Wisp2, which I hypothesize, may regulate SSC
diversity and heterogeneity. Proposed experiments will also address its potential connection to new concepts
of stem cell aging such as adverse clonal skeletogenesis. Importantly, I will determine the unexplored identity of
the Wisp2 receptor in SSCs by highly sensitive proximity-dependent labeling to identify targetable pathways
involved in SSC-mediated skeletal aging. The guidance and research environment provided by the expert
mentors from Stanford and the NIH is cutting-edge and highly relevant to the purpose of this proposal allowing
implementation of the latest transcriptomic and proteomic methods, including SmartSeq2 single-cell RNA-
sequencing, RNAScope, and TurboID, to interrogate the proposed aims. These studies will establish ...

## Key facts

- **NIH application ID:** 10127477
- **Project number:** 1K99AG066963-01A1
- **Recipient organization:** STANFORD UNIVERSITY
- **Principal Investigator:** Thomas Hans Ambrosi
- **Activity code:** K99 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $113,696
- **Award type:** 1
- **Project period:** 2021-04-01 → 2023-03-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10127477

## Citation

> US National Institutes of Health, RePORTER application 10127477, Reversing Skeletal Aging by Restoring Functional Skeletal Stem Cell Diversity (1K99AG066963-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10127477. Licensed CC0.

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